Support source maps in server mode

lib/src/codegen/js_printer.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 dev_compiler.src.codegen.js_printer;
 
 import 'dart:convert' show JSON, JsonEncoder;
 import 'dart:io' show Directory, File, Platform, Process;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:path/path.dart' as path;
 import 'package:source_maps/source_maps.dart' as srcmaps show Printer;
 import 'package:source_maps/source_maps.dart' show SourceMapSpan;
 import 'package:source_span/source_span.dart' show SourceLocation;
 
 import '../js/js_ast.dart' as JS;
 import '../utils.dart' show computeHash, locationForOffset;
 
 import 'js_names.dart' show TemporaryNamer;
 
-String writeJsLibrary(JS.Program jsTree, String outputPath,
+String writeJsLibrary(
+    JS.Program jsTree, String outputPath, String inputDir, Uri serverUri,
     {bool emitSourceMaps: false, bool arrowFnBindThisWorkaround: false}) {
   var outFilename = path.basename(outputPath);
   var outDir = path.dirname(outputPath);
   new Directory(outDir).createSync(recursive: true);
 
   JS.JavaScriptPrintingContext context;
   if (emitSourceMaps) {
     var printer = new srcmaps.Printer(outFilename);
-    context = new SourceMapPrintingContext(printer, outDir);
+    context =
+        new SourceMapPrintingContext(printer, outDir, inputDir, serverUri);
   } else {
     context = new JS.SimpleJavaScriptPrintingContext();
   }
 
   var opts = new JS.JavaScriptPrintingOptions(
       allowKeywordsInProperties: true,
       allowSingleLineIfStatements: true,
       arrowFnBindThisWorkaround: arrowFnBindThisWorkaround);
   var jsNamer = new TemporaryNamer(jsTree);
   jsTree.accept(new JS.Printer(opts, context, localNamer: jsNamer));
@@ skipping 25 matching lines @@
     // TODO(jmesserly): should only do this if the input file was executable?
     if (!Platform.isWindows) Process.runSync('chmod', ['+x', outputPath]);
   }
 
   return computeHash(text);
 }
 
 class SourceMapPrintingContext extends JS.JavaScriptPrintingContext {
   final srcmaps.Printer printer;
   final String outputDir;
+  final String inputDir;
+
+  // TODO(vsm): we could abstract this out and have a generic Uri mapping
+  // instead of hardcoding a notion of a server uri.
+  final Uri serverUri;
 
   CompilationUnit unit;
   Uri uri;
 
-  SourceMapPrintingContext(this.printer, this.outputDir);
+  SourceMapPrintingContext(
+      this.printer, this.outputDir, this.inputDir, this.serverUri);
 
   void emit(String string) {
     printer.add(string);
   }
 
   AstNode _currentTopLevelDeclaration;
 
   void enterNode(JS.Node jsNode) {
     AstNode node = jsNode.sourceInformation;
     if (node == null || node.offset == -1) return;
     if (unit == null) {
       // This is a top-level declaration.  Note: consecutive top-level
       // declarations may come from different compilation units due to
       // parts.
       _currentTopLevelDeclaration = node;
       unit = node.getAncestor((n) => n is CompilationUnit);
       uri = _makeRelativeUri(unit.element.source.uri);
     }
+    if (unit == null) return;
 
     assert(unit != null);
     var loc = _location(node.offset);
     var name = _getIdentifier(node);
     if (name != null) {
       // TODO(jmesserly): mark only uses the beginning of the span, but
       // we're required to pass this as a valid span.
       var end = _location(node.end);
       printer.mark(new SourceMapSpan(loc, end, name, isIdentifier: true));
     } else {
       printer.mark(loc);
     }
   }
 
   SourceLocation _location(int offset) =>
       locationForOffset(unit.lineInfo, uri, offset);
 
   Uri _makeRelativeUri(Uri src) {
-    return new Uri(path: path.relative(src.path, from: outputDir));
+    if (serverUri == null) {
+      return new Uri(path: path.relative(src.path, from: outputDir));
+    } else {
+      if (src.path.startsWith('/')) {
+        return serverUri.resolve(path.relative(src.path, from: inputDir));
+      } else {
+        return serverUri.resolve(path.join('packages', src.path));
+      }
+    }
   }
 
   void exitNode(JS.Node jsNode) {
     AstNode node = jsNode.sourceInformation;
     if (unit == null || node == null || node.offset == -1) return;
 
     // TODO(jmesserly): in many cases marking the end will be unnecessary.
     printer.mark(_location(node.end));
 
     if (_currentTopLevelDeclaration == node) {
       unit = null;
       uri = null;
       _currentTopLevelDeclaration == null;
       return;
     }
   }
 
   String _getIdentifier(AstNode node) {
     if (node is SimpleIdentifier) return node.name;
     return null;
   }
 }