Fix memory leaks via auto-unsubscribing and DI

This commit simplifies event handling, providing a unified and robust
way to handle event lifecycling. This way, it fixes events not being
unsubscribed when state is changed.

Introduce a new function in `EventSubscriptionCollection` to remove
existing events and adding new events. This provides an easier to use
API, which leads to code that's easier to understand. It also prevents
potential bugs that may occur due to forgetting to call both functions.
It fixes `TheScriptsMenu` not unregistering events on state change.
Other improvements include:
  - Include a getter to get total amount of registered subcriptions.
    This helps in unit testing.
  - Have nullish checks to prevent potential errors further down the
    execution.
  - Use array instead of rest parameters to increase readability and
    simplify tests.

Ensure `SliderHandler` stops resizes on unmount, unsubscribing from all
events and resetting state to default.

Update `injectionKeys` to do imports as types to avoid circular
dependencies. Simplify importing `injectionKeys` to enable and strict
typings for iterating injection keys.

Add tests covering new behavior.

docs/presentation.md

@@ -14,12 +14,12 @@ The presentation layer uses an event-driven architecture for bidirectional react
   - [**`bootstrapping/`**](./../src/presentation/bootstrapping/): Registers Vue components and plugins.
   - [**`components/`**](./../src/presentation/components/): Contains Vue components and helpers.
     - [**`Shared/`**](./../src/presentation/components/Shared): Contains shared Vue components and helpers.
-      - [**`hooks`**](../src/presentation/components/Shared/Hooks): Hooks used by components through [dependency injection](#dependency-injections).
+      - [**`Hooks`**](../src/presentation/components/Shared/Hooks): Hooks used by components through [dependency injection](#dependency-injections).
   - [**`/public/`**](../src/presentation/public/): Contains static assets.
   - [**`assets/`**](./../src/presentation/assets/styles/): Contains assets processed by Vite.
     - [**`fonts/`**](./../src/presentation/assets/fonts/): Contains fonts.
     - [**`styles/`**](./../src/presentation/assets/styles/): Contains shared styles.
-      - [**`components/`**](./../src/presentation/assets/styles/components): Contains styles for Vue components.
+      - [**`components/`**](./../src/presentation/assets/styles/components): Contains styles coupled to Vue components.
       - [**`vendors-extensions/`**](./../src/presentation/assets/styles/third-party-extensions): Contains styles for third-party components.
       - [**`main.scss`**](./../src/presentation/assets/styles/main.scss): Main Sass file, imported by other components as single entrypoint.
   - [**`main.ts`**](./../src/presentation/main.ts): Starts Vue app.

src/infrastructure/Events/EventSubscriptionCollection.ts

@@ -1,10 +1,20 @@
-import { IEventSubscription } from './IEventSource';
 import { IEventSubscriptionCollection } from './IEventSubscriptionCollection';
+import { IEventSubscription } from './IEventSource';
 
 export class EventSubscriptionCollection implements IEventSubscriptionCollection {
   private readonly subscriptions = new Array<IEventSubscription>();
 
-  public register(...subscriptions: IEventSubscription[]) {
+  public get subscriptionCount() {
+    return this.subscriptions.length;
+  }
+
+  public register(subscriptions: IEventSubscription[]) {
+    if (!subscriptions || subscriptions.length === 0) {
+      throw new Error('missing subscriptions');
+    }
+    if (subscriptions.some((subscription) => !subscription)) {
+      throw new Error('missing subscription in list');
+    }
     this.subscriptions.push(...subscriptions);
   }
 
@@ -12,4 +22,9 @@ export class EventSubscriptionCollection implements IEventSubscriptionCollection
     this.subscriptions.forEach((listener) => listener.unsubscribe());
     this.subscriptions.splice(0, this.subscriptions.length);
   }
+
+  public unsubscribeAllAndRegister(subscriptions: IEventSubscription[]) {
+    this.unsubscribeAll();
+    this.register(subscriptions);
+  }
 }

src/infrastructure/Events/IEventSubscriptionCollection.ts

@@ -1,7 +1,9 @@
 import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 
 export interface IEventSubscriptionCollection {
-  register(...subscriptions: IEventSubscription[]);
+  readonly subscriptionCount: number;
 
-  unsubscribeAll();
+  register(subscriptions: IEventSubscription[]): void;
+  unsubscribeAll(): void;
+  unsubscribeAllAndRegister(subscriptions: IEventSubscription[]);
 }

src/presentation/bootstrapping/DependencyProvider.ts

@@ -1,28 +1,31 @@
-import { InjectionKey, provide } from 'vue';
+import { InjectionKey, provide, inject } from 'vue';
 import { useCollectionState } from '@/presentation/components/Shared/Hooks/UseCollectionState';
 import { useApplication } from '@/presentation/components/Shared/Hooks/UseApplication';
-import {
-  useCollectionStateKey, useApplicationKey, useRuntimeEnvironmentKey,
-} from '@/presentation/injectionSymbols';
+import { useAutoUnsubscribedEvents } from '@/presentation/components/Shared/Hooks/UseAutoUnsubscribedEvents';
 import { IApplicationContext } from '@/application/Context/IApplicationContext';
 import { RuntimeEnvironment } from '@/infrastructure/RuntimeEnvironment/RuntimeEnvironment';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 
-export function provideDependencies(context: IApplicationContext) {
-  registerSingleton(useApplicationKey, useApplication(context.app));
-  registerTransient(useCollectionStateKey, () => useCollectionState(context));
-  registerSingleton(useRuntimeEnvironmentKey, RuntimeEnvironment.CurrentEnvironment);
-}
-
-function registerSingleton<T>(
-  key: InjectionKey<T>,
-  value: T,
+export function provideDependencies(
+  context: IApplicationContext,
+  api: VueDependencyInjectionApi = { provide, inject },
 ) {
-  provide(key, value);
-}
-
-function registerTransient<T>(
+  const registerSingleton = <T>(key: InjectionKey<T>, value: T) => api.provide(key, value);
+  const registerTransient = <T>(
     key: InjectionKey<() => T>,
     factory: () => T,
-) {
-  provide(key, factory);
+  ) => api.provide(key, factory);
+
+  registerSingleton(InjectionKeys.useApplication, useApplication(context.app));
+  registerSingleton(InjectionKeys.useRuntimeEnvironment, RuntimeEnvironment.CurrentEnvironment);
+  registerTransient(InjectionKeys.useAutoUnsubscribedEvents, () => useAutoUnsubscribedEvents());
+  registerTransient(InjectionKeys.useCollectionState, () => {
+    const { events } = api.inject(InjectionKeys.useAutoUnsubscribedEvents)();
+    return useCollectionState(context, events);
+  });
+}
+
+export interface VueDependencyInjectionApi {
+  provide<T>(key: InjectionKey<T>, value: T): void;
+  inject<T>(key: InjectionKey<T>): T;
 }

src/presentation/components/Code/CodeButtons/Instructions/InstructionList.vue

@@ -59,7 +59,7 @@ import {
   defineComponent, PropType, computed,
   inject,
 } from 'vue';
-import { useApplicationKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { OperatingSystem } from '@/domain/OperatingSystem';
 import TooltipWrapper from '@/presentation/components/Shared/TooltipWrapper.vue';
 import CodeInstruction from './CodeInstruction.vue';
@@ -77,7 +77,7 @@ export default defineComponent({
     },
   },
   setup(props) {
-    const { info } = inject(useApplicationKey);
+    const { info } = inject(InjectionKeys.useApplication);
 
     const appName = computed<string>(() => info.name);
 

src/presentation/components/Code/CodeButtons/TheCodeButtons.vue

@@ -29,7 +29,7 @@
 import {
   defineComponent, ref, computed, inject,
 } from 'vue';
-import { useCollectionStateKey, useRuntimeEnvironmentKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { SaveFileDialog, FileType } from '@/infrastructure/SaveFileDialog';
 import { Clipboard } from '@/infrastructure/Clipboard';
 import ModalDialog from '@/presentation/components/Shared/Modal/ModalDialog.vue';
@@ -53,9 +53,10 @@ export default defineComponent({
   },
   setup() {
     const {
-      currentState, currentContext, onStateChange, events,
-    } = inject(useCollectionStateKey)();
-    const { os, isDesktop } = inject(useRuntimeEnvironmentKey);
+      currentState, currentContext, onStateChange,
+    } = inject(InjectionKeys.useCollectionState)();
+    const { os, isDesktop } = inject(InjectionKeys.useRuntimeEnvironment);
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const areInstructionsVisible = ref(false);
     const canRun = computed<boolean>(() => getCanRunState(currentState.value.os, isDesktop, os));
@@ -81,15 +82,18 @@ export default defineComponent({
     }
 
