Fix type annotations for headers

`ResponseInterface::getHeaders()` only ever returns  `array<string, string[]>`, let’s work with that internally.

Author: jtojnar

src/ContentTypeExtractor.php

@@ -37,7 +37,8 @@ public static function getContentTypeFromHeader(array $headers, string $targetEn
 
         if (\is_array($contentType)) {
             // Multiple Content-Type headers are not permitted, as the header does not accept a comma-separated list:
-            // https://tools.ietf.org/html/rfc2616#section-4.2
+            // https://www.rfc-editor.org/rfc/rfc2616#section-4.2
+            // https://www.rfc-editor.org/rfc/rfc2616#section-14.17
             // We are attempting to handle it gracefully by dropping all but the first instance.
             $contentType = $contentType[0];
         }

src/GuzzleTranscoder.php

@@ -56,7 +56,7 @@ private function createTranscoder(): TranscoderInterface {
     public function convert(ResponseInterface $response): ResponseInterface {
         $stream = $response->getBody();
 
-        /** @var array<string, array<string>|string> */
+        /** @var array<string, string[]> */
         $headers = $response->getHeaders();
         $result = $this->convertResponse($headers, (string) $stream);
         if ($result !== null) {
@@ -100,14 +100,13 @@ public function __invoke(callable $handler): callable {
      *
      * Otherwise an array containing the new headers and content is returned.
      *
-     * @param array<string, array<string>|string> $headers
+     * @param array<string, string[]> $headers
      *
-     * @return ?array{headers: array<string, array<string>|string>, content: string}
+     * @return ?array{headers: array<string, string[]>, content: string}
      */
     public function convertResponse(array $headers, string $content): ?array {
         $headerDeclaredEncoding = null;
         $bodyDeclaredEncoding = null;
-        /** @var array<string, array<string>|string> */
         $headerReplacements = [];
         $contentReplacements = [];
 
@@ -116,7 +115,7 @@ public function convertResponse(array $headers, string $content): ?array {
         if ($type !== null) {
             [$contentType, $headerDeclaredEncoding, $params] = $type;
 
-            $headerReplacements['content-type'] = $contentType . (\count($params) > 0 ? '; ' . Utils::joinHttpHeaderWords($params) : '');
+            $headerReplacements['content-type'] = [$contentType . (\count($params) > 0 ? '; ' . Utils::joinHttpHeaderWords($params) : '')];
         } else {
             return null;
         }

tests/GuzzleTranscoderTest.php

@@ -214,7 +214,7 @@ public function testConvertResponse(): void {
      * Gets the headers from a HTTP response as one dimensional associative array
      * with header names as keys. The header values will not be parsed but saved as-is!
      *
-     * @return array{headers: array<string>, body: string}
+     * @return array{headers: array<string, string[]>, body: string}
      */
     private function splitHeadersAndContentFromHttpResponseString(string $responseString): array {
         $lines = explode("\n", $responseString);
@@ -225,13 +225,9 @@ private function splitHeadersAndContentFromHttpResponseString(string $responseSt
             if ($line === '') {
                 break;
             }
-            $parts = explode(':', $line);
-            $key = array_shift($parts);
-            if (\count($parts) > 0) {
-                $headers[$key] = trim(implode(':', $parts));
-            } else {
-                $headers[$key] = '';
-            }
+            $parts = explode(':', $line, 2);
+            $key = $parts[0];
+            $headers[$key] = \count($parts) > 1 ? [trim($parts[1])] : [];
         }
         $body = implode("\n", \array_slice($lines, $i + 1));