Implement safe token reads when parsing message body parts

src/BodyStructurePart.php

@@ -43,18 +43,46 @@ protected static function parse(array $tokens, string $partNumber): static
     {
         return new static(
             partNumber: $partNumber,
-            type: isset($tokens[0]) ? strtolower($tokens[0]->value) : 'text',
-            subtype: isset($tokens[1]) ? strtolower($tokens[1]->value) : 'plain',
+            type: strtolower(static::tokenValueAt($tokens, 0) ?? 'text'),
+            subtype: strtolower(static::tokenValueAt($tokens, 1) ?? 'plain'),
             parameters: isset($tokens[2]) && $tokens[2] instanceof ListData ? $tokens[2]->toKeyValuePairs() : [],
-            id: isset($tokens[3]) && ! $tokens[3] instanceof Nil ? $tokens[3]->value : null,
-            description: isset($tokens[4]) && ! $tokens[4] instanceof Nil ? $tokens[4]->value : null,
-            encoding: isset($tokens[5]) && ! $tokens[5] instanceof Nil ? $tokens[5]->value : null,
-            size: isset($tokens[6]) && ! $tokens[6] instanceof Nil ? (int) $tokens[6]->value : null,
-            lines: isset($tokens[7]) && ! $tokens[7] instanceof Nil ? (int) $tokens[7]->value : null,
+            id: static::tokenValueAt($tokens, 3),
+            description: static::tokenValueAt($tokens, 4),
+            encoding: static::tokenValueAt($tokens, 5),
+            size: static::tokenIntValueAt($tokens, 6),
+            lines: static::tokenIntValueAt($tokens, 7),
             disposition: ContentDisposition::parse($tokens),
         );
     }
 
+    /**
+     * Safely read a scalar token value from the parsed body structure.
+     *
+     * @param  array<Token|ListData>  $tokens
+     */
+    protected static function tokenValueAt(array $tokens, int $index): ?string
+    {
+        $token = $tokens[$index] ?? null;
+
+        if (! $token instanceof Token || $token instanceof Nil) {
+            return null;
+        }
+
+        return $token->value;
+    }
+
+    /**
+     * Safely read an integer token value from the parsed body structure.
+     *
+     * @param  array<Token|ListData>  $tokens
+     */
+    protected static function tokenIntValueAt(array $tokens, int $index): ?int
+    {
+        $value = static::tokenValueAt($tokens, $index);
+
+        return $value === null ? null : (int) $value;
+    }
+
     /**
      * Get the part number (e.g., "1", "1.2", "2.1.3").
      */

tests/Unit/BodyStructureTest.php

@@ -152,6 +152,26 @@ function parseBodyStructureResponse(string $response): ListData
     expect($imagePart->id())->toBe('<cid123>');
 });
 
+test('it does not emit warnings when non-scalar tokens appear in message/rfc822 structure fields', function () {
+    $listData = parseBodyStructureResponse(
+        '* 1 FETCH (BODYSTRUCTURE ("MESSAGE" "RFC822" NIL NIL NIL "7BIT" 3456 (NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL) ("TEXT" "PLAIN" ("charset" "utf-8") NIL NIL "7BIT" 100 10 NIL NIL NIL) 42) UID 1)'
+    );
+
+    set_error_handler(static function (int $severity, string $message, string $file, int $line): never {
+        throw new ErrorException($message, 0, $severity, $file, $line);
+    });
+
+    try {
+        $part = BodyStructurePart::fromListData($listData);
+    } finally {
+        restore_error_handler();
+    }
+
+    expect($part->contentType())->toBe('message/rfc822');
+    expect($part->size())->toBe(3456);
+    expect($part->lines())->toBeNull();
+});
+
 test('it makes BodyStructureCollection countable', function () {
     $listData = parseBodyStructureResponse(
         '* 1 FETCH (BODYSTRUCTURE (("text" "plain" ("charset" "utf-8") NIL NIL "7bit" 100 5 NIL NIL NIL) ("text" "html" ("charset" "utf-8") NIL NIL "7bit" 200 10 NIL NIL NIL) "alternative" ("boundary" "abc") NIL NIL) UID 1)'