     onStateChange((newState) => {
+      updateCurrentCode(newState.code.current);
       subscribeToCodeChanges(newState.code);
     }, { immediate: true });
 
     function subscribeToCodeChanges(code: IApplicationCode) {
-      hasCode.value = code.current && code.current.length > 0;
-      events.unsubscribeAll();
-      events.register(code.changed.on((newCode) => {
-        hasCode.value = newCode && newCode.code.length > 0;
-      }));
+      events.unsubscribeAllAndRegister([
+        code.changed.on((newCode) => updateCurrentCode(newCode.code)),
+      ]);
+    }
+
+    function updateCurrentCode(code: string) {
+      hasCode.value = code && code.length > 0;
     }
 
     async function getCurrentCode(): Promise<IApplicationCode> {

src/presentation/components/Code/TheCodeArea.vue

@@ -13,7 +13,7 @@
 import {
   defineComponent, onUnmounted, onMounted, inject,
 } from 'vue';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { ICodeChangedEvent } from '@/application/Context/State/Code/Event/ICodeChangedEvent';
 import { IScript } from '@/domain/IScript';
 import { ScriptingLanguage } from '@/domain/ScriptingLanguage';
@@ -37,7 +37,8 @@ export default defineComponent({
     NonCollapsing,
   },
   setup(props) {
-    const { onStateChange, currentState, events } = inject(useCollectionStateKey)();
+    const { onStateChange, currentState } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const editorId = 'codeEditor';
     let editor: ace.Ace.Editor | undefined;
@@ -61,19 +62,20 @@ export default defineComponent({
         newState.collection.scripting.language,
       );
       const appCode = newState.code;
-      const innerCode = appCode.current || getDefaultCode(newState.collection.scripting.language);
-      editor.setValue(innerCode, 1);
-      events.unsubscribeAll();
-      events.register(appCode.changed.on((code) => updateCode(code)));
+      updateCode(appCode.current, newState.collection.scripting.language);
+      events.unsubscribeAllAndRegister([
+        appCode.changed.on((code) => handleCodeChange(code)),
+      ]);
     }
 
-    function updateCode(event: ICodeChangedEvent) {
-      removeCurrentHighlighting();
-      if (event.isEmpty()) {
-        const defaultCode = getDefaultCode(currentState.value.collection.scripting.language);
-        editor.setValue(defaultCode, 1);
-        return;
+    function updateCode(code: string, language: ScriptingLanguage) {
+      const innerCode = code || getDefaultCode(language);
+      editor.setValue(innerCode, 1);
     }
+
+    function handleCodeChange(event: ICodeChangedEvent) {
+      removeCurrentHighlighting();
+      updateCode(event.code, currentState.value.collection.scripting.language);
       editor.setValue(event.code, 1);
       if (event.addedScripts?.length > 0) {
         reactToChanges(event, event.addedScripts);

src/presentation/components/Scripts/Menu/Selector/TheSelector.vue

@@ -66,9 +66,10 @@
 
 <script lang="ts">
 import { defineComponent, ref, inject } from 'vue';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import TooltipWrapper from '@/presentation/components/Shared/TooltipWrapper.vue';
 import { ICategoryCollectionState } from '@/application/Context/State/ICategoryCollectionState';
+import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 import MenuOptionList from '../MenuOptionList.vue';
 import MenuOptionListItem from '../MenuOptionListItem.vue';
 import { SelectionType, SelectionTypeHandler } from './SelectionTypeHandler';
@@ -80,28 +81,27 @@ export default defineComponent({
     TooltipWrapper,
   },
   setup() {
-    const { modifyCurrentState, onStateChange, events } = inject(useCollectionStateKey)();
+    const { modifyCurrentState, onStateChange } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const currentSelection = ref(SelectionType.None);
 
     let selectionTypeHandler: SelectionTypeHandler;
 
     onStateChange(() => {
-      unregisterMutators();
-
       modifyCurrentState((state) => {
-        registerStateMutator(state);
+        selectionTypeHandler = new SelectionTypeHandler(state);
+        updateSelections();
+        events.unsubscribeAllAndRegister([
+          subscribeAndUpdateSelections(state),
+        ]);
       });
     }, { immediate: true });
 
-    function unregisterMutators() {
-      events.unsubscribeAll();
-    }
-
-    function registerStateMutator(state: ICategoryCollectionState) {
-      selectionTypeHandler = new SelectionTypeHandler(state);
-      updateSelections();
-      events.register(state.selection.changed.on(() => updateSelections()));
+    function subscribeAndUpdateSelections(
+      state: ICategoryCollectionState,
+    ): IEventSubscription {
+      return state.selection.changed.on(() => updateSelections());
     }
 
     function selectType(type: SelectionType) {

src/presentation/components/Scripts/Menu/TheOsChanger.vue

@@ -14,7 +14,7 @@
 import {
   defineComponent, computed, inject,
 } from 'vue';
-import { useApplicationKey, useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { OperatingSystem } from '@/domain/OperatingSystem';
 import MenuOptionList from './MenuOptionList.vue';
 import MenuOptionListItem from './MenuOptionListItem.vue';
@@ -30,8 +30,8 @@ export default defineComponent({
     MenuOptionListItem,
   },
   setup() {
-    const { modifyCurrentContext, currentState } = inject(useCollectionStateKey)();
-    const { application } = inject(useApplicationKey);
+    const { modifyCurrentContext, currentState } = inject(InjectionKeys.useCollectionState)();
+    const { application } = inject(InjectionKeys.useApplication);
 
     const allOses = computed<ReadonlyArray<IOsViewModel>>(() => (
       application.getSupportedOsList() ?? [])

src/presentation/components/Scripts/Menu/TheScriptsMenu.vue

@@ -11,10 +11,11 @@
 
 <script lang="ts">
 import {
-  defineComponent, ref, onUnmounted, inject,
+  defineComponent, ref, inject,
 } from 'vue';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { IReadOnlyUserFilter } from '@/application/Context/State/Filter/IUserFilter';
+import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 import TheOsChanger from './TheOsChanger.vue';
 import TheSelector from './Selector/TheSelector.vue';
 import TheViewChanger from './View/TheViewChanger.vue';
@@ -26,31 +27,26 @@ export default defineComponent({
     TheViewChanger,
   },
   setup() {
-    const { onStateChange, events } = inject(useCollectionStateKey)();
+    const { onStateChange } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const isSearching = ref(false);
 
     onStateChange((state) => {
-      subscribeToFilterChanges(state.filter);
+      events.unsubscribeAllAndRegister([
+        subscribeToFilterChanges(state.filter),
+      ]);
     }, { immediate: true });
 
-    onUnmounted(() => {
-      unsubscribeAll();
-    });
-
-    function subscribeToFilterChanges(filter: IReadOnlyUserFilter) {
-      events.register(
-        filter.filterChanged.on((event) => {
+    function subscribeToFilterChanges(
+      filter: IReadOnlyUserFilter,
+    ): IEventSubscription {
+      return filter.filterChanged.on((event) => {
         event.visit({
           onApply: () => { isSearching.value = true; },
           onClear: () => { isSearching.value = false; },
         });
-        }),
-      );
-    }
-
-    function unsubscribeAll() {
-      events.unsubscribeAll();
+      });
     }
 
     return {

src/presentation/components/Scripts/Slider/SliderHandle.vue

@@ -13,7 +13,7 @@
 </template>
 
 <script lang="ts">
-import { defineComponent } from 'vue';
+import { defineComponent, onUnmounted } from 'vue';
 
 export default defineComponent({
   emits: {
@@ -46,6 +46,10 @@ export default defineComponent({
       event.preventDefault();
     }
 
