Support 'dart.library.X' env variables in the VM.

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 "lib/stacktrace.h"
@@ skipping 4927 matching lines @@
   Isolate* isolate = arguments->thread()->isolate();
   ASSERT(isolate == Isolate::Current());
   ASSERT(isolate->api_state() != NULL &&
          (isolate->api_state()->IsValidWeakPersistentHandle(rval)));
 #endif
   Api::SetWeakHandleReturnValue(arguments, rval);
 }
 
 
 // --- Environment ---
+RawString* Api::GetEnvironmentValue(Thread* thread, const String& name) {
+  String& result = String::Handle(CallEnvironmentCallback(thread, name));
+  if (result.IsNull()) {
+    // Every 'dart:X' library introduces an environment variable

[rmacnak, 2016/02/05 00:38:46]

Presumably we want these to answer false.
  dart.library._internal
  dart.library._builtin
  dart.library._blink

[Ivan Posva, 2016/02/05 01:10:53]

That is a very good point. Any private dart: library should be hidden by
default.

[floitsch, 2016/02/08 16:49:12]

Done.

+    // 'dart.library.X' that is set to 'true'.
+    const String& prefix = Symbols::DartLibrary();

[rmacnak, 2016/02/05 00:38:46]

if (!FLAG_enable_mirrors && name == "dart.library.mirrors")
  return false;

[floitsch, 2016/02/08 16:49:13]

Done.

+    if (name.StartsWith(prefix)) {
+      const String& library_name =
+          String::Handle(String::SubString(name, prefix.Length()));
+      if (!library_name.IsNull()) {
+        const String& dart_library_name =
+            String::Handle(String::Concat(Symbols::DartScheme(), library_name));
+        const Library& library =
+            Library::Handle(Library::LookupLibrary(dart_library_name));
+        if (!library.IsNull()) {
+          return Symbols::True().raw();
+        }
+      }
+    }
+    // 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();
+}
+
+
 RawString* Api::CallEnvironmentCallback(Thread* thread, const String& name) {
   Isolate* isolate = thread->isolate();
   Dart_EnvironmentCallback callback = isolate->environment_callback();
   String& result = String::Handle(thread->zone());
   if (callback != NULL) {
     TransitionVMToNative transition(thread);
     Scope api_scope(thread);
     Dart_Handle response = callback(Api::NewHandle(thread, name.raw()));
     if (::Dart_IsString(response)) {
       result ^= Api::UnwrapHandle(response);
     } else if (::Dart_IsError(response)) {
       const Object& error = Object::Handle(
           thread->zone(), 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();
@@ skipping 1112 matching lines @@
   return Api::Success();
 }
 #endif  // DART_PRECOMPILER
 
 
 DART_EXPORT bool Dart_IsRunningPrecompiledCode() {
   return Dart::IsRunningPrecompiledCode();
 }
 
 }  // namespace dart