Fix variadic function as callback

Author: kubawerlos

.psalm/baseline.xml

@@ -442,7 +442,7 @@
                 'arguments_call'     => $this->argumentsForCall,
                 'return_declaration' => !empty($this->returnType->asString()) ? (': ' . $this->returnType->asString()) : '',
                 'return_type'        => $this->returnType->asString(),
-                'arguments_count'    => !empty($this->argumentsForCall) ? substr_count($this->argumentsForCall, ',') + 1 : 0,
+                'arguments_count'    => $argumentsCount,
                 'class_name'         => $this->className,
                 'method_name'        => $this->methodName,
                 'modifier'           => $this->modifier,

src/Framework/Constraint/Callback.php

@@ -9,6 +9,8 @@
  */
 namespace PHPUnit\Framework\Constraint;
 
+use ReflectionFunction;
+
 /**
  * @psalm-template CallbackInput of mixed
  *
@@ -37,14 +39,32 @@ public function toString(): string
         return 'is accepted by specified callback';
     }
 
+    /**
+     * @psalm-suppress ArgumentTypeCoercion
+     */
+    public function hasVariadicParam(): bool
+    {
+        foreach ((new ReflectionFunction($this->callback))->getParameters() as $parameter) {
+            if ($parameter->isVariadic()) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     /**
      * Evaluates the constraint for parameter $value. Returns true if the
      * constraint is met, false otherwise.
      *
      * @psalm-param CallbackInput $other
+     *
+     * @psalm-suppress InvalidArgument
      */
     protected function matches(mixed $other): bool
     {
-        return ($this->callback)($other);
+        return $this->hasVariadicParam()
+            ? ($this->callback)(...$other)
+            : ($this->callback)($other);
     }
 }

src/Framework/MockObject/Generator/MockMethod.php

@@ -9,6 +9,7 @@
  */
 namespace PHPUnit\Framework\MockObject\Generator;
 
+use const PHP_INT_MAX;
 use function count;
 use function explode;
 use function implode;
@@ -17,6 +18,7 @@
 use function preg_match;
 use function preg_replace;
 use function sprintf;
+use function str_contains;
 use function strlen;
 use function strpos;
 use function substr;
@@ -211,13 +213,21 @@ public function generateCode(): string
 
         $template = $this->loadTemplate($templateFile);
 
+        $argumentsCount = 0;
+
+        if (str_contains($this->argumentsForCall, '...')) {
+            $argumentsCount = PHP_INT_MAX; // @todo: change it to null and update end-to-end tests
+        } elseif (!empty($this->argumentsForCall)) {
+            $argumentsCount = substr_count($this->argumentsForCall, ',') + 1;
+        }
+
         $template->setVar(
             [
                 'arguments_decl'     => $this->argumentsForDeclaration,
                 'arguments_call'     => $this->argumentsForCall,
                 'return_declaration' => !empty($this->returnType->asString()) ? (': ' . $this->returnType->asString()) : '',
                 'return_type'        => $this->returnType->asString(),
-                'arguments_count'    => !empty($this->argumentsForCall) ? substr_count($this->argumentsForCall, ',') + 1 : 0,
+                'arguments_count'    => $argumentsCount,
                 'class_name'         => $this->className,
                 'method_name'        => $this->methodName,
                 'modifier'           => $this->modifier,

src/Framework/MockObject/Runtime/Rule/Parameters.php

@@ -12,6 +12,7 @@
 use function count;
 use function sprintf;
 use Exception;
+use PHPUnit\Framework\Constraint\Callback;
 use PHPUnit\Framework\Constraint\Constraint;
 use PHPUnit\Framework\Constraint\IsAnything;
 use PHPUnit\Framework\Constraint\IsEqual;
@@ -108,8 +109,13 @@ private function doVerify(): bool
         }
 
         foreach ($this->parameters as $i => $parameter) {
+            if ($parameter instanceof Callback && $parameter->hasVariadicParam()) {
+                $other = $this->invocation->parameters();
+            } else {
+                $other = $this->invocation->parameters()[$i];
+            }
             $parameter->evaluate(
-                $this->invocation->parameters()[$i],
+                $other,
                 sprintf(
                     'Parameter %s for invocation %s does not match expected ' .
                     'value.',