+    onUnmounted(() => {
+      stopResize();
+    });
+
     return {
       cursorCssValue,
       startResize,

src/presentation/components/Scripts/View/Cards/CardList.vue

@@ -37,7 +37,7 @@ import {
   defineComponent, ref, onMounted, onUnmounted, computed,
   inject,
 } from 'vue';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import SizeObserver from '@/presentation/components/Shared/SizeObserver.vue';
 import { hasDirective } from './NonCollapsingDirective';
 import CardListItem from './CardListItem.vue';
@@ -48,7 +48,7 @@ export default defineComponent({
     SizeObserver,
   },
   setup() {
-    const { currentState, onStateChange } = inject(useCollectionStateKey)();
+    const { currentState, onStateChange } = inject(InjectionKeys.useCollectionState)();
 
     const width = ref<number>(0);
     const categoryIds = computed<ReadonlyArray<number>>(() => currentState

src/presentation/components/Scripts/View/Cards/CardListItem.vue

@@ -52,7 +52,7 @@ import {
   defineComponent, ref, watch, computed,
   inject,
 } from 'vue';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import ScriptsTree from '@/presentation/components/Scripts/View/ScriptsTree/ScriptsTree.vue';
 import { sleep } from '@/infrastructure/Threading/AsyncSleep';
 
@@ -76,7 +76,8 @@ export default defineComponent({
     /* eslint-enable @typescript-eslint/no-unused-vars */
   },
   setup(props, { emit }) {
-    const { events, onStateChange, currentState } = inject(useCollectionStateKey)();
+    const { onStateChange, currentState } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const isExpanded = computed({
       get: () => {
@@ -106,12 +107,13 @@ export default defineComponent({
       isExpanded.value = false;
     }
 
-    onStateChange(async (state) => {
-      events.unsubscribeAll();
-      events.register(state.selection.changed.on(
+    onStateChange((state) => {
+      events.unsubscribeAllAndRegister([
+        state.selection.changed.on(
           () => updateSelectionIndicators(props.categoryId),
-      ));
-      await updateSelectionIndicators(props.categoryId);
+        ),
+      ]);
+      updateSelectionIndicators(props.categoryId);
     }, { immediate: true });
 
     watch(
@@ -124,7 +126,7 @@ export default defineComponent({
       cardElement.value.scrollIntoView({ behavior: 'smooth' });
     }
 
-    async function updateSelectionIndicators(categoryId: number) {
+    function updateSelectionIndicators(categoryId: number) {
       const category = currentState.value.collection.findCategory(categoryId);
       const { selection } = currentState.value;
       isAnyChildSelected.value = category ? selection.isAnySelected(category) : false;

src/presentation/components/Scripts/View/ScriptsTree/ScriptsTree.vue

@@ -17,12 +17,13 @@
 import {
   defineComponent, watch, ref, inject,
 } from 'vue';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { IScript } from '@/domain/IScript';
 import { ICategory } from '@/domain/ICategory';
 import { ICategoryCollectionState, IReadOnlyCategoryCollectionState } from '@/application/Context/State/ICategoryCollectionState';
 import { IFilterResult } from '@/application/Context/State/Filter/IFilterResult';
 import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
+import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 import {
   parseAllCategories, parseSingleCategory, getScriptNodeId, getCategoryNodeId, getCategoryId,
   getScriptId,
@@ -43,8 +44,9 @@ export default defineComponent({
   },
   setup(props) {
     const {
-      modifyCurrentState, currentState, onStateChange, events,
-    } = inject(useCollectionStateKey)();
+      modifyCurrentState, currentState, onStateChange,
+    } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const nodes = ref<ReadonlyArray<INodeContent>>([]);
     const selectedNodeIds = ref<ReadonlyArray<string>>([]);
@@ -54,7 +56,7 @@ export default defineComponent({
 
     watch(
       () => props.categoryId,
-      async (newCategoryId) => { await setNodes(newCategoryId); },
+      (newCategoryId) => setNodes(newCategoryId),
       { immediate: true },
     );
 
@@ -63,8 +65,7 @@ export default defineComponent({
       if (!props.categoryId) {
         nodes.value = parseAllCategories(state.collection);
       }
-      events.unsubscribeAll();
-      subscribeToState(state);
+      events.unsubscribeAllAndRegister(subscribeToState(state));
     }, { immediate: true });
 
     function toggleNodeSelection(event: INodeSelectedEvent) {
@@ -87,7 +88,7 @@ export default defineComponent({
         || containsCategory(node, filtered.categoryMatches);
     }
 
-    async function setNodes(categoryId?: number) {
+    function setNodes(categoryId?: number) {
       if (categoryId) {
         nodes.value = parseSingleCategory(categoryId, currentState.value.collection);
       } else {
@@ -97,8 +98,10 @@ export default defineComponent({
         .map((selected) => getScriptNodeId(selected.script));
     }
 
-    function subscribeToState(state: IReadOnlyCategoryCollectionState) {
-      events.register(
+    function subscribeToState(
+      state: IReadOnlyCategoryCollectionState,
+    ): IEventSubscription[] {
+      return [
         state.selection.changed.on((scripts) => handleSelectionChanged(scripts)),
         state.filter.filterChanged.on((event) => {
           event.visit({
@@ -111,7 +114,7 @@ export default defineComponent({
             },
           });
         }),
-      );
+      ];
     }
 
     function setCurrentFilter(currentFilter: IFilterResult | undefined) {

src/presentation/components/Scripts/View/ScriptsTree/SelectableTree/Node/RevertToggle.vue

@@ -12,7 +12,7 @@ import {
   computed, inject,
 } from 'vue';
 import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { IReverter } from './Reverter/IReverter';
 import { INodeContent } from './INodeContent';
 import { getReverter } from './Reverter/ReverterFactory';
@@ -30,8 +30,9 @@ export default defineComponent({
   },
   setup(props) {
     const {
-      currentState, modifyCurrentState, onStateChange, events,
-    } = inject(useCollectionStateKey)();
+      currentState, modifyCurrentState, onStateChange,
+    } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const isReverted = ref(false);
 
@@ -39,24 +40,23 @@ export default defineComponent({
 
     watch(
       () => props.node,
-      async (node) => { await onNodeChanged(node); },
+      (node) => onNodeChanged(node),
       { immediate: true },
     );
 
     onStateChange((newState) => {
       updateRevertStatusFromState(newState.selection.selectedScripts);
-      events.unsubscribeAll();
-      events.register(
+      events.unsubscribeAllAndRegister([
         newState.selection.changed.on((scripts) => updateRevertStatusFromState(scripts)),
-      );
+      ]);
     }, { immediate: true });
 
-    async function onNodeChanged(node: INodeContent) {
+    function onNodeChanged(node: INodeContent) {
       handler = getReverter(node, currentState.value.collection);
       updateRevertStatusFromState(currentState.value.selection.selectedScripts);
     }
 
-    async function updateRevertStatusFromState(scripts: ReadonlyArray<SelectedScript>) {
+    function updateRevertStatusFromState(scripts: ReadonlyArray<SelectedScript>) {
       isReverted.value = handler?.getState(scripts) ?? false;
     }
 

src/presentation/components/Scripts/View/TheScriptsView.vue

@@ -41,7 +41,7 @@ import {
   defineComponent, PropType, ref, computed,
   inject,
 } from 'vue';
-import { useApplicationKey, useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import ScriptsTree from '@/presentation/components/Scripts/View/ScriptsTree/ScriptsTree.vue';
 import CardList from '@/presentation/components/Scripts/View/Cards/CardList.vue';
 import { ViewType } from '@/presentation/components/Scripts/Menu/View/ViewType';
@@ -60,8 +60,9 @@ export default defineComponent({
     },
   },
   setup() {
-    const { modifyCurrentState, onStateChange, events } = inject(useCollectionStateKey)();
-    const { info } = inject(useApplicationKey);
+    const { modifyCurrentState, onStateChange } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
+    const { info } = inject(InjectionKeys.useApplication);
 
     const repositoryUrl = computed<string>(() => info.repositoryWebUrl);
     const searchQuery = ref<string | undefined>();
@@ -77,9 +78,10 @@ export default defineComponent({
     });
 
     onStateChange((newState) => {
-      events.unsubscribeAll();
       updateFromInitialFilter(newState.filter.currentFilter);
-      subscribeToFilterChanges(newState.filter);
+      events.unsubscribeAllAndRegister([
+        subscribeToFilterChanges(newState.filter),
+      ]);
     }, { immediate: true });
 
