Fix handling of backtrace frames (#1862)

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

Author: cleptric

src/FrameBuilder.php

@@ -221,11 +221,8 @@ private function getFunctionArgumentValues(\ReflectionFunctionAbstract $reflecti
 
             if ($reflectionParameter->isVariadic()) {
                 // For variadic parameters, collect all remaining arguments into an array
-                $variadicArgs = [];
-                for ($i = $parameterPosition; $i < \count($backtraceFrameArgs); ++$i) {
-                    $variadicArgs[] = $backtraceFrameArgs[$i];
-                }
-                $argumentValues[$reflectionParameter->getName()] = $variadicArgs;
+                $variadicArgs = \array_slice($backtraceFrameArgs, $parameterPosition);
+                $argumentValues[$reflectionParameter->getName()] = array_values($variadicArgs);
                 // Variadic parameter is always the last one, so we can break
                 break;
             }

tests/FrameBuilderTest.php

@@ -395,4 +395,39 @@ public function testGetFunctionArgumentsWithNullValues(): void
         $this->assertArrayHasKey('rest', $result);
         $this->assertSame(['extra1', null, 'extra3'], $result['rest']);
     }
+
+    public function testGetFunctionArgumentsWithGapsInBacktraceArrayIndices(): void
+    {
+        $options = new Options([]);
+        $frameBuilder = new FrameBuilder($options, new RepresentationSerializer($options));
+
+        $testFunction = function (string $first, int $second, ...$rest) {
+        };
+
+        $backtraceFrameArgs = [];
+        $backtraceFrameArgs[0] = 'hello';      // first parameter
+        $backtraceFrameArgs[1] = 42;           // second parameter
+        $backtraceFrameArgs[3] = 'extra1';     // gap at index 2, starts variadic args
+        $backtraceFrameArgs[5] = 'extra2';     // gap at index 4
+        $backtraceFrameArgs[7] = 'extra3';     // gap at index 6
+
+        $backtraceFrame = [
+            'function' => 'testGapsFunction',
+            'args' => $backtraceFrameArgs,
+        ];
+
+        $reflectionClass = new \ReflectionClass($frameBuilder);
+        $getFunctionArgumentValuesMethod = $reflectionClass->getMethod('getFunctionArgumentValues');
+        $getFunctionArgumentValuesMethod->setAccessible(true);
+
+        $reflectionFunction = new \ReflectionFunction($testFunction);
+
+        $result = $getFunctionArgumentValuesMethod->invoke($frameBuilder, $reflectionFunction, $backtraceFrame['args']);
+
+        $this->assertSame('hello', $result['first']);
+        $this->assertSame(42, $result['second']);
+
+        $this->assertArrayHasKey('rest', $result);
+        $this->assertSame(['extra1', 'extra2', 'extra3'], $result['rest']);
+    }
 }