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//
// Gendarme.Rules.Maintainability.AvoidComplexMethodsRule class
//
// Authors:
// Cedric Vivier <cedricv@neonux.com>
//
// (C) 2008 Cedric Vivier
//
// 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 Mono.Cecil;
using Mono.Cecil.Cil;
using Gendarme.Framework;
using Gendarme.Framework.Rocks;
namespace Gendarme.Rules.Maintainability {
// TODO: Is this really configureable? It would be nice if this rule did check anonymous methods.
/// <summary>
/// This rule compute the cyclomatic complexity (CC) for every method and reports any method
/// with a CC over 25 (this limit is configurable). Large CC value often indicate complex
/// code that is hard to understand and maintain. It's likely that breaking the
/// method into several methods would help readability. This rule won't report any defects
/// on code generated by the compiler or by tools.
/// </summary>
/// <remarks>This rule is available since Gendarme 2.0</remarks>
[Problem ("Methods with a cyclomatic complexity equal or greater than 25 are harder to understand and maintain.")]
[Solution ("Simplify the method using refactors like Extract Method.")]
[FxCopCompatibility ("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity")]
public class AvoidComplexMethodsRule : Rule, IMethodRule {
// defaults match fxcop rule http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1575061&SiteID=1
// so people using both tools should not see conflicting results
public AvoidComplexMethodsRule ()
{
SuccessThreshold = 25;
}
public override void Initialize (IRunner runner)
{
base.Initialize (runner);
// works if only SuccessThreshold is configured in rules.xml
if (LowThreshold == 0)
LowThreshold = SuccessThreshold * 2;
if (MediumThreshold == 0)
MediumThreshold = SuccessThreshold * 3;
if (HighThreshold == 0)
HighThreshold = SuccessThreshold * 4;
}
public int SuccessThreshold { get; set; }
public int LowThreshold { get; set; }
public int MediumThreshold { get; set; }
public int HighThreshold { get; set; }
public RuleResult CheckMethod (MethodDefinition method)
{
//does rule apply?
if (!method.HasBody || method.IsGeneratedCode () || method.IsCompilerControlled)
return RuleResult.DoesNotApply;
//yay! rule do apply!
// quick optimization: if the number of instructions is lower
// than our SuccessThreshold then it cannot be too complex
if (method.Body.Instructions.Count < SuccessThreshold)
return RuleResult.Success;
int cc = GetCyclomaticComplexityForMethod(method);
if (cc < SuccessThreshold)
return RuleResult.Success;
//how's severity?
Severity sev = GetCyclomaticComplexitySeverity(cc);
Runner.Report (method, sev, Confidence.High, String.Format ("Method's cyclomatic complexity : {0}.", cc));
return RuleResult.Failure;
}
public Severity GetCyclomaticComplexitySeverity(int cc)
{
// 25 <= CC < 50 is not good but not catastrophic either
if (cc < LowThreshold)
return Severity.Low;
// 50 <= CC < 75 this should be refactored asap
if (cc < MediumThreshold)
return Severity.Medium;
// 75 <= CC < 100 this SHOULD be refactored asap
if (cc < HighThreshold)
return Severity.High;
// CC > 100, don't touch it since it may become a classic in textbooks
// anyway probably no one can understand it ;-)
return Severity.Critical;
}
public int GetCyclomaticComplexityForMethod (MethodDefinition method)
{
if ((method == null) || !method.HasBody)
return 1;
int cc = 1;
foreach (Instruction inst in method.Body.Instructions)
{
if (FlowControl.Branch == inst.OpCode.FlowControl)
{
//detect ternary pattern
// FIXME: nice case to look if using a OpCodeBitmask would be faster
if (null != inst && null != inst.Previous && inst.Previous.OpCode.Name.StartsWith ("ld", StringComparison.Ordinal))
cc++;
}
if (FlowControl.Cond_Branch != inst.OpCode.FlowControl)
{
continue;
}
if (inst.OpCode.Code == Code.Switch)
{
cc += GetNumberOfSwitchTargets(inst);
}
else //'normal' conditional branch
{
cc++;
}
}
return cc;
}
List<Instruction> targets = new List<Instruction> ();
private int GetNumberOfSwitchTargets (Instruction inst)
{
targets.Clear ();
foreach (Instruction target in ((Instruction[]) inst.Operand))
{
if (!targets.Contains (target))
{
targets.Add (target);
}
}
int nTargets = targets.Count;
//detect 'default' branch
if (FlowControl.Branch == inst.Next.OpCode.FlowControl)
{
if (inst.Next.Operand != FindFirstUnconditionalBranchTarget (targets[0]))
{
nTargets++;
}
}
return nTargets;
}
private static Instruction FindFirstUnconditionalBranchTarget(Instruction inst)
{
while (null != inst)
{
if (FlowControl.Branch == inst.OpCode.FlowControl)
{
return ((Instruction) inst.Operand);
}
inst = inst.Next;
}
return null;
}
}
}
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