Surviving pitest mutations for conditions reducing time complexity at PackageObjectFactory #11902
Description
Two mutation cases to discuss, these conditions are present to reduce the time complexity.
checkstyle/config/pitest-suppressions/pitest-common-suppressions.xml
Lines 210 to 217 in a583508
<mutation unstable="false">
<sourceFile>PackageObjectFactory.java</sourceFile>
<mutatedClass>com.puppycrawl.tools.checkstyle.PackageObjectFactory</mutatedClass>
<mutatedMethod>createModule</mutatedMethod>
<mutator>org.pitest.mutationtest.engine.gregor.mutators.RemoveConditionalMutator_EQUAL_IF</mutator>
<description>removed conditional - replaced equality check with true</description>
<lineContent>if (thirdPartyNameToFullModuleNames == null) {</lineContent>
</mutation>
Complete relevant code
This null check is present to reduce the time complexity, the method generateThirdPartyNameToFullModuleName(..) uses moduleClassLoader (final instance field) and packages (another final instance field) so even if thirdPartyNameToFullModuleNames is recalculated again and again the result will be the same. The only way it can change is if you access the internal fields, for eg - packages using reflections and add an element to the set. But in the current code those fields are not modified.
<mutation unstable="false">
<sourceFile>PackageObjectFactory.java</sourceFile>
<mutatedClass>com.puppycrawl.tools.checkstyle.PackageObjectFactory</mutatedClass>
<mutatedMethod>createModule</mutatedMethod>
<mutator>org.pitest.mutationtest.engine.gregor.mutators.RemoveConditionalMutator_EQUAL_IF</mutator>
<description>removed conditional - replaced equality check with true</description>
<lineContent>if (!name.contains(PACKAGE_SEPARATOR)) {</lineContent>
</mutation>
Complete relevant code
The mutation is replacing the condition with true, if there is some name with PACKAGE_SEPARATOR that enters this branch, then it is guaranteed that it will still remain null.
createFromStandardCheckSet(..) the standard check set does not contain any module which has PACKAGE_SEPARATOR in its short name.
generateThirdPartyNameToFullModuleName(..) implementation guarantees it that there are no short names which contain PACKAGE_SEPARATOR as it uses Class#getSimpleName() to get the short name.
This condition is only present to reduce the time complexity. But this time complexity is enormous, 4 min to 36 minutes for "mvn verify" , see #13752 (comment)