[vm] Fix resolution of native extensions imported within packages.

We need to use the actual file URL of the importing library to find the extension library,
such as "file:///library/lib.dart" rather than the package URL (like "package:library/lib.dart").


Change-Id: I32a36f7a67321f356c9af34d1a458aeb122d0c24
Reviewed-on: https://dart-review.googlesource.com/71167
Commit-Queue: Samir Jindel <sjindel@google.com>
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>

runtime/bin/loader.cc

@@ -682,12 +682,15 @@ Dart_Handle Loader::LibraryTagHandler(Dart_LibraryTag tag,
     const char* path = DartUtils::RemoveScheme(url_string);
 
     const char* lib_uri = NULL;
-    result = Dart_StringToCString(Dart_LibraryUrl(library), &lib_uri);
+    result = Dart_StringToCString(Dart_LibraryResolvedUrl(library), &lib_uri);
     RETURN_ERROR(result);
 
+    UriDecoder decoder(lib_uri);
+    lib_uri = decoder.decoded();
+
     char* lib_path = NULL;
     if (strncmp(lib_uri, "file://", 7) == 0) {
-      lib_path = DartUtils::DirName(DartUtils::RemoveScheme(lib_uri));
+      lib_path = DartUtils::DirName(lib_uri + 7);
     } else {
       lib_path = strdup(lib_uri);
     }
@@ -699,7 +702,10 @@ Dart_Handle Loader::LibraryTagHandler(Dart_LibraryTag tag,
           path);
     }
 
-    return Extensions::LoadExtension(lib_path, path, library);
+    Dart_Handle result =
+        Extensions::LoadExtension(decoder.decoded(), path, library);
+    free(lib_path);
+    return result;
   }
   if (tag != Dart_kScriptTag) {
     // Special case for handling dart: imports and parts.

runtime/include/dart_api.h

@@ -3053,10 +3053,16 @@ DART_EXPORT Dart_Handle Dart_GetClass(Dart_Handle library,
  * of it are removed from the embedder code. */
 
 /**
- * Returns the url from which a library was loaded.
+ * Returns an import path to a Library, such as "file:///test.dart" or
+ * "dart:core".
  */
 DART_EXPORT Dart_Handle Dart_LibraryUrl(Dart_Handle library);
 
+/**
+ * Returns a URL from which a Library was loaded.
+ */
+DART_EXPORT Dart_Handle Dart_LibraryResolvedUrl(Dart_Handle library);
+
 /**
  * \return An array of libraries.
  */

runtime/vm/dart_api_impl.cc

@@ -5301,6 +5301,21 @@ DART_EXPORT Dart_Handle Dart_LibraryUrl(Dart_Handle library) {
   return Api::NewHandle(T, url.raw());
 }
 
+DART_EXPORT Dart_Handle Dart_LibraryResolvedUrl(Dart_Handle library) {
+  DARTSCOPE(Thread::Current());
+  const Library& lib = Api::UnwrapLibraryHandle(Z, library);
+  if (lib.IsNull()) {
+    RETURN_TYPE_ERROR(Z, library, Library);
+  }
+  const Class& toplevel = Class::Handle(lib.toplevel_class());
+  ASSERT(!toplevel.IsNull());
+  const Script& script = Script::Handle(toplevel.script());
+  ASSERT(!script.IsNull());
+  const String& url = String::Handle(script.resolved_url());
+  ASSERT(!url.IsNull());
+  return Api::NewHandle(T, url.raw());
+}
+
 DART_EXPORT Dart_Handle Dart_GetLoadedLibraries() {
   DARTSCOPE(Thread::Current());
   Isolate* I = T->isolate();