     function clearSearchQuery() {
@@ -95,8 +97,7 @@ export default defineComponent({
     }
 
     function subscribeToFilterChanges(filter: IReadOnlyUserFilter) {
-      events.register(
-        filter.filterChanged.on((event) => {
+      return filter.filterChanged.on((event) => {
         event.visit({
           onApply: (newFilter) => {
             searchQuery.value = newFilter.query;
@@ -106,8 +107,7 @@ export default defineComponent({
             searchQuery.value = undefined;
           },
         });
-        }),
-      );
+      });
     }
 
     return {

src/presentation/components/Shared/Hooks/UseAutoUnsubscribedEvents.ts

@@ -0,0 +1,19 @@
+import { onUnmounted } from 'vue';
+import { EventSubscriptionCollection } from '@/infrastructure/Events/EventSubscriptionCollection';
+import { IEventSubscriptionCollection } from '@/infrastructure/Events/IEventSubscriptionCollection';
+
+export function useAutoUnsubscribedEvents(
+  events: IEventSubscriptionCollection = new EventSubscriptionCollection(),
+) {
+  if (events.subscriptionCount > 0) {
+    throw new Error('there are existing subscriptions, this may lead to side-effects');
+  }
+
+  onUnmounted(() => {
+    events.unsubscribeAll();
+  });
+
+  return {
+    events,
+  };
+}

src/presentation/components/Shared/Hooks/UseCollectionState.ts

@@ -1,23 +1,27 @@
-import { ref, computed, readonly } from 'vue';
+import {
+  ref, computed, readonly,
+} from 'vue';
 import { IApplicationContext, IReadOnlyApplicationContext } from '@/application/Context/IApplicationContext';
 import { ICategoryCollectionState, IReadOnlyCategoryCollectionState } from '@/application/Context/State/ICategoryCollectionState';
-import { EventSubscriptionCollection } from '@/infrastructure/Events/EventSubscriptionCollection';
 import { IEventSubscriptionCollection } from '@/infrastructure/Events/IEventSubscriptionCollection';
 
-export function useCollectionState(context: IApplicationContext) {
+export function useCollectionState(
+  context: IApplicationContext,
+  events: IEventSubscriptionCollection,
+) {
   if (!context) {
     throw new Error('missing context');
   }
-
-  const events = new EventSubscriptionCollection();
-  const ownEvents = new EventSubscriptionCollection();
+  if (!events) {
+    throw new Error('missing events');
+  }
 
   const currentState = ref<ICategoryCollectionState>(context.state);
-  ownEvents.register(
+  events.register([
     context.contextChanged.on((event) => {
       currentState.value = event.newState;
     }),
-  );
+  ]);
 
   const defaultSettings: IStateCallbackSettings = {
     immediate: false,
@@ -29,11 +33,11 @@ export function useCollectionState(context: IApplicationContext) {
     if (!handler) {
       throw new Error('missing state handler');
     }
-    ownEvents.register(
+    events.register([
       context.contextChanged.on((event) => {
         handler(event.newState, event.oldState);
       }),
-    );
+    ]);
     const defaultedSettings: IStateCallbackSettings = {
       ...defaultSettings,
       ...settings,

src/presentation/components/TheFooter/DownloadUrlList.vue

@@ -20,7 +20,7 @@
 <script lang="ts">
 import { defineComponent, inject } from 'vue';
 import { OperatingSystem } from '@/domain/OperatingSystem';
-import { useRuntimeEnvironmentKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import DownloadUrlListItem from './DownloadUrlListItem.vue';
 
 const supportedOperativeSystems: readonly OperatingSystem[] = [
@@ -34,7 +34,7 @@ export default defineComponent({
     DownloadUrlListItem,
   },
   setup() {
-    const { os: currentOs } = inject(useRuntimeEnvironmentKey);
+    const { os: currentOs } = inject(InjectionKeys.useRuntimeEnvironment);
     const supportedDesktops = [
       ...supportedOperativeSystems,
     ].sort((os) => (os === currentOs ? 0 : 1));

src/presentation/components/TheFooter/DownloadUrlListItem.vue

@@ -14,7 +14,7 @@ import {
   defineComponent, PropType, computed,
   inject,
 } from 'vue';
-import { useApplicationKey, useRuntimeEnvironmentKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { OperatingSystem } from '@/domain/OperatingSystem';
 
 export default defineComponent({
@@ -25,8 +25,8 @@ export default defineComponent({
     },
   },
   setup(props) {
-    const { info } = inject(useApplicationKey);
-    const { os: currentOs } = inject(useRuntimeEnvironmentKey);
+    const { info } = inject(InjectionKeys.useApplication);
+    const { os: currentOs } = inject(InjectionKeys.useRuntimeEnvironment);
 
     const isCurrentOs = computed<boolean>(() => {
       return currentOs === props.operatingSystem;

src/presentation/components/TheFooter/PrivacyPolicy.vue

@@ -42,12 +42,12 @@
 
 <script lang="ts">
 import { defineComponent, computed, inject } from 'vue';
-import { useApplicationKey, useRuntimeEnvironmentKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 
 export default defineComponent({
   setup() {
-    const { info } = inject(useApplicationKey);
-    const { isDesktop } = inject(useRuntimeEnvironmentKey);
+    const { info } = inject(InjectionKeys.useApplication);
+    const { isDesktop } = inject(InjectionKeys.useRuntimeEnvironment);
 
     const repositoryUrl = computed<string>(() => info.repositoryUrl);
     const feedbackUrl = computed<string>(() => info.feedbackUrl);

src/presentation/components/TheFooter/TheFooter.vue

@@ -48,7 +48,7 @@ import {
   defineComponent, ref, computed, inject,
 } from 'vue';
 import ModalDialog from '@/presentation/components/Shared/Modal/ModalDialog.vue';
-import { useApplicationKey, useRuntimeEnvironmentKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import DownloadUrlList from './DownloadUrlList.vue';
 import PrivacyPolicy from './PrivacyPolicy.vue';
 
@@ -59,8 +59,8 @@ export default defineComponent({
     DownloadUrlList,
   },
   setup() {
-    const { info } = inject(useApplicationKey);
-    const { isDesktop } = inject(useRuntimeEnvironmentKey);
+    const { info } = inject(InjectionKeys.useApplication);
+    const { isDesktop } = inject(InjectionKeys.useRuntimeEnvironment);
 
     const isPrivacyDialogVisible = ref(false);
 

src/presentation/components/TheHeader.vue

@@ -7,11 +7,11 @@
 
 <script lang="ts">
 import { defineComponent, computed, inject } from 'vue';
-import { useApplicationKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 
 export default defineComponent({
   setup() {
-    const { info } = inject(useApplicationKey);
+    const { info } = inject(InjectionKeys.useApplication);
 
     const title = computed(() => info.name);
     const subtitle = computed(() => info.slogan);

src/presentation/components/TheSearchBar.vue

@@ -17,10 +17,11 @@ import {
   defineComponent, ref, watch, computed,
   inject,
 } from 'vue';
-import { useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { NonCollapsing } from '@/presentation/components/Scripts/View/Cards/NonCollapsingDirective';
 import { IReadOnlyUserFilter } from '@/application/Context/State/Filter/IUserFilter';
 import { IFilterResult } from '@/application/Context/State/Filter/IFilterResult';
+import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 
 export default defineComponent({
   directives: {
@@ -28,8 +29,9 @@ export default defineComponent({
   },
   setup() {
     const {
-      modifyCurrentState, onStateChange, events, currentState,
-    } = inject(useCollectionStateKey)();
+      modifyCurrentState, onStateChange, currentState,
+    } = inject(InjectionKeys.useCollectionState)();
+    const { events } = inject(InjectionKeys.useAutoUnsubscribedEvents)();
 
     const searchPlaceholder = computed<string>(() => {
       const { totalScripts } = currentState.value.collection;
@@ -51,18 +53,20 @@ export default defineComponent({
     }
 
     onStateChange((newState) => {
-      events.unsubscribeAll();
       updateFromInitialFilter(newState.filter.currentFilter);
-      subscribeToFilterChanges(newState.filter);
+      events.unsubscribeAllAndRegister([
+        subscribeToFilterChanges(newState.filter),
+      ]);
     }, { immediate: true });
 
     function updateFromInitialFilter(filter?: IFilterResult) {
       searchQuery.value = filter?.query || '';
     }
 
