Add the generator and the generated files

pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart

Index: pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart
diff --git a/pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart b/pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart
new file mode 100644
index 0000000000000000000000000000000000000000..285f0961cb818389354d4a6501e1e77faf770af1
--- /dev/null
+++ b/pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart
@@ -0,0 +1,1276 @@
+// Copyright (c) 2017, 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:convert';
+
+import 'package:analyzer/src/codegen/tools.dart';
+import 'package:html/dom.dart' as dom;
+
+import 'api.dart';
+import 'codegen_dart.dart';
+import 'from_html.dart';
+import 'implied_types.dart';
+import 'to_html.dart';
+
+/**
+ * Special flags that need to be inserted into the declaration of the Element
+ * class.
+ */
+const Map<String, String> specialElementFlags = const {
+  'abstract': '0x01',
+  'const': '0x02',
+  'final': '0x04',
+  'static': '0x08',
+  'private': '0x10',
+  'deprecated': '0x20'
+};
+
+final GeneratedFile target =
+    new GeneratedFile('lib/protocol/generated_protocol.dart', (String pkgPath) {
+  CodegenProtocolVisitor visitor = new CodegenProtocolVisitor(readApi(pkgPath));
+  return visitor.collectCode(visitor.visitApi);
+});
+
+/**
+ * Callback type used to represent arbitrary code generation.
+ */
+typedef void CodegenCallback();
+
+typedef String FromJsonSnippetCallback(String jsonPath, String json);
+
+typedef String ToJsonSnippetCallback(String value);
+
+/**
+ * Visitor which produces Dart code representing the API.
+ */
+class CodegenProtocolVisitor extends DartCodegenVisitor with CodeGenerator {
+  /**
+   * Class members for which the constructor argument should be optional, even
+   * if the member is not an optional part of the protocol.  For list types,
+   * the constructor will default the member to the empty list.
+   */
+  static const Map<String, List<String>> _optionalConstructorArguments = const {
+    'AnalysisErrorFixes': const ['fixes'],
+    'SourceChange': const ['edits', 'linkedEditGroups'],
+    'SourceFileEdit': const ['edits'],
+    'TypeHierarchyItem': const ['interfaces', 'mixins', 'subclasses'],
+  };
+
+  /**
+   * The disclaimer added to the documentation comment for each of the classes
+   * that are generated.
+   */
+  static const String disclaimer =
+      'Clients may not extend, implement or mix-in this class.';
+
+  /**
+   * Visitor used to produce doc comments.
+   */
+  final ToHtmlVisitor toHtmlVisitor;
+
+  /**
+   * Types implied by the API.  This includes types explicitly named in the
+   * API as well as those implied by the definitions of requests, responses,
+   * notifications, etc.
+   */
+  final Map<String, ImpliedType> impliedTypes;
+
+  CodegenProtocolVisitor(Api api)
+      : toHtmlVisitor = new ToHtmlVisitor(api),
+        impliedTypes = computeImpliedTypes(api),
+        super(api) {
+    codeGeneratorSettings.commentLineLength = 79;
+    codeGeneratorSettings.languageName = 'dart';
+  }
+
+  /**
+   * Compute the code necessary to compare two objects for equality.
+   */
+  String compareEqualsCode(TypeDecl type, String thisVar, String otherVar) {
+    TypeDecl resolvedType = resolveTypeReferenceChain(type);
+    if (resolvedType is TypeReference ||
+        resolvedType is TypeEnum ||
+        resolvedType is TypeObject ||
+        resolvedType is TypeUnion) {
+      return '$thisVar == $otherVar';
+    } else if (resolvedType is TypeList) {
+      String itemTypeName = dartType(resolvedType.itemType);
+      String subComparison = compareEqualsCode(resolvedType.itemType, 'a', 'b');
+      String closure = '($itemTypeName a, $itemTypeName b) => $subComparison';
+      return 'listEqual($thisVar, $otherVar, $closure)';
+    } else if (resolvedType is TypeMap) {
+      String valueTypeName = dartType(resolvedType.valueType);
+      String subComparison =
+          compareEqualsCode(resolvedType.valueType, 'a', 'b');
+      String closure = '($valueTypeName a, $valueTypeName b) => $subComparison';
+      return 'mapEqual($thisVar, $otherVar, $closure)';
+    }
+    throw new Exception(
+        "Don't know how to compare for equality: $resolvedType");
+  }
+
+  /**
+   * Translate each type implied by the API to a class.
+   */
+  void emitClasses() {
+    List<ImpliedType> types = impliedTypes.values.toList();
+    types.sort((first, second) =>
+        capitalize(first.camelName).compareTo(capitalize(second.camelName)));
+    for (ImpliedType impliedType in types) {
+      TypeDecl type = impliedType.type;
+      String dartTypeName = capitalize(impliedType.camelName);
+      if (type == null) {
+        writeln();
+        emitEmptyObjectClass(dartTypeName, impliedType);
+      } else if (type is TypeObject) {
+        writeln();
+        emitObjectClass(dartTypeName, type, impliedType);
+      } else if (type is TypeEnum) {
+        writeln();
+        emitEnumClass(dartTypeName, type, impliedType);
+      }
+    }
+  }
+
+  /**
+   * Emit a convenience constructor for decoding a piece of protocol, if
+   * appropriate.  Return true if a constructor was emitted.
