Migrate codebase from JavaScript to TypeScript (#255)

* Migrate codebase from JavaScript to TypeScript

- Convert all 7 source files (utils, parse, parseXml, junitXml, multiFiles, index, cli) to TypeScript
- Add shared type definitions in src/types.d.ts
- Add 91 unit tests using Vitest with V8 coverage (~91% statement coverage)
- Add CI workflow for format, lint, build, test and coverage badge
- Configure TypeScript, ESLint, Vitest, Prettier for TypeScript
- Bump version to 1.6.0
- Update dev dependencies to latest compatible versions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Address code review findings from Copilot, Cubic, and CodeRabbit

- Fix env var restoration in test (delete when originally undefined)
- Fix vacuous test assertions (parseXml skip-covered, parse branch coverage)
- Log xml2js parse errors instead of silently ignoring them
- Add testsuites structure guard to prevent crash on malformed XML
- Add permissions block to CI workflow
- Fix package.json main field to point to dist/index.js
- Fix onlyChnaged typo in parse.ts
- Remove redundant noImplicitAny from tsconfig (covered by strict)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: MishaKav

.github/workflows/update-coverage-in-readme.yml

@@ -0,0 +1,87 @@
+name: Update Coverage in README
+on:
+  push:
+    paths-ignore:
+      - '**/*.md'
+      - '**/*.yml'
+      - '.github/**'
+      - 'data/**'
+      - 'dist/**'
+
+permissions:
+  contents: read
+
+jobs:
+  update-coverage-in-readme:
+    name: Update Coverage in README
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: NPM Cache
+        id: npm-cache
+        uses: actions/cache@v5
+        with:
+          path: '**/node_modules'
+          key: ${{ runner.os }}-npm-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-npm
+
+      - name: Install Dependencies
+        if: steps.npm-cache.outputs.cache-hit != 'true'
+        run: npm ci
+
+      - name: Check Format
+        run: npm run format-check
+
+      - name: Check Lint
+        run: npm run lint
+
+      - name: Check Build
+        run: npm run build
+
+      - name: Run Tests
+        run: npm run test:coverage
+
+      - name: Jest Coverage Comment
+        id: coverageComment
+        uses: MishaKav/jest-coverage-comment@main
+        with:
+          hide-comment: true
+          coverage-summary-path: ./coverage/coverage-summary.json
+          junitxml-path: ./coverage/junit.xml
+
+      - name: Check the output coverage
+        run: |
+          echo "Summary Report"
+          echo "Coverage Percentage - ${{ steps.coverageComment.outputs.coverage }}"
+          echo "Coverage Color - ${{ steps.coverageComment.outputs.color }}"
+          echo "Summary Html - ${{ steps.coverageComment.outputs.summaryHtml }}"
+
+          echo "JUnit Report"
+          echo "tests - ${{ steps.coverageComment.outputs.tests }}"
+          echo "skipped - ${{ steps.coverageComment.outputs.skipped }}"
+          echo "failures - ${{ steps.coverageComment.outputs.failures }}"
+          echo "errors - ${{ steps.coverageComment.outputs.errors }}"
+          echo "time - ${{ steps.coverageComment.outputs.time }}"
+
+          echo "Coverage Report"
+          echo "lines - ${{ steps.coverageComment.outputs.lines }}"
+          echo "branches - ${{ steps.coverageComment.outputs.branches }}"
+          echo "functions - ${{ steps.coverageComment.outputs.functions }}"
+          echo "statements - ${{ steps.coverageComment.outputs.statements }}"
+          echo "coverage - ${{ steps.coverageComment.outputs.coverage }}"
+          echo "color - ${{ steps.coverageComment.outputs.color }}"
+          echo "Coverage Html - ${{ steps.coverageComment.outputs.coverageHtml }}"
+
+      - name: Create the badge
+        if: github.ref == 'refs/heads/main'
+        uses: schneegans/dynamic-badges-action@v1.7.0
+        with:
+          auth: ${{ secrets.JEST_COVERAGE_COMMENT }}
+          gistID: 5e90d640f8c212ab7bbac38f72323f80
+          filename: pytest-coverage-comment__main.json
+          label: coverage
+          message: ${{ steps.coverageComment.outputs.coverage }}%
+          color: ${{ steps.coverageComment.outputs.color }}
+          namedLogo: typescript