-    function subscribeToFilterChanges(filter: IReadOnlyUserFilter) {
-      events.register(
-        filter.filterChanged.on((event) => {
+    function subscribeToFilterChanges(
+      filter: IReadOnlyUserFilter,
+    ): IEventSubscription {
+      return filter.filterChanged.on((event) => {
         event.visit({
           onApply: (result) => {
             searchQuery.value = result.query;
@@ -71,8 +75,7 @@ export default defineComponent({
             searchQuery.value = '';
           },
         });
-        }),
-      );
+      });
     }
 
     return {

src/presentation/injectionSymbols.ts

@@ -1,16 +1,20 @@
 import { useCollectionState } from '@/presentation/components/Shared/Hooks/UseCollectionState';
 import { useApplication } from '@/presentation/components/Shared/Hooks/UseApplication';
 import { useRuntimeEnvironment } from '@/presentation/components/Shared/Hooks/UseRuntimeEnvironment';
+import type { useAutoUnsubscribedEvents } from './components/Shared/Hooks/UseAutoUnsubscribedEvents';
 import type { InjectionKey } from 'vue';
 
-export const useCollectionStateKey = defineTransientKey<ReturnType<typeof useCollectionState>>('useCollectionState');
-export const useApplicationKey = defineSingletonKey<ReturnType<typeof useApplication>>('useApplication');
-export const useRuntimeEnvironmentKey = defineSingletonKey<ReturnType<typeof useRuntimeEnvironment>>('useRuntimeEnvironment');
+export const InjectionKeys = {
+  useCollectionState: defineTransientKey<ReturnType<typeof useCollectionState>>('useCollectionState'),
+  useApplication: defineSingletonKey<ReturnType<typeof useApplication>>('useApplication'),
+  useRuntimeEnvironment: defineSingletonKey<ReturnType<typeof useRuntimeEnvironment>>('useRuntimeEnvironment'),
+  useAutoUnsubscribedEvents: defineTransientKey<ReturnType<typeof useAutoUnsubscribedEvents>>('useAutoUnsubscribedEvents'),
+};
 
-function defineSingletonKey<T>(key: string) {
+function defineSingletonKey<T>(key: string): InjectionKey<T> {
   return Symbol(key) as InjectionKey<T>;
 }
 
-function defineTransientKey<T>(key: string) {
+function defineTransientKey<T>(key: string): InjectionKey<() => T> {
   return Symbol(key) as InjectionKey<() => T>;
 }

tests/unit/infrastructure/Events/EventSubscriptionCollection.spec.ts

@@ -1,21 +1,172 @@
 import { describe, it, expect } from 'vitest';
 import { EventSubscriptionCollection } from '@/infrastructure/Events/EventSubscriptionCollection';
+import { EventSubscriptionStub } from '@tests/unit/shared/Stubs/EventSubscriptionStub';
+import { itEachAbsentCollectionValue, itEachAbsentObjectValue } from '@tests/unit/shared/TestCases/AbsentTests';
 import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 
 describe('EventSubscriptionCollection', () => {
-  it('unsubscribeAll unsubscribes from all registered subscriptions', () => {
+  describe('register', () => {
+    it('increments `subscriptionCount` for each registration', () => {
       // arrange
       const sut = new EventSubscriptionCollection();
-    const expected = ['unsubscribed1', 'unsubscribed2'];
-    const actual = new Array<string>();
-    const subscriptions: IEventSubscription[] = [
-      { unsubscribe: () => actual.push(expected[0]) },
-      { unsubscribe: () => actual.push(expected[1]) },
-    ];
+      const subscriptions = createSubscriptionStubList(2);
+
       // act
-    sut.register(...subscriptions);
-    sut.unsubscribeAll();
+      sut.register(subscriptions);
+
       // assert
-    expect(actual).to.deep.equal(expected);
+      expect(sut.subscriptionCount).to.equal(2);
+    });
+    it('retains the subscribed state of registrations', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      const subscriptions = createSubscriptionStubList(2);
+
+      // act
+      sut.register(subscriptions);
+
+      // assert
+      expectAllSubscribed(subscriptions);
+    });
+    describe('validation', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      // act
+      const act = (
+        subscriptions: IEventSubscription[],
+      ) => sut.register(subscriptions);
+      /// assert
+      describeSubscriptionValidations(act);
     });
   });
+  describe('unsubscribeAll', () => {
+    it('unsubscribes all registrations', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      const subscriptions = createSubscriptionStubList(2);
+
+      // act
+      sut.register(subscriptions);
+      sut.unsubscribeAll();
+
+      // assert
+      expectAllUnsubscribed(subscriptions);
+    });
+    it('resets `subscriptionCount` to zero', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      const subscriptions = createSubscriptionStubList(2);
+      sut.register(subscriptions);
+
+      // act
+      sut.unsubscribeAll();
+
+      // assert
+      expect(sut.subscriptionCount).to.equal(0);
+    });
+  });
+  describe('unsubscribeAllAndRegister', () => {
+    it('unsubscribes all previous registrations', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      const oldSubscriptions = createSubscriptionStubList(2);
+      sut.register(oldSubscriptions);
+      const newSubscriptions = createSubscriptionStubList(1);
+
+      // act
+      sut.unsubscribeAllAndRegister(newSubscriptions);
+
+      // assert
+      expectAllUnsubscribed(oldSubscriptions);
+    });
+    it('retains the subscribed state of new registrations', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      const oldSubscriptions = createSubscriptionStubList(2);
+      sut.register(oldSubscriptions);
+      const newSubscriptions = createSubscriptionStubList(2);
+
+      // act
+      sut.unsubscribeAllAndRegister(newSubscriptions);
+
+      // assert
+      expectAllSubscribed(newSubscriptions);
+    });
+    it('updates `subscriptionCount` to match new registration count', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      const initialSubscriptionAmount = 1;
+      const expectedSubscriptionAmount = 3;
+      const oldSubscriptions = createSubscriptionStubList(initialSubscriptionAmount);
+      sut.register(oldSubscriptions);
+      const newSubscriptions = createSubscriptionStubList(expectedSubscriptionAmount);
+
+      // act
+      sut.unsubscribeAllAndRegister(newSubscriptions);
+
+      // assert
+      expect(sut.subscriptionCount).to.equal(expectedSubscriptionAmount);
+    });
+
+    describe('validation', () => {
+      // arrange
+      const sut = new EventSubscriptionCollection();
+      // act
+      const act = (
+        subscriptions: IEventSubscription[],
+      ) => sut.unsubscribeAllAndRegister(subscriptions);
+      /// assert
+      describeSubscriptionValidations(act);
+    });
+  });
+});
+
+function expectAllSubscribed(subscriptions: EventSubscriptionStub[]) {
+  expect(subscriptions.every((subscription) => subscription.isSubscribed)).to.equal(true);
+}
+
+function expectAllUnsubscribed(subscriptions: EventSubscriptionStub[]) {
+  expect(subscriptions.every((subscription) => subscription.isUnsubscribed)).to.equal(true);
+}
+
+function createSubscriptionStubList(amount: number): EventSubscriptionStub[] {
+  if (amount <= 0) {
+    throw new Error(`unexpected amount of subscriptions: ${amount}`);
+  }
+  return Array.from({ length: amount }, () => new EventSubscriptionStub());
+}
+
+function describeSubscriptionValidations(
+  handleValue: (subscriptions: IEventSubscription[]) => void,
+) {
+  describe('throws error if no subscriptions are provided', () => {
+    itEachAbsentCollectionValue((absentValue) => {
+      // arrange
+      const expectedError = 'missing subscriptions';
+
+      // act
+      const act = () => handleValue(absentValue);
+
+      // assert
+      expect(act).to.throw(expectedError);
+    });
+  });
+
+  describe('throws error if nullish subscriptions are provided', () => {
+    itEachAbsentObjectValue((absentValue) => {
+      // arrange
+      const expectedError = 'missing subscription in list';
+      const subscriptions = [
+        new EventSubscriptionStub(),
+        absentValue,
+        new EventSubscriptionStub(),
+      ];
+
+      // act
+      const act = () => handleValue(subscriptions);
+
+      // assert
+      expect(act).to.throw(expectedError);
+    });
+  });
+}