+   */
+  bool emitConvenienceConstructor(String className, ImpliedType impliedType) {
+    // The type of object from which this piece of protocol should be decoded.
+    String inputType;
+    // The name of the input object.
+    String inputName;
+    // The field within the input object to decode.
+    String fieldName;
+    // Constructor call to create the JsonDecoder object.
+    String makeDecoder;
+    // Name of the constructor to create.
+    String constructorName;
+    // Extra arguments for the constructor.
+    List<String> extraArgs = <String>[];
+    switch (impliedType.kind) {
+      case 'requestParams':
+        inputType = 'Request';
+        inputName = 'request';
+        fieldName = 'params';
+        makeDecoder = 'new RequestDecoder(request)';
+        constructorName = 'fromRequest';
+        break;
+      case 'requestResult':
+        inputType = 'Response';
+        inputName = 'response';
+        fieldName = 'result';
+        makeDecoder =
+            'new ResponseDecoder(REQUEST_ID_REFACTORING_KINDS.remove(response.id))';
+        constructorName = 'fromResponse';
+        break;
+      case 'notificationParams':
+        inputType = 'Notification';
+        inputName = 'notification';
+        fieldName = 'params';
+        makeDecoder = 'new ResponseDecoder(null)';
+        constructorName = 'fromNotification';
+        break;
+      case 'refactoringOptions':
+        inputType = 'EditGetRefactoringParams';
+        inputName = 'refactoringParams';
+        fieldName = 'options';
+        makeDecoder = 'new RequestDecoder(request)';
+        constructorName = 'fromRefactoringParams';
+        extraArgs.add('Request request');
+        break;
+      default:
+        return false;
+    }
+    List<String> args = ['$inputType $inputName'];
+    args.addAll(extraArgs);
+    writeln('factory $className.$constructorName(${args.join(', ')}) {');
+    indent(() {
+      String fieldNameString =
+          literalString(fieldName.replaceFirst(new RegExp('^_'), ''));
+      if (className == 'EditGetRefactoringParams') {
+        writeln('var params = new $className.fromJson(');
+        writeln('    $makeDecoder, $fieldNameString, $inputName.$fieldName);');
+        writeln('REQUEST_ID_REFACTORING_KINDS[request.id] = params.kind;');
+        writeln('return params;');
+      } else {
+        writeln('return new $className.fromJson(');
+        writeln('    $makeDecoder, $fieldNameString, $inputName.$fieldName);');
+      }
+    });
+    writeln('}');
+    return true;
+  }
+
+  /**
+   * Emit a class representing an data structure that doesn't exist in the
+   * protocol because it is empty (e.g. the "params" object for a request that
+   * doesn't have any parameters).
+   */
+  void emitEmptyObjectClass(String className, ImpliedType impliedType) {
+    docComment(toHtmlVisitor.collectHtml(() {
+      toHtmlVisitor.p(() {
+        toHtmlVisitor.write(impliedType.humanReadableName);
+      });
+      toHtmlVisitor.p(() {
+        toHtmlVisitor.write(disclaimer);
+      });
+    }));
+    write('class $className');
+    if (impliedType.kind == 'refactoringFeedback') {
+      writeln(' extends RefactoringFeedback implements HasToJson {');
+    } else if (impliedType.kind == 'refactoringOptions') {
+      writeln(' extends RefactoringOptions implements HasToJson {');
+    } else if (impliedType.kind == 'requestResult') {
+      writeln(' implements ResponseResult {');
+    } else {
+      writeln(' {');
+    }
+    indent(() {
+      if (impliedType.kind == 'requestResult') {
+        emitEmptyToJsonMember();
+        writeln();
+      }
+      if (emitToRequestMember(impliedType)) {
+        writeln();
+      }
+      if (emitToResponseMember(impliedType)) {
+        writeln();
+      }
+      if (emitToNotificationMember(impliedType)) {
+        writeln();
+      }
+      emitObjectEqualsMember(null, className);
+      writeln();
+      emitObjectHashCode(null, className);
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the toJson() code for an empty class.
+   */
+  void emitEmptyToJsonMember() {
+    writeln('@override');
+    writeln('Map<String, dynamic> toJson() => <String, dynamic>{};');
+  }
+
+  /**
+   * Emit a class to encapsulate an enum.
