Support Dart core libraries in source maps.

sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart

 // 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.
 
 library pub.dart2js_transformer;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 167 matching lines @@
   }
 }
 
 /// Defines an interface for dart2js to communicate with barback and pub.
 ///
 /// Note that most of the implementation of diagnostic handling here was
 /// copied from [FormattingDiagnosticHandler] in dart2js. The primary
 /// difference is that it uses barback's logging code and, more importantly, it
 /// handles missing source files more gracefully.
 class _BarbackCompilerProvider implements dart.CompilerProvider {
+  Uri get libraryRoot => Uri.parse("${path.toUri(_libraryRootPath)}/");
+
   final BuildEnvironment _environment;
   final Transform _transform;
+  String _libraryRootPath;
 
   /// The map of previously loaded files.
   ///
   /// Used to show where an error occurred in a source file.
   final _sourceFiles = new Map<String, SourceFile>();
 
   // TODO(rnystrom): Make these configurable.
   /// Whether or not warnings should be logged.
   var _showWarnings = true;
 
@@ skipping 15 matching lines @@
   compiler.Diagnostic _lastKind = null;
 
   static final int _FATAL =
       compiler.Diagnostic.CRASH.ordinal |
       compiler.Diagnostic.ERROR.ordinal;
   static final int _INFO =
       compiler.Diagnostic.INFO.ordinal |
       compiler.Diagnostic.VERBOSE_INFO.ordinal;
 
   _BarbackCompilerProvider(this._environment, this._transform,
-      {this.generateSourceMaps: true});
+      {this.generateSourceMaps: true}) {
+    // Dart2js outputs source maps that reference the Dart SDK sources. For
+    // that to work, those sources need to be inside the build environment. We
+    // do that by placing them in a special "$sdk" pseudo-package. In order for
+    // dart2js to generate the right URLs to point to that package, we give it
+    // a library root that corresponds to where that package can be found
+    // relative to the public build directory containing that entrypoint.
+    //
+    // For example, say the package being compiled is "/dev/myapp", the
+    // entrypoint is "web/sub/foo/bar.dart", and the build directory is
+    // "web/sub". This means the SDK sources will be (conceptually) at:
+    //
+    //     /dev/myapp/web/sub/packages/$sdk/lib/
+    //
+    // This implies that the asset path for a file in the SDK is:
+    //
+    //     $sdk|lib/lib/...
+    //
+    // TODO(rnystrom): Fix this if $17751 is fixed.

[nweiz, 2014/03/24 23:17:14]

"$" -> "#"

[Bob Nystrom, 2014/03/25 00:49:27]

Done.

+    var buildDir = _environment.getBuildDirectoryContaining(
+        _transform.primaryInput.id.path);
+    _libraryRootPath = path.join(_environment.rootPackage.dir,
+        buildDir, "packages", r"$sdk");
+  }
 
   /// A [CompilerInputProvider] for dart2js.
   Future<String> provideInput(Uri resourceUri) {
     // We only expect to get absolute "file:" URLs from dart2js.
     assert(resourceUri.isAbsolute);
     assert(resourceUri.scheme == "file");
 
     var sourcePath = path.fromUri(resourceUri);
     return _readResource(resourceUri).then((source) {
       _sourceFiles[resourceUri.toString()] =
@@ skipping 86 matching lines @@
       }
     }
 
     if (fatal && _throwOnError) {
       _isAborting = true;
       throw new AbortLeg(message);
     }
   }
 
   Future<String> _readResource(Uri url) {
-    // See if the path is within a package. If so, use Barback so we can use
-    // generated Dart assets.
-
+    // Find the corresponding asset in barback.
     var id = _sourceUrlToId(url);
     if (id != null) return _transform.readInputAsString(id);
 
-    // If we get here, the path doesn't appear to be in a package, so we'll
-    // skip Barback and just hit the file system. This will occur at the very
-    // least for dart2js's implementations of the core libraries.
+    // If we get here, the path doesn't appear to be in any package, so we'll
+    // skip Barback and just hit the file system. This will only occur for
+    // absolute file paths in imports that don't touch a package.
     var sourcePath = path.fromUri(url);
     return Chain.track(new File(sourcePath).readAsString());
   }
 
   AssetId _sourceUrlToId(Uri url) {
     // See if it's a special path with "packages" or "assets" in it.
     var id = specialUrlToId(url);
     if (id != null) return id;
 
     // See if it's a path to a "public" asset within the root package. All
@@ skipping 11 matching lines @@
   }
 }
 
 /// An [EventSink] that discards all data. Provided to dart2js when we don't
 /// want an actual output.
 class NullSink<T> implements EventSink<T> {
   void add(T event) {}
   void addError(errorEvent, [StackTrace stackTrace]) {}
   void close() {}
 }