tests/unit/presentation/bootstrapping/DependencyProvider.spec.ts

@@ -0,0 +1,99 @@
+import { describe } from 'vitest';
+import { VueDependencyInjectionApiStub } from '@tests/unit/shared/Stubs/VueDependencyInjectionApiStub';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
+import { provideDependencies, VueDependencyInjectionApi } from '@/presentation/bootstrapping/DependencyProvider';
+import { ApplicationContextStub } from '@tests/unit/shared/Stubs/ApplicationContextStub';
+import { itIsSingleton } from '@tests/unit/shared/TestCases/SingletonTests';
+
+describe('DependencyProvider', () => {
+  describe('provideDependencies', () => {
+    const testCases: {
+      readonly [K in keyof typeof InjectionKeys]: (injectionKey: symbol) => void;
+    } = {
+      useCollectionState: createTransientTests(),
+      useApplication: createSingletonTests(),
+      useRuntimeEnvironment: createSingletonTests(),
+      useAutoUnsubscribedEvents: createTransientTests(),
+    };
+    Object.entries(testCases).forEach(([key, runTests]) => {
+      describe(`Key: "${key}"`, () => {
+        runTests(InjectionKeys[key]);
+      });
+    });
+  });
+});
+
+function createTransientTests() {
+  return (injectionKey: symbol) => {
+    it('should register a function when transient dependency is resolved', () => {
+      // arrange
+      const api = new VueDependencyInjectionApiStub();
+      // act
+      new ProvideDependenciesBuilder()
+        .withApi(api)
+        .provideDependencies();
+      // expect
+      const registeredObject = api.inject(injectionKey);
+      expect(registeredObject).to.be.instanceOf(Function);
+    });
+    it('should return different instances for transient dependency', () => {
+      // arrange
+      const api = new VueDependencyInjectionApiStub();
+      // act
+      new ProvideDependenciesBuilder()
+        .withApi(api)
+        .provideDependencies();
+      // expect
+      const registeredObject = api.inject(injectionKey);
+      const factory = registeredObject as () => unknown;
+      const firstResult = factory();
+      const secondResult = factory();
+      expect(firstResult).to.not.equal(secondResult);
+    });
+  };
+}
+
+function createSingletonTests() {
+  return (injectionKey: symbol) => {
+    it('should register an object when singleton dependency is resolved', () => {
+      // arrange
+      const api = new VueDependencyInjectionApiStub();
+      // act
+      new ProvideDependenciesBuilder()
+        .withApi(api)
+        .provideDependencies();
+      // expect
+      const registeredObject = api.inject(injectionKey);
+      expect(registeredObject).to.be.instanceOf(Object);
+    });
+    it('should return the same instance for singleton dependency', () => {
+      itIsSingleton({
+        getter: () => {
+          // arrange
+          const api = new VueDependencyInjectionApiStub();
+          // act
+          new ProvideDependenciesBuilder()
+            .withApi(api)
+            .provideDependencies();
+          // expect
+          const registeredObject = api.inject(injectionKey);
+          return registeredObject;
+        },
+      });
+    });
+  };
+}
+class ProvideDependenciesBuilder {
+  private context = new ApplicationContextStub();
+
+  private api: VueDependencyInjectionApi = new VueDependencyInjectionApiStub();
+
+  public withApi(api: VueDependencyInjectionApi): this {
+    this.api = api;
+    return this;
+  }
+
+  public provideDependencies() {
+    return provideDependencies(this.context, this.api);
+  }
+}

tests/unit/presentation/components/Scripts/View/TheScriptsView.spec.ts

@@ -6,13 +6,14 @@ import CardList from '@/presentation/components/Scripts/View/Cards/CardList.vue'
 import { ViewType } from '@/presentation/components/Scripts/Menu/View/ViewType';
 import { useCollectionState } from '@/presentation/components/Shared/Hooks/UseCollectionState';
 import { UseCollectionStateStub } from '@tests/unit/shared/Stubs/UseCollectionStateStub';
-import { useApplicationKey, useCollectionStateKey } from '@/presentation/injectionSymbols';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { UseApplicationStub } from '@tests/unit/shared/Stubs/UseApplicationStub';
 import { UserFilterMethod, UserFilterStub } from '@tests/unit/shared/Stubs/UserFilterStub';
 import { FilterResultStub } from '@tests/unit/shared/Stubs/FilterResultStub';
 import { FilterChange } from '@/application/Context/State/Filter/Event/FilterChange';
 import { IFilterResult } from '@/application/Context/State/Filter/IFilterResult';
 import { IFilterChangeDetails } from '@/application/Context/State/Filter/Event/IFilterChangeDetails';
+import { UseAutoUnsubscribedEventsStub } from '@tests/unit/shared/Stubs/UseAutoUnsubscribedEventsStub';
 
 const DOM_SELECTOR_NO_MATCHES = '.search-no-matches';
 const DOM_SELECTOR_CLOSE_BUTTON = '.search__query__close-button';
@@ -404,10 +405,12 @@ function mountComponent(options?: {
 }) {
   return shallowMount(TheScriptsView, {
     provide: {
-      [useCollectionStateKey as symbol]:
+      [InjectionKeys.useCollectionState as symbol]:
         () => options?.useCollectionState ?? new UseCollectionStateStub().get(),
-      [useApplicationKey as symbol]:
+      [InjectionKeys.useApplication as symbol]:
         new UseApplicationStub().get(),
+      [InjectionKeys.useAutoUnsubscribedEvents as symbol]:
+        () => new UseAutoUnsubscribedEventsStub().get(),
     },
     propsData: {
       currentView: options?.viewType === undefined ? ViewType.Tree : options.viewType,

tests/unit/presentation/components/Shared/Hooks/UseAutoUnsubscribedEvents.spec.ts

@@ -0,0 +1,68 @@
+import { describe, it, expect } from 'vitest';
+import { shallowMount } from '@vue/test-utils';
+import { useAutoUnsubscribedEvents } from '@/presentation/components/Shared/Hooks/UseAutoUnsubscribedEvents';
+import { EventSubscriptionCollectionStub } from '@tests/unit/shared/Stubs/EventSubscriptionCollectionStub';
+import { EventSubscriptionStub } from '@tests/unit/shared/Stubs/EventSubscriptionStub';
+import { EventSubscriptionCollection } from '@/infrastructure/Events/EventSubscriptionCollection';
+import { FunctionKeys } from '@/TypeHelpers';
+
+describe('UseAutoUnsubscribedEvents', () => {
+  describe('event collection handling', () => {
+    it('returns the provided event collection when initialized', () => {
+      // arrange
+      const expectedEvents = new EventSubscriptionCollectionStub();
+
+      // act
+      const { events: actualEvents } = useAutoUnsubscribedEvents(expectedEvents);
+
+      // assert
+      expect(actualEvents).to.equal(expectedEvents);
+    });
+
+    it('uses a default event collection when none is provided during initialization', () => {
+      // arrange
+      const expectedType = EventSubscriptionCollection;
+
+      // act
+      const { events: actualEvents } = useAutoUnsubscribedEvents();
+
+      // assert
+      expect(actualEvents).to.be.instanceOf(expectedType);
+    });
+
+    it('throws error when there are existing subscriptions', () => {
+      // arrange
+      const expectedError = 'there are existing subscriptions, this may lead to side-effects';
+      const events = new EventSubscriptionCollectionStub();
+      events.register([new EventSubscriptionStub(), new EventSubscriptionStub()]);
+
+      // act
+      const act = () => useAutoUnsubscribedEvents(events);
+
+      // assert
+      expect(act).to.throw(expectedError);
+    });
+  });
+  describe('event unsubscription', () => {
+    it('unsubscribes from all events when the associated component is destroyed', () => {
+      // arrange
+      const events = new EventSubscriptionCollectionStub();
+      const expectedCall: FunctionKeys<EventSubscriptionCollection> = 'unsubscribeAll';
+      const stubComponent = shallowMount({
+        setup() {
+          useAutoUnsubscribedEvents(events);
+          events.register([new EventSubscriptionStub(), new EventSubscriptionStub()]);
+        },
+        template: '<div></div>',
+      });
+      events.callHistory.length = 0;
+
+      // act
+      stubComponent.destroy();
+
+      // assert
+      expect(events.callHistory).to.have.lengthOf(1);
+      expect(events.callHistory[0].methodName).to.equal(expectedCall);
+    });
+  });
+});