+   */
+  void emitEnumClass(String className, TypeEnum type, ImpliedType impliedType) {
+    docComment(toHtmlVisitor.collectHtml(() {
+      toHtmlVisitor.p(() {
+        toHtmlVisitor.write(impliedType.humanReadableName);
+      });
+      if (impliedType.type != null) {
+        toHtmlVisitor.showType(null, impliedType.type);
+      }
+      toHtmlVisitor.p(() {
+        toHtmlVisitor.write(disclaimer);
+      });
+    }));
+    writeln('class $className implements Enum {');
+    indent(() {
+      if (emitSpecialStaticMembers(className)) {
+        writeln();
+      }
+      for (TypeEnumValue value in type.values) {
+        docComment(toHtmlVisitor.collectHtml(() {
+          toHtmlVisitor.translateHtml(value.html);
+        }));
+        String valueString = literalString(value.value);
+        writeln(
+            'static const $className ${value.value} = const $className._($valueString);');
+        writeln();
+      }
+
+      writeln('/**');
+      writeln(' * A list containing all of the enum values that are defined.');
+      writeln(' */');
+      write('static const List<');
+      write(className);
+      write('> VALUES = const <');
+      write(className);
+      write('>[');
+      bool first = true;
+      for (TypeEnumValue value in type.values) {
+        if (first) {
+          first = false;
+        } else {
+          write(', ');
+        }
+        write(value.value);
+      }
+      writeln('];');
+      writeln();
+
+      writeln('@override');
+      writeln('final String name;');
+      writeln();
+      writeln('const $className._(this.name);');
+      writeln();
+      emitEnumClassConstructor(className, type);
+      writeln();
+      emitEnumFromJsonConstructor(className, type, impliedType);
+      writeln();
+      if (emitSpecialConstructors(className)) {
+        writeln();
+      }
+      if (emitSpecialGetters(className)) {
+        writeln();
+      }
+      if (emitSpecialMethods(className)) {
+        writeln();
+      }
+      writeln('@override');
+      writeln('String toString() => "$className.\$name";');
+      writeln();
+      writeln('String toJson() => name;');
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the constructor for an enum class.
+   */
+  void emitEnumClassConstructor(String className, TypeEnum type) {
+    writeln('factory $className(String name) {');
+    indent(() {
+      writeln('switch (name) {');
+      indent(() {
+        for (TypeEnumValue value in type.values) {
+          String valueString = literalString(value.value);
+          writeln('case $valueString:');
+          indent(() {
+            writeln('return ${value.value};');
+          });
+        }
+      });
+      writeln('}');
+      writeln(r"throw new Exception('Illegal enum value: $name');");
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the method for decoding an enum from JSON.
+   */
+  void emitEnumFromJsonConstructor(
+      String className, TypeEnum type, ImpliedType impliedType) {
+    writeln(
+        'factory $className.fromJson(JsonDecoder jsonDecoder, String jsonPath, Object json) {');
+    indent(() {
+      writeln('if (json is String) {');
+      indent(() {
+        writeln('try {');
+        indent(() {
+          writeln('return new $className(json);');
+        });
+        writeln('} catch(_) {');
+        indent(() {
+          writeln('// Fall through');
+        });
+        writeln('}');
+      });
+      writeln('}');
+      String humanReadableNameString =
+          literalString(impliedType.humanReadableName);
+      writeln(
+          'throw jsonDecoder.mismatch(jsonPath, $humanReadableNameString, json);');
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the class to encapsulate an object type.
+   */
+  void emitObjectClass(
+      String className, TypeObject type, ImpliedType impliedType) {
+    docComment(toHtmlVisitor.collectHtml(() {
+      toHtmlVisitor.p(() {
+        toHtmlVisitor.write(impliedType.humanReadableName);
+      });
+      if (impliedType.type != null) {
+        toHtmlVisitor.showType(null, impliedType.type);
+      }
+      toHtmlVisitor.p(() {
+        toHtmlVisitor.write(disclaimer);
+      });
+    }));
+    write('class $className');
+    if (impliedType.kind == 'refactoringFeedback') {
+      writeln(' extends RefactoringFeedback {');
+    } else if (impliedType.kind == 'refactoringOptions') {
+      writeln(' extends RefactoringOptions {');
+    } else if (impliedType.kind == 'requestResult') {
+      writeln(' implements ResponseResult {');
+    } else {
+      writeln(' implements HasToJson {');
+    }
+    indent(() {
+      if (emitSpecialStaticMembers(className)) {
+        writeln();
+      }
+      for (TypeObjectField field in type.fields) {
+        if (field.value != null) {
+          continue;
+        }
+        writeln('${dartType(field.type)} _${field.name};');
+        writeln();
+      }
+      for (TypeObjectField field in type.fields) {
+        if (field.value != null) {
+          continue;
+        }
+        docComment(toHtmlVisitor.collectHtml(() {
+          toHtmlVisitor.translateHtml(field.html);
+        }));
+        writeln('${dartType(field.type)} get ${field.name} => _${field.name};');
+        writeln();
+        docComment(toHtmlVisitor.collectHtml(() {
+          toHtmlVisitor.translateHtml(field.html);
+        }));
+        writeln('void set ${field.name}(${dartType(field.type)} value) {');
+        indent(() {
+          if (!field.optional) {
+            writeln('assert(value != null);');
+          }
+          writeln('this._${field.name} = value;');
+        });
+        writeln('}');
+        writeln();
+      }
+      emitObjectConstructor(type, className);
+      writeln();
+      emitObjectFromJsonConstructor(className, type, impliedType);
+      writeln();
+      if (emitConvenienceConstructor(className, impliedType)) {
+        writeln();
+      }
+      if (emitSpecialConstructors(className)) {
+        writeln();
+      }
+      if (emitSpecialGetters(className)) {
+        writeln();
+      }
+      emitToJsonMember(type);
+      writeln();
+      if (emitToRequestMember(impliedType)) {
+        writeln();
+      }
+      if (emitToResponseMember(impliedType)) {
+        writeln();
+      }
+      if (emitToNotificationMember(impliedType)) {
+        writeln();
+      }
+      if (emitSpecialMethods(className)) {
+        writeln();
+      }
+      writeln('@override');
+      writeln('String toString() => JSON.encode(toJson());');
+      writeln();
+      emitObjectEqualsMember(type, className);
+      writeln();
+      emitObjectHashCode(type, className);
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the constructor for an object class.
