SONARPHP-1535 S1172 should not raise an issue on throwaway variables (#…

…1325)
SonarSource · Nov 21, 2024 · d0f423e · d0f423e
1 parent f2451ea
commit d0f423e
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Showing 2 changed files with 19 additions and 3 deletions.
diff --git a/php-checks/src/main/java/org/sonar/php/checks/UnusedFunctionParametersCheck.java b/php-checks/src/main/java/org/sonar/php/checks/UnusedFunctionParametersCheck.java
@@ -46,8 +46,8 @@ public class UnusedFunctionParametersCheck extends PHPVisitorCheck {
 
   public static final String KEY = "S1172";
   private static final String MESSAGE = "Remove the unused function parameter \"%s\".";
-  Deque<Boolean> hasFuncGetArgsStack = new ArrayDeque<>();
-  List<IdentifierTree> constructorPromotedProperties = new ArrayList<>();
+  private final Deque<Boolean> hasFuncGetArgsStack = new ArrayDeque<>();
+  private List<IdentifierTree> constructorPromotedProperties = new ArrayList<>();
 
   @Override
   public void visitFunctionCall(FunctionCallTree tree) {
@@ -94,7 +94,7 @@ private void checkParameters(FunctionTree tree) {
       List<IdentifierTree> unused = new ArrayList<>();
 
       for (Symbol symbol : scope.getSymbols(Symbol.Kind.PARAMETER)) {
-        if (symbol.usages().isEmpty() && !constructorPromotedProperties.contains(symbol.declaration())) {
+        if (!isExcluded(symbol) && symbol.usages().isEmpty() && !constructorPromotedProperties.contains(symbol.declaration())) {
           unused.add(symbol.declaration());
         }
       }
@@ -124,4 +124,10 @@ private static boolean isExcluded(MethodDeclarationTree tree) {
       || (methodSymbol.visibility() != Visibility.PRIVATE && methodSymbol.owner().is(ClassSymbol.Kind.ABSTRACT));
   }
 
+  private static boolean isExcluded(Symbol symbol) {
+    return symbol.name().chars()
+      // skip the leading '$'
+      .skip(1)
+      .allMatch(c -> '_' == c);
+  }
 }
diff --git a/php-checks/src/test/resources/checks/UnusedFunctionParametersCheck.php b/php-checks/src/test/resources/checks/UnusedFunctionParametersCheck.php
@@ -227,3 +227,13 @@ public function __construct($a) {} // Noncompliant
   public function __construct(private $a, $b) {} // Noncompliant
 //                                        ^^
 }
+
+// Compliant: exclude underscore as a convention for unused variable
+$x = function($p1, $_, $__) {
+  return $p1;
+};
+
+// Underscore as a prefix has no special meaning
+$x = function($p1, $_p2, $__p3) { // Noncompliant 2
+  return $p1;
+};