Update coverage tooling to use c8 instead of nyc and adjust related configurations

Author: Hannia Valera

.github/PULL_REQUEST_TEMPLATE/coverage.md

@@ -27,7 +27,7 @@ about: PR opened by the Copilot coverage agent
 - [ ] `yarn lint` passes
 - [ ] `CHANGELOG.md` has an entry under `Improvements:`
 
-### Coverage delta (paste `nyc` text report here)
+### Coverage delta (paste `c8` text report here)
 ```
-(paste output of: npx nyc report --reporter=text)
+(paste output of: npx c8 report --reporter=text)
 ```

.github/copilot-test-coverage.md

@@ -40,7 +40,7 @@ yarn backendTests
 yarn unitTests
 
 # 5. Confirm coverage improved for the specific file
-npx nyc --reporter=text \
+npx c8 --reporter=text --src=src \
   node ./node_modules/mocha/bin/_mocha \
     -u tdd --timeout 999999 --colors \
     -r ts-node/register \

.github/scripts/check-coverage-and-open-issue.mjs

@@ -2,6 +2,7 @@
 // @ts-check
 import { readFileSync } from 'fs';
 import { execSync } from 'child_process';
+import { relative, resolve } from 'path';
 
 const THRESHOLD = Number(process.env.THRESHOLD ?? 60);
 const SUMMARY_PATH = 'coverage/coverage-summary.json';
@@ -19,17 +20,24 @@ try {
 
 // ── 2. Find files below threshold ────────────────────────────────────────────
 const belowThreshold = [];
+const repoRoot = resolve('.');
 
 for (const [file, metrics] of Object.entries(summary)) {
     if (file === 'total') continue;
-    if (!file.startsWith('src/')) continue;
+
+    // Normalize: c8/Istanbul may emit absolute paths or repo-relative paths
+    const relPath = file.startsWith('/') || /^[A-Za-z]:[/\\]/.test(file)
+        ? relative(repoRoot, file).replace(/\\/g, '/')
+        : file;
+
+    if (!relPath.startsWith('src/')) continue;
 
     const linePct   = metrics.lines.pct    ?? 0;
     const branchPct = metrics.branches.pct ?? 0;
     const fnPct     = metrics.functions.pct ?? 0;
 
     if (linePct < THRESHOLD || fnPct < THRESHOLD) {
-        belowThreshold.push({ file, linePct, branchPct, fnPct });
+        belowThreshold.push({ file: relPath, linePct, branchPct, fnPct });
     }
 }
 
@@ -44,7 +52,21 @@ if (belowThreshold.length === 0 && totalLines >= THRESHOLD) {
     process.exit(0);
 }
 
-// ── 3. Build the issue body (this is the Copilot agent's instruction set) ────
+// ── 3. Check for existing open coverage issue (avoid duplicates) ─────────────
+try {
+    const existing = execSync(
+        `gh issue list --repo ${REPO} --label test-coverage --state open --json number --jq '.[0].number'`,
+        { encoding: 'utf8' }
+    ).trim();
+    if (existing) {
+        console.log(`\n⏭️  Open coverage issue already exists: #${existing} — skipping.`);
+        process.exit(0);
+    }
+} catch {
+    // gh CLI may fail if label doesn't exist yet — continue to create
+}
+
+// ── 4. Build the issue body (this is the Copilot agent's instruction set) ────
 belowThreshold.sort((a, b) => a.linePct - b.linePct);  // worst files first
 
 const tableRows = belowThreshold
@@ -111,7 +133,17 @@ For each file:
 - Do **not** touch source files outside \`test/\`
 `;
 
-// ── 4. Open the issue via gh CLI ──────────────────────────────────────────────
+// ── 5. Ensure the test-coverage label exists ─────────────────────────────────
+try {
+    execSync(
+        `gh label create test-coverage --repo ${REPO} --color 0075ca --description "Opened by the coverage agent" --force`,
+        { stdio: 'inherit' }
+    );
+} catch {
+    // --force handles existing labels; ignore unexpected errors
+}
+
+// ── 6. Open the issue via gh CLI ──────────────────────────────────────────────
 const title = `chore: improve test coverage -- ${belowThreshold.length} files below ${THRESHOLD}% (run ${new Date().toISOString().slice(0, 10)})`;
 
 const cmd = [

.github/workflows/coverage-agent.yml

@@ -1,12 +1,8 @@
 name: Coverage Agent
 
 on:
-  push:
-    branches: [ main, 'release/**' ]
-  pull_request:
-    branches: [ main, 'release/**' ]
   schedule:
-    - cron: '0 3 * * 1'   # weekly Monday 03:00 UTC — keeps noise low
+    - cron: '0 3 * * 1'   # weekly Monday 03:00 UTC
   workflow_dispatch:
     inputs:
       threshold:
@@ -25,9 +21,9 @@ jobs:
       issues: write
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
-      - uses: actions/setup-node@v3
+      - uses: actions/setup-node@v4
         with:
           node-version: 20
 
@@ -40,43 +36,29 @@ jobs:
       - name: Build (test config)
         run: yarn pretest          # tsc -p test.tsconfig.json
 
-      # ── Coverage: backend tests (pure Mocha — nyc wraps directly) ──────────
+      # ── Coverage: backend tests (c8 uses V8 native coverage) ───────────
       - name: Run backend tests with coverage
         run: |
-          npx nyc \
-            --reporter=json \
+          npx c8 \
+            --reporter=json-summary \
             --reporter=text \
+            --src=src \
             --include='src/**/*.ts' \
             --exclude='src/**/*.d.ts' \
-            --temp-dir=.nyc_output \
+            -o coverage \
             node ./node_modules/mocha/bin/_mocha \
               -u tdd --timeout 999999 --colors \
               -r ts-node/register \
               -r tsconfig-paths/register \
               "./test/unit-tests/backend/**/*.test.ts"
 
-      # ── Coverage: unit tests (VS Code extension host — via xvfb) ──────────
-      - name: Run unit tests with coverage
+      # ── Unit tests (extension host — coverage not collected here) ──────
+      # c8/nyc cannot instrument the VS Code extension-host child process.
+      # This step validates tests pass; coverage comes from backend tests.
+      - name: Run unit tests
         uses: GabrielBB/[email protected]
         with:
-          run: |
-            npx nyc \
-              --reporter=json \
-              --include='src/**/*.ts' \
-              --exclude='src/**/*.d.ts' \
-              --temp-dir=.nyc_output \
-              node ./out/test/unit-tests/runTest.js
-        continue-on-error: true   # coverage report still matters even if some tests fail
-
-      # ── Merge all coverage runs and emit summary ──────────────────────────
-      - name: Merge coverage and generate summary
-        run: |
-          npx nyc merge .nyc_output coverage/coverage-combined.json
-          npx nyc report \
-            --reporter=json-summary \
-            --reporter=lcov \
-            --temp-dir=coverage \
-            -t .nyc_output
+          run: node ./out/test/unit-tests/runTest.js
 
       - name: Upload coverage artifacts
         uses: actions/upload-artifact@v4

.gitignore

@@ -1,5 +1,7 @@
+.nyc_output/
 .vscode-test/
 build/
+coverage/
 dist/
 node_modules/
 out/

package.json

@@ -4428,6 +4428,7 @@
     "chai": "^4.3.0",
     "chai-as-promised": "^7.1.1",
     "chai-string": "^1.5.0",
+    "c8": "^10.1.0",
     "eslint": "^8.42.0",
     "eslint-plugin-import": "^2.29.1",
     "eslint-plugin-jsdoc": "^48.2.8",