This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:
- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
`get` prefix for those that always return a value.
This commit improves the dependency injection mechanism by introducing a
custom `injectKey` function.
Key improvements are:
- Enforced type consistency during dependency registration and
instantiation.
- Simplified injection process, abstracting away the complexity with a
uniform API, regardless of the dependency's lifetime.
- Eliminated the possibility of `undefined` returns during dependency
injection, promoting fail-fast behavior.
- Removed the necessity for type casting to `symbol` for injection keys
in unit tests by using existing types.
- Consalidated imports, combining keys and injection functions in one
`import` statement.