tests/unit/presentation/components/Shared/Hooks/UseCollectionState.spec.ts

@@ -6,30 +6,89 @@ import { IReadOnlyCategoryCollectionState } from '@/application/Context/State/IC
 import { ApplicationContextChangedEventStub } from '@tests/unit/shared/Stubs/ApplicationContextChangedEventStub';
 import { OperatingSystem } from '@/domain/OperatingSystem';
 import { itEachAbsentObjectValue } from '@tests/unit/shared/TestCases/AbsentTests';
+import { IApplicationContext } from '@/application/Context/IApplicationContext';
+import { IEventSubscriptionCollection } from '@/infrastructure/Events/IEventSubscriptionCollection';
+import { EventSubscriptionCollectionStub } from '@tests/unit/shared/Stubs/EventSubscriptionCollectionStub';
 
 describe('UseCollectionState', () => {
-  describe('context is absent', () => {
+  describe('parameter validation', () => {
+    describe('absent context', () => {
       itEachAbsentObjectValue((absentValue) => {
         // arrange
         const expectedError = 'missing context';
         const contextValue = absentValue;
         // act
-      const act = () => useCollectionState(contextValue);
+        const act = () => new UseCollectionStateBuilder()
+          .withContext(contextValue)
+          .build();
         // assert
         expect(act).to.throw(expectedError);
       });
     });
+    describe('absent events', () => {
+      itEachAbsentObjectValue((absentValue) => {
+        // arrange
+        const expectedError = 'missing events';
+        const eventsValue = absentValue;
+        // act
+        const act = () => new UseCollectionStateBuilder()
+          .withEvents(eventsValue)
+          .build();
+        // assert
+        expect(act).to.throw(expectedError);
+      });
+    });
+  });
+
+  describe('listens to contextChanged event', () => {
+    it('registers new event listener', () => {
+      // arrange
+      const events = new EventSubscriptionCollectionStub();
+      const expectedSubscriptionsCount = 1;
+      // act
+      new UseCollectionStateBuilder()
+        .withEvents(events)
+        .build();
+      // assert
+      const actualSubscriptionsCount = events.subscriptionCount;
+      expect(actualSubscriptionsCount).to.equal(expectedSubscriptionsCount);
+    });
+    it('does not modify the state after event listener is unsubscribed', () => {
+      // arrange
+      const events = new EventSubscriptionCollectionStub();
+      const oldState = new CategoryCollectionStateStub();
+      const newState = new CategoryCollectionStateStub();
+      const context = new ApplicationContextStub()
+        .withState(oldState);
+
+      // act
+      const { currentState } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .withEvents(events)
+        .build();
+      const stateModifierEvent = events.mostRecentSubscription;
+      stateModifierEvent.unsubscribe();
+      context.dispatchContextChange(
+        new ApplicationContextChangedEventStub().withNewState(newState),
+      );
+
+      // assert
+      expect(currentState.value).to.equal(oldState);
+    });
+  });
 
   describe('currentContext', () => {
     it('returns current context', () => {
       // arrange
-      const expected = new ApplicationContextStub();
+      const expectedContext = new ApplicationContextStub();
 
       // act
-      const { currentContext } = useCollectionState(expected);
+      const { currentContext } = new UseCollectionStateBuilder()
+        .withContext(expectedContext)
+        .build();
 
       // assert
-      expect(currentContext).to.equal(expected);
+      expect(currentContext).to.equal(expectedContext);
     });
   });
 
@@ -41,24 +100,28 @@ describe('UseCollectionState', () => {
         .withState(expected);
 
       // act
-      const { currentState } = useCollectionState(context);
+      const { currentState } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
 
       // assert
       expect(currentState.value).to.equal(expected);
     });
     it('returns changed collection state', () => {
       // arrange
-      const newState = new CategoryCollectionStateStub();
+      const expectedNewState = new CategoryCollectionStateStub();
       const context = new ApplicationContextStub();
-      const { currentState } = useCollectionState(context);
+      const { currentState } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
 
       // act
       context.dispatchContextChange(
-        new ApplicationContextChangedEventStub().withNewState(newState),
+        new ApplicationContextChangedEventStub().withNewState(expectedNewState),
       );
 
       // assert
-      expect(currentState.value).to.equal(newState);
+      expect(currentState.value).to.equal(expectedNewState);
     });
   });
 
@@ -67,8 +130,7 @@ describe('UseCollectionState', () => {
       itEachAbsentObjectValue((absentValue) => {
         // arrange
         const expectedError = 'missing state handler';
-        const context = new ApplicationContextStub();
-        const { onStateChange } = useCollectionState(context);
+        const { onStateChange } = new UseCollectionStateBuilder().build();
         // act
         const act = () => onStateChange(absentValue);
         // assert
@@ -79,7 +141,9 @@ describe('UseCollectionState', () => {
       // arrange
       const expected = true;
       const context = new ApplicationContextStub();
-      const { onStateChange } = useCollectionState(context);
+      const { onStateChange } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
       let wasCalled = false;
 
       // act
@@ -94,8 +158,7 @@ describe('UseCollectionState', () => {
     it('call handler immediately when immediate is true', () => {
       // arrange
       const expected = true;
-      const context = new ApplicationContextStub();
-      const { onStateChange } = useCollectionState(context);
+      const { onStateChange } = new UseCollectionStateBuilder().build();
       let wasCalled = false;
 
       // act
@@ -109,8 +172,7 @@ describe('UseCollectionState', () => {
     it('does not call handler immediately when immediate is false', () => {
       // arrange
       const expected = false;
-      const context = new ApplicationContextStub();
-      const { onStateChange } = useCollectionState(context);
+      const { onStateChange } = new UseCollectionStateBuilder().build();
       let wasCalled = false;
 
       // act
@@ -125,7 +187,9 @@ describe('UseCollectionState', () => {
       // arrange
       const expected = 5;
       const context = new ApplicationContextStub();
-      const { onStateChange } = useCollectionState(context);
+      const { onStateChange } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
       let totalCalled = 0;
 
       // act
@@ -144,7 +208,9 @@ describe('UseCollectionState', () => {
       const expected = new CategoryCollectionStateStub();
       let actual: IReadOnlyCategoryCollectionState;
       const context = new ApplicationContextStub();
-      const { onStateChange } = useCollectionState(context);
+      const { onStateChange } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
 
       // act
       onStateChange((newState) => {
@@ -159,21 +225,57 @@ describe('UseCollectionState', () => {
     });
     it('call handler with old state after state changes', () => {
       // arrange
-      const expected = new CategoryCollectionStateStub();
-      let actual: IReadOnlyCategoryCollectionState;
+      const expectedState = new CategoryCollectionStateStub();
+      let actualState: IReadOnlyCategoryCollectionState;
       const context = new ApplicationContextStub();
-      const { onStateChange } = useCollectionState(context);
+      const { onStateChange } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
 
       // act
       onStateChange((_, oldState) => {
-        actual = oldState;
+        actualState = oldState;
       });
       context.dispatchContextChange(
-        new ApplicationContextChangedEventStub().withOldState(expected),
+        new ApplicationContextChangedEventStub().withOldState(expectedState),
       );
 
       // assert
-      expect(actual).to.equal(expected);
+      expect(actualState).to.equal(expectedState);
+    });
+    describe('listens to contextChanged event', () => {
+      it('registers new event listener', () => {
+        // arrange
+        const events = new EventSubscriptionCollectionStub();
+        const { onStateChange } = new UseCollectionStateBuilder()
+          .withEvents(events)
+          .build();
+        const expectedSubscriptionsCount = 1;
+        // act
+        events.unsubscribeAll(); // clean count for event subscriptions before
+        onStateChange(() => { /* NO OP */ });
+        // assert
+        const actualSubscriptionsCount = events.subscriptionCount;
+        expect(actualSubscriptionsCount).to.equal(expectedSubscriptionsCount);
+      });
+      it('onStateChange is not called once event is unsubscribed', () => {
+        // arrange
+        let isCallbackCalled = false;
+        const callback = () => { isCallbackCalled = true; };
+        const context = new ApplicationContextStub();
+        const events = new EventSubscriptionCollectionStub();
+        const { onStateChange } = new UseCollectionStateBuilder()
+          .withEvents(events)
+          .withContext(context)
+          .build();
+        // act
+        onStateChange(callback);
+        const stateChangeEvent = events.mostRecentSubscription;
+        stateChangeEvent.unsubscribe();
+        context.dispatchContextChange();
+        // assert
+        expect(isCallbackCalled).to.equal(false);
+      });
     });
   });
 
