test_runner: fix typescript coverage

lib/internal/test_runner/coverage.js

@@ -338,7 +338,7 @@ function mapRangeToLines(range, lines) {
     mid = MathFloor((start + end) / 2);
     let line = lines[mid];
 
-    if (startOffset >= line.startOffset && startOffset <= line.endOffset) {
+    if (startOffset >= line?.startOffset && startOffset <= line?.endOffset) {
       while (endOffset > line?.startOffset) {
         // If the range is not covered, and the range covers the entire line,
         // then mark that line as not covered.
@@ -363,7 +363,7 @@ function mapRangeToLines(range, lines) {
       }
 
       break;
-    } else if (startOffset >= line.endOffset) {
+    } else if (startOffset >= line?.endOffset) {
       start = mid + 1;
     } else {
       end = mid - 1;

lib/internal/test_runner/test.js

@@ -737,6 +737,8 @@ class Test extends AsyncResource {
       this.reported = true;
       reporter.plan(nesting, loc, harness.counters.topLevel);
 
+      // Call this harness.coverage() before collecting diagnostics, since failure to collect coverage is a diagnostic.
+      const coverage = harness.coverage();
       for (let i = 0; i < diagnostics.length; i++) {
         reporter.diagnostic(nesting, loc, diagnostics[i]);
       }
@@ -750,8 +752,6 @@ class Test extends AsyncResource {
       reporter.diagnostic(nesting, loc, `todo ${harness.counters.todo}`);
       reporter.diagnostic(nesting, loc, `duration_ms ${this.duration()}`);
 
-      const coverage = harness.coverage();
-
       if (coverage) {
         reporter.coverage(nesting, loc, coverage);
       }

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

@@ -0,0 +1,14 @@
+// Flags: --expose-internals --experimental-test-coverage
+
+'use strict';
+require('../../../common');
+const { setupCoverage } = require('internal/test_runner/coverage');
+const { test } = require('node:test');
+const TestCoverage = setupCoverage().__proto__.constructor;
+
+TestCoverage.prototype.summary = function() {
+  throw new Error('Failed to collect coverage');
+};
+
+test('ok');
+

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

@@ -0,0 +1,16 @@
+TAP version 13
+# Subtest: ok
+ok 1 - ok
+  ---
+  duration_ms: *
+  ...
+1..1
+# Warning: Could not report code coverage. Error: Failed to collect coverage
+# tests 1
+# suites 0
+# pass 1
+# fail 0
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms *

test/parallel/test-runner-output.mjs

@@ -87,6 +87,7 @@ const tests = [
       replaceTestDuration,
     ),
   },
+  { name: 'test-runner/output/coverage_failure.js' },
 ]
 .filter(Boolean)
 .map(({ name, tty, transform }) => ({