// // StringIsNullOrEmptyInspector.cs // // Author: // Mike Krüger // // Copyright (c) 2012 Xamarin // // 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.Collections.Generic; using System.Linq; using ICSharpCode.NRefactory.PatternMatching; namespace ICSharpCode.NRefactory.CSharp.Refactoring { /// /// Checks for str == null && str == "" /// Converts to: string.IsNullOrEmpty (str) /// [IssueDescription("Use string.IsNullOrEmpty", Description = "Uses shorter string.IsNullOrEmpty call instead of a longer condition.", Category = IssueCategories.Improvements, Severity = Severity.Suggestion)] public class StringIsNullOrEmptyIssue : ICodeIssueProvider { static readonly Pattern pattern = new Choice { // str == null || str == "" new BinaryOperatorExpression ( PatternHelper.CommutativeOperator(new AnyNode ("str"), BinaryOperatorType.Equality, new NullReferenceExpression ()), BinaryOperatorType.ConditionalOr, PatternHelper.CommutativeOperator(new Backreference ("str"), BinaryOperatorType.Equality, new PrimitiveExpression ("")) ), // str == "" || str == null new BinaryOperatorExpression ( PatternHelper.CommutativeOperator(new AnyNode ("str"), BinaryOperatorType.Equality, new PrimitiveExpression ("")), BinaryOperatorType.ConditionalOr, PatternHelper.CommutativeOperator(new Backreference ("str"), BinaryOperatorType.Equality, new NullReferenceExpression ()) ), }; static readonly Pattern negPattern = new Choice { // str != null && str != "" new BinaryOperatorExpression ( PatternHelper.CommutativeOperator(new AnyNode ("str"), BinaryOperatorType.InEquality, new NullReferenceExpression ()), BinaryOperatorType.ConditionalAnd, PatternHelper.CommutativeOperator(new Backreference ("str"), BinaryOperatorType.InEquality, new PrimitiveExpression ("")) ), // str != "" && str != null new BinaryOperatorExpression ( PatternHelper.CommutativeOperator(new AnyNode ("str"), BinaryOperatorType.InEquality, new PrimitiveExpression ("")), BinaryOperatorType.ConditionalAnd, PatternHelper.CommutativeOperator(new Backreference ("str"), BinaryOperatorType.InEquality, new NullReferenceExpression ()) ), }; public IEnumerable GetIssues(BaseRefactoringContext context) { return new GatherVisitor(context, this).GetIssues(); } class GatherVisitor : GatherVisitorBase { readonly StringIsNullOrEmptyIssue inspector; public GatherVisitor (BaseRefactoringContext ctx, StringIsNullOrEmptyIssue inspector) : base (ctx) { this.inspector = inspector; } public override void VisitBinaryOperatorExpression(BinaryOperatorExpression binaryOperatorExpression) { base.VisitBinaryOperatorExpression(binaryOperatorExpression); Match m = pattern.Match(binaryOperatorExpression); bool isNegated = false; if (!m.Success) { m = negPattern.Match(binaryOperatorExpression); isNegated = true; } if (m.Success) { var str = m.Get("str").Single(); AddIssue(binaryOperatorExpression, ctx.TranslateString("Use string.IsNullOrEmpty"), script => { Expression expr = new PrimitiveType ("string").Invoke("IsNullOrEmpty", str.Clone()); if (isNegated) expr = new UnaryOperatorExpression (UnaryOperatorType.Not, expr); script.Replace(binaryOperatorExpression, expr); }); return; } } } } }