[4.x] Make error renderers in the error handler customizable

Slim/Handlers/ErrorHandler.php

@@ -32,16 +32,19 @@
 class ErrorHandler implements ErrorHandlerInterface
 {
     /**
-     * Known handled content types
-     *
-     * @var array
+     * @var string
+     */
+    protected $defaultErrorRenderer = HtmlErrorRenderer::class;
+
+    /**
+     * @var string[]
      */
-    protected $knownContentTypes = [
-        'application/json',
-        'application/xml',
-        'text/xml',
-        'text/html',
-        'text/plain'
+    protected $errorRenderers = [
+        'application/json' => JsonErrorRenderer::class,
+        'application/xml' => XmlErrorRenderer::class,
+        'text/xml' => XmlErrorRenderer::class,
+        'text/html' => HtmlErrorRenderer::class,
+        'text/plain' => PlainTextErrorRenderer::class,
     ];
 
     /**
@@ -166,7 +169,10 @@ protected function determineStatusCode(): int
     protected function determineContentType(ServerRequestInterface $request): string
     {
         $acceptHeader = $request->getHeaderLine('Accept');
-        $selectedContentTypes = array_intersect(explode(',', $acceptHeader), $this->knownContentTypes);
+        $selectedContentTypes = array_intersect(
+            explode(',', $acceptHeader),
+            array_keys($this->errorRenderers)
+        );
         $count = count($selectedContentTypes);
 
         if ($count) {
@@ -185,7 +191,7 @@ protected function determineContentType(ServerRequestInterface $request): string
 
         if (preg_match('/\+(json|xml)/', $acceptHeader, $matches)) {
             $mediaType = 'application/' . $matches[1];
-            if (in_array($mediaType, $this->knownContentTypes, true)) {
+            if (array_key_exists($mediaType, $this->errorRenderers)) {
                 return $mediaType;
             }
         }
@@ -218,30 +224,37 @@ protected function determineRenderer(): ErrorRendererInterface
         }
 
         if ($renderer === null) {
-            switch ($this->contentType) {
-                case 'application/json':
-                    $renderer = JsonErrorRenderer::class;
-                    break;
-
-                case 'text/xml':
-                case 'application/xml':
-                    $renderer = XmlErrorRenderer::class;
-                    break;
-
-                case 'text/plain':
-                    $renderer = PlainTextErrorRenderer::class;
-                    break;
-
-                default:
-                case 'text/html':
-                    $renderer = HtmlErrorRenderer::class;
-                    break;
+            if (array_key_exists($this->contentType, $this->errorRenderers)) {
+                $renderer = $this->errorRenderers[$this->contentType];
+            } else {
+                $renderer = $this->defaultErrorRenderer;
             }
         }
 
         return new $renderer();
     }
 
+    /**
+     * Register an error renderer for a specific content-type
+     *
+     * @param string $contentType   The content-type this renderer should be registered to
+     * @param string $errorRenderer The error renderer class name
+     */
+    public function registerErrorRenderer(string $contentType, string $errorRenderer): void
+    {
+        $this->errorRenderers[$contentType] = $errorRenderer;
+    }
+
+    /**
+     * Set the default error renderer
+     *
+     * @param string $errorRenderer The default error renderer class name
+     */
+    public function setDefaultErrorRenderer(string $errorRenderer): void
+    {
+        $this->defaultErrorRenderer = $errorRenderer;
+    }
+
     /**
      * Write to the error log if $logErrors has been set to true
      *

tests/Handlers/ErrorHandlerTest.php

@@ -11,6 +11,7 @@
 
 use Psr\Http\Message\ResponseInterface;
 use ReflectionClass;
+use Slim\Error\Renderers\HtmlErrorRenderer;
 use Slim\Error\Renderers\JsonErrorRenderer;
 use Slim\Error\Renderers\PlainTextErrorRenderer;
 use Slim\Error\Renderers\XmlErrorRenderer;
@@ -87,6 +88,11 @@ public function testDetermineRenderer()
         $reflectionProperty->setValue($handler, 'text/plain');
         $renderer = $method->invoke($handler);
         $this->assertInstanceOf(PlainTextErrorRenderer::class, $renderer);
+
+        // Test the default error renderer
+        $reflectionProperty->setValue($handler, 'text/unknown');
+        $renderer = $method->invoke($handler);
+        $this->assertInstanceOf(HtmlErrorRenderer::class, $renderer);
     }
 
     public function testDetermineStatusCode()
@@ -128,10 +134,10 @@ public function testHalfValidContentType()
             ->getMockBuilder(ErrorHandler::class)
             ->disableOriginalConstructor()
             ->getMock();
-        $newTypes = [
-            'application/xml',
-            'text/xml',
-            'text/html',
+        $newErrorRenderers = [
+            'application/xml' => XmlErrorRenderer::class,
+            'text/xml' => XmlErrorRenderer::class,
+            'text/html' => HtmlErrorRenderer::class,
         ];
 
