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//
// StringIsNullOrEmptyInspector.cs
//
// Author:
// Mike Krüger <mkrueger@xamarin.com>
//
// Copyright (c) 2012 Xamarin <http://xamarin.com>
//
// 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;
using ICSharpCode.NRefactory.Refactoring;
namespace ICSharpCode.NRefactory.CSharp.Refactoring
{
/// <summary>
/// Checks for str == null && str == " "
/// Converts to: string.IsNullOrEmpty (str)
/// </summary>
[IssueDescription("Use 'String.IsNullOrEmpty'",
Description = "Uses shorter string.IsNullOrEmpty call instead of a longer condition.",
Category = IssueCategories.PracticesAndImprovements,
Severity = Severity.Suggestion,
ResharperDisableKeyword = "ReplaceWithStringIsNullOrEmpty")]
public class ReplaceWithStringIsNullOrEmptyIssue : ICodeIssueProvider
{
static readonly Pattern pattern = new Choice {
// str == null || str == ""
// str == null || str.Length == 0
new BinaryOperatorExpression (
PatternHelper.CommutativeOperator (new AnyNode ("str"), BinaryOperatorType.Equality, new NullReferenceExpression ()),
BinaryOperatorType.ConditionalOr,
new Choice {
PatternHelper.CommutativeOperator (new Backreference ("str"), BinaryOperatorType.Equality, new PrimitiveExpression ("")),
PatternHelper.CommutativeOperator (
new MemberReferenceExpression (new Backreference ("str"), "Length"),
BinaryOperatorType.Equality,
new PrimitiveExpression (0)
)
}
),
// 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 != ""
// str != null && str.Length != 0
// str != null && str.Length > 0
new BinaryOperatorExpression (
PatternHelper.CommutativeOperator(new AnyNode ("str"), BinaryOperatorType.InEquality, new NullReferenceExpression ()),
BinaryOperatorType.ConditionalAnd,
new Choice {
PatternHelper.CommutativeOperator (new Backreference ("str"), BinaryOperatorType.InEquality, new PrimitiveExpression ("")),
PatternHelper.CommutativeOperator (
new MemberReferenceExpression (new Backreference ("str"), "Length"),
BinaryOperatorType.InEquality,
new PrimitiveExpression (0)
),
new BinaryOperatorExpression (
new MemberReferenceExpression (new Backreference ("str"), "Length"),
BinaryOperatorType.GreaterThan,
new PrimitiveExpression (0)
)
}
),
// 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<CodeIssue> GetIssues(BaseRefactoringContext context)
{
return new GatherVisitor(context).GetIssues();
}
class GatherVisitor : GatherVisitorBase<ReplaceWithStringIsNullOrEmptyIssue>
{
public GatherVisitor (BaseRefactoringContext ctx) : base (ctx)
{
}
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<Expression>("str").Single();
var def = ctx.Resolve (str).Type.GetDefinition ();
if (def == null || def.KnownTypeCode != ICSharpCode.NRefactory.TypeSystem.KnownTypeCode.String)
return;
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;
}
}
}
}
}
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