add a JsonInfoCodec class

lib/info.dart

Index: lib/info.dart
diff --git a/lib/info.dart b/lib/info.dart
index 27e1fe77a4cf40b1b6138a3116909f7b295d891a..5e79a70e973fd0fbf084ecb364fd985dd61b0635 100644
--- a/lib/info.dart
+++ b/lib/info.dart
@@ -5,9 +5,13 @@
 /// Data produced by dart2js when run with the `--dump-info` flag.
 library dart2js_info.info;
 
+import 'dart:convert';
+
 import 'src/measurements.dart';
 export 'src/measurements.dart';
 
+part 'json_info_codec.dart';
+
 /// Common interface to many pieces of information generated by the dart2js
 /// compiler that are directly associated with an element (compilation unit,
 /// library, class, function, or field).
@@ -35,12 +39,7 @@ abstract class Info {
   /// Info of the enclosing element.
   Info parent;
 
-  /// Serializes the information into a JSON format.
-  // TODO(sigmund): refactor and put toJson outside the class, so we can have 2
-  // different serializer/deserializers at once.
-  Map toJson();
-
-  void accept(InfoVisitor visitor);
+  dynamic accept(InfoVisitor visitor);
 }
 
 /// Common information used for most kind of elements.
@@ -68,21 +67,6 @@ abstract class BasicInfo implements Info {
       : kind = _kindFromSerializedId(serializedId),
         id = _idFromSerializedId(serializedId);
 
-  Map toJson() {
-    var res = {
-      'id': serializedId,
-      'kind': _kindToString(kind),
-      'name': name,
-      'size': size,
-    };
-    // TODO(sigmund): Omit this also when outputUnit.id == 0 (most code is in
-    // the main output unit by default).
-    if (outputUnit != null) res['outputUnit'] = outputUnit.serializedId;
-    if (coverageId != null) res['coverageId'] = coverageId;
-    if (parent != null) res['parent'] = parent.serializedId;
-    return res;
-  }
-
   String toString() => '$serializedId $name [$size]';
 }
 
@@ -150,57 +134,7 @@ class AllInfo {
 
   AllInfo();
 
-  // TODO(het): Remove this when we have an external InfoCodec, see
-  // https://github.com/dart-lang/dart2js_info/issues/4
-  factory AllInfo.fromJson(Map json) => new _ParseHelper().parseAll(json);
-
-  Map _listAsJsonMap(List<Info> list) {
-    var map = <String, Map>{};
-    for (var info in list) {
-      map['${info.id}'] = info.toJson();
-    }
-    return map;
-  }
-
-  Map _extractHoldingInfo() {
-    var map = <String, List>{};
-    void helper(CodeInfo info) {
-      if (info.uses.isEmpty) return;
-      map[info.serializedId] = info.uses.map((u) => u.toJson()).toList();
-    }
-    functions.forEach(helper);
-    fields.forEach(helper);
-    return map;
-  }
-
-  Map _extractDependencies() {
-    var map = <String, List>{};
-    dependencies.forEach((k, v) {
-      map[k.serializedId] = v.map((i) => i.serializedId).toList();
-    });
-    return map;
-  }
-
-  Map toJson() => {
-        'elements': {
-          'library': _listAsJsonMap(libraries),
-          'class': _listAsJsonMap(classes),
-          'function': _listAsJsonMap(functions),
-          'typedef': _listAsJsonMap(typedefs),
-          'field': _listAsJsonMap(fields),
-          'constant': _listAsJsonMap(constants),
-        },
-        'holding': _extractHoldingInfo(),
-        'dependencies': _extractDependencies(),
-        'outputUnits': outputUnits.map((u) => u.toJson()).toList(),
-        'dump_version': version,
-        'deferredFiles': deferredFiles,
-        'dump_minor_version': '$minorVersion',
-        // TODO(sigmund): change viewer to accept an int?
-        'program': program.toJson(),
-      };
-
-  void accept(InfoVisitor visitor) => visitor.visitAll(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitAll(this);
 }
 
 class ProgramInfo {
@@ -226,216 +160,7 @@ class ProgramInfo {
       this.noSuchMethodEnabled,
       this.minified});
 