+   */
+  void emitObjectConstructor(TypeObject type, String className) {
+    List<String> args = <String>[];
+    List<String> optionalArgs = <String>[];
+    List<CodegenCallback> extraInitCode = <CodegenCallback>[];
+    for (TypeObjectField field in type.fields) {
+      if (field.value != null) {
+        continue;
+      }
+      String arg = '${dartType(field.type)} ${field.name}';
+      String setValueFromArg = 'this.${field.name} = ${field.name};';
+      if (isOptionalConstructorArg(className, field)) {
+        optionalArgs.add(arg);
+        if (!field.optional) {
+          // Optional constructor arg, but non-optional field.  If no arg is
+          // given, the constructor should populate with the empty list.
+          TypeDecl fieldType = field.type;
+          if (fieldType is TypeList) {
+            extraInitCode.add(() {
+              writeln('if (${field.name} == null) {');
+              indent(() {
+                writeln(
+                    'this.${field.name} = <${dartType(fieldType.itemType)}>[];');
+              });
+              writeln('} else {');
+              indent(() {
+                writeln(setValueFromArg);
+              });
+              writeln('}');
+            });
+          } else {
+            throw new Exception(
+                "Don't know how to create default field value.");
+          }
+        } else {
+          extraInitCode.add(() {
+            writeln(setValueFromArg);
+          });
+        }
+      } else {
+        args.add(arg);
+        extraInitCode.add(() {
+          writeln(setValueFromArg);
+        });
+      }
+    }
+    if (optionalArgs.isNotEmpty) {
+      args.add('{${optionalArgs.join(', ')}}');
+    }
+    write('$className(${args.join(', ')})');
+    if (extraInitCode.isEmpty) {
+      writeln(';');
+    } else {
+      writeln(' {');
+      indent(() {
+        for (CodegenCallback callback in extraInitCode) {
+          callback();
+        }
+      });
+      writeln('}');
+    }
+  }
+
+  /**
+   * Emit the operator== code for an object class.
+   */
+  void emitObjectEqualsMember(TypeObject type, String className) {
+    writeln('@override');
+    writeln('bool operator==(other) {');
+    indent(() {
+      writeln('if (other is $className) {');
+      indent(() {
+        var comparisons = <String>[];
+        if (type != null) {
+          for (TypeObjectField field in type.fields) {
+            if (field.value != null) {
+              continue;
+            }
+            comparisons.add(compareEqualsCode(
+                field.type, field.name, 'other.${field.name}'));
+          }
+        }
+        if (comparisons.isEmpty) {
+          writeln('return true;');
+        } else {
+          String concatenated = comparisons.join(' &&\n    ');
+          writeln('return $concatenated;');
+        }
+      });
+      writeln('}');
+      writeln('return false;');
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the method for decoding an object from JSON.
+   */
+  void emitObjectFromJsonConstructor(
+      String className, TypeObject type, ImpliedType impliedType) {
+    String humanReadableNameString =
+        literalString(impliedType.humanReadableName);
+    if (className == 'RefactoringFeedback') {
+      writeln('factory RefactoringFeedback.fromJson(JsonDecoder jsonDecoder, '
+          'String jsonPath, Object json, Map responseJson) {');
+      indent(() {
+        writeln('return refactoringFeedbackFromJson(jsonDecoder, jsonPath, '
+            'json, responseJson);');
+      });
+      writeln('}');
+      return;
+    }
+    if (className == 'RefactoringOptions') {
+      writeln('factory RefactoringOptions.fromJson(JsonDecoder jsonDecoder, '
+          'String jsonPath, Object json, RefactoringKind kind) {');
+      indent(() {
+        writeln('return refactoringOptionsFromJson(jsonDecoder, jsonPath, '
+            'json, kind);');
+      });
+      writeln('}');
+      return;
+    }
+    writeln(
+        'factory $className.fromJson(JsonDecoder jsonDecoder, String jsonPath, Object json) {');
+    indent(() {
+      writeln('if (json == null) {');
+      indent(() {
+        writeln('json = {};');
+      });
+      writeln('}');
+      writeln('if (json is Map) {');
+      indent(() {
+        List<String> args = <String>[];
+        List<String> optionalArgs = <String>[];
+        for (TypeObjectField field in type.fields) {
+          String fieldNameString = literalString(field.name);
+          String fieldAccessor = 'json[$fieldNameString]';
+          String jsonPath = 'jsonPath + ${literalString('.${field.name}')}';
+          if (field.value != null) {
+            String valueString = literalString(field.value);
+            writeln('if ($fieldAccessor != $valueString) {');
+            indent(() {
+              writeln(
+                  'throw jsonDecoder.mismatch(jsonPath, "equal " + $valueString, json);');
+            });
+            writeln('}');
+            continue;
+          }
+          if (isOptionalConstructorArg(className, field)) {
+            optionalArgs.add('${field.name}: ${field.name}');
+          } else {
+            args.add(field.name);
+          }
+          TypeDecl fieldType = field.type;
+          String fieldDartType = dartType(fieldType);
+          writeln('$fieldDartType ${field.name};');
+          writeln('if (json.containsKey($fieldNameString)) {');
+          indent(() {
+            String fromJson =
+                fromJsonCode(fieldType).asSnippet(jsonPath, fieldAccessor);
+            writeln('${field.name} = $fromJson;');
+          });
+          write('}');
+          if (!field.optional) {
+            writeln(' else {');
+            indent(() {
+              writeln(
+                  "throw jsonDecoder.mismatch(jsonPath, $fieldNameString);");
+            });
+            writeln('}');
+          } else {
+            writeln();
+          }
+        }
+        args.addAll(optionalArgs);
+        writeln('return new $className(${args.join(', ')});');
+      });
+      writeln('} else {');
+      indent(() {
+        writeln(
+            'throw jsonDecoder.mismatch(jsonPath, $humanReadableNameString, json);');
+      });
+      writeln('}');
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the hashCode getter for an object class.
