Fix additional cases where analysis server might send null, violating protocol.

pkg/analysis_server/tool/spec/codegen_dart_protocol.dart

 // Copyright (c) 2014, 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 codegen.protocol;
 
 import 'dart:convert';
 
 import 'package:html5lib/dom.dart' as dom;
 
 import 'api.dart';
 import 'codegen_dart.dart';
 import 'codegen_tools.dart';
 import 'from_html.dart';
 import 'implied_types.dart';
 import 'to_html.dart';
 
 /**
+ * Translate spec_input.html into protocol_matchers.dart.
+ */
+main() {
+  target.generate();
+}
+
+/**
  * 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/src/generated_protocol.dart', () {
   CodegenProtocolVisitor visitor = new CodegenProtocolVisitor(readApi());
   return visitor.collectCode(visitor.visitApi);
 });
 
 /**
- * Translate spec_input.html into protocol_matchers.dart.
- */
-main() {
-  target.generate();
-}
-
-/**
  * 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.
@@ skipping 321 matching lines @@
     }
     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)} ${field.name};');
+        writeln('${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._${field.name} = value;');
+        });
+        writeln('}');
         writeln();
       }
       emitObjectConstructor(type, className);
       writeln();
       emitObjectFromJsonConstructor(className, type, impliedType);
       writeln();
       if (emitConvenienceConstructor(className, impliedType)) {
         writeln();
       }
       if (emitSpecialConstructors(className)) {
@@ skipping 30 matching lines @@
    * Emit the constructor for an object class.
    */
   void emitObjectConstructor(TypeObject type, String className) {
     List<String> args = <String>[];
     List<String> optionalArgs = <String>[];
     List<CodegenCallback> extraInitCode = <CodegenCallback>[];
     for (TypeObjectField field in type.fields) {
       if (field.value != null) {
         continue;
       }
-      String arg = 'this.${field.name}';
+      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('${field.name} = <${dartType(fieldType.itemType)}>[];');
+                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(' {');
@@ skipping 719 matching lines @@
 
   @override
   String get asClosure => '($type value) => ${callback('value')}';
 
   @override
   bool get isIdentity => false;
 
   @override
   String asSnippet(String value) => callback(value);
 }