Support generating inlined source maps and wrapping module contents within a JavaScript eval block …

pkg/dev_compiler/lib/src/compiler/compiler.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:collection' show HashSet, Queue;
-import 'dart:convert' show JSON;
+import 'dart:convert' show BASE64, JSON, UTF8;
 import 'dart:io' show File;
 import 'package:analyzer/dart/element/element.dart' show LibraryElement;
 import 'package:analyzer/analyzer.dart'
     show AnalysisError, CompilationUnit, ErrorSeverity;
 import 'package:analyzer/file_system/file_system.dart' show ResourceProvider;
 import 'package:analyzer/src/generated/engine.dart' show AnalysisContext;
 import 'package:analyzer/src/generated/source.dart' show DartUriResolver;
 import 'package:analyzer/src/generated/source_io.dart'
     show Source, SourceKind, UriResolver;
 import 'package:analyzer/src/summary/package_bundle_reader.dart'
@@ skipping 137 matching lines @@
   /// Whether to emit the source mapping file.
   ///
   /// This supports debugging the original source code instead of the generated
   /// code.
   final bool sourceMap;
 
   /// If [sourceMap] is emitted, this will emit a `sourceMappingUrl` comment
   /// into the output JavaScript module.
   final bool sourceMapComment;
 
+  /// Whether to emit the source mapping file inline as a data url.
+  final bool inlineSourceMap;
+
+  /// Wrap each module in an JavaScript eval call.
+  /// This makes debugging concatenated sources more productive due to the eval
+  /// script sourceURL directive.
+  final bool wrapInEval;
+
   /// Whether to emit a summary file containing API signatures.
   ///
   /// This is required for a modular build process.
   final bool summarizeApi;
 
   /// The file extension for summaries.
   final String summaryExtension;
 
   /// Whether to preserve metdata only accessible via mirrors
   final bool emitMetadata;
@@ skipping 27 matching lines @@
   /// Supporting the syntax:
   /// * Chrome Canary (51)
   /// * Firefox
   ///
   /// Not yet supporting:
   /// * Atom (1.5.4)
   /// * Electron (0.36.3)
   // TODO(ochafik): Simplify this code when our target platforms catch up.
   final bool destructureNamedParams;
 
+  /// Mapping from absolte file path to paths to use in source maps.
+  final Map<String, String> fileMappings;
+
   const CompilerOptions(
       {this.sourceMap: true,
       this.sourceMapComment: true,
+      this.inlineSourceMap: false,
+      this.wrapInEval: false,
       this.summarizeApi: true,
       this.summaryExtension: 'sum',
       this.unsafeForceCompile: false,
       this.emitMetadata: false,
       this.closure: false,
       this.destructureNamedParams: false,
       this.hoistInstanceCreation: true,
       this.hoistSignatureTypes: false,
       this.nameTypeTests: true,
       this.hoistTypeTests: true,
-      this.useAngular2Whitelist: false});
+      this.useAngular2Whitelist: false,
+      this.fileMappings: const {}});
 
   CompilerOptions.fromArguments(ArgResults args)
       : sourceMap = args['source-map'],
         sourceMapComment = args['source-map-comment'],
+        inlineSourceMap = args['inline-source-map'],
+        wrapInEval = args['wrap-in-eval'],
         summarizeApi = args['summarize'],
         summaryExtension = args['summary-extension'],
         unsafeForceCompile = args['unsafe-force-compile'],
         emitMetadata = args['emit-metadata'],
         closure = args['closure-experimental'],
         destructureNamedParams = args['destructure-named-params'],
         hoistInstanceCreation = args['hoist-instance-creation'],
         hoistSignatureTypes = args['hoist-signature-types'],
         nameTypeTests = args['name-type-tests'],
         hoistTypeTests = args['hoist-type-tests'],
-        useAngular2Whitelist = args['unsafe-angular2-whitelist'];
+        useAngular2Whitelist = args['unsafe-angular2-whitelist'],
+        fileMappings = _parseFileMappings(args['file-mapping']);
 