-  Map toJson() => {
-        'entrypoint': entrypoint.serializedId,
-        'size': size,
-        'dart2jsVersion': dart2jsVersion,
-        'compilationMoment': '$compilationMoment',
-        'compilationDuration': '${compilationDuration}',
-        'toJsonDuration': toJsonDuration,
-        'dumpInfoDuration': '$dumpInfoDuration',
-        'noSuchMethodEnabled': noSuchMethodEnabled,
-        'minified': minified,
-      };
-
-  void accept(InfoVisitor visitor) => visitor.visitProgram(this);
-}
-
-// TODO(sigmund): add unit tests.
-class _ParseHelper {
-  Map<String, Info> registry = {};
-
-  AllInfo parseAll(Map json) {
-    var result = new AllInfo();
-    var elements = json['elements'];
-    result.libraries.addAll(elements['library'].values.map(parseLibrary));
-    result.classes.addAll(elements['class'].values.map(parseClass));
-    result.functions.addAll(elements['function'].values.map(parseFunction));
-    result.fields.addAll(elements['field'].values.map(parseField));
-    result.typedefs.addAll(elements['typedef'].values.map(parseTypedef));
-
-    // TODO(sigmund): remove null check on next breaking version
-    var constants = elements['constant'];
-    if (constants != null) {
-      result.constants.addAll(constants.values.map(parseConstant));
-    }
-
-    var idMap = {};
-    for (var f in result.functions) {
-      idMap[f.serializedId] = f;
-    }
-    for (var f in result.fields) {
-      idMap[f.serializedId] = f;
-    }
-
-    json['holding'].forEach((k, deps) {
-      var src = idMap[k];
-      assert(src != null);
-      for (var dep in deps) {
-        var target = idMap[dep['id']];
-        assert(target != null);
-        src.uses.add(new DependencyInfo(target, dep['mask']));
-      }
-    });
-
-    json['dependencies']?.forEach((k, deps) {
-      result.dependencies[idMap[k]] = deps.map((d) => idMap[d]).toList();
-    });
-
-    result.program = parseProgram(json['program']);
-    // todo: version, etc
-    return result;
-  }
-
-  LibraryInfo parseLibrary(Map json) {
-    LibraryInfo result = parseId(json['id']);
-    result
-      ..name = json['name']
-      ..uri = Uri.parse(json['canonicalUri'])
-      ..outputUnit = parseId(json['outputUnit'])
-      ..size = json['size'];
-    for (var child in json['children'].map(parseId)) {
-      if (child is FunctionInfo) {
-        result.topLevelFunctions.add(child);
-      } else if (child is FieldInfo) {
-        result.topLevelVariables.add(child);
-      } else if (child is ClassInfo) {
-        result.classes.add(child);
-      } else {
-        assert(child is TypedefInfo);
-        result.typedefs.add(child);
-      }
-    }
-    return result;
-  }
-
-  ClassInfo parseClass(Map json) {
-    ClassInfo result = parseId(json['id']);
-    result
-      ..name = json['name']
-      ..parent = parseId(json['parent'])
-      ..outputUnit = parseId(json['outputUnit'])
-      ..size = json['size']
-      ..isAbstract = json['modifiers']['abstract'] == true;
-    assert(result is ClassInfo);
-    for (var child in json['children'].map(parseId)) {
-      if (child is FunctionInfo) {
-        result.functions.add(child);
-      } else {
-        assert(child is FieldInfo);
-        result.fields.add(child);
-      }
-    }
-    return result;
-  }
-
-  FieldInfo parseField(Map json) {
-    FieldInfo result = parseId(json['id']);
-    return result
-      ..name = json['name']
-      ..parent = parseId(json['parent'])
-      ..coverageId = json['coverageId']
-      ..outputUnit = parseId(json['outputUnit'])
-      ..size = json['size']
-      ..type = json['type']
