Remove special list behavior in analysis server 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 'api.dart';
 import 'codegen_dart.dart';
@@ skipping 602 matching lines @@
     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.${field.name}';
       if (isOptionalConstructorArg(className, field)) {
         optionalArgs.add(arg);
-        TypeDecl fieldType = field.type;
-        if (fieldType is TypeList) {
-          extraInitCode.add(() {
-            writeln('if (${field.name} == null) {');
-            indent(() {
-              writeln('${field.name} = <${dartType(fieldType.itemType)}>[];');
+        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} = <${dartType(fieldType.itemType)}>[];');
+              });
+              writeln('}');
             });
-            writeln('}');
-          });
+          } else {
+            throw new Exception(
+                "Don't know how to create default field value.");
+          }
         }
       } else {
         args.add(arg);
       }
     }
     if (optionalArgs.isNotEmpty) {
       args.add('{${optionalArgs.join(', ')}}');
     }
     write('$className(${args.join(', ')})');
     if (extraInitCode.isEmpty) {
@@ skipping 32 matching lines @@
       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] = $fieldToJson;';
         if (field.optional) {
-          String condition;
-          if (field.type is TypeList) {
-            condition = '${field.name}.isNotEmpty';
-          } else {
-            condition = '${field.name} != null';
-          }
-          writeln('if ($condition) {');
+          writeln('if (${field.name} != null) {');
           indent(() {
             writeln(populateField);
           });
           writeln('}');
         } else {
           writeln(populateField);
         }
       }
       writeln('return result;');
     });
@@ skipping 341 matching lines @@
             writeln('${field.name} = $fromJson;');
           });
           write('}');
           if (!field.optional) {
             writeln(' else {');
             indent(() {
               writeln(
                   "throw jsonDecoder.missingKey(jsonPath, $fieldNameString);");
             });
             writeln('}');
-          } else if (fieldType is TypeList) {
-            writeln(' else {');
-            indent(() {
-              writeln('${field.name} = <${dartType(fieldType.itemType)}>[];');
-            });
-            writeln('}');
           } else {
             writeln();
           }
         }
         args.addAll(optionalArgs);
         writeln('return new $className(${args.join(', ')});');
       });
       writeln('} else {');
       indent(() {
         writeln(
@@ skipping 217 matching lines @@
   CodegenProtocolVisitor visitor = new CodegenProtocolVisitor(readApi());
   return visitor.collectCode(visitor.visitApi);
 });
 
 /**
  * Translate spec_input.html into protocol_matchers.dart.
  */
 main() {
   target.generate();
 }