Fix ICS escapeString to comply with RFC 5545 section 3.3.11

- Escape backslashes to \\ (was missing entirely)
- Normalize \r\n, \r, and \n to \n (RFC only defines \n, not \r)
- Use str_replace instead of addcslashes for correct ordering
  (backslash must be escaped first to avoid double-escaping)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: alies-dev

src/Generators/Ics.php

@@ -110,7 +110,11 @@ protected function buildFile(array $propertiesAndComponents): string
     /** @see https://tools.ietf.org/html/rfc5545.html#section-3.3.11 */
     protected function escapeString(string $field): string
     {
-        return addcslashes($field, "\r\n,;");
+        return str_replace(
+            ['\\', ';', ',', "\r\n", "\r", "\n"],
+            ['\\\\', '\\;', '\\,', '\\n', '\\n', '\\n'],
+            $field
+        );
     }
 
     /** @see https://tools.ietf.org/html/rfc5545#section-3.8.4.7 */

tests/Generators/IcsGeneratorTest.php

@@ -8,6 +8,7 @@
 use DateTimeZone;
 use Spatie\CalendarLinks\Generator;
 use Spatie\CalendarLinks\Generators\Ics;
+use Spatie\CalendarLinks\Link;
 use Spatie\CalendarLinks\Tests\TestCase;
 
 /**
@@ -94,4 +95,33 @@ public function it_can_generate_with_a_custom_reminder(): void
             ]])->generate($this->createShortEventLink())
         );
     }
+
+    /** @test */
+    public function it_escapes_backslashes_in_text_fields(): void
+    {
+        $link = Link::create(
+            'Event with \\ backslash',
+            DateTime::createFromFormat('Y-m-d H:i', '2024-01-01 09:00', new DateTimeZone('UTC')),
+            DateTime::createFromFormat('Y-m-d H:i', '2024-01-01 10:00', new DateTimeZone('UTC')),
+        )->description('Path: C:\\Users\\test');
+
+        $output = $this->generator()->generate($link);
+
+        $this->assertStringContainsString('SUMMARY:Event with \\\\ backslash', $output);
+        $this->assertStringContainsString('DESCRIPTION:Path: C:\\\\Users\\\\test', $output);
+    }
+
+    /** @test */
+    public function it_escapes_newlines_as_backslash_n(): void
+    {
+        $link = Link::create(
+            'Event',
+            DateTime::createFromFormat('Y-m-d H:i', '2024-01-01 09:00', new DateTimeZone('UTC')),
+            DateTime::createFromFormat('Y-m-d H:i', '2024-01-01 10:00', new DateTimeZone('UTC')),
+        )->description("Line 1\r\nLine 2\rLine 3\nLine 4");
+
+        $output = $this->generator()->generate($link);
+
+        $this->assertStringContainsString('DESCRIPTION:Line 1\\nLine 2\\nLine 3\\nLine 4', $output);
+    }
 }