test_runner: exclude BRDA entries for ignored lines in LCOV reporter

lib/internal/test_runner/reporter/lcov.js

@@ -2,6 +2,7 @@
 
 const { relative } = require('path');
 const Transform = require('internal/streams/transform');
+const { SafeSet } = require('internal/primordials');
 
 // This reporter is based on the LCOV format, as described here:
 // https://ltp.sourceforge.net/coverage/lcov/geninfo.1.php
@@ -68,7 +69,20 @@ class LcovReporter extends Transform {
         // Taken is either '-' if the basic block containing the branch was
         // never executed or a number indicating how often that branch was
         // taken.
+        // Build set of ignored line numbers from coverage data.
+        // A line is ignored if it appears with ignore=true in the file.lines array.
+        const ignoredLineSet = new SafeSet();
+        for (let k = 0; k < file.lines.length; k++) {
+          if (file.lines[k].ignore) {
+            ignoredLineSet.add(file.lines[k].line);
+          }
+        }
+
         for (let j = 0; j < file.branches.length; j++) {
+          // Skip branches that point to ignored lines.
+          if (ignoredLineSet.has(file.branches[j].line)) {
+            continue;
+          }
           lcov += `BRDA:${file.branches[j].line},${j},0,${file.branches[j].count}\n`;
         }
 
@@ -104,4 +118,4 @@ class LcovReporter extends Transform {
   }
 }
 
-module.exports = LcovReporter;
+module.exports = LcovReporter;

test/fixtures/test-runner/output/brda_ignore_output.js

@@ -0,0 +1,16 @@
+'use strict';
+require('../../../common');
+const test = require('node:test');
+
+function funcWithIgnoredBranch(value) {
+  /* node:coverage ignore next */
+  if (value > 0) { // This branch should be ignored
+    return 'positive';
+  } else {
+    return 'negative';
+  }
+}
+
+test('should not report BRDA for ignored branch', () => {
+  funcWithIgnoredBranch(1); // Only call one path of the branch
+});

test/fixtures/test-runner/output/lcov_reporter_brda_ignore.js

@@ -0,0 +1,16 @@
+'use strict';
+require('../../../common');
+const fixtures = require('../../../common/fixtures');
+const spawn = require('node:child_process').spawn;
+
+spawn(
+  process.execPath,
+  [
+    '--no-warnings',
+    '--experimental-test-coverage',
+    '--test-coverage-exclude=!test/**',
+    '--test-reporter', 'lcov',
+    fixtures.path('test-runner/output/brda_ignore_output.js'),
+  ],
+  { stdio: 'inherit' },
+);

test/fixtures/test-runner/output/lcov_reporter_brda_ignore.snapshot

@@ -0,0 +1,32 @@
+TN:
+SF:test/fixtures/test-runner/output/brda_ignore_output.js
+FN:5,funcWithIgnoredBranch
+FN:14,anonymous_1
+FNDA:1,funcWithIgnoredBranch
+FNDA:1,anonymous_1
+FNF:2
+FNH:2
+BRDA:1,0,0,1
+BRDA:5,1,0,1
+BRDA:9,2,0,0
+BRDA:14,3,0,1
+BRF:4
+BRH:3
+DA:1,1
+DA:2,1
+DA:3,1
+DA:4,1
+DA:5,1
+DA:6,1
+DA:8,1
+DA:9,1
+DA:10,0
+DA:11,0
+DA:12,1
+DA:13,1
+DA:14,1
+DA:15,1
+DA:16,1
+LH:14
+LF:16
+end_of_record

test/test-runner/test-output-lcov-reporter-brda-ignore.mjs

@@ -0,0 +1,13 @@
+import * as common from '../common/index.mjs';
+import * as fixtures from '../common/fixtures.mjs';
+import { spawnAndAssert, lcovTransform, ensureCwdIsProjectRoot } from '../common/assertSnapshot.js';
+
+if (!process.features.inspector) {
+  common.skip('inspector support required');
+}
+
+ensureCwdIsProjectRoot();
+await spawnAndAssert(
+  fixtures.path('test-runner/output/lcov_reporter_brda_ignore.js'),
+  lcovTransform,
+);