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//
// ConvertIfToNullCoalescingAction.cs
//
// Author:
// Luís Reis <luiscubal@gmail.com>
//
// Copyright (c) 2013 Luís Reis
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
using System;
using System.Linq;
using ICSharpCode.NRefactory.PatternMatching;
namespace ICSharpCode.NRefactory.CSharp.Refactoring
{
[ContextAction ("Convert 'if' to '??' expression",
Category = IssueCategories.Opportunities,
Description = "Convert 'if' statement to '??' expression.")]
public class ConvertIfToNullCoalescingAction : SpecializedCodeAction <IfElseStatement>
{
const string expressionGroupName = "expression";
const string comparedNodeGroupName = "comparedNode";
const string valueOnNullGroupName = "valueOnNull";
Expression ActionPattern;
public ConvertIfToNullCoalescingAction()
{
var leftPattern = PatternHelper.OptionalParentheses(new AnyNode(comparedNodeGroupName));
var rightPattern = PatternHelper.OptionalParentheses(new NullReferenceExpression());
var choicePattern = new Choice();
var equalityPattern = PatternHelper.CommutativeOperator(leftPattern, BinaryOperatorType.Equality, rightPattern);
var inequalityPattern = PatternHelper.CommutativeOperator(leftPattern.Clone(), BinaryOperatorType.InEquality, rightPattern.Clone());
choicePattern.Add(equalityPattern);
choicePattern.Add(inequalityPattern);
var namedChoicePattern = new NamedNode(expressionGroupName, choicePattern);
ActionPattern = PatternHelper.OptionalParentheses(namedChoicePattern);
}
protected override CodeAction GetAction (RefactoringContext context, IfElseStatement node)
{
var match = ActionPattern.Match(node.Condition);
if (!match.Success) {
return null;
}
var conditionExpression = match.Get<BinaryOperatorExpression>(expressionGroupName).Single();
bool isEqualityComparison = conditionExpression.Operator == BinaryOperatorType.Equality;
Expression comparedNode = match.Get<Expression>(comparedNodeGroupName).Single();
Statement contentStatement;
if (isEqualityComparison) {
contentStatement = node.TrueStatement;
if (!IsEmpty(node.FalseStatement)) {
return null;
}
} else {
contentStatement = node.FalseStatement;
if (!IsEmpty(node.TrueStatement)) {
return null;
}
}
contentStatement = GetSimpleStatement(contentStatement);
if (contentStatement == null) {
return null;
}
var leftExpressionPattern = PatternHelper.OptionalParentheses(comparedNode);
var expressionPattern = new AssignmentExpression(leftExpressionPattern, AssignmentOperatorType.Assign, new AnyNode(valueOnNullGroupName));
var statementPattern = new ExpressionStatement(PatternHelper.OptionalParentheses(expressionPattern));
var statementMatch = statementPattern.Match(contentStatement);
if (!statementMatch.Success) {
return null;
}
var rightSide = statementMatch.Get<Expression>(valueOnNullGroupName).Single();
return new CodeAction(context.TranslateString("Convert if statement to ?? expression"),
script => {
var previousNode = node.GetPrevSibling(sibling => sibling is Statement);
var previousDeclaration = previousNode as VariableDeclarationStatement;
if (previousDeclaration != null && previousDeclaration.Variables.Count() == 1) {
var variable = previousDeclaration.Variables.First();
var comparedNodeIdentifierExpression = comparedNode as IdentifierExpression;
if (comparedNodeIdentifierExpression != null &&
comparedNodeIdentifierExpression.Identifier == variable.Name) {
script.Replace(variable.Initializer, new BinaryOperatorExpression(variable.Initializer.Clone(),
BinaryOperatorType.NullCoalescing,
rightSide.Clone()));
script.Remove(node);
return;
}
}
var previousExpressionStatement = previousNode as ExpressionStatement;
if (previousExpressionStatement != null)
{
var previousAssignment = previousExpressionStatement.Expression as AssignmentExpression;
if (previousAssignment != null &&
comparedNode.IsMatch(previousAssignment.Left)) {
var newExpression = new BinaryOperatorExpression(previousAssignment.Right.Clone(),
BinaryOperatorType.NullCoalescing,
rightSide.Clone());
script.Replace(previousAssignment.Right, newExpression);
script.Remove(node);
return;
}
}
var coalescedExpression = new BinaryOperatorExpression(comparedNode.Clone(),
BinaryOperatorType.NullCoalescing,
rightSide.Clone());
var newAssignment = new ExpressionStatement(new AssignmentExpression(comparedNode.Clone(), coalescedExpression));
script.Replace(node, newAssignment);
}, node);
}
Statement GetSimpleStatement (Statement statement)
{
BlockStatement blockStatement;
while ((blockStatement = statement as BlockStatement) != null) {
var statements = blockStatement.Descendants.OfType<Statement>()
.Where(descendant => !IsEmpty(descendant)).ToList();
if (statements.Count() != 1) {
return null;
}
statement = statements.First();
}
return statement;
}
bool IsEmpty (Statement statement)
{
if (statement.IsNull) {
return true;
}
return !statement.DescendantsAndSelf.OfType<Statement>()
.Any(descendant => !(descendant is EmptyStatement || descendant is BlockStatement));
}
}
}
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