Issue #13167: Fix NPE in UnusedLocalVariable check

config/pitest-suppressions/pitest-coding-2-suppressions.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<suppressedMutations>
+ <!-- until https://github.com/checkstyle/checkstyle/issues/14894 -->
+ <mutation unstable="false">
+ <sourceFile>UnusedLocalVariableCheck.java</sourceFile>
+ <mutatedClass>com.puppycrawl.tools.checkstyle.checks.coding.UnusedLocalVariableCheck</mutatedClass>
+ <mutatedMethod>getBlockContainingLocalAnonInnerClass</mutatedMethod>
+ <mutator>org.pitest.mutationtest.engine.gregor.mutators.NegateConditionalsMutator</mutator>
+ <description>negated conditional</description>
+ <lineContent>if (currentAst.getType() == TokenTypes.LAMBDA) {</lineContent>
+ </mutation>
+
+ <mutation unstable="false">
+ <sourceFile>UnusedLocalVariableCheck.java</sourceFile>
+ <mutatedClass>com.puppycrawl.tools.checkstyle.checks.coding.UnusedLocalVariableCheck</mutatedClass>
+ <mutatedMethod>getBlockContainingLocalAnonInnerClass</mutatedMethod>
+ <mutator>org.pitest.mutationtest.engine.gregor.mutators.RemoveConditionalMutator_EQUAL_IF</mutator>
+ <description>removed conditional - replaced equality check with true</description>
+ <lineContent>if (currentAst.getType() == TokenTypes.LAMBDA) {</lineContent>
+ </mutation>
+
+ <mutation unstable="false">
+ <sourceFile>UnusedLocalVariableCheck.java</sourceFile>
+ <mutatedClass>com.puppycrawl.tools.checkstyle.checks.coding.UnusedLocalVariableCheck</mutatedClass>
+ <mutatedMethod>isInsideLocalAnonInnerClass</mutatedMethod>
+ <mutator>org.pitest.mutationtest.engine.gregor.mutators.NegateConditionalsMutator</mutator>
+ <description>negated conditional</description>
+ <lineContent>if (currentAst.getType() == TokenTypes.SLIST) {</lineContent>
+ </mutation>
+
+ <mutation unstable="false">
+ <sourceFile>UnusedLocalVariableCheck.java</sourceFile>
+ <mutatedClass>com.puppycrawl.tools.checkstyle.checks.coding.UnusedLocalVariableCheck</mutatedClass>
+ <mutatedMethod>isInsideLocalAnonInnerClass</mutatedMethod>
+ <mutator>org.pitest.mutationtest.engine.gregor.mutators.RemoveConditionalMutator_EQUAL_IF</mutator>
+ <description>removed conditional - replaced equality check with true</description>
+ <lineContent>if (currentAst.getType() == TokenTypes.SLIST) {</lineContent>
+ </mutation>
+</suppressedMutations>

config/spotbugs-exclude.xml

@@ -315,4 +315,11 @@
  </Or>
  <Bug pattern="CT_CONSTRUCTOR_THROW"/>
  </Match>
+ <Match>
+ <!-- variable is just being saved for further analysis and isn't the main decider
+ of the loop if it is done or not -->
+ <Class name="com.puppycrawl.tools.checkstyle.checks.coding.UnusedLocalVariableCheck"/>
+ <Method name="getBlockContainingLocalAnonInnerClass"/>
+ <Bug pattern="SLS_SUSPICIOUS_LOOP_SEARCH"/>
+ </Match>
 </FindBugsFilter>

src/main/java/com/puppycrawl/tools/checkstyle/checks/coding/UnusedLocalVariableCheck.java

@@ -413,16 +413,18 @@ private static boolean isNonLocalTypeDeclaration(DetailAST typeDeclAst) {
  private static DetailAST getBlockContainingLocalAnonInnerClass(DetailAST literalNewAst) {
  DetailAST currentAst = literalNewAst;
  DetailAST result = null;
- while (!TokenUtil.isOfType(currentAst, CONTAINERS_FOR_ANON_INNERS)) {
- if (currentAst.getType() == TokenTypes.LAMBDA
- && currentAst.getParent()
- .getParent().getParent().getType() == TokenTypes.OBJBLOCK) {
- result = currentAst;
- break;
+ DetailAST topMostLambdaAst = null;
+ while (currentAst != null && !TokenUtil.isOfType(currentAst, CONTAINERS_FOR_ANON_INNERS)) {
+ if (currentAst.getType() == TokenTypes.LAMBDA) {
+ topMostLambdaAst = currentAst;
  }
  currentAst = currentAst.getParent();
  result = currentAst;
  }
+
+ if (currentAst == null) {
+ result = topMostLambdaAst;
+ }
  return result;
  }
 

src/test/java/com/puppycrawl/tools/checkstyle/checks/coding/UnusedLocalVariableCheckTest.java

