Fixing layout in js output (use full paths rather than just the library name)

lib/src/codegen/js_codegen.dart

 // Copyright (c) 2015, 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 ddc.src.codegen.js_codegen;
 
 import 'dart:io' show Directory, File;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/src/generated/ast.dart' hide ConstantEvaluator;
@@ skipping 1271 matching lines @@
   visitThrowExpression(ThrowExpression node) {
     var expr = _visit(node.expression);
     if (node.parent is ExpressionStatement) {
       return js.statement('throw #;', expr);
     } else {
       return js.call('dart.throw_(#)', expr);
     }
   }
 
   @override
-  visitRethrowExpression(RethrowExpression node){
+  visitRethrowExpression(RethrowExpression node) {
     if (node.parent is ExpressionStatement) {
       return js.statement('throw #;', _catchParameter);
     } else {
       return js.call('dart.throw_(#)', _catchParameter);
     }
   }
 
   @override
   JS.If visitIfStatement(IfStatement node) {
     return new JS.If(_visit(node.condition), _visit(node.thenStatement),
@@ skipping 437 matching lines @@
   final JSCodeOptions options;
 
   JSGenerator(String outDir, Uri root, TypeRules rules, this.options)
       : super(outDir, root, rules);
 
   void generateLibrary(Iterable<CompilationUnit> units, LibraryInfo info,
       CheckerReporter reporter) {
     JS.Block jsTree =
         new JSCodegenVisitor(info, rules).generateLibrary(units, reporter);
 
-    var outputPath = path.join(outDir, jsOutputPath(info));
+    var outputPath = path.join(outDir, jsOutputPath(info, root));
     new Directory(path.dirname(outputPath)).createSync(recursive: true);
 
     if (options.emitSourceMaps) {
       var outFilename = path.basename(outputPath);
       var printer = new srcmaps.Printer(outFilename);
       var context =
           new SourceMapPrintingContext(printer, path.dirname(outputPath));
       _writeLibrary(context, jsTree);
       printer.add('//# sourceMappingURL=$outFilename.map');
       // Write output file and source map
@@ skipping 21 matching lines @@
   new JS.Printer(opts, context).visit(node);
   // Write output file and source map
   return context.getText();
 }
 
 /// Choose a canonical name from the library element.
 /// This never uses the library's name (the identifier in the `library`
 /// declaration) as it doesn't have any meaningful rules enforced.
 String jsLibraryName(LibraryElement library) => canonicalLibraryName(library);
 
-/// Path to file that will be generated for [info].
-// TODO(jmesserly): library directory should be relative to its package
-// root. For example, "package:dev_compiler/src/codegen/js_codegen.dart" would be:
-// "ddc/src/codegen/js_codegen.js" under the output directory.
-String jsOutputPath(LibraryInfo info) => '${info.name}/${info.name}.js';
+/// Path to file that will be generated for [info]. In case it's url is a
+/// `file:` url, we use [root] to determine the relative path from the entry
+/// point file.
+String jsOutputPath(LibraryInfo info, Uri root) {
+  var uri = info.library.source.uri;
+  var filepath = '${path.withoutExtension(uri.path)}.js';
+  if (uri.scheme == 'dart') {
+    filepath = 'dart/$filepath';
+  } else if (uri.scheme == 'file') {
+    filepath = path.relative(filepath, from: path.dirname(root.path));
+  } else {
+    assert(uri.scheme == 'package');
+    // filepath is good here, we want the output to start with a directory
+    // matching the package name.
+  }
+  return filepath;
+}
 
 class SourceMapPrintingContext extends JS.JavaScriptPrintingContext {
   final srcmaps.Printer printer;
   final String outputDir;
 
   CompilationUnit unit;
   Uri uri;
 
   SourceMapPrintingContext(this.printer, this.outputDir);
 
@@ skipping 45 matching lines @@
 
     // TODO(jmesserly): in many cases marking the end will be unncessary.
     printer.mark(_location(node.end));
   }
 
   String _getIdentifier(AstNode node) {
     if (node is SimpleIdentifier) return node.name;
     return null;
   }
 }