feat(formatter): add maxTraceLength config option to NormalizerFormatter (#2015)

Add maxTraceLength property to NormalizerFormatter to limit the number
of stack trace frames included when normalizing exceptions.

Allows users who need control over their log length to avoid
truncating the log and causing invalid json syntax

src/Monolog/Formatter/NormalizerFormatter.php

@@ -28,6 +28,7 @@ class NormalizerFormatter implements FormatterInterface
     protected string $dateFormat;
     protected int $maxNormalizeDepth = 9;
     protected int $maxNormalizeItemCount = 1000;
+    protected ?int $maxTraceLength = null;
 
     private int $jsonEncodeOptions = Utils::DEFAULT_JSON_FLAGS;
 
@@ -122,6 +123,24 @@ class NormalizerFormatter implements FormatterInterface
         return $this;
     }
 
+    /**
+     * The maximum number of stack trace frames to include
+     */
+    public function getMaxTraceLength(): ?int
+    {
+        return $this->maxTraceLength;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setMaxTraceLength(?int $maxTraceLength): self
+    {
+        $this->maxTraceLength = $maxTraceLength;
+
+        return $this;
+    }
+
     /**
      * Enables `json_encode` pretty print.
      *
@@ -290,7 +309,7 @@ class NormalizerFormatter implements FormatterInterface
             }
         }
 
-        $trace = $e->getTrace();
+        $trace = array_slice($e->getTrace(), 0, $this->maxTraceLength);
         foreach ($trace as $frame) {
             if (isset($frame['file'], $frame['line'])) {
                 $file = $frame['file'];

tests/Monolog/Formatter/NormalizerFormatterTest.php

@@ -439,6 +439,102 @@ class NormalizerFormatterTest extends \Monolog\Test\MonologTestCase
         ], $result['context']['object']);
     }
 
+    public function testMaxTraceLengthDefault()
+    {
+        $formatter = new NormalizerFormatter();
+        $this->assertNull($formatter->getMaxTraceLength());
+    }
+
+    public function testMaxTraceLengthSetter()
+    {
+        $formatter = new NormalizerFormatter();
+        $formatter->setMaxTraceLength(5);
+        $this->assertEquals(5, $formatter->getMaxTraceLength());
+
+        $formatter->setMaxTraceLength(null);
+        $this->assertNull($formatter->getMaxTraceLength());
+    }
+
+    public function testMaxTraceLengthLimitsTrace()
+    {
+        $formatter = new NormalizerFormatter();
+        $formatter->setMaxTraceLength(2);
+
+        $exception = $this->createDeepTraceException();
+        $formatted = $formatter->normalizeValue(['exception' => $exception]);
+
+        $this->assertArrayHasKey('trace', $formatted['exception']);
+        $this->assertCount(2, $formatted['exception']['trace']);
+    }
+
+    public function testMaxTraceLengthZeroDoesNotIncludeTrace()
+    {
+        $formatter = new NormalizerFormatter();
+        $formatter->setMaxTraceLength(0);
+
+        $exception = $this->createDeepTraceException();
+        $formatted = $formatter->normalizeValue(['exception' => $exception]);
+
+        $this->assertArrayNotHasKey('trace', $formatted['exception']);
+    }
+
+    public function testMaxTraceLengthNullAllowsUnlimited()
+    {
+        $formatter = new NormalizerFormatter();
+        $formatter->setMaxTraceLength(null);
+
+        $exception = $this->createDeepTraceException();
+        $formatted = $formatter->normalizeValue(['exception' => $exception]);
+
+        $this->assertArrayHasKey('trace', $formatted['exception']);
+        $this->assertGreaterThan(2, count($formatted['exception']['trace']));
+    }
+
+    public function testMaxTraceLengthWithPreviousException()
+    {
+        $formatter = new NormalizerFormatter();
+        $formatter->setMaxTraceLength(1);
+
+        $previous = new \RuntimeException('Previous exception');
+        $exception = new \LogicException('Main exception', 0, $previous);
+        $formatted = $formatter->normalizeValue(['exception' => $exception]);
+
+        $this->assertArrayHasKey('trace', $formatted['exception']);
+        $this->assertCount(1, $formatted['exception']['trace']);
+        $this->assertArrayHasKey('previous', $formatted['exception']);
+        $this->assertArrayHasKey('trace', $formatted['exception']['previous']);
+        $this->assertCount(1, $formatted['exception']['previous']['trace']);
+    }
+
+    public function testMaxTraceLengthWithBasePath()
+    {
+        $formatter = new NormalizerFormatter();
+        $formatter->setMaxTraceLength(3);
+        $formatter->setBasePath(dirname(__DIR__, 3));
+
+        $exception = $this->createDeepTraceException();
+        $formatted = $formatter->normalizeValue(['exception' => $exception]);
+
+        $this->assertArrayHasKey('trace', $formatted['exception']);
+        $this->assertCount(3, $formatted['exception']['trace']);
+
+        foreach ($formatted['exception']['trace'] as $traceItem) {
+            $this->assertStringNotContainsString(dirname(__DIR__, 3), $traceItem);
+        }
+    }
+
+    private function createDeepTraceException(): \Exception
+    {
+        $createException = function(int $depth) use (&$createException): \Exception {
+            if ($depth <= 0) {
+                return new \RuntimeException('Test exception with deep trace');
+            }
+            return $createException($depth - 1);
+        };
+
+        return $createException(3);
+    }
+
     private function throwHelper($arg)
     {
         throw new \RuntimeException('Thrown');