dart2js: Add a header to the output of the startup emitter.

pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.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 dart2js.js_emitter.startup_emitter.model_emitter;
 
 import 'dart:convert' show JsonEncoder;
 
 import '../../common.dart';
 
@@ skipping 16 matching lines @@
     JavaScriptBackend,
     Namer,
     ConstantEmitter;
 
 import '../../util/util.dart' show
     NO_LOCATION_SPANNABLE;
 
 import '../../util/uri_extras.dart' show
     relativize;
 
+import '../headers.dart';
 import '../js_emitter.dart' show AstContainer, NativeEmitter;
 
 import 'package:js_runtime/shared/embedded_names.dart' show
     CLASS_FIELDS_EXTRACTOR,
     CLASS_ID_EXTRACTOR,
     CREATE_NEW_ISOLATE,
     DEFERRED_INITIALIZED,
     DEFERRED_LIBRARY_URIS,
     DEFERRED_LIBRARY_HASHES,
     GET_TYPE_FROM_NAME,
@@ skipping 164 matching lines @@
 
     if (compiler.deferredMapUri != null) {
       writeDeferredMap();
     }
     
     // Return the total program size.
     return outputBuffers.values.fold(0, (a, b) => a + b.length);
   }
 
   /// Generates a simple header that provides the compiler's build id.
-  String buildGeneratedBy(compiler) {
-    var suffix = '';
-    if (compiler.hasBuildId) suffix = ' version: ${compiler.buildId}';
-    return '// Generated by dart2js (fast startup), '
-        'the Dart to JavaScript compiler$suffix.\n';
+  String buildGeneratedBy() {
+    return new jsAst.Comment(generatedBy(compiler));

[Siggi Cherem (dart-lang), 2015/08/04 16:42:48]

should we add an argument to generatedBy so we can indicate which emitter we
used? (we used to have the "(fast startup)" as part of this header before).
Another idea is to print out all the flags/options in the header.

[floitsch, 2015/08/05 11:46:50]

I added a 'flavor' argument to 'generatedBy'. That should bring us back to what
we had before. (Even more, since I take mirrors and CSP into account).
I think we don't want to print *all* options, but it is an option, and I
wouldn't be entirely against it. Up to you.

[Siggi Cherem (dart-lang), 2015/08/05 15:53:36]

I have a feeling that all flags might be too noisy too, but there might be some
others for which it may be useful (e.g. trust-type-annotations). We don't need
to add them now.

   }
 
   /// Writes all deferred fragment's code into files.
   ///
   /// Returns a map from fragment to its hashcode (as used for the deferred
   /// library code).
   ///
   /// Updates the shared [outputBuffers] field with the output.
   Map<DeferredFragment, String> writeDeferredFragments(
       Map<DeferredFragment, js.Expression> fragmentsCode) {
@@ skipping 15 matching lines @@
     if (shouldGenerateSourceMap) {
       lineColumnCollector = new LineColumnCollector();
       codeOutputListeners = <CodeOutputListener>[lineColumnCollector];
     }
 
     CodeOutput mainOutput = new StreamCodeOutput(
             compiler.outputProvider('', 'js'),
             codeOutputListeners);
     outputBuffers[fragment] = mainOutput;
 
-    mainOutput.addBuffer(js.prettyPrint(code, compiler,
+    js.Program program = new js.Program([
+        new js.Comment(generatedBy(compiler)),
+        new js.Comment(HOOKS_API_USAGE),
+        code]);
+
+    mainOutput.addBuffer(js.prettyPrint(program, compiler,
         monitor: compiler.dumpInfoTask));
 
     if (shouldGenerateSourceMap) {
       mainOutput.add(
           generateSourceMapTag(compiler.sourceMapUri, compiler.outputUri));
     }
 
     mainOutput.close();
 
     if (shouldGenerateSourceMap) {
@@ skipping 28 matching lines @@
 
     // The [code] contains the function that must be invoked when the deferred
     // hunk is loaded.
     // That function must be in a map from its hashcode to the function. Since
     // we don't know the hash before we actually emit the code we store the
     // function in a temporary field first:
     //
     //   deferredInitializer.current = <pretty-printed code>;
     //   deferredInitializer[<hash>] = deferredInitializer.current;
 
-    output.add('\n${deferredInitializersGlobal}.current = ');
+    js.Program program = new js.Program([
+        new js.Comment(generatedBy(compiler)),
+        js.js.statement('$deferredInitializersGlobal.current = #', code)]);
 
-    output.addBuffer(js.prettyPrint(code, compiler,
+    output.addBuffer(js.prettyPrint(program, compiler,
         monitor: compiler.dumpInfoTask));
 
     // Make a unique hash of the code (before the sourcemaps are added)
     // This will be used to retrieve the initializing function from the global
     // variable.
     String hash = hasher.getHash();
 
     // Now we copy the deferredInitializer.current into its correct hash.
     output.add('\n${deferredInitializersGlobal}["$hash"] = '
         '${deferredInitializersGlobal}.current');
@@ skipping 66 matching lines @@
     // Json does not support comments, so we embed the explanation in the
     // data.
     mapping["_comment"] = "This mapping shows which compiled `.js` files are "
         "needed for a given deferred library import.";
     mapping.addAll(compiler.deferredLoadTask.computeDeferredMap());
     compiler.outputProvider(compiler.deferredMapUri.path, 'deferred_map')
       ..add(const JsonEncoder.withIndent("  ").convert(mapping))
       ..close();
   }
 }