CHANGELOG.md

@@ -1,5 +1,16 @@
 # Changelog of the Pytest Coverage Comment
 
+## [Pytest Coverage Comment 1.6.0](https://github.com/MishaKav/pytest-coverage-comment/tree/v1.6.0)
+
+**Release Date:** 2026-03-06
+
+#### Changes
+
+- migrate codebase from JavaScript to TypeScript
+- add unit tests (91 tests) using Vitest with V8 coverage
+
+**Note:** This is an internal rewrite — no changes to action inputs, outputs, or behavior. Fully backward compatible.
+
 ## [Pytest Coverage Comment 1.5.0](https://github.com/MishaKav/pytest-coverage-comment/tree/v1.5.0)
 
 **Release Date:** 2026-02-28

CLAUDE.md

@@ -9,50 +9,85 @@ pytest-coverage-comment is a GitHub Action that comments on pull requests with p
 ## Development Commands
 
 ### Build and Bundle
+
 ```bash
-npm run build      # Bundle the action with ncc into dist/index.js
-npm run all        # Run lint, format, and build in sequence
+npm run build      # Bundle the action with ncc (compiles TS + bundles) into dist/index.js
+npm run all        # Run typecheck, lint, format, test, and build in sequence
 ```
 
-### Code Quality
+### Type Checking and Code Quality
+
 ```bash
-npm run lint       # Run ESLint on src/**/*.js
+npm run typecheck  # Run tsc --noEmit (type-check only, no output)
+npm run lint       # Run ESLint on src/**/*.ts
 npm run format     # Format code with Prettier
 npm run format-check # Check formatting without changing files
 ```
 
+### Testing
+
+```bash
+npm test           # Run Vitest tests (vitest run)
+npm run test:watch # Run Vitest in watch mode
+npm run test:coverage # Run tests with V8 coverage
+```
+
 ### Version Management
+
 ```bash
 npm run bump-version # Increment patch version
 ```
 
 ### Local Testing
-The `src/cli.js` file contains a CLI tool for local testing of coverage parsing functionality. It can be run directly to test coverage report generation without GitHub Actions.
+
+The `src/cli.ts` file contains a CLI tool for local testing of coverage parsing functionality. It can be run directly to test coverage report generation without GitHub Actions.
 
 ## Architecture Overview
 
-The codebase is a Node.js GitHub Action with the following key components:
+The codebase is a TypeScript GitHub Action with the following key components:
 
 ### Entry Points
-- **src/index.js**: Main GitHub Action entry point that orchestrates the entire workflow
-- **src/cli.js**: CLI utility for local testing and development
+
+- **src/index.ts**: Main GitHub Action entry point that orchestrates the entire workflow
+- **src/cli.ts**: CLI utility for local testing and development
+
+### Type Definitions
+
+- **src/types.d.ts**: All shared TypeScript interfaces (Options, CoverageLine, TotalLine, etc.)
 
 ### Core Parsing Modules
-- **src/parse.js**: Parses pytest text coverage output (e.g., from `pytest --cov`)
-- **src/parseXml.js**: Parses XML coverage reports (e.g., from `pytest --cov-report=xml`)
-- **src/junitXml.js**: Parses JUnit XML test results for test statistics
+
+- **src/parse.ts**: Parses pytest text coverage output (e.g., from `pytest --cov`)
+- **src/parseXml.ts**: Parses XML coverage reports (e.g., from `pytest --cov-report=xml`)
+- **src/junitXml.ts**: Parses JUnit XML test results for test statistics
 