@@ -183,9 +285,13 @@ describe('UseCollectionState', () => {
         // arrange
         const expectedError = 'missing state mutator';
         const context = new ApplicationContextStub();
-        const { modifyCurrentState } = useCollectionState(context);
+        const { modifyCurrentState } = new UseCollectionStateBuilder()
+          .withContext(context)
+          .build();
+
         // act
         const act = () => modifyCurrentState(absentValue);
+
         // assert
         expect(act).to.throw(expectedError);
       });
@@ -198,7 +304,9 @@ describe('UseCollectionState', () => {
         .withOs(oldOs);
       const context = new ApplicationContextStub()
         .withState(state);
-      const { modifyCurrentState } = useCollectionState(context);
+      const { modifyCurrentState } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
 
       // act
       modifyCurrentState((mutableState) => {
@@ -217,8 +325,7 @@ describe('UseCollectionState', () => {
       itEachAbsentObjectValue((absentValue) => {
         // arrange
         const expectedError = 'missing context mutator';
-        const context = new ApplicationContextStub();
-        const { modifyCurrentContext } = useCollectionState(context);
+        const { modifyCurrentContext } = new UseCollectionStateBuilder().build();
         // act
         const act = () => modifyCurrentContext(absentValue);
         // assert
@@ -233,7 +340,9 @@ describe('UseCollectionState', () => {
         .withOs(OperatingSystem.macOS);
       const context = new ApplicationContextStub()
         .withState(oldState);
-      const { modifyCurrentContext } = useCollectionState(context);
+      const { modifyCurrentContext } = new UseCollectionStateBuilder()
+        .withContext(context)
+        .build();
 
       // act
       modifyCurrentContext((mutableContext) => {
@@ -247,3 +356,23 @@ describe('UseCollectionState', () => {
     });
   });
 });
+
+class UseCollectionStateBuilder {
+  private context: IApplicationContext = new ApplicationContextStub();
+
+  private events: IEventSubscriptionCollection = new EventSubscriptionCollectionStub();
+
+  public withContext(context: IApplicationContext): this {
+    this.context = context;
+    return this;
+  }
+
+  public withEvents(events: IEventSubscriptionCollection): this {
+    this.events = events;
+    return this;
+  }
+
+  public build(): ReturnType<typeof useCollectionState> {
+    return useCollectionState(this.context, this.events);
+  }
+}

tests/unit/presentation/injectionSymbols.ts

@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
+
+describe('injectionSymbols', () => {
+  Object.entries(InjectionKeys).forEach(([key, symbol]) => {
+    describe(`symbol for ${key}`, () => {
+      it('should be a symbol type', () => {
+        // arrange
+        const expectedType = Symbol;
+        // act
+        // assert
+        expect(symbol).to.be.instanceOf(expectedType);
+      });
+      it(`should have a description matching the key "${key}"`, () => {
+        // arrange
+        const expected = key;
+        // act
+        const actual = symbol.description;
+        // assert
+        expect(expected).to.equal(actual);
+      });
+    });
+  });
+});

tests/unit/shared/Stubs/EventSubscriptionCollectionStub.ts

@@ -1,14 +1,50 @@
 import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 import { IEventSubscriptionCollection } from '@/infrastructure/Events/IEventSubscriptionCollection';
+import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
 
-export class EventSubscriptionCollectionStub implements IEventSubscriptionCollection {
+export class EventSubscriptionCollectionStub
+  extends StubWithObservableMethodCalls<IEventSubscriptionCollection>
+  implements IEventSubscriptionCollection {
   private readonly subscriptions = new Array<IEventSubscription>();
 
-  public register(...subscriptions: IEventSubscription[]) {
+  public get mostRecentSubscription(): IEventSubscription | undefined {
+    if (this.subscriptions.length === 0) {
+      return undefined;
+    }
+    return this.subscriptions[this.subscriptions.length - 1];
+  }
+
+  public get subscriptionCount(): number {
+    return this.subscriptions.length;
+  }
+
+  public register(
+    subscriptions: IEventSubscription[],
+  ): void {
+    this.registerMethodCall({
+      methodName: 'register',
+      args: [subscriptions],
+    });
     this.subscriptions.push(...subscriptions);
   }
 
-  public unsubscribeAll() {
+  public unsubscribeAll(): void {
+    this.registerMethodCall({
+      methodName: 'unsubscribeAll',
+      args: [],
+    });
+    this.subscriptions.forEach((subscription) => subscription.unsubscribe());
     this.subscriptions.length = 0;
   }
+
+  public unsubscribeAllAndRegister(
+    subscriptions: IEventSubscription[],
+  ): void {
+    this.registerMethodCall({
+      methodName: 'unsubscribeAllAndRegister',
+      args: [subscriptions],
+    });
+    this.unsubscribeAll();
+    this.register(subscriptions);
+  }
 }

tests/unit/shared/Stubs/EventSubscriptionStub.ts

@@ -1,8 +1,16 @@
 import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
 
-type UnsubscribeCallback = () => void;
-
 export class EventSubscriptionStub implements IEventSubscription {
+  private currentState = SubscriptionState.Subscribed;
+
+  public get isUnsubscribed(): boolean {
+    return this.currentState === SubscriptionState.Unsubscribed;
+  }
+
+  public get isSubscribed(): boolean {
+    return this.currentState === SubscriptionState.Subscribed;
+  }
+
   private readonly onUnsubscribe = new Array<UnsubscribeCallback>();
 
   constructor(unsubscribeCallback?: UnsubscribeCallback) {
@@ -15,5 +23,13 @@ export class EventSubscriptionStub implements IEventSubscription {
     for (const callback of this.onUnsubscribe) {
       callback();
     }
+    this.currentState = SubscriptionState.Unsubscribed;
   }
 }
+
+type UnsubscribeCallback = () => void;
+
+enum SubscriptionState {
+  Subscribed,
+  Unsubscribed,
+}

tests/unit/shared/Stubs/UseAutoUnsubscribedEventsStub.ts

@@ -0,0 +1,10 @@
+import { useAutoUnsubscribedEvents } from '@/presentation/components/Shared/Hooks/UseAutoUnsubscribedEvents';
+import { EventSubscriptionCollectionStub } from './EventSubscriptionCollectionStub';
+
+export class UseAutoUnsubscribedEventsStub {
+  public get(): ReturnType<typeof useAutoUnsubscribedEvents> {
+    return {
+      events: new EventSubscriptionCollectionStub(),
+    };
+  }
+}

tests/unit/shared/Stubs/VueDependencyInjectionApiStub.ts

@@ -0,0 +1,14 @@
+import { InjectionKey } from 'vue';
+import { VueDependencyInjectionApi } from '@/presentation/bootstrapping/DependencyProvider';
+
+export class VueDependencyInjectionApiStub implements VueDependencyInjectionApi {
+  private readonly injections = new Map<unknown, unknown>();
+
+  public provide<T>(key: InjectionKey<T>, value: T): void {
+    this.injections.set(key, value);
+  }
+
+  public inject<T>(key: InjectionKey<T>): T {
+    return this.injections.get(key) as T;
+  }
+}

tests/unit/shared/TestCases/SingletonTests.ts

@@ -3,16 +3,18 @@ import { Constructible } from '@/TypeHelpers';
 
 interface ISingletonTestData<T> {
   getter: () => T;
-  expectedType: Constructible<T>;
+  expectedType?: Constructible<T>;
 }
 
 export function itIsSingleton<T>(test: ISingletonTestData<T>): void {
+  if (test.expectedType !== undefined) {
     it('gets the expected type', () => {
       // act
       const instance = test.getter();
       // assert
       expect(instance).to.be.instanceOf(test.expectedType);
     });
+  }
   it('multiple calls get the same instance', () => {
     // act
     const instance1 = test.getter();