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

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

Index: pkg/dev_compiler/lib/src/compiler/compiler.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/compiler.dart b/pkg/dev_compiler/lib/src/compiler/compiler.dart
index b47ad2505d00328c0b6c2d803c8738dfa042f76b..4b2620cd6321d416c3298b08725906799959d99f 100644
--- a/pkg/dev_compiler/lib/src/compiler/compiler.dart
+++ b/pkg/dev_compiler/lib/src/compiler/compiler.dart
@@ -3,7 +3,7 @@
 // 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'
@@ -161,6 +161,14 @@ class CompilerOptions {
   /// 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.
@@ -208,9 +216,14 @@ class CompilerOptions {
   // 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,
@@ -221,11 +234,14 @@ class CompilerOptions {
       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'],
@@ -236,7 +252,8 @@ class CompilerOptions {
         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
@@ -251,6 +268,10 @@ class CompilerOptions {
               '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)
@@ -276,7 +297,24 @@ class CompilerOptions {
           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;
   }
 }
 
@@ -362,18 +400,29 @@ class JSModuleFile {
     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 (sourceMap != null) {
-      builtMap = placeSourceMap(sourceMap.build(jsUrl), mapUrl);
+    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');
+      }
     }
+
     return new JSModuleCode(printer.getText(), builtMap);
   }
 
@@ -381,11 +430,17 @@ class JSModuleFile {
   ///
   /// 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));
     }
   }
@@ -411,17 +466,23 @@ class JSModuleCode {
 /// 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);
-  List list = new List.from(map['sources']);
+  var list = new List.from(map['sources']);
   map['sources'] = list;
-  String relative(String uri) =>
-      path.toUri(path.relative(path.fromUri(uri), from: dir)).toString();
+  String transformUri(String uri) {
+    var match = fileMappings[path.absolute(uri)];
+    if (match != null) return match;
+
+    // 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;
 }