[VM Service] Fix Windows expression evaluation type crash in experimental service

Correctly define `kRootLibraryUri` constant and forward `rootLibraryUri`
to the resident frontend compiler.

TAG=agy
CONV=ae3a29f5-e2c8-499c-b221-ff61e40f5f1f

Change-Id: Ie4c87857744d9b32165ea7d0f8004d6d6c337886
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/505161
Auto-Submit: Ben Konyi <bkonyi@google.com>
Reviewed-by: Nicholas Shahan <nshahan@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dart_runtime_service_vm/lib/src/vm_expression_evaluator.dart

@@ -53,6 +53,7 @@ final class VmExpressionEvaluator extends ExpressionEvaluator {
   static const kKlass = 'klass';
   static const kMethod = 'method';
   static const kScriptUri = 'scriptUri';
+  static const kRootLibraryUri = 'rootLibraryUri';
 
   // Keys for scope response.
   static const kParamNames = 'param_names';
@@ -250,6 +251,7 @@ final class VmExpressionEvaluator extends ExpressionEvaluator {
         offset: scope[kTokenPos] as int,
         scriptUri: scriptUri,
         isStatic: isStatic,
+        rootLibraryUri: scope[kRootLibraryUri] as String?,
         serverInfoFile: backend.residentCompilerInfoFile!,
       );
       return {kKernelBytes: result.kernelBytes};

pkg/frontend_server/lib/resident_frontend_server_utils.dart

@@ -247,6 +247,7 @@ Future<CompileExpressionResult> invokeCompileExpression({
   required int offset,
   required String? scriptUri,
   required bool isStatic,
+  String? rootLibraryUri,
   required File serverInfoFile,
 }) async {
   final Map<String, Object?> response = await sendAndReceiveResponse(
@@ -264,6 +265,7 @@ Future<CompileExpressionResult> invokeCompileExpression({
       'offset': offset,
       if (scriptUri != null) 'scriptUri': scriptUri,
       'isStatic': isStatic,
+      if (rootLibraryUri != null) 'rootLibraryUri': rootLibraryUri,
       'useCachedCompilerOptionsAsBase': true,
     }),
     serverInfoFile,

pkg/frontend_server/lib/src/resident_frontend_server.dart

@@ -48,6 +48,22 @@ extension on DateTime {
   }
 }
 
+/// Safely converts [maybeUri] to a local file path.
+///
+/// Returns [maybeUri] as-is if it is already a raw path (e.g. `C:\foo.dart`
+/// or `/foo.dart`) or a non-file URI. This avoids crashes on Windows where
+/// drive letters (like `C:`) are incorrectly interpreted as URI schemes by
+/// [Uri.parse].
+String _maybeUriToFilename(String maybeUri) {
+  final Uri? uri = Uri.tryParse(maybeUri);
+  if (uri != null && (uri.scheme == 'file' || uri.scheme == '')) {
+    try {
+      return uri.toFilePath();
+    } catch (_) {}
+  }
+  return maybeUri;
+}
+
 enum _ResidentState { waitingForFirstCompile, compiling, waitingForRecompile }
 
 /// A wrapper around the FrontendCompiler, along with all the state needed
@@ -520,16 +536,16 @@ class ResidentFrontendServer {
         // evaluation is taking place to compute [canonicalizedLibraryPath]
         // instead.
         canonicalizedLibraryPath = path.canonicalize(
-          Uri.parse(request[_rootLibraryUriString]).toFilePath(),
+          _maybeUriToFilename(request[_rootLibraryUriString]),
         );
       } else {
         canonicalizedLibraryPath = path.canonicalize(
-          Uri.parse(request[_libraryUriString]).toFilePath(),
+          _maybeUriToFilename(request[_libraryUriString]),
         );
       }
-    } catch (e) {
+    } catch (e, st) {
       return _encodeErrorMessage(
-        "Request contains invalid '$_libraryUriString' property",
+        "Request contains invalid '$_libraryUriString' property: $e\n$st",
       );
     }