   static void addArguments(ArgParser parser) {
     parser
       ..addFlag('summarize', help: 'emit an API summary file', defaultsTo: true)
       ..addOption('summary-extension',
           help: 'file extension for Dart summary files',
           defaultsTo: 'sum',
           hide: true)
       ..addFlag('source-map', help: 'emit source mapping', defaultsTo: true)
       ..addFlag('source-map-comment',
           help: 'adds a sourceMappingURL comment to the end of the JS,\n'
               'disable if using X-SourceMap header',
           defaultsTo: true,
           hide: true)
+      ..addFlag('inline-source-map',
+          help: 'emit source mapping inline', defaultsTo: false)
+      ..addFlag('wrap-in-eval',
+          help: 'wrap library definition in eval', defaultsTo: false)
       ..addFlag('emit-metadata',
           help: 'emit metadata annotations queriable via mirrors',
           defaultsTo: false)
       ..addFlag('closure-experimental',
           help: 'emit Closure Compiler-friendly code (experimental)',
           defaultsTo: false)
       ..addFlag('destructure-named-params',
           help: 'Destructure named parameters', defaultsTo: false, hide: true)
       ..addFlag('unsafe-force-compile',
           help: 'Compile code even if it has errors. ಠ_ಠ\n'
               'This has undefined behavior!',
           defaultsTo: false,
           hide: true)
       ..addFlag('hoist-instance-creation',
           help: 'Hoist the class type from generic instance creations',
           defaultsTo: true,
           hide: true)
       ..addFlag('hoist-signature-types',
           help: 'Hoist types from class signatures',
           defaultsTo: false,
           hide: true)
       ..addFlag('name-type-tests',
           help: 'Name types used in type tests', defaultsTo: true, hide: true)
       ..addFlag('hoist-type-tests',
           help: 'Hoist types used in type tests', defaultsTo: true, hide: true)
-      ..addFlag('unsafe-angular2-whitelist', defaultsTo: false, hide: true);
+      ..addFlag('unsafe-angular2-whitelist', defaultsTo: false, hide: true)
+      ..addOption('file-mapping',

[vsm, 2016/09/13 22:08:20]

Can you include an example of how this is used (e.g., in a Bazel context)?  Not
clear what "short_path" means in your comment.

[vsm, 2016/09/13 22:17:32]

This might make more sense as --bazel-mapping.  The logic seems very bazel
specific.

[Jennifer Messerly, 2016/09/13 22:43:39]

yeah ... if some of these options are meant to go together can we merge them
please? We already have unfixed bugs about how awful DDC's command line UX is,
and I had to apologize and make a note to self to be more stringent in code
reviews :)

also if it doesn't make sense for a user to pass it, use "hide: true"

+          help:
+              '--file-mapping=/full/path/to/library.dart,to/library.dart uses\n'
+              'to/library.dart as the short_path for library.dart".',
+          allowMultiple: true,
+          splitCommas: false);
+  }
+
+  static Map<String, String> _parseFileMappings(Iterable argument) {
+    var mappings = <String, String>{};
+    for (var mapping in argument) {
+      var splitMapping = mapping.split(',');
+      if (splitMapping.length >= 2) {
+        mappings[path.absolute(splitMapping[0])] = splitMapping[1];
+      }
+    }
+    return mappings;
   }
 }
 
 /// A unit of Dart code that can be built into a single JavaScript module.
 class BuildUnit {
   /// The name of this module.
   final String name;
 
   /// All library names are relative to this path/prefix.
   final String libraryRoot;
@@ skipping 65 matching lines @@
       sourceMap = sourceMapContext.sourceMap;
       printer = sourceMapContext;
     } else {
       printer = new JS.SimpleJavaScriptPrintingContext();
     }
 
     var tree = transformModuleFormat(format, moduleTree);
     tree.accept(
         new JS.Printer(opts, printer, localNamer: new JS.TemporaryNamer(tree)));
 
