test_runner: ignore unmapped lines for coverage

PR-URL: https://github.com/nodejs/node/pull/55228
Refs: https://github.com/nodejs/node/issues/55106
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

lib/internal/test_runner/coverage.js

@@ -1,6 +1,7 @@
 'use strict';
 const {
   ArrayFrom,
+  ArrayPrototypeForEach,
   ArrayPrototypeMap,
   ArrayPrototypePush,
   JSONParse,
@@ -57,12 +58,21 @@ class CoverageLine {
 }
 
 class TestCoverage {
-  constructor(coverageDirectory, originalCoverageDirectory, workingDirectory, excludeGlobs, includeGlobs, thresholds) {
+  constructor(
+    coverageDirectory,
+    originalCoverageDirectory,
+    workingDirectory,
+    excludeGlobs,
+    includeGlobs,
+    sourceMaps,
+    thresholds,
+  ) {
     this.coverageDirectory = coverageDirectory;
     this.originalCoverageDirectory = originalCoverageDirectory;
     this.workingDirectory = workingDirectory;
     this.excludeGlobs = excludeGlobs;
     this.includeGlobs = includeGlobs;
+    this.sourceMaps = sourceMaps;
     this.thresholds = thresholds;
   }
 
@@ -366,7 +376,13 @@ class TestCoverage {
           this.getLines(data.sources[j], data.sourcesContent[j]);
         }
       }
+
       const sourceMap = new SourceMap(data, { __proto__: null, lineLengths });
+      const linesToCover = new SafeSet();
+
+      for (let i = 0; i < sourceMap[kMappings].length; i++) {
+        linesToCover.add(sourceMap[kMappings][i][3] + 1);
+      }
 
       for (let j = 0; j < functions.length; ++j) {
         const { ranges, functionName, isBlockCoverage } = functions[j];
@@ -415,6 +431,15 @@ class TestCoverage {
           // No mappable ranges. Skip the function.
           continue;
         }
+
+        if (this.sourceMaps) {
+          ArrayPrototypeForEach(this.getLines(newUrl), (mappedLine) => {
+            if (!linesToCover.has(mappedLine.line)) {
+              mappedLine.ignore = true;
+            }
+          });
+        }
+
         const newScript = newResult.get(newUrl) ?? { __proto__: null, url: newUrl, functions: [] };
         ArrayPrototypePush(newScript.functions, { __proto__: null, functionName, ranges: newRanges, isBlockCoverage });
         newResult.set(newUrl, newScript);
@@ -516,6 +541,7 @@ function setupCoverage(options) {
     options.cwd,
     options.coverageExcludeGlobs,
     options.coverageIncludeGlobs,
+    options.sourceMaps,
     {
       __proto__: null,
       line: options.lineCoverage,

test/parallel/test-runner-coverage-source-map.js

@@ -45,6 +45,31 @@ describe('Coverage with source maps', async () => {
     t.assert.strictEqual(spawned.code, 1);
   });
 
+  it('accounts only mapped lines when --enable-source-maps is provided', async (t) => {
+    const report = generateReport([
+      '# --------------------------------------------------------------',
+      '# file          | line % | branch % | funcs % | uncovered lines',
+      '# --------------------------------------------------------------',
+      '# a.test.ts     | 100.00 |   100.00 |  100.00 | ', // part of a bundle
+      '# b.test.ts     |  88.89 |   100.00 |  100.00 | 1', // part of a bundle
+      '# index.test.js |  71.43 |    66.67 |  100.00 | 6-7', // no source map
+      '# stdin.test.ts | 100.00 |   100.00 |  100.00 | ', // Source map without original file
+      '# --------------------------------------------------------------',
+      '# all files     |  91.67 |    87.50 |  100.00 | ',
+      '# --------------------------------------------------------------',
+    ]);
+
+    const spawned = await common.spawnPromisified(process.execPath, [
+      '--test', '--experimental-test-coverage', '--enable-source-maps', '--test-reporter', 'tap',
+    ], {
+      cwd: fixtures.path('test-runner', 'coverage')
+    });
+
+    t.assert.strictEqual(spawned.stderr, '');
+    t.assert.ok(spawned.stdout.includes(report));
+    t.assert.strictEqual(spawned.code, 1);
+  });
+
   await it('properly accounts for line endings in source maps', async (t) => {
     const report = generateReport([
       '# ------------------------------------------------------------------',
@@ -89,6 +114,7 @@ describe('Coverage with source maps', async () => {
       const spawned = await common.spawnPromisified(process.execPath, [...flags, file]);
 
       const error = `The source map for '${pathToFileURL(file)}' does not exist or is corrupt`;
+
       t.assert.strictEqual(spawned.stderr, '');
       t.assert.ok(spawned.stdout.includes(error));
       t.assert.strictEqual(spawned.code, 1);