Simplify conversion of empty lists to null.

pkg/analysis_server/lib/src/computer/computer_outline.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 computer.outline;
 
+import 'package:analysis_server/src/collections.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart' as engine;
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 
 /**
  * A computer for [CompilationUnit] outline.
  */
@@ skipping 154 matching lines @@
         name,
         Element.makeFlags(
             isPrivate: Identifier.isPrivateName(name),
             isDeprecated: _isDeprecated(classDeclaration),
             isAbstract: classDeclaration.isAbstract),
         location: _getLocationNode(nameNode));
     return new Outline(
         element,
         sourceRegion.offset,
         sourceRegion.length,
-        children: classContents.isEmpty ? null : classContents);
+        children: nullIfEmpty(classContents));

[scheglov, 2014/10/06 17:53:35]

Actually, we could probably change the Outline constructor and put this check in
there...

   }
 
   Outline _newClassTypeAlias(ClassTypeAlias alias) {
     SimpleIdentifier nameNode = alias.name;
     String name = nameNode.name;
     _SourceRegion sourceRegion = _getSourceRegion(alias);
     Element element = new Element(
         ElementKind.CLASS_TYPE_ALIAS,
         name,
         Element.makeFlags(
@@ skipping 27 matching lines @@
         Element.makeFlags(
             isPrivate: isPrivate,
             isDeprecated: _isDeprecated(constructor)),
         location: _getLocationOffsetLength(offset, length),
         parameters: parametersStr);
     List<Outline> contents = _addLocalFunctionOutlines(constructor.body);
     Outline outline = new Outline(
         element,
         sourceRegion.offset,
         sourceRegion.length,
-        children: contents.isEmpty ? null : contents);
+        children: nullIfEmpty(contents));
     return outline;
   }
 
   Outline _newFunctionOutline(FunctionDeclaration function, bool isStatic) {
     TypeName returnType = function.returnType;
     SimpleIdentifier nameNode = function.name;
     String name = nameNode.name;
     FunctionExpression functionExpression = function.functionExpression;
     FormalParameterList parameters = functionExpression.parameters;
     ElementKind kind;
@@ skipping 15 matching lines @@
             isDeprecated: _isDeprecated(function),
             isStatic: isStatic),
         location: _getLocationNode(nameNode),
         parameters: parametersStr,
         returnType: returnTypeStr);
     List<Outline> contents = _addLocalFunctionOutlines(functionExpression.body);
     Outline outline = new Outline(
         element,
         sourceRegion.offset,
         sourceRegion.length,
-        children: contents.isEmpty ? null : contents);
+        children: nullIfEmpty(contents));
     return outline;
   }
 
   Outline _newFunctionTypeAliasOutline(FunctionTypeAlias alias) {
     TypeName returnType = alias.returnType;
     SimpleIdentifier nameNode = alias.name;
     String name = nameNode.name;
     _SourceRegion sourceRegion = _getSourceRegion(alias);
     FormalParameterList parameters = alias.parameters;
     String parametersStr = parameters != null ? parameters.toSource() : '';
@@ skipping 35 matching lines @@
             isAbstract: method.isAbstract,
             isStatic: method.isStatic),
         location: _getLocationNode(nameNode),
         parameters: parametersStr,
         returnType: returnTypeStr);
     List<Outline> contents = _addLocalFunctionOutlines(method.body);
     Outline outline = new Outline(
         element,
         sourceRegion.offset,
         sourceRegion.length,
-        children: contents.isEmpty ? null : contents);
+        children: nullIfEmpty(contents));
     return outline;
   }
 
   Outline _newUnitOutline(List<Outline> unitContents) {
     Element element = new Element(
         ElementKind.COMPILATION_UNIT,
         '<unit>',
         Element.makeFlags(),
         location: _getLocationNode(_unit));
     return new Outline(
         element,
         _unit.offset,
         _unit.length,
-        children: unitContents.isEmpty ? null : unitContents);
+        children: nullIfEmpty(unitContents));
   }
 
   Outline _newVariableOutline(String typeName, ElementKind kind,
       VariableDeclaration variable, bool isStatic) {
     SimpleIdentifier nameNode = variable.name;
     String name = nameNode.name;
     _SourceRegion sourceRegion = _getSourceRegion(variable);
     Element element = new Element(
         kind,
         name,
@@ skipping 37 matching lines @@
 
 
 /**
  * A range of characters.
  */
 class _SourceRegion {
   final int length;
   final int offset;
   _SourceRegion(this.offset, this.length);
 }