test_runner: exclude BRDA entries for ignored lines in LCOV reporter

When a line is marked with /* node:coverage ignore next */, the DA entry
for that line is correctly excluded from the LCOV output. However, the
corresponding BRDA entry was still being emitted, causing branch coverage
to report incorrect percentages when using the lcov reporter.

PR-URL: #62740

Author: Code Clawd

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;