+   */
+  void emitObjectHashCode(TypeObject type, String className) {
+    writeln('@override');
+    writeln('int get hashCode {');
+    indent(() {
+      if (type == null) {
+        writeln('return ${className.hashCode};');
+      } else {
+        writeln('int hash = 0;');
+        for (TypeObjectField field in type.fields) {
+          String valueToCombine;
+          if (field.value != null) {
+            valueToCombine = field.value.hashCode.toString();
+          } else {
+            valueToCombine = '${field.name}.hashCode';
+          }
+          writeln('hash = JenkinsSmiHash.combine(hash, $valueToCombine);');
+        }
+        writeln('return JenkinsSmiHash.finish(hash);');
+      }
+    });
+    writeln('}');
+  }
+
+  /**
+   * If the class named [className] requires special constructors, emit them
+   * and return true.
+   */
+  bool emitSpecialConstructors(String className) {
+    switch (className) {
+      case 'LinkedEditGroup':
+        docComment([new dom.Text('Construct an empty LinkedEditGroup.')]);
+        writeln(
+            'LinkedEditGroup.empty() : this(<Position>[], 0, <LinkedEditSuggestion>[]);');
+        return true;
+      case 'RefactoringProblemSeverity':
+        docComment([
+          new dom.Text(
+              'Returns the [RefactoringProblemSeverity] with the maximal severity.')
+        ]);
+        writeln(
+            'static RefactoringProblemSeverity max(RefactoringProblemSeverity a, RefactoringProblemSeverity b) =>');
+        writeln('    maxRefactoringProblemSeverity(a, b);');
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  /**
+   * If the class named [className] requires special getters, emit them and
+   * return true.
+   */
+  bool emitSpecialGetters(String className) {
+    switch (className) {
+      case 'Element':
+        for (String name in specialElementFlags.keys) {
+          String flag = 'FLAG_${name.toUpperCase()}';
+          writeln(
+              'bool get ${camelJoin(['is', name])} => (flags & $flag) != 0;');
+        }
+        return true;
+      case 'SourceEdit':
+        docComment([new dom.Text('The end of the region to be modified.')]);
+        writeln('int get end => offset + length;');
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  /**
+   * If the class named [className] requires special methods, emit them and
+   * return true.
+   */
+  bool emitSpecialMethods(String className) {
+    switch (className) {
+      case 'LinkedEditGroup':
+        docComment([new dom.Text('Add a new position and change the length.')]);
+        writeln('void addPosition(Position position, int length) {');
+        indent(() {
+          writeln('positions.add(position);');
+          writeln('this.length = length;');
+        });
+        writeln('}');
+        writeln();
+        docComment([new dom.Text('Add a new suggestion.')]);
+        writeln('void addSuggestion(LinkedEditSuggestion suggestion) {');
+        indent(() {
+          writeln('suggestions.add(suggestion);');
+        });
+        writeln('}');
+        return true;
+      case 'SourceChange':
+        docComment([
+          new dom.Text('Adds [edit] to the [FileEdit] for the given [file].')
+        ]);
+        writeln('void addEdit(String file, int fileStamp, SourceEdit edit) =>');
+        writeln('    addEditToSourceChange(this, file, fileStamp, edit);');
+        writeln();
+        docComment([new dom.Text('Adds the given [FileEdit].')]);
+        writeln('void addFileEdit(SourceFileEdit edit) {');
+        indent(() {
+          writeln('edits.add(edit);');
+        });
+        writeln('}');
+        writeln();
+        docComment([new dom.Text('Adds the given [LinkedEditGroup].')]);
+        writeln('void addLinkedEditGroup(LinkedEditGroup linkedEditGroup) {');
+        indent(() {
+          writeln('linkedEditGroups.add(linkedEditGroup);');
+        });
+        writeln('}');
+        writeln();
+        docComment([
+          new dom.Text(
+              'Returns the [FileEdit] for the given [file], maybe `null`.')
+        ]);
+        writeln('SourceFileEdit getFileEdit(String file) =>');
+        writeln('    getChangeFileEdit(this, file);');
+        return true;
+      case 'SourceEdit':
+        docComment([
+          new dom.Text(
+              'Get the result of applying the edit to the given [code].')