-    if (options.sourceMap && options.sourceMapComment) {
-      var relativeMapUrl = path
-          .toUri(path.relative(path.fromUri(mapUrl), from: path.dirname(jsUrl)))
-          .toString();
-      assert(path.dirname(jsUrl) == path.dirname(mapUrl));
-      printer.emit('\n//# sourceMappingURL=$relativeMapUrl\n');
+    Map builtMap;
+    if (options.sourceMap && sourceMap != null) {
+      builtMap =
+          placeSourceMap(sourceMap.build(jsUrl), mapUrl, options.fileMappings);
+
+      if (options.sourceMapComment) {
+        var relativeMapUrl = path
+            .toUri(
+                path.relative(path.fromUri(mapUrl), from: path.dirname(jsUrl)))
+            .toString();
+        assert(path.dirname(jsUrl) == path.dirname(mapUrl));
+        printer.emit('\n//# sourceMappingURL=');
+        if (options.inlineSourceMap) {
+          var bytes = UTF8.encode(JSON.encode(builtMap));
+          var base64 = BASE64.encode(bytes);
+          printer..emit('data:application/json;base64,')..emit(base64);
+        } else {
+          printer.emit(relativeMapUrl);
+        }
+        printer.emit('\n');
+      }
     }
 
-    Map builtMap;
-    if (sourceMap != null) {
-      builtMap = placeSourceMap(sourceMap.build(jsUrl), mapUrl);
-    }
     return new JSModuleCode(printer.getText(), builtMap);
   }
 
   /// Similar to [getCode] but immediately writes the resulting files.
   ///
   /// If [mapPath] is not supplied but [options.sourceMap] is set, mapPath
   /// will default to [jsPath].map.
-  void writeCodeSync(ModuleFormat format, String jsPath, [String mapPath]) {
-    if (mapPath == null) mapPath = jsPath + '.map';
+  void writeCodeSync(ModuleFormat format, String jsPath) {
+    String mapPath = jsPath + '.map';
     var code = getCode(format, jsPath, mapPath);
-    new File(jsPath).writeAsStringSync(code.code);
-    if (code.sourceMap != null) {
+    var c = code.code;
+    if (options.wrapInEval) {

[Jennifer Messerly, 2016/09/13 23:00:33]

this is not the right place for this. I'm not sure the goal here but this should
part of JS code gen or module transform, not something that gets done by the
"write code" method...

As it is, could you do this in a post process step? it doesn't seem like
something that makes sense for our compiler to being doing.

+      // Add sourceURL to improve the debugging experience.
+      c += '\n//# sourceURL=${name}.js\n';
+      c = 'eval(${JSON.encode(c)});\n';
+    }
+    new File(jsPath).writeAsStringSync(c);
+    if (code.sourceMap != null && !options.inlineSourceMap) {
       new File(mapPath).writeAsStringSync(JSON.encode(code.sourceMap));
     }
   }
 }
 
 /// The output of compiling a JavaScript module in a particular format.
 class JSModuleCode {
   /// The JavaScript code for this module.
   ///
   /// If a [sourceMap] is available, this will include the `sourceMappingURL`
   /// comment at end of the file.
   final String code;
 
   /// The JSON of the source map, if generated, otherwise `null`.
   ///
   /// The source paths will initially be absolute paths. They can be adjusted
   /// using [placeSourceMap].
   final Map sourceMap;
 
   JSModuleCode(this.code, this.sourceMap);
 }
 
 /// Adjusts the source paths in [sourceMap] to be relative to [sourceMapPath],
 /// and returns the new map.
 // TODO(jmesserly): find a new home for this.
-Map placeSourceMap(Map sourceMap, String sourceMapPath) {
+Map placeSourceMap(
+    Map sourceMap, String sourceMapPath, Map<String, String> fileMappings) {
   var dir = path.dirname(sourceMapPath);
+  var map = new Map.from(sourceMap);
+  var list = new List.from(map['sources']);
+  map['sources'] = list;
+  String transformUri(String uri) {
+    var match = fileMappings[path.absolute(uri)];
+    if (match != null) return match;
 
-  var map = new Map.from(sourceMap);
-  List list = new List.from(map['sources']);
-  map['sources'] = list;
-  String relative(String uri) =>
-      path.toUri(path.relative(path.fromUri(uri), from: dir)).toString();
+    // Fall back to a relative path.
+    return path.toUri(path.relative(path.fromUri(uri), from: dir)).toString();
+  }
+
   for (int i = 0; i < list.length; i++) {
-    list[i] = relative(list[i]);
+    list[i] = transformUri(list[i]);
   }
-  map['file'] = relative(map['file']);
+  map['file'] = transformUri(map['file']);
   return map;
 }