test_runner: exclude ignored branches from lcov output

lib/internal/test_runner/coverage.js

@@ -263,14 +263,16 @@ class TestCoverage {
           ObjectAssign(range, mapRangeToLines(range, lines));
 
           if (isBlockCoverage) {
+            const ignored = range.ignoredLines === range.lines.length;
+
             ArrayPrototypePush(branchReports, {
               __proto__: null,
               line: range.lines[0]?.line,
               count: range.count,
+              ignored,
             });
 
-            if (range.count !== 0 ||
-                range.ignoredLines === range.lines.length) {
+            if (range.count !== 0 || ignored) {
               branchesCovered++;
             }
 

lib/internal/test_runner/reporter/lcov.js

@@ -34,6 +34,7 @@ class LcovReporter extends Transform {
         // containing filename and coverage data:
         // ## SF:\<path to the source file\>
         lcov += `SF:${relative(workingDirectory, file.path)}\n`;
+        const branches = file.branches.filter((branch) => !branch.ignored);
 
         // Following is a list of line numbers for each function name found in
         // the source file:
@@ -68,15 +69,15 @@ 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.
-        for (let j = 0; j < file.branches.length; j++) {
-          lcov += `BRDA:${file.branches[j].line},${j},0,${file.branches[j].count}\n`;
+        for (let j = 0; j < branches.length; j++) {
+          lcov += `BRDA:${branches[j].line},${j},0,${branches[j].count}\n`;
         }
 
         // 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:${branches.length}\n`;
+        lcov += `BRH:${branches.filter((branch) => branch.count !== 0).length}\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

@@ -310,9 +310,11 @@ test('coverage reports on lines, functions, and branches', skipIfNoInspector, as
   await t.test('reports on branch coverage', () => {
     const uncalledBranch = file.branches.find((b) => b.line === 6);
     assert.strictEqual(uncalledBranch.count, 0);
+    assert.strictEqual(uncalledBranch.ignored, true);
 
     const calledTwice = file.branches.find((b) => b.line === 35);
     assert.strictEqual(calledTwice.count, 2);
+    assert.strictEqual(calledTwice.ignored, false);
   });
 
   await t.test('reports on line coverage', () => {

test/parallel/test-runner-reporters.js

@@ -4,9 +4,11 @@ require('../common');
 const fixtures = require('../common/fixtures');
 const tmpdir = require('../common/tmpdir');
 const { describe, it } = require('node:test');
+const { once } = require('node:events');
 const { spawnSync } = require('node:child_process');
 const assert = require('node:assert');
 const fs = require('node:fs');
+const LcovReporter = require('internal/test_runner/reporter/lcov');
 
 const testFile = fixtures.path('test-runner/reporters.js');
 tmpdir.refresh();
@@ -105,6 +107,46 @@ describe('node:test reporters', { concurrency: true }, () => {
     assert.match(file2Contents, /✖ failing/);
   });
 
+  it('should omit ignored branches from lcov output', async () => {
+    const reporter = new LcovReporter();
+    const chunks = [];
+    reporter.setEncoding('utf8');
+    reporter.on('data', common.mustCallAtLeast((chunk) => {
+      chunks.push(chunk);
+    }));
+
+    reporter.end({
+      type: 'test:coverage',
+      data: {
+        summary: {
+          workingDirectory: '/tmp/project',
+          files: [{
+            path: '/tmp/project/file.js',
+            functions: [],
+            totalFunctionCount: 0,
+            coveredFunctionCount: 0,
+            branches: [
+              { line: 1, count: 0, ignored: true },
+              { line: 2, count: 1, ignored: false },
+            ],
+            totalBranchCount: 2,
+            coveredBranchCount: 1,
+            lines: [],
+            totalLineCount: 0,
+            coveredLineCount: 0,
+          }],
+        },
+      },
+    });
+
+    await once(reporter, 'finish');
+    const output = chunks.join('');
+    assert.match(output, /BRDA:2,0,0,1/);
+    assert(!output.includes('BRDA:1,0,0,0'));
+    assert.match(output, /BRF:1/);
+    assert.match(output, /BRH:1/);
+  });
+
   ['js', 'cjs', 'mjs'].forEach((ext) => {
     it(`should support a '${ext}' file as a custom reporter`, async () => {
       const filename = `custom.${ext}`;