Steps towards making dart2js JS AST templates an indepentent library.

pkg/compiler/lib/src/js/js.dart

Index: pkg/compiler/lib/src/js/js.dart
diff --git a/pkg/compiler/lib/src/js/js.dart b/pkg/compiler/lib/src/js/js.dart
index fac460db21e1eb06b98edb6564ef455db4cc36a8..0e17ab9ffff7c6ba89b964e8edf2bf4740451c9a 100644
--- a/pkg/compiler/lib/src/js/js.dart
+++ b/pkg/compiler/lib/src/js/js.dart
@@ -1,23 +1,64 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// 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 js;
 
-import 'precedence.dart';
-import '../util/characters.dart' as charCodes;
-import '../util/util.dart';
+// TODO(sra): This will become a package import.
+import 'js_ast.dart';
+export 'js_ast.dart';
+
 import '../io/code_output.dart' show CodeBuffer;
 import '../io/source_information.dart' show SourceInformation;
 import '../js_emitter/js_emitter.dart' show USE_NEW_EMITTER;
-
-// TODO(floitsch): remove this dependency (currently necessary for the
-// CodeBuffer).
 import '../dart2jslib.dart' as leg;
+import '../util/util.dart' show NO_LOCATION_SPANNABLE;
+import '../dump_info.dart' show DumpInfoTask;
+
+
+CodeBuffer prettyPrint(Node node, leg.Compiler compiler,
+                       {DumpInfoTask monitor,
+                        bool allowVariableMinification: true}) {
+  JavaScriptPrintingOptions options = new JavaScriptPrintingOptions(
+      shouldCompressOutput: compiler.enableMinification,
+      minifyLocalVariables: allowVariableMinification,
+      preferSemicolonToNewlineInMinifiedOutput: USE_NEW_EMITTER);
+  Dart2JSJavaScriptPrintingContext context =
+      new Dart2JSJavaScriptPrintingContext(compiler, monitor);
+  Printer printer = new Printer(options, context);
+  printer.visit(node);
+  return context.outBuffer;
+}
+
+class Dart2JSJavaScriptPrintingContext extends JavaScriptPrintingContext {

[floitsch, 2015/02/11 16:01:13]

I'm not sure I like this.

The JavaScriptPrintingContext has a buffer field that has a StringBuffer. That
one seems to be unused now.

I wouldn't feel comfortable that I caught all overloads where I have to replace
"buffer" with "outBuffer". That is, if we add an "emitAll" to the
JavaScriptPrintingContext that does buffer.addAll(strings) we would silently
break this class.

I would rather make JavaScriptPrintingContext an interface and remove the
"buffer" from it.

[sra1, 2015/02/11 18:20:19]

I agree.

JavaScriptPrintingContext *is* the interface you desire.

SimpleJavaScriptPrintingContext, not used here, is the class with a buffer. It
is used from a test and presumably a new client of the library.

Since all dummy methods are overridden, I have changed 'extends' to
'implements'.

+  final leg.Compiler compiler;
+  final DumpInfoTask monitor;
+  final CodeBuffer outBuffer = new CodeBuffer();
+
+  Dart2JSJavaScriptPrintingContext(leg.Compiler this.compiler,
+      DumpInfoTask this.monitor);
+
+  void error(String message) {
+    compiler.internalError(NO_LOCATION_SPANNABLE, message);
+  }
+
+  void emit(String string) {
+    outBuffer.add(string);
+  }
 
-import '../dump_info.dart';
+  void enterNode(Node node) {
+    SourceInformation sourceInformation = node.sourceInformation;
+    if (sourceInformation != null) {
+      sourceInformation.beginMapping(outBuffer);
+    }
+    if (monitor != null) monitor.enteringAst(node, outBuffer.length);
+  }
 
-part 'nodes.dart';
-part 'builder.dart';
-part 'printer.dart';
-part 'template.dart';
+  void exitNode(Node node) {
+    if (monitor != null) monitor.exitingAst(node, outBuffer.length);
+    SourceInformation sourceInformation = node.sourceInformation;
+    if (sourceInformation != null) {
+      sourceInformation.endMapping(outBuffer);
+    }
+  }
+}