+        ]);
+        writeln('String apply(String code) => applyEdit(code, this);');
+        return true;
+      case 'SourceFileEdit':
+        docComment([new dom.Text('Adds the given [Edit] to the list.')]);
+        writeln('void add(SourceEdit edit) => addEditForSource(this, edit);');
+        writeln();
+        docComment([new dom.Text('Adds the given [Edit]s.')]);
+        writeln('void addAll(Iterable<SourceEdit> edits) =>');
+        writeln('    addAllEditsForSource(this, edits);');
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  /**
+   * If the class named [className] requires special static members, emit them
+   * and return true.
+   */
+  bool emitSpecialStaticMembers(String className) {
+    switch (className) {
+      case 'Element':
+        List<String> makeFlagsArgs = <String>[];
+        List<String> makeFlagsStatements = <String>[];
+        specialElementFlags.forEach((String name, String value) {
+          String flag = 'FLAG_${name.toUpperCase()}';
+          String camelName = camelJoin(['is', name]);
+          writeln('static const int $flag = $value;');
+          makeFlagsArgs.add('$camelName: false');
+          makeFlagsStatements.add('if ($camelName) flags |= $flag;');
+        });
+        writeln();
+        writeln('static int makeFlags({${makeFlagsArgs.join(', ')}}) {');
+        indent(() {
+          writeln('int flags = 0;');
+          for (String statement in makeFlagsStatements) {
+            writeln(statement);
+          }
+          writeln('return flags;');
+        });
+        writeln('}');
+        return true;
+      case 'SourceEdit':
+        docComment([
+          new dom.Text('Get the result of applying a set of ' +
+              '[edits] to the given [code].  Edits are applied in the order ' +
+              'they appear in [edits].')
+        ]);
+        writeln(
+            'static String applySequence(String code, Iterable<SourceEdit> edits) =>');
+        writeln('    applySequenceOfEdits(code, edits);');
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  /**
+   * Emit the toJson() code for an object class.
+   */
+  void emitToJsonMember(TypeObject type) {
+    writeln('@override');
+    writeln('Map<String, dynamic> toJson() {');
+    indent(() {
+      writeln('Map<String, dynamic> result = {};');
+      for (TypeObjectField field in type.fields) {
+        String fieldNameString = literalString(field.name);
+        if (field.value != null) {
+          writeln('result[$fieldNameString] = ${literalString(field.value)};');
+          continue;
+        }
+        String fieldToJson = toJsonCode(field.type).asSnippet(field.name);
+        String populateField = 'result[$fieldNameString] = $fieldToJson;';
+        if (field.optional) {
+          writeln('if (${field.name} != null) {');
+          indent(() {
+            writeln(populateField);
+          });
+          writeln('}');
+        } else {
+          writeln(populateField);
+        }
+      }
+      writeln('return result;');
+    });
+    writeln('}');
+  }
+
+  /**
+   * Emit the toNotification() code for a class, if appropriate.  Returns true
+   * if code was emitted.
+   */
+  bool emitToNotificationMember(ImpliedType impliedType) {
+    if (impliedType.kind == 'notificationParams') {
+      writeln('Notification toNotification() {');
+      indent(() {
+        String eventString =
+            literalString((impliedType.apiNode as Notification).longEvent);
+        String jsonPart = impliedType.type != null ? 'toJson()' : 'null';
+        writeln('return new Notification($eventString, $jsonPart);');
+      });
+      writeln('}');
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Emit the toRequest() code for a class, if appropriate.  Returns true if
+   * code was emitted.
+   */
+  bool emitToRequestMember(ImpliedType impliedType) {
+    if (impliedType.kind == 'requestParams') {
+      writeln('Request toRequest(String id) {');
+      indent(() {
+        String methodString =
+            literalString((impliedType.apiNode as Request).longMethod);
+        String jsonPart = impliedType.type != null ? 'toJson()' : 'null';
+        writeln('return new Request(id, $methodString, $jsonPart);');
+      });
+      writeln('}');
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Emit the toResponse() code for a class, if appropriate.  Returns true if
+   * code was emitted.
+   */
+  bool emitToResponseMember(ImpliedType impliedType) {
+    if (impliedType.kind == 'requestResult') {
+      writeln('@override');
+      writeln('Response toResponse(String id) {');
+      indent(() {
+        String jsonPart = impliedType.type != null ? 'toJson()' : 'null';
+        writeln('return new Response(id, result: $jsonPart);');
+      });
+      writeln('}');
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Compute the code necessary to translate [type] from JSON.