-      ..inferredType = json['inferredType']
-      ..code = json['code']
-      ..isConst = json['const'] ?? false
-      ..initializer = parseId(json['initializer'])
-      ..closures = json['children'].map(parseId).toList();
-  }
-
-  ConstantInfo parseConstant(Map json) {
-    ConstantInfo result = parseId(json['id']);
-    return result
-      ..code = json['code']
-      ..size = json['size'];
-  }
-
-  TypedefInfo parseTypedef(Map json) {
-    TypedefInfo result = parseId(json['id']);
-    return result
-      ..name = json['name']
-      ..parent = parseId(json['parent'])
-      ..type = json['type']
-      ..size = 0;
-  }
-
-  ProgramInfo parseProgram(Map json) => new ProgramInfo()
-    ..size = json['size']
-    ..entrypoint = parseId(json['entrypoint']);
-
-  FunctionInfo parseFunction(Map json) {
-    FunctionInfo result = parseId(json['id']);
-    return result
-      ..name = json['name']
-      ..parent = parseId(json['parent'])
-      ..coverageId = json['coverageId']
-      ..outputUnit = parseId(json['outputUnit'])
-      ..size = json['size']
-      ..type = json['type']
-      ..returnType = json['returnType']
-      ..inferredReturnType = json['inferredReturnType']
-      ..parameters = json['parameters'].map(parseParameter).toList()
-      ..code = json['code']
-      ..sideEffects = json['sideEffects']
-      ..modifiers = parseModifiers(json['modifiers'])
-      ..closures = json['children'].map(parseId).toList()
-      ..measurements = parseMeasurements(json['measurements']);
-  }
-
-  ParameterInfo parseParameter(Map json) =>
-      new ParameterInfo(json['name'], json['type'], json['declaredType']);
-
-  Measurements parseMeasurements(Map json) {
-    if (json == null) return null;
-    var uri = json['sourceFile'];
-    var res = new Measurements(uri == null ? null : Uri.parse(uri));
-    for (var key in json.keys) {
-      var value = json[key];
-      if (value == null) continue;
-      if (key == 'entries') {
-        value.forEach((metricName, entries) {
-          var metric = Metric.fromJson(metricName);
-          for (var i = 0; i < entries.length; i += 2) {
-            res.record(metric, entries[i], entries[i + 1]);
-          }
-        });
-      } else {
-        res.counters[Metric.fromJson(key)] = value;
-      }
-    }
-    return res;
-  }
-
-  FunctionModifiers parseModifiers(Map<String, bool> json) {
-    return new FunctionModifiers(
-        isStatic: json['static'] == true,
-        isConst: json['const'] == true,
-        isFactory: json['factory'] == true,
-        isExternal: json['external'] == true);
-  }
-
-  Info parseId(String serializedId) => registry.putIfAbsent(serializedId, () {
-        if (serializedId == null) {
-          return null;
-        } else if (serializedId.startsWith('function/')) {
-          return new FunctionInfo._(serializedId);
-        } else if (serializedId.startsWith('library/')) {
-          return new LibraryInfo._(serializedId);
-        } else if (serializedId.startsWith('class/')) {
-          return new ClassInfo._(serializedId);
-        } else if (serializedId.startsWith('field/')) {
-          return new FieldInfo._(serializedId);
-        } else if (serializedId.startsWith('constant/')) {
-          return new ConstantInfo._(serializedId);
-        } else if (serializedId.startsWith('typedef/')) {
-          return new TypedefInfo._(serializedId);
-        } else if (serializedId.startsWith('outputUnit/')) {
-          return new OutputUnitInfo._(serializedId);
-        }
-        assert(false);
-      });
+  dynamic accept(InfoVisitor visitor) => visitor.visitProgram(this);
 }
 
