Keep called method in RemoveEmptyClassMethodRector (#5425)

* Create keep_used_method.php.inc #8382

Rector should not remove empty private methods that are called from somewhere

* Keep called method in RemoveEmptyClassMethodRector

---------

Co-authored-by: noother <noothy@gmail.com>

rules-tests/DeadCode/Rector/ClassMethod/RemoveEmptyClassMethodRector/Fixture/keep_used_method.php.inc

@@ -0,0 +1,13 @@
+<?php
+
+namespace Rector\Tests\DeadCode\Rector\ClassMethod\RemoveEmptyClassMethodRector\Fixture;
+
+final class KeepUsedMethod {
+	public function bar()
+    {
+		$this->gaz();
+	}
+
+	private function gaz() {
+	}
+}

rules/DeadCode/Rector/ClassMethod/RemoveEmptyClassMethodRector.php

@@ -5,6 +5,8 @@
 namespace Rector\DeadCode\Rector\ClassMethod;
 
 use PhpParser\Node;
+use PhpParser\Node\Expr\MethodCall;
+use PhpParser\Node\Expr\Variable;
 use PhpParser\Node\Name\FullyQualified;
 use PhpParser\Node\Stmt\Class_;
 use PhpParser\Node\Stmt\ClassMethod;
@@ -14,6 +16,7 @@
 use Rector\DeadCode\NodeManipulator\ControllerClassMethodManipulator;
 use Rector\NodeAnalyzer\ParamAnalyzer;
 use Rector\NodeManipulator\ClassMethodManipulator;
+use Rector\PhpParser\Node\BetterNodeFinder;
 use Rector\Rector\AbstractRector;
 use Rector\ValueObject\MethodName;
 use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
@@ -29,6 +32,7 @@ public function __construct(
         private readonly ControllerClassMethodManipulator $controllerClassMethodManipulator,
         private readonly ParamAnalyzer $paramAnalyzer,
         private readonly PhpDocInfoFactory $phpDocInfoFactory,
+        private readonly BetterNodeFinder $betterNodeFinder
     ) {
     }
 
@@ -127,6 +131,19 @@ private function shouldSkipNonFinalNonPrivateClassMethod(Class_ $class, ClassMet
 
     private function shouldSkipClassMethod(Class_ $class, ClassMethod $classMethod): bool
     {
+        $desiredClassMethodName = $this->getName($classMethod);
+
+        // is method called somewhere else in the class?
+        foreach ($class->getMethods() as $anotherClassMethod) {
+            if ($anotherClassMethod === $classMethod) {
+                continue;
+            }
+
+            if ($this->containsMethodCall($anotherClassMethod, $desiredClassMethodName)) {
+                return true;
+            }
+        }
+
         if ($this->classMethodManipulator->isNamedConstructor($classMethod)) {
             return true;
         }
@@ -164,4 +181,25 @@ private function hasDeprecatedAnnotation(ClassMethod $classMethod): bool
 
         return $phpDocInfo->hasByType(DeprecatedTagValueNode::class);
     }
+
+    private function containsMethodCall(ClassMethod $anotherClassMethod, string $desiredClassMethodName): bool
+    {
+        return (bool) $this->betterNodeFinder->findFirst($anotherClassMethod, function (Node $node) use (
+            $desiredClassMethodName
+        ): bool {
+            if (! $node instanceof MethodCall) {
+                return false;
+            }
+
+            if (! $node->var instanceof Variable) {
+                return false;
+            }
+
+            if (! $this->isName($node->var, 'this')) {
+                return false;
+            }
+
+            return $this->isName($node->name, $desiredClassMethodName);
+        });
+    }
 }