test_runner: exclude ignored branches from lcov output

lib/internal/test_runner/reporter/lcov.js

@@ -68,15 +68,38 @@ 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.
+        let branchCount = 0;
+        let coveredBranchCount = 0;
+
         for (let j = 0; j < file.branches.length; j++) {
-          lcov += `BRDA:${file.branches[j].line},${j},0,${file.branches[j].count}\n`;
+          const branch = file.branches[j];
+          let lineReported = false;
+
+          for (let k = 0; k < file.lines.length; k++) {
+            if (file.lines[k].line === branch.line) {
+              lineReported = true;
+              break;
+            }
+          }
+
+          if (!lineReported) {
+            continue;
+          }
+
+          lcov += `BRDA:${branch.line},${branchCount},0,${branch.count}\n`;
+
+          branchCount++;
+
+          if (branch.count !== 0) {
+            coveredBranchCount++;
+          }
         }
 
         // Branch coverage summaries are stored in two lines:
         // ## BRF:\<number of branches found\>
         // ## BRH:\<number of branches hit\>
-        lcov += `BRF:${file.totalBranchCount}\n`;
-        lcov += `BRH:${file.coveredBranchCount}\n`;
+        lcov += `BRF:${branchCount}\n`;
+        lcov += `BRH:${coveredBranchCount}\n`;
 
         // Then there is a list of execution counts for each instrumented line
         // (i.e. a line which resulted in executable code):

test/parallel/test-runner-coverage.js

@@ -2,7 +2,7 @@
 const common = require('../common');
 const assert = require('node:assert');
 const { spawnSync } = require('node:child_process');
-const { readdirSync } = require('node:fs');
+const { readdirSync, writeFileSync } = require('node:fs');
 const { test } = require('node:test');
 const fixtures = require('../common/fixtures');
 const tmpdir = require('../common/tmpdir');
@@ -77,6 +77,43 @@ function getSpecCoverageFixtureReport() {
   return report;
 }
 
+test('lcov reporter excludes BRDA entries for ignored lines', skipIfNoInspector, () => {
+  const fixture = tmpdir.resolve('lcov-ignore-branch.test.js');
+
+  writeFileSync(fixture, `
+'use strict';
+
+const test = require('node:test');
+
+test('ignored branch', () => {
+  // node:coverage ignore next
+  if (false) {
+    throw new Error('ignored');
+  }
+
+  if (true) {
+    // Covered branch to ensure LCOV still reports branch data.
+  }
+});
+`);
+
+  const child = spawnSync(process.execPath, [
+    '--test',
+    '--experimental-test-coverage',
+    '--test-reporter',
+    'lcov',
+    fixture,
+  ]);
+
+  assert.strictEqual(child.stderr.toString(), '');
+  assert.strictEqual(child.status, 0);
+
+  const stdout = child.stdout.toString();
+
+  assert(!stdout.includes('BRDA:8,'));
+  assert.match(stdout, /BRDA:/);
+});
+
 test('test coverage report', async (t) => {
   await t.test('handles the inspector not being available', (t) => {
     if (process.features.inspector) {