test_runner: report error on missing sourcemap source

doc/api/errors.md

@@ -2573,6 +2573,12 @@ disconnected socket.
 
 A call was made and the UDP subsystem was not running.
 
+<a id="ERR_SOURCE_MAP_MISSING_SOURCE"></a>
+
+### `ERR_SOURCE_MAP_MISSING_SOURCE`
+
+A file imported from a source map was not found.
+
 <a id="ERR_SQLITE_ERROR"></a>
 
 ### `ERR_SQLITE_ERROR`

lib/internal/errors.js

@@ -1704,6 +1704,7 @@ E('ERR_SOCKET_CONNECTION_TIMEOUT',
 E('ERR_SOCKET_DGRAM_IS_CONNECTED', 'Already connected', Error);
 E('ERR_SOCKET_DGRAM_NOT_CONNECTED', 'Not connected', Error);
 E('ERR_SOCKET_DGRAM_NOT_RUNNING', 'Not running', Error);
+E('ERR_SOURCE_MAP_MISSING_SOURCE', `Cannot find '%s' imported from the source map for '%s'`, Error);
 E('ERR_SRI_PARSE',
   'Subresource Integrity string %j had an unexpected %j at position %d',
   SyntaxError);

lib/internal/test_runner/coverage.js

@@ -30,6 +30,11 @@ const { tmpdir } = require('os');
 const { join, resolve, relative, matchesGlob } = require('path');
 const { fileURLToPath } = require('internal/url');
 const { kMappings, SourceMap } = require('internal/source_map/source_map');
+const {
+  codes: {
+    ERR_SOURCE_MAP_MISSING_SOURCE,
+  },
+} = require('internal/errors');
 const kCoverageFileRegex = /^coverage-(\d+)-(\d{13})-(\d+)\.json$/;
 const kIgnoreRegex = /\/\* node:coverage ignore next (?<count>\d+ )?\*\//;
 const kLineEndingRegex = /\r?\n$/u;
@@ -390,6 +395,9 @@ class TestCoverage {
 
           newUrl ??= startEntry?.originalSource;
           const mappedLines = this.getLines(newUrl);
+          if (!mappedLines) {
+            throw new ERR_SOURCE_MAP_MISSING_SOURCE(newUrl, url);
+          }
           const mappedStartOffset = this.entryToOffset(startEntry, mappedLines);
           const mappedEndOffset = this.entryToOffset(endEntry, mappedLines) + 1;
           for (let l = startEntry.originalLine; l <= endEntry.originalLine; l++) {

test/parallel/test-runner-coverage.js

@@ -6,6 +6,7 @@ const { readdirSync } = require('node:fs');
 const { test } = require('node:test');
 const fixtures = require('../common/fixtures');
 const tmpdir = require('../common/tmpdir');
+const { pathToFileURL } = require('node:url');
 const skipIfNoInspector = {
   skip: !process.features.inspector ? 'inspector disabled' : false
 };
@@ -320,6 +321,20 @@ test('coverage with source maps', skipIfNoInspector, () => {
   assert.strictEqual(result.status, 1);
 });
 
+test('coverage with source maps missing sources', skipIfNoInspector, () => {
+  const file = fixtures.path('test-runner', 'source-map', 'missing-sources', 'index.js');
+  const missing = fixtures.path('test-runner', 'source-map', 'missing-sources', 'nonexistent.js');
+  const result = spawnSync(process.execPath, [
+    '--test',
+    '--experimental-test-coverage',
+    file,
+  ]);
+
+  const error = `Cannot find '${pathToFileURL(missing)}' imported from the source map for '${pathToFileURL(file)}'`;
+  assert(result.stdout.toString().includes(error));
+  assert.strictEqual(result.status, 1);
+});
+
 test('coverage with ESM hook - source irrelevant', skipIfNoInspector, () => {
   let report = [
     '# start of coverage report',
@@ -487,24 +502,25 @@ test('coverage with included and excluded files', skipIfNoInspector, () => {
 });
 
 test('properly accounts for line endings in source maps', skipIfNoInspector, () => {
-  const fixture = fixtures.path('test-runner', 'source-map-line-lengths', 'index.js');
+  const fixture = fixtures.path('test-runner', 'source-map', 'line-lengths', 'index.js');
   const args = [
     '--test', '--experimental-test-coverage', '--test-reporter', 'tap',
     fixture,
   ];
   const report = [
     '# start of coverage report',
-    '# ----------------------------------------------------------------------------',
-    '# file                        | line % | branch % | funcs % | uncovered lines',
-    '# ----------------------------------------------------------------------------',
-    '# test                        |        |          |         | ',
-    '#  fixtures                   |        |          |         | ',
-    '#   test-runner               |        |          |         | ',
-    '#    source-map-line-lengths  |        |          |         | ',
-    '#     index.ts                | 100.00 |   100.00 |  100.00 | ',
-    '# ----------------------------------------------------------------------------',
-    '# all files                   | 100.00 |   100.00 |  100.00 | ',
-    '# ----------------------------------------------------------------------------',
+    '# ------------------------------------------------------------------',
+    '# file              | line % | branch % | funcs % | uncovered lines',
+    '# ------------------------------------------------------------------',
+    '# test              |        |          |         | ',
+    '#  fixtures         |        |          |         | ',
+    '#   test-runner     |        |          |         | ',
+    '#    source-map     |        |          |         | ',
+    '#     line-lengths  |        |          |         | ',
+    '#      index.ts     | 100.00 |   100.00 |  100.00 | ',
+    '# ------------------------------------------------------------------',
+    '# all files         | 100.00 |   100.00 |  100.00 | ',
+    '# ------------------------------------------------------------------',
     '# end of coverage report',
   ].join('\n');