- Refactor the way X.fromEnvironment is implemented.

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
@@ skipping 4703 matching lines @@
   ASSERT(isolate == Isolate::Current());
   ASSERT(isolate->api_state() != NULL &&
          (isolate->api_state()->IsValidWeakPersistentHandle(rval) ||
           isolate->api_state()->IsValidPrologueWeakPersistentHandle(rval)));
 #endif
   Api::SetWeakHandleReturnValue(arguments, rval);
 }
 
 
 // --- Environment ---
+RawString* Api::CallEnvironmentCallback(Isolate* isolate, const String& name) {
+  Scope api_scope(isolate);
+  Dart_EnvironmentCallback callback = isolate->environment_callback();
+  String& result = String::Handle(isolate);
+  if (callback != NULL) {
+    Dart_Handle response = callback(Api::NewHandle(isolate, name.raw()));
+    if (::Dart_IsString(response)) {
+      result ^= Api::UnwrapHandle(response);
+    } else if (::Dart_IsError(response)) {
+      const Object& error =
+          Object::Handle(isolate, Api::UnwrapHandle(response));
+      Exceptions::ThrowArgumentError(
+          String::Handle(String::New(Error::Cast(error).ToErrorCString())));
+    } else if (!::Dart_IsNull(response)) {
+      // At this point everything except null are invalid environment values.
+      Exceptions::ThrowArgumentError(
+          String::Handle(String::New("Illegal environment value")));
+    }
+  }
+  if (result.IsNull()) {
+    // TODO(iposva): Determine whether builtin values can be overriden by the
+    // embedder.
+    // Check for default VM provided values. If it was not overriden on the
+    // command line.
+    if (Symbols::DartIsVM().Equals(name)) {
+      return Symbols::True().raw();
+    }
+  }
+  return result.raw();
+}
+
+
 DART_EXPORT Dart_Handle Dart_SetEnvironmentCallback(
     Dart_EnvironmentCallback callback) {
   Isolate* isolate = Isolate::Current();
   CHECK_ISOLATE(isolate);
   isolate->set_environment_callback(callback);
   return Api::Success();
 }
 
 
 // --- Scripts and Libraries ---
@@ skipping 621 matching lines @@
 
 
 DART_EXPORT void Dart_RegisterRootServiceRequestCallback(
     const char* name,
     Dart_ServiceRequestCallback callback,
     void* user_data) {
   Service::RegisterRootEmbedderCallback(name, callback, user_data);
 }
 
 }  // namespace dart