 ### Supporting Modules
-- **src/multiFiles.js**: Handles multiple coverage files (useful for monorepos)
-- **src/utils.js**: Shared utilities for file operations, color determination, and GitHub API interactions
+
+- **src/multiFiles.ts**: Handles multiple coverage files (useful for monorepos)
+- **src/utils.ts**: Shared utilities for file operations, color determination, and GitHub API interactions
+
+### Test Infrastructure
+
+- **\_\_tests\_\_/setup.ts**: Global test setup with `spyCore` mocks for `@actions/core`
+- **\_\_tests\_\_/\*.test.ts**: Vitest unit tests for each module (91 tests total)
+- Uses `exportedForTesting` pattern to expose internal functions for testing
+- Test fixtures in `data/` directory (pytest coverage txt, coverage xml, junit xml)
+
+### Build System
+
+- TypeScript is used for type-checking only (`noEmit: true` in tsconfig)
+- `@vercel/ncc` compiles TS and bundles directly to `dist/index.js` in a single step
+- No intermediate `lib/` or `outDir` needed
 
 ### Data Flow
+
 1. Action receives coverage files (txt/xml) and JUnit XML as inputs
 2. Parsers extract coverage percentages, file details, and test statistics
 3. HTML report is generated with file links pointing to the repository
 4. Comment is created/updated on PR using GitHub API with coverage badge and collapsible report
 
 ### GitHub Integration
+
 - Uses `@actions/core` for input/output handling
 - Uses `@actions/github` for API interactions (creating/updating PR comments)
 - Supports comment watermarking to update existing comments instead of creating duplicates
@@ -63,4 +98,7 @@ The codebase is a Node.js GitHub Action with the following key components:
 - Maximum comment length: 65,536 characters (GitHub limit)
 - Supports filtering to show only changed files in the current commit
 - Can skip files with 100% coverage from XML reports
-- Handles both absolute and relative file paths for coverage inputs
+- Handles both absolute and relative file paths for coverage inputs
+- xml2js `parseString` is used synchronously via callback pattern (not async)
+- `@actions/github` has ESM/CJS compatibility issues in test context — mock it with `vi.mock()` in tests
+- `@actions/core` v3+ and `@actions/github` v9+ are pure ESM — incompatible with ncc's webpack CJS bundling. Must stay on `@actions/core` v2.x and `@actions/github` v8.x until ncc supports ESM or the project switches bundlers

__tests__/index.test.ts

@@ -0,0 +1,44 @@
+import { expect, test, describe, vi } from 'vitest';
+
+// Mock @actions/github before importing index to avoid ESM/CJS issues
+vi.mock('@actions/github', () => ({
+  context: {
+    repo: { repo: 'test', owner: 'owner' },
+    eventName: 'push',
+    payload: {},
+    job: 'test-job',
+    ref: 'refs/heads/main',
+    sha: 'abc123',
+    serverUrl: 'https://github.com',
+  },
+  getOctokit: vi.fn(),
+}));
+
+import { truncateSummary } from '../src/index';
+
+describe('truncateSummary', () => {
+  test('should return content as-is when under limit', () => {
+    const content = 'Short content';
+    expect(truncateSummary(content, 1000)).toBe(content);
+  });
+
+  test('should truncate content that exceeds limit', () => {
+    const content = 'A'.repeat(2000);
+    const result = truncateSummary(content, 1000);
+    expect(result.length).toBeLessThanOrEqual(1000);
+    expect(result).toContain('**Warning: Summary truncated');
+  });
+
+  test('should try to break at newline', () => {
+    const lines = Array.from({ length: 100 }, (_, i) => `Line ${i}`).join(
+      '\n',
+    );
+    const result = truncateSummary(lines, 500);
+    expect(result).toContain('**Warning: Summary truncated');
+  });
+
+  test('should handle exact limit', () => {
+    const content = 'Exact';
+    expect(truncateSummary(content, 5)).toBe('Exact');
+  });
+});