Remove stray lockfiles and packageconfigs from workspace

lib/src/entrypoint.dart

@@ -581,6 +581,8 @@ To update `$lockFilePath` run `$topLevelProgram pub get`$suffix without
     _lockFile = newLockFile;
 
     if (!dryRun) {
+      _removeStrayLockAndConfigFiles();
+
       /// Build a package graph from the version solver results so we don't
       /// have to reload and reparse all the pubspecs.
       _packageGraph = Future.value(PackageGraph.fromSolveResult(this, result));
@@ -1216,4 +1218,18 @@ See https://dart.dev/go/sdk-constraint
     }
     return true;
   }
+
+  /// Remove any `pubspec.lock` or `.dart_tool/package_config.json` files in
+  /// workspace packages that are not the root package.
+  ///
+  /// This is to avoid surprises if a package is turned into a workspace member
+  /// but still has an old package config or lockfile.
+  void _removeStrayLockAndConfigFiles() {
+    for (final package in workspaceRoot.transitiveWorkspace) {
+      if (package.pubspec.resolution == Resolution.workspace) {
+        deleteEntry(p.join(package.dir, 'pubspec.lock'));
+        deleteEntry(p.join(package.dir, '.dart_tool', 'package_config.json'));
+      }
+    }
+  }
 }

test/workspace_test.dart

@@ -259,4 +259,50 @@ void main() {
       output: contains('Resolving dependencies in `..`...'),
     );
   });
+
+  test('Removes lock files and package configs from workspace members',
+      () async {
+    await dir(appPath, [
+      libPubspec(
+        'myapp',
+        '1.2.3',
+        extras: {
+          'workspace': ['pkgs/a'],
+        },
+        sdk: '^3.7.0',
+      ),
+      dir('pkgs', [
+        dir(
+          'a',
+          [
+            libPubspec('a', '1.1.1', resolutionWorkspace: true),
+          ],
+        ),
+      ]),
+    ]).create();
+    final aDir = p.join(sandbox, appPath, 'pkgs', 'a');
+    final pkgsDir = p.join(sandbox, appPath, 'pkgs');
+    final strayLockFile = File(p.join(aDir, 'pubspec.lock'));
+    final strayPackageConfig =
+        File(p.join(aDir, '.dart_tool', 'package_config.json'));
+
+    final unmanagedLockFile = File(p.join(pkgsDir, 'pubspec.lock'));
+    final unmanagedPackageConfig =
+        File(p.join(pkgsDir, '.dart_tool', 'package_config.json'));
+    strayPackageConfig.createSync(recursive: true);
+    strayLockFile.createSync(recursive: true);
+
+    unmanagedPackageConfig.createSync(recursive: true);
+    unmanagedLockFile.createSync(recursive: true);
+
+    await pubGet(environment: {'_PUB_TEST_SDK_VERSION': '3.7.0'});
+
+    expect(strayLockFile.statSync().type, FileSystemEntityType.notFound);
+    expect(strayPackageConfig.statSync().type, FileSystemEntityType.notFound);
+
+    // We only delete stray files from directories that contain an actual
+    // package.
+    expect(unmanagedLockFile.statSync().type, FileSystemEntityType.file);
+    expect(unmanagedPackageConfig.statSync().type, FileSystemEntityType.file);
+  });
 }