+   */
+  FromJsonCode fromJsonCode(TypeDecl type) {
+    if (type is TypeReference) {
+      TypeDefinition referencedDefinition = api.types[type.typeName];
+      if (referencedDefinition != null) {
+        TypeDecl referencedType = referencedDefinition.type;
+        if (referencedType is TypeObject || referencedType is TypeEnum) {
+          return new FromJsonSnippet((String jsonPath, String json) {
+            String typeName = dartType(type);
+            if (typeName == 'RefactoringFeedback') {
+              return 'new $typeName.fromJson(jsonDecoder, $jsonPath, $json, json)';
+            } else if (typeName == 'RefactoringOptions') {
+              return 'new $typeName.fromJson(jsonDecoder, $jsonPath, $json, kind)';
+            } else {
+              return 'new $typeName.fromJson(jsonDecoder, $jsonPath, $json)';
+            }
+          });
+        } else {
+          return fromJsonCode(referencedType);
+        }
+      } else {
+        switch (type.typeName) {
+          case 'String':
+            return new FromJsonFunction('jsonDecoder.decodeString');
+          case 'bool':
+            return new FromJsonFunction('jsonDecoder.decodeBool');
+          case 'int':
+          case 'long':
+            return new FromJsonFunction('jsonDecoder.decodeInt');
+          case 'object':
+            return new FromJsonIdentity();
+          default:
+            throw new Exception('Unexpected type name ${type.typeName}');
+        }
+      }
+    } else if (type is TypeMap) {
+      FromJsonCode keyCode;
+      if (dartType(type.keyType) != 'String') {
+        keyCode = fromJsonCode(type.keyType);
+      } else {
+        keyCode = new FromJsonIdentity();
+      }
+      FromJsonCode valueCode = fromJsonCode(type.valueType);
+      if (keyCode.isIdentity && valueCode.isIdentity) {
+        return new FromJsonFunction('jsonDecoder.decodeMap');
+      } else {
+        return new FromJsonSnippet((String jsonPath, String json) {
+          StringBuffer result = new StringBuffer();
+          result.write('jsonDecoder.decodeMap($jsonPath, $json');
+          if (!keyCode.isIdentity) {
+            result.write(', keyDecoder: ${keyCode.asClosure}');
+          }
+          if (!valueCode.isIdentity) {
+            result.write(', valueDecoder: ${valueCode.asClosure}');
+          }
+          result.write(')');
+          return result.toString();
+        });
+      }
+    } else if (type is TypeList) {
+      FromJsonCode itemCode = fromJsonCode(type.itemType);
+      if (itemCode.isIdentity) {
+        return new FromJsonFunction('jsonDecoder.decodeList');
+      } else {
+        return new FromJsonSnippet((String jsonPath, String json) =>
+            'jsonDecoder.decodeList($jsonPath, $json, ${itemCode.asClosure})');
+      }
+    } else if (type is TypeUnion) {
+      List<String> decoders = <String>[];
+      for (TypeDecl choice in type.choices) {
+        TypeDecl resolvedChoice = resolveTypeReferenceChain(choice);
+        if (resolvedChoice is TypeObject) {
+          TypeObjectField field = resolvedChoice.getField(type.field);
+          if (field == null) {
+            throw new Exception(
+                'Each choice in the union needs a field named ${type.field}');
+          }
+          if (field.value == null) {
+            throw new Exception(
+                'Each choice in the union needs a constant value for the field ${type.field}');
+          }
+          String closure = fromJsonCode(choice).asClosure;
+          decoders.add('${literalString(field.value)}: $closure');
+        } else {
+          throw new Exception('Union types must be unions of objects.');
+        }
+      }
+      return new FromJsonSnippet((String jsonPath, String json) =>
+          'jsonDecoder.decodeUnion($jsonPath, $json, ${literalString(type.field)}, {${decoders.join(', ')}})');
+    } else {
+      throw new Exception("Can't convert $type from JSON");
+    }
+  }
+
+  /**
+   * True if the constructor argument for the given field should be optional.
+   */
+  bool isOptionalConstructorArg(String className, TypeObjectField field) {
+    if (field.optional) {
+      return true;
+    }
+    List<String> forceOptional = _optionalConstructorArguments[className];
+    if (forceOptional != null && forceOptional.contains(field.name)) {
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Create a string literal that evaluates to [s].
+   */
+  String literalString(String s) {
+    return JSON.encode(s);
+  }
+
+  /**
+   * Compute the code necessary to convert [type] to JSON.
