Allow set return content type

src/ErrorHandler/ErrorCatcher.php

@@ -32,6 +32,7 @@ final class ErrorCatcher implements MiddlewareInterface
     private ResponseFactoryInterface $responseFactory;
     private ErrorHandler $errorHandler;
     private ContainerInterface $container;
+    private ?string $contentType = null;
 
     public function __construct(
         ResponseFactoryInterface $responseFactory,
@@ -46,14 +47,7 @@ public function __construct(
     public function withRenderer(string $mimeType, string $rendererClass): self
     {
         $this->validateMimeType($mimeType);
-
-        if (trim($rendererClass) === '') {
-            throw new \InvalidArgumentException('The renderer class cannot be an empty string.');
-        }
-
-        if ($this->container->has($rendererClass) === false) {
-            throw new \InvalidArgumentException("The renderer \"$rendererClass\" cannot be found.");
-        }
+        $this->validateRenderer($rendererClass);
 
         $new = clone $this;
         $new->renderers[$this->normalizeMimeType($mimeType)] = $rendererClass;
@@ -77,9 +71,26 @@ public function withoutRenderers(string ...$mimeTypes): self
         return $new;
     }
 
+    /**
+     * Force content type to respond with regardless of request
+     * @param string $contentType
+     * @return $this
+     */
+    public function forceContentType(string $contentType): self
+    {
+        $this->validateMimeType($contentType);
+        if (!isset($this->renderers[$contentType])) {
+            throw new \InvalidArgumentException(sprintf('The renderer for %s is not set.', $contentType));
+        }
+
+        $new = clone $this;
+        $new->contentType = $contentType;
+        return $new;
+    }
+
     private function handleException(\Throwable $e, ServerRequestInterface $request): ResponseInterface
     {
-        $contentType = $this->getContentType($request);
+        $contentType = $this->contentType ?? $this->getContentType($request);
         $renderer = $this->getRenderer(strtolower($contentType));
         if ($renderer !== null) {
             $renderer->setRequest($request);
@@ -136,4 +147,15 @@ private function normalizeMimeType(string $mimeType): string
     {
         return strtolower(trim($mimeType));
     }
+
+    private function validateRenderer(string $rendererClass): void
+    {
+        if (trim($rendererClass) === '') {
+            throw new \InvalidArgumentException('The renderer class cannot be an empty string.');
+        }
+
+        if ($this->container->has($rendererClass) === false) {
+            throw new \InvalidArgumentException("The renderer \"$rendererClass\" cannot be found.");
+        }
+    }
 }

tests/Middleware/ErrorCatcherTest.php

@@ -110,6 +110,24 @@ public function testDefaultContentType(): void
         $this->assertSame($expectedRendererOutput, $content);
     }
 
+    public function testForceContentType(): void
+    {
+        $catcher = $this->getErrorCatcher(new Container())->forceContentType('application/json');
+        $response = $catcher->process(
+            new ServerRequest('GET', '/', ['Accept' => ['text/xml']]),
+            (new MockRequestHandler())->setHandleExcaption(new \RuntimeException())
+        );
+        $response->getBody()->rewind();
+        $this->assertSame('application/json', $response->getHeaderLine('Content-Type'));
+    }
+
+    public function testForceContentTypeSetInvalidType(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectErrorMessage('The renderer for image/gif is not set.');
+        $this->getErrorCatcher(new Container())->forceContentType('image/gif');
+    }
+
     private function getContainerWithThrowableRenderer(string $id, string $expectedOutput): Container
     {
         return new Container(