feat: Add test coverage reporting to PRs (#8)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: marcelomendoncasoares <6807059+marcelomendoncasoares@users.noreply.github.com>

.github/workflows/ci.yaml

@@ -69,6 +69,9 @@ jobs:
     needs: generate
     name: dart test
     runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      contents: read
     steps:
       - uses: actions/checkout@v4
       - name: Set up Dart
@@ -81,8 +84,20 @@ jobs:
         uses: actions/download-artifact@v4
         with:
           name: generated-code
-      - name: Run tests
+      - name: Run tests with coverage
-        run: dart test --reporter=failures-only
+        run: dart test --coverage=coverage --reporter=failures-only
+      - name: Activate coverage package
+        run: dart pub global activate coverage
+      - name: Format coverage
+        run: dart pub global run coverage:format_coverage --lcov --in=coverage --out=coverage/lcov.info --report-on=lib --check-ignore --ignore-files="**/*.g.dart"
+      - name: Generate coverage report
+        run: dart scripts/coverage_report.dart --ci > coverage-results.txt
+      - name: Comment on PR
+        if: github.event_name == 'pull_request'
+        uses: thollander/actions-comment-pull-request@v3
+        with:
+          file-path: coverage-results.txt
+          comment-tag: coverage-results
 
   benchmarks:
     needs: generate

.gitignore

@@ -8,3 +8,7 @@ pubspec.lock
 
 .vscode/
 *.g.dart
+
+# Coverage reports
+coverage/
+coverage-results.txt

scripts/coverage_report.dart

@@ -0,0 +1,170 @@
+// Coverage Reporter
+//
+// This script generates markdown-formatted test coverage reports for GitHub PRs.
+//
+// ## Usage
+//
+// The script reads an `lcov.info` file generated by the Dart coverage tool and
+// outputs a markdown report showing:
+// - Overall coverage percentage
+// - Lines covered vs total lines
+// - Per-file coverage breakdown sorted by coverage percentage
+//
+// ### Local Usage
+//
+// ```bash
+// # Run tests with coverage
+// dart test --coverage=coverage
+//
+// # Format coverage to lcov
+// dart pub global activate coverage
+// dart pub global run coverage:format_coverage --lcov --in=coverage --out=coverage/lcov.info --report-on=lib --check-ignore --ignore-files="**/*.g.dart"
+//
+// # Generate markdown report
+// dart scripts/coverage_report.dart
+//
+// # For CI mode (no decorations)
+// dart scripts/coverage_report.dart --ci
+// ```
+//
+// ### CI Usage
+//
+// This script is automatically run as part of the CI pipeline in the `tests`
+// job. The generated report is posted as a comment on pull requests.
+
+import 'dart:io';
+
+Future<void> main(List<String> args) async {
+  final runningInCI = args.contains('--ci');
+  final lcovFile = File('coverage/lcov.info');
+
+  if (!lcovFile.existsSync()) {
+    stderr.writeln('Error: coverage/lcov.info not found');
+    exit(1);
+  }
+
+  final String lcovContent;
+  try {
+    lcovContent = lcovFile.readAsStringSync();
+  } on Exception catch (e) {
+    stderr.writeln('Error reading coverage/lcov.info: $e');
+    exit(1);
+  }
+
+  final coverage = _parseLcov(lcovContent);
+  final totalLines = coverage['total_lines'] as int;
+  final coveredLines = coverage['covered_lines'] as int;
+  final percentage = totalLines > 0
+      ? (coveredLines / totalLines * 100).toStringAsFixed(2)
+      : '0.00';
+
+  if (!runningInCI) print('\n${'=' * 60}');
+  print('## Test Coverage Report\n');
+  print(
+    [
+      'This report shows the test coverage for the project.',
+    ].join(runningInCI ? '' : '\n'),
+  );
+  if (!runningInCI) print('-' * 60);
+  print('');
+  print('**Total Coverage: $percentage%**');
+  print('');
+  print('- Lines covered: $coveredLines / $totalLines');
+  print('');
+
+  // Print per-file coverage in a collapsible section
+  final files = coverage['files'] as Map<String, Map<String, int>>;
+  if (files.isNotEmpty) {
+    print('<details>');
+    print('<summary>File Coverage</summary>');
+    print('');
+    final sortedFiles = files.entries.toList()
+      ..sort((a, b) {
+        final aTotal = a.value['total']!;
+        final bTotal = b.value['total']!;
+        if (aTotal == 0 && bTotal == 0) return 0;
+        if (aTotal == 0) return 1;
+        if (bTotal == 0) return -1;
+        final aPercent = a.value['covered']! / aTotal;
+        final bPercent = b.value['covered']! / bTotal;
+        return bPercent.compareTo(aPercent);
+      });
+
+    for (final entry in sortedFiles) {
+      final fileName = entry.key.split('/').last;
+      final covered = entry.value['covered']!;
+      final total = entry.value['total']!;
+      final filePercentage = total > 0
+          ? (covered / total * 100).toStringAsFixed(1)
+          : '0.0';
+      print('- `$fileName`: $filePercentage% ($covered/$total lines)');
+    }
+    print('');
+    print('</details>');
+  }
+
+  if (!runningInCI) print('\n${'=' * 60}\n');
+}
+
+Map<String, dynamic> _parseLcov(String lcovContent) {
+  final lines = lcovContent.split('\n');
+  var totalLines = 0;
+  var coveredLines = 0;
+  final files = <String, Map<String, int>>{};
+
+  String? currentFile;
+  var currentFileLines = 0;
+  var currentFileCovered = 0;
+
+  for (final line in lines) {
+    if (line.startsWith('SF:')) {
+      // Save previous file data if it exists (handles malformed lcov)
+      if (currentFile != null && currentFileLines > 0) {
+        totalLines += currentFileLines;
+        coveredLines += currentFileCovered;
+        files[currentFile] = {
+          'total': currentFileLines,
+          'covered': currentFileCovered,
+        };
+      }
+      currentFile = line.substring(3);
+      currentFileLines = 0;
+      currentFileCovered = 0;
+    } else if (line.startsWith('DA:')) {
+      final parts = line.substring(3).split(',');
+      if (parts.length >= 2) {
+        final hits = int.tryParse(parts[1]) ?? 0;
+        currentFileLines++;
+        if (hits > 0) {
+          currentFileCovered++;
+        }
+      }
+    } else if (line == 'end_of_record' && currentFile != null) {
+      if (currentFileLines > 0) {
+        totalLines += currentFileLines;
+        coveredLines += currentFileCovered;
+        files[currentFile] = {
+          'total': currentFileLines,
+          'covered': currentFileCovered,
+        };
+      }
+      currentFile = null;
+    }
+  }
+
+  // Handle case where file ends without 'end_of_record'
+  if (currentFile != null && currentFileLines > 0) {
+    totalLines += currentFileLines;
+    coveredLines += currentFileCovered;
+    files[currentFile] = {
+      'total': currentFileLines,
+      'covered': currentFileCovered,
+    };
+  }
+
+  return {
+    'total_lines': totalLines,
+    'covered_lines': coveredLines,
+    'files': files,
+  };
+}