refactor: migrate action to TypeScript

[parkerbxyz]

This pull request migrates the codebase from JavaScript to TypeScript, updates documentation and testing conventions, and improves build and test tooling. The most important changes are the conversion of main source files and type annotations to TypeScript, updates to documentation to reflect the new language and file structure, and improvements to build and test scripts to use TypeScript-compatible tools.

[Copilot]

Pull Request Overview

This pull request migrates the codebase from JavaScript to TypeScript, providing stronger type safety and improved developer experience. The migration includes converting the main source files to TypeScript, updating build and test tooling to support TypeScript, and modernizing the project configuration.

Key changes:

• Source code migrated from JavaScript with JSDoc annotations to native TypeScript with type definitions
• Test suite updated to use tsx for running TypeScript tests directly
• New tsconfig.json added with strict type checking enabled
• Documentation updated to reflect TypeScript usage

Reviewed Changes

Copilot reviewed 9 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/index.ts	Main source file converted from JS to TS with native type annotations
src/types.ts	New TypeScript types file centralizing all type definitions
tsconfig.json	New TypeScript configuration with strict mode enabled
package.json	Updated scripts to use tsx and added TypeScript dependencies
package-lock.json	Added TypeScript, tsx, and esbuild dependencies
test/*.test.ts	Test files updated to import from TypeScript source
test/README.md	Documentation updated for TypeScript testing approach
.github/copilot-instructions.md	Updated to reflect TypeScript instead of JavaScript
dist/index.js	Compiled output from TypeScript source

Comments suppressed due to low confidence (1)

src/index.ts:785

• The type assertion as ReviewEvent on line 785 is unsafe. The getInput('event') returns a string, and after calling toUpperCase(), there's no guarantee that the result is a valid ReviewEvent value. If an invalid event type is passed, this could cause runtime errors. Consider adding validation to ensure the value is a valid ReviewEvent before the type assertion, or define a helper function that validates and returns the correct type.

[Copilot]

Pull Request Overview

Copilot reviewed 9 out of 13 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (6)

src/index.ts:180

• [nitpick] The explicit type annotation c: AnyLineChange in the lambda function is redundant since TypeScript can infer the type from the group parameter which is already typed as AnyLineChange[].

Suggested fix:

const lastChange = group.findLast((c) => isDeletedLine(c) || isAddedLine(c))

This is more idiomatic and cleaner in TypeScript.
src/index.ts:354

• The deletedLines variable is being extracted twice from filterChangesByType(changes) - once at line 348 and again at line 354. This is redundant and inefficient. Since deletedLines is also used at line 378 in the "Mixed changes" section, it should be extracted once at the beginning of the function along with addedLines and unchangedLines (line 292-293).

Suggested fix: Add deletedLines to the destructuring at line 292-293:

const { addedLines, deletedLines, unchangedLines } = filterChangesByType(changes)

Then remove the duplicate extractions at lines 348 and 354.
src/index.ts:391

• The deletedLines variable is being extracted from filterChangesByType(groupChanges) here, but it's not used in this function. This call was likely added by mistake during the TypeScript migration. The deletedLines is only needed in generateSuggestionBody(), not in calculateLinePosition().

Suggested fix: Remove this line as it serves no purpose and creates unnecessary overhead.
src/index.ts:552

• Using as any to bypass TypeScript's type checking defeats the purpose of the TypeScript migration. The octokit.pulls.get method should be properly typed or the type assertion should be more specific.

Consider using a more specific type assertion like:

typeof (octokit as { pulls?: { get?: unknown } }).pulls?.get !== 'function'

Or better yet, check if the migration to TypeScript provides proper types for the Octokit instance that would make this check unnecessary.
src/index.ts:558

• Using as any to bypass TypeScript's type checking defeats the purpose of the TypeScript migration. The octokit.pulls.get call should be properly typed.

Consider defining a proper interface for the Octokit pulls API or using the existing types from @octokit/types to avoid using any.
src/index.ts:780

• Using any type for the file parameter defeats the purpose of the TypeScript migration. The type should be properly defined based on the Octokit API response.

Consider using the proper type from @octokit/types:

.data.map((file: Endpoints['GET /repos/{owner}/{repo}/pulls/{pull_number}/files']['response']['data'][number]) => file.filename)

Or define a more concise type alias in src/types.ts for this.

[Copilot]

Pull Request Overview

Copilot reviewed 9 out of 13 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (2)

src/index.ts:785

• The event variable is cast to ReviewEvent after calling toUpperCase(), but there's no validation that the result is actually a valid ReviewEvent value. If a user provides an invalid event value (e.g., 'invalid'), this could cause runtime errors when the value is passed to the GitHub API. Consider adding validation to ensure the value is one of the valid review event types ('APPROVE', 'REQUEST_CHANGES', 'COMMENT').
  test/unit.test.ts:9
• [nitpick] The indentation of the import statement has changed to use 4 spaces per level instead of 2, which is inconsistent with the project's Prettier configuration that uses 2 spaces (as seen in package.json). Consider running Prettier to ensure consistent formatting.

[Copilot]

Pull Request Overview

Copilot reviewed 9 out of 13 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (2)

src/index.ts:788

• The as any type assertion bypasses TypeScript's type safety. Instead, use a proper type guard to check if the string is a valid event type. Consider: if (!validEvents.includes(eventInput as ReviewEvent)) or create a type guard function isValidEvent(value: string): value is ReviewEvent.
  test/unit.test.ts:170
• Using @ts-ignore suppresses type checking. Consider using @ts-expect-error instead, which will error if the line is actually valid, helping catch unnecessary suppressions. Alternatively, define a proper mock type that satisfies the required interface.