fix: resolve dart coverage package_config in pub workspaces

lib/src/cli/test_cli_runner.dart

@@ -198,25 +198,35 @@ class TestCLIRunner {
                     p.join(cwd, 'coverage'),
                   );
 
-                  final packagesPath = p.join(
-                    '.dart_tool',
-                    'package_config.json',
-                  );
+                  // Resolve package_config.json the way dart does: start at
+                  // the package cwd and walk up. In a pub workspace the file
+                  // lives at the workspace root, not in the member package.
+                  //
+                  // Canonicalize cwd first. On Windows the temp/workspace
+                  // directory is often a junction, and package:coverage
+                  // resolves files through that real path. reportOn: ['lib']
+                  // is canonicalized against the unresolved cwd, so the
+                  // prefix check drops every file and lcov comes out empty.
+                  final resolvedCwd = Directory(cwd).resolveSymbolicLinksSync();
+                  final resolvedReportOn = [
+                    for (final path in reportOn ?? ['lib'])
+                      p.isAbsolute(path) ? path : p.join(resolvedCwd, path),
+                  ];
+
                   final hitmap = await coverage.HitMap.parseFiles(
                     files,
-                    packagePath: packagesPath,
+                    packagePath: resolvedCwd,
                     checkIgnoredLines: checkIgnore,
                   );
 
                   final resolver = await coverage.Resolver.create(
-                    packagesPath: packagesPath,
-                    packagePath: packagesPath,
+                    packagePath: resolvedCwd,
                   );
 
                   final output = hitmap.formatLcov(
                     resolver,
-                    reportOn: reportOn ?? ['lib'],
-                    basePath: cwd,
+                    reportOn: resolvedReportOn,
+                    basePath: resolvedCwd,
                   );
 
                   // Write the lcov output to the file.

test/src/cli/test_cli_runner_test.dart

@@ -778,6 +778,73 @@ void main() {
         expect(testRunnerArgs, equals(['--coverage=coverage']));
       });
 
+      test(
+        'resolves dart coverage package_config from the pub workspace root',
+        () async {
+          final workspaceRoot = Directory.systemTemp.createTempSync();
+          addTearDown(() => workspaceRoot.deleteSync(recursive: true));
+
+          final member = Directory(
+            p.join(workspaceRoot.path, 'packages', 'foo'),
+          )..createSync(recursive: true);
+          File(p.join(member.path, 'pubspec.yaml')).createSync();
+          Directory(p.join(member.path, 'test')).createSync();
+          File(p.join(member.path, 'lib', 'foo.dart'))
+            ..createSync(recursive: true)
+            ..writeAsStringSync('void foo() {}');
+
+          // Pub workspaces only write package_config.json at the root.
+          File(p.join(workspaceRoot.path, '.dart_tool', 'package_config.json'))
+            ..createSync(recursive: true)
+            ..writeAsStringSync(
+              '{"configVersion":2,"packages":['
+              '{"name":"foo","rootUri":"../packages/foo","packageUri":"lib/"}'
+              ']}',
+            );
+
+          File(p.join(member.path, 'coverage', 'coverage.json'))
+            ..createSync(recursive: true)
+            ..writeAsStringSync(
+              '{"coverage":[{"source":"package:foo/foo.dart","hits":[1,1]}]}',
+            );
+
+          final lcovFile = File(p.join(member.path, 'coverage', 'lcov.info'));
+
+          final originalCwd = Directory.current;
+          addTearDown(() => Directory.current = originalCwd);
+          Directory.current = member;
+
+          await expectLater(
+            TestCLIRunner.test(
+              testType: TestRunType.dart,
+              cwd: member.path,
+              collectCoverage: true,
+              stdout: stdoutLogs.add,
+              stderr: stderrLogs.add,
+              overrideTestRunner: testRunner(
+                Stream.fromIterable([
+                  const DoneTestEvent(success: true, time: 0),
+                  const ExitTestEvent(exitCode: 0, time: 0),
+                ]),
+              ),
+              logger: logger,
+            ),
+            completion(equals([ExitCode.success.code])),
+          );
+          expect(
+            File(
+              p.join(member.path, '.dart_tool', 'package_config.json'),
+            ).existsSync(),
+            isFalse,
+          );
+          expect(lcovFile.existsSync(), isTrue);
+          expect(
+            lcovFile.readAsStringSync(),
+            contains('SF:${p.join('lib', 'foo.dart')}'),
+          );
+        },
+      );
+
       test('runs dart tests w/coverage and checkIgnore', () async {
         final tempDirectory = Directory.systemTemp.createTempSync();
         addTearDown(() => tempDirectory.deleteSync(recursive: true));