+   */
+  ToJsonCode toJsonCode(TypeDecl type) {
+    TypeDecl resolvedType = resolveTypeReferenceChain(type);
+    if (resolvedType is TypeReference) {
+      return new ToJsonIdentity(dartType(type));
+    } else if (resolvedType is TypeList) {
+      ToJsonCode itemCode = toJsonCode(resolvedType.itemType);
+      if (itemCode.isIdentity) {
+        return new ToJsonIdentity(dartType(type));
+      } else {
+        return new ToJsonSnippet(dartType(type),
+            (String value) => '$value.map(${itemCode.asClosure}).toList()');
+      }
+    } else if (resolvedType is TypeMap) {
+      ToJsonCode keyCode;
+      if (dartType(resolvedType.keyType) != 'String') {
+        keyCode = toJsonCode(resolvedType.keyType);
+      } else {
+        keyCode = new ToJsonIdentity(dartType(resolvedType.keyType));
+      }
+      ToJsonCode valueCode = toJsonCode(resolvedType.valueType);
+      if (keyCode.isIdentity && valueCode.isIdentity) {
+        return new ToJsonIdentity(dartType(resolvedType));
+      } else {
+        return new ToJsonSnippet(dartType(type), (String value) {
+          StringBuffer result = new StringBuffer();
+          result.write('mapMap($value');
+          if (!keyCode.isIdentity) {
+            result.write(', keyCallback: ${keyCode.asClosure}');
+          }
+          if (!valueCode.isIdentity) {
+            result.write(', valueCallback: ${valueCode.asClosure}');
+          }
+          result.write(')');
+          return result.toString();
+        });
+      }
+    } else if (resolvedType is TypeUnion) {
+      for (TypeDecl choice in resolvedType.choices) {
+        if (resolveTypeReferenceChain(choice) is! TypeObject) {
+          throw new Exception('Union types must be unions of objects');
+        }
+      }
+      return new ToJsonSnippet(
+          dartType(type), (String value) => '$value.toJson()');
+    } else if (resolvedType is TypeObject || resolvedType is TypeEnum) {
+      return new ToJsonSnippet(
+          dartType(type), (String value) => '$value.toJson()');
+    } else {
+      throw new Exception("Can't convert $resolvedType from JSON");
+    }
+  }
+
+  @override
+  visitApi() {
+    outputHeader(year: '2017');
+    writeln();
+    writeln("import 'dart:convert' hide JsonDecoder;");
+    writeln();
+    writeln("import 'package:analyzer/src/generated/utilities_general.dart';");
+    writeln("import 'package:analyzer_plugin/protocol/protocol.dart';");
+    writeln(
+        "import 'package:analyzer_plugin/src/protocol/protocol_internal.dart';");
+    emitClasses();
+  }
+}
+
+/**
+ * Container for code that can be used to translate a data type from JSON.
+ */
+abstract class FromJsonCode {
+  /**
+   * Get the translation code in the form of a closure.
+   */
+  String get asClosure;
+
+  /**
+   * True if the data type is already in JSON form, so the translation is the
+   * identity function.
+   */
+  bool get isIdentity;
+
+  /**
+   * Get the translation code in the form of a code snippet, where [jsonPath]
+   * is the variable holding the JSON path, and [json] is the variable holding
+   * the raw JSON.
+   */
+  String asSnippet(String jsonPath, String json);
+}
+
+/**
+ * Representation of FromJsonCode for a function defined elsewhere.
+ */
+class FromJsonFunction extends FromJsonCode {
+  @override
+  final String asClosure;
+
+  FromJsonFunction(this.asClosure);
+
+  @override
+  bool get isIdentity => false;
+
+  @override
+  String asSnippet(String jsonPath, String json) =>
+      '$asClosure($jsonPath, $json)';
+}
+
+/**
+ * Representation of FromJsonCode for the identity transformation.
+ */
+class FromJsonIdentity extends FromJsonSnippet {
+  FromJsonIdentity() : super((String jsonPath, String json) => json);
+
+  @override
+  bool get isIdentity => true;
+}
+
+/**
+ * Representation of FromJsonCode for a snippet of inline code.
+ */
+class FromJsonSnippet extends FromJsonCode {
+  /**
+   * Callback that can be used to generate the code snippet, once the names
+   * of the [jsonPath] and [json] variables are known.
+   */
+  final FromJsonSnippetCallback callback;
+
+  FromJsonSnippet(this.callback);
+
+  @override
+  String get asClosure =>
+      '(String jsonPath, Object json) => ${callback('jsonPath', 'json')}';
+
+  @override
+  bool get isIdentity => false;
+
+  @override
+  String asSnippet(String jsonPath, String json) => callback(jsonPath, json);
+}
+
+/**
+ * Container for code that can be used to translate a data type to JSON.
+ */
+abstract class ToJsonCode {
+  /**
+   * Get the translation code in the form of a closure.
+   */
+  String get asClosure;
+
+  /**
+   * True if the data type is already in JSON form, so the translation is the
+   * identity function.
+   */
+  bool get isIdentity;
+
+  /**
+   * Get the translation code in the form of a code snippet, where [value]
+   * is the variable holding the object to be translated.
+   */
+  String asSnippet(String value);
+}
+
+/**
+ * Representation of ToJsonCode for a function defined elsewhere.
+ */
+class ToJsonFunction extends ToJsonCode {
+  @override
+  final String asClosure;
+
+  ToJsonFunction(this.asClosure);
+
+  @override
+  bool get isIdentity => false;
+
+  @override
+  String asSnippet(String value) => '$asClosure($value)';
+}
+
+/**
+ * Representation of FromJsonCode for the identity transformation.
+ */
+class ToJsonIdentity extends ToJsonSnippet {
+  ToJsonIdentity(String type) : super(type, (String value) => value);
+
+  @override
+  bool get isIdentity => true;
+}
+
+/**
+ * Representation of ToJsonCode for a snippet of inline code.
+ */
+class ToJsonSnippet extends ToJsonCode {
+  /**
+   * Callback that can be used to generate the code snippet, once the name
+   * of the [value] variable is known.
+   */
+  final ToJsonSnippetCallback callback;
+
+  /**
+   * Dart type of the [value] variable.
+   */
+  final String type;
+
+  ToJsonSnippet(this.type, this.callback);
+
+  @override
+  String get asClosure => '($type value) => ${callback('value')}';
+
+  @override
+  bool get isIdentity => false;
+
+  @override
+  String asSnippet(String value) => callback(value);
+}