 /// Info associated with a library element.
@@ -470,17 +195,7 @@ class LibraryInfo extends BasicInfo {
 
   LibraryInfo._(String serializedId) : super._fromId(serializedId);
 
-  Map toJson() => super.toJson()
-    ..addAll({
-      'children': []
-        ..addAll(topLevelFunctions.map((f) => f.serializedId))
-        ..addAll(topLevelVariables.map((v) => v.serializedId))
-        ..addAll(classes.map((c) => c.serializedId))
-        ..addAll(typedefs.map((t) => t.serializedId)),
-      'canonicalUri': '$uri',
-    });
-
-  void accept(InfoVisitor visitor) => visitor.visitLibrary(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitLibrary(this);
 }
 
 /// Information about an output unit. Normally there is just one for the entire
@@ -493,7 +208,7 @@ class OutputUnitInfo extends BasicInfo {
 
   OutputUnitInfo._(String serializedId) : super._fromId(serializedId);
 
-  void accept(InfoVisitor visitor) => visitor.visitOutput(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitOutput(this);
 }
 
 /// Information about a class element.
@@ -517,16 +232,7 @@ class ClassInfo extends BasicInfo {
 
   ClassInfo._(String serializedId) : super._fromId(serializedId);
 
-  Map toJson() => super.toJson()
-    ..addAll({
-      // TODO(sigmund): change format, include only when abstract is true.
-      'modifiers': {'abstract': isAbstract},
-      'children': []
-        ..addAll(fields.map((f) => f.serializedId))
-        ..addAll(functions.map((m) => m.serializedId))
-    });
-
-  void accept(InfoVisitor visitor) => visitor.visitClass(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitClass(this);
 }
 
 /// Information about a constant value.
@@ -542,9 +248,7 @@ class ConstantInfo extends BasicInfo {
 
   ConstantInfo._(String serializedId) : super._fromId(serializedId);
 
-  Map toJson() => super.toJson()..addAll({'code': code});
-
-  void accept(InfoVisitor visitor) => visitor.visitConstant(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitConstant(this);
 }
 
 /// Information about a field element.
@@ -582,22 +286,7 @@ class FieldInfo extends BasicInfo with CodeInfo {
 
   FieldInfo._(String serializedId) : super._fromId(serializedId);
 
-  Map toJson() {
-    var result = super.toJson()
-      ..addAll({
-        'children': closures.map((i) => i.serializedId).toList(),
-        'inferredType': inferredType,
-        'code': code,
-        'type': type,
-      });
-    if (isConst) {
-      result['const'] = true;
-      if (initializer != null) result['initializer'] = initializer.serializedId;
-    }
-    return result;
-  }
-
-  void accept(InfoVisitor visitor) => visitor.visitField(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitField(this);
 }
 
 /// Information about a typedef declaration.
@@ -611,9 +300,7 @@ class TypedefInfo extends BasicInfo {
 
   TypedefInfo._(String serializedId) : super._fromId(serializedId);
 
-  Map toJson() => super.toJson()..['type'] = '$type';
-
-  void accept(InfoVisitor visitor) => visitor.visitTypedef(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitTypedef(this);
 }
 
 /// Information about a function or method.
@@ -678,23 +365,7 @@ class FunctionInfo extends BasicInfo with CodeInfo {
 
   FunctionInfo._(String serializedId) : super._fromId(serializedId);
 
-  Map toJson() => super.toJson()
-    ..addAll({
-      'children': closures.map((i) => i.serializedId).toList(),
-      'modifiers': modifiers.toJson(),
-      'returnType': returnType,
-      'inferredReturnType': inferredReturnType,
-      'parameters': parameters.map((p) => p.toJson()).toList(),
-      'sideEffects': sideEffects,
-      'inlinedCount': inlinedCount,
-      'code': code,
-      'type': type,
-      'measurements': measurements?.toJson(),
-      // Note: version 3.2 of dump-info serializes `uses` in a section called
-      // `holding` at the top-level.
-    });
-
-  void accept(InfoVisitor visitor) => visitor.visitFunction(this);
+  dynamic accept(InfoVisitor visitor) => visitor.visitFunction(this);
 }
 