@@ -327,6 +327,36 @@ public void testUnusedLocalVarEnum() throws Exception {
  expected);
  }
 
+ @Test
+ public void testUnusedLocalVarLambdas() throws Exception {
+ final String[] expected = {
+ "14:9: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "hoo"),
+ "20:17: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "j"),
+ "31:9: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "hoo2"),
+ "32:9: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "hoo3"),
+ "33:15: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "myComponent"),
+ "34:19: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "myComponent3"),
+ "40:25: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "j"),
+ "52:21: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "j"),
+ "65:17: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "ja"),
+ "73:9: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "k"),
+ };
+ verifyWithInlineConfigParser(
+ getPath("InputUnusedLocalVariableLambdaExpression.java"),
+ expected);
+ }
+
+ @Test
+ public void testUnusedLocalVariableLocalClasses() throws Exception {
+ final String[] expected = {
+ "14:9: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "a"),
+ "15:9: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "ab"),
+ };
+ verifyWithInlineConfigParser(
+ getPath("InputUnusedLocalVariableLocalClasses.java"),
+ expected);
+ }
+
  @Test
  public void testUnusedLocalVarRecords() throws Exception {
  final String[] expected = {

src/test/resources/com/puppycrawl/tools/checkstyle/checks/coding/unusedlocalvariable/InputUnusedLocalVariableLambdaExpression.java

@@ -0,0 +1,92 @@
+/*
+UnusedLocalVariable
+
+
+*/
+
+package com.puppycrawl.tools.checkstyle.checks.coding.unusedlocalvariable;
+
+import java.util.function.Supplier;
+
+public class InputUnusedLocalVariableLambdaExpression {
+ private final LambdaTest<String> myComponent = LambdaTest.lazy(() -> {
+ String foo = "";
+ String hoo = ""; // violation
+ new Runnable() {
+ String hoo = "";
+
+ @Override
+ public void run() {
+ String j = hoo; // violation
+ String ja = foo;
+ ja += "asd";
+ }
+ };
+ return "";
+ });
+
+ final LambdaTest<String> nestedLambdas = LambdaTest.lazy(() -> {
+ String foo = "";
+ String hoo = "";
+ String hoo2 = ""; // violation
+ String hoo3 = ""; // violation
+ final LambdaTest<String> myComponent = LambdaTest.lazy(() -> { // violation
+ final LambdaTest<String> myComponent3 = LambdaTest.lazy(() -> { // violation
+ new Runnable() {
+ String hoo2 = "";
+
+ @Override
+ public void run() {
+ String j = hoo; // violation
+ String ja = foo;
+ ja += hoo2;
+ }
+ };
+ return "";
+ });
+ new Runnable() {
+ String hoo3 = "";
+
+ @Override
+ public void run() {
+ String j = hoo3; // violation
+ String ja = foo;
+ ja += "asd";
+ }
+ };
+ return "";
+ });
+ new Runnable() {
+ String hoo2 = "";
+
+ @Override
+ public void run() {
+ String j = hoo2;
+ String ja = foo; // violation
+ j += hoo2;
+ }
+ };
+ return "";
+ });
+
+ final LambdaTest<String> nestedLambdas2 = LambdaTest.lazy(() -> {
+ String k = ""; // violation
+ final LambdaTest<String> nestedLambdas = LambdaTest.lazy(() -> {
+ new LambdaTest<String>() {
+ void foo() {
+ String j = k;
+ j += "asd";
+ }
+ };
+ return "";
+ });
+ return nestedLambdas.toString();
+ });
+}
+
+class LambdaTest<T> {
+ String k = "";
+ public static <T> LambdaTest<T> lazy(Supplier<T> supplier) {
+ return new LambdaTest<>();
+ }
+}

src/test/resources/com/puppycrawl/tools/checkstyle/checks/coding/unusedlocalvariable/InputUnusedLocalVariableLocalClasses.java

@@ -0,0 +1,26 @@
+/*
+UnusedLocalVariable
+
+
+*/
+
+package com.puppycrawl.tools.checkstyle.checks.coding.unusedlocalvariable;
+
+public class InputUnusedLocalVariableLocalClasses {
+
+ int a = 12;
+
+ void foo() {
+ int a = 12; // violation
+ int ab = 1; // violation
+
+ class asd {
+ InputUnusedLocalVariableLocalClasses a = new InputUnusedLocalVariableLocalClasses() {
+ void asd() {
+ System.out.println(a);
+ }
+ };
+ }
+ }
+
+}