Add ability to indent stack traces in LineFormatter, fixes #1835

src/Monolog/Formatter/LineFormatter.php

@@ -32,6 +32,7 @@ class LineFormatter extends NormalizerFormatter
     protected bool $ignoreEmptyContextAndExtra;
     protected bool $includeStacktraces;
     protected ?int $maxLevelNameLength = null;
+    protected string $indentStacktraces = '';
     protected Closure|null $stacktracesParser = null;
 
     /**
@@ -64,6 +65,19 @@ class LineFormatter extends NormalizerFormatter
         return $this;
     }
 
+    /**
+     * Indent stack traces to separate them a bit from the main log record messages
+     *
+     * @param string $indent The string used to indent, for example "    "
+     * @return $this
+     */
+    public function indentStacktraces(string $indent): self
+    {
+        $this->indentStacktraces = $indent;
+
+        return $this;
+    }
+
     /**
      * @return $this
      */
@@ -261,7 +275,11 @@ class LineFormatter extends NormalizerFormatter
             $trace = $this->stacktracesParserCustom($trace);
         }
 
-        return "\n[stacktrace]\n" . $trace . "\n";
+        if ($this->indentStacktraces !== '') {
+            $trace = str_replace("\n", "\n{$this->indentStacktraces}", $trace);
+        }
+
+        return "\n{$this->indentStacktraces}[stacktrace]\n{$this->indentStacktraces}" . $trace . "\n";
     }
 
     private function stacktracesParserCustom(string $trace): string

tests/Monolog/Formatter/LineFormatterTest.php

@@ -13,6 +13,7 @@ namespace Monolog\Formatter;
 
 use Monolog\Test\TestCase;
 use Monolog\Level;
+use RuntimeException;
 
 /**
  * @covers Monolog\Formatter\LineFormatter
@@ -277,6 +278,19 @@ class LineFormatterTest extends TestCase
         $this->assertMatchesRegularExpression('/foo\nbar/', $message);
     }
 
+    public function testIndentStackTraces(): void
+    {
+        $formatter = new LineFormatter();
+        $formatter->includeStacktraces();
+        //$formatter->allowInlineLineBreaks();
+        $formatter->indentStackTraces('    ');
+        $message = $formatter->format($this->getRecord(message: "foo", context: ['exception' => new RuntimeException('lala')]));
+
+        $this->assertStringContainsString('    [stacktrace]', $message);
+        $this->assertStringContainsString('    #0', $message);
+        $this->assertStringContainsString('    #1', $message);
+    }
+
     /**
      * @dataProvider providerMaxLevelNameLength
      */