 /// Information about how a dependency is used.
@@ -708,8 +379,6 @@ class DependencyInfo {
   final String mask;
 
   DependencyInfo(this.target, this.mask);
-
-  Map toJson() => {'id': target.serializedId, 'mask': mask};
 }
 
 /// Name and type information about a function parameter.
@@ -719,8 +388,6 @@ class ParameterInfo {
   final String declaredType;
 
   ParameterInfo(this.name, this.type, this.declaredType);
-
-  Map toJson() => {'name': name, 'type': type, 'declaredType': declaredType};
 }
 
 /// Modifiers that may apply to methods.
@@ -735,22 +402,6 @@ class FunctionModifiers {
       this.isConst: false,
       this.isFactory: false,
       this.isExternal: false});
-
-  // TODO(sigmund): exclude false values (requires bumping the format version):
-  //   Map toJson() {
-  //     var res = <String, bool>{};
-  //     if (isStatic) res['static'] = true;
-  //     if (isConst) res['const'] = true;
-  //     if (isFactory) res['factory'] = true;
-  //     if (isExternal) res['external'] = true;
-  //     return res;
-  //   }
-  Map toJson() => {
-        'static': isStatic,
-        'const': isConst,
-        'factory': isFactory,
-        'external': isExternal,
-      };
 }
 
 /// Possible values of the `kind` field in the serialied infos.
@@ -813,16 +464,16 @@ InfoKind _kindFromString(String kind) {
 }
 
 /// A simple visitor for information produced by the dart2js compiler.
-class InfoVisitor {
-  visitAll(AllInfo info) {}
-  visitProgram(ProgramInfo info) {}
-  visitLibrary(LibraryInfo info) {}
-  visitClass(ClassInfo info) {}
-  visitField(FieldInfo info) {}
-  visitConstant(ConstantInfo info) {}
-  visitFunction(FunctionInfo info) {}
-  visitTypedef(TypedefInfo info) {}
-  visitOutput(OutputUnitInfo info) {}
+abstract class InfoVisitor<T> {
+  T visitAll(AllInfo info);
+  T visitProgram(ProgramInfo info);
+  T visitLibrary(LibraryInfo info);
+  T visitClass(ClassInfo info);
+  T visitField(FieldInfo info);
+  T visitConstant(ConstantInfo info);
+  T visitFunction(FunctionInfo info);
+  T visitTypedef(TypedefInfo info);
+  T visitOutput(OutputUnitInfo info);
 }
 
 /// A visitor that recursively walks each portion of the program. Because the
@@ -831,7 +482,7 @@ class InfoVisitor {
 /// visitAll contains references to functions, this visitor only recurses to
 /// visit libraries, then from each library we visit functions and classes, and
 /// so on.
-class RecursiveInfoVisitor extends InfoVisitor {
+class RecursiveInfoVisitor extends InfoVisitor<Null> {
   visitAll(AllInfo info) {
     // Note: we don't visit functions, fields, classes, and typedefs because
     // they are reachable from the library info.
@@ -839,6 +490,8 @@ class RecursiveInfoVisitor extends InfoVisitor {
     info.constants.forEach(visitConstant);
   }
 
+  visitProgram(ProgramInfo info) {}
+
   visitLibrary(LibraryInfo info) {
     info.topLevelFunctions.forEach(visitFunction);
     info.topLevelVariables.forEach(visitField);
@@ -855,7 +508,12 @@ class RecursiveInfoVisitor extends InfoVisitor {
     info.closures.forEach(visitFunction);
   }
 
+  visitConstant(ConstantInfo info) {}
+
   visitFunction(FunctionInfo info) {
     info.closures.forEach(visitFunction);
   }
+
+  visitTypedef(TypedefInfo info) {}
+  visitOutput(OutputUnitInfo info) {}
 }