         $class = new ReflectionClass(ErrorHandler::class);
@@ -140,9 +146,9 @@ public function testHalfValidContentType()
         $reflectionProperty->setAccessible(true);
         $reflectionProperty->setValue($handler, $this->getResponseFactory());
 
-        $reflectionProperty = $class->getProperty('knownContentTypes');
+        $reflectionProperty = $class->getProperty('errorRenderers');
         $reflectionProperty->setAccessible(true);
-        $reflectionProperty->setValue($handler, $newTypes);
+        $reflectionProperty->setValue($handler, $newErrorRenderers);
 
         $method = $class->getMethod('determineContentType');
         $method->setAccessible(true);
@@ -164,9 +170,9 @@ public function testDetermineContentTypeTextPlainMultiAcceptHeader()
             ->disableOriginalConstructor()
             ->getMock();
 
-        $knownContentTypes = [
-            'text/plain',
-            'text/xml',
+        $errorRenderers = [
+            'text/plain' => PlainTextErrorRenderer::class,
+            'text/xml' => XmlErrorRenderer::class,
         ];
 
         $class = new ReflectionClass(ErrorHandler::class);
@@ -175,9 +181,9 @@ public function testDetermineContentTypeTextPlainMultiAcceptHeader()
         $reflectionProperty->setAccessible(true);
         $reflectionProperty->setValue($handler, $this->getResponseFactory());
 
-        $reflectionProperty = $class->getProperty('knownContentTypes');
+        $reflectionProperty = $class->getProperty('errorRenderers');
         $reflectionProperty->setAccessible(true);
-        $reflectionProperty->setValue($handler, $knownContentTypes);
+        $reflectionProperty->setValue($handler, $errorRenderers);
 
         $method = $class->getMethod('determineContentType');
         $method->setAccessible(true);
@@ -199,8 +205,8 @@ public function testDetermineContentTypeApplicationJsonOrXml()
             ->disableOriginalConstructor()
             ->getMock();
 
-        $knownContentTypes = [
-            'application/xml'
+        $errorRenderers = [
+            'application/xml' => XmlErrorRenderer::class
         ];
 
         $class = new ReflectionClass(ErrorHandler::class);
@@ -209,9 +215,9 @@ public function testDetermineContentTypeApplicationJsonOrXml()
         $reflectionProperty->setAccessible(true);
         $reflectionProperty->setValue($handler, $this->getResponseFactory());
 
-        $reflectionProperty = $class->getProperty('knownContentTypes');
+        $reflectionProperty = $class->getProperty('errorRenderers');
         $reflectionProperty->setAccessible(true);
-        $reflectionProperty->setValue($handler, $knownContentTypes);
+        $reflectionProperty->setValue($handler, $errorRenderers);
 
         $method = $class->getMethod('determineContentType');
         $method->setAccessible(true);
@@ -252,6 +258,32 @@ public function testAcceptableMediaTypeIsNotFirstInList()
         $this->assertEquals('text/html', $return);
     }
 
+    public function testRegisterErrorRenderer()
+    {
+        $handler = new ErrorHandler($this->getResponseFactory());
+        $handler->registerErrorRenderer('application/slim', PlainTextErrorRenderer::class);
+
+        $reflectionClass = new ReflectionClass(ErrorHandler::class);
+        $reflectionProperty = $reflectionClass->getProperty('errorRenderers');
+        $reflectionProperty->setAccessible(true);
+        $errorRenderers = $reflectionProperty->getValue($handler);
+
+        $this->assertArrayHasKey('application/slim', $errorRenderers);
+    }
+
+    public function testSetDefaultErrorRenderer()
+    {
+        $handler = new ErrorHandler($this->getResponseFactory());
+        $handler->setDefaultErrorRenderer(PlainTextErrorRenderer::class);
+
+        $reflectionClass = new ReflectionClass(ErrorHandler::class);
+        $reflectionProperty = $reflectionClass->getProperty('defaultErrorRenderer');
+        $reflectionProperty->setAccessible(true);
+        $defaultErrorRenderer = $reflectionProperty->getValue($handler);
+
+        $this->assertEquals(PlainTextErrorRenderer::class, $defaultErrorRenderer);
+    }
+
     public function testOptions()
     {
         $request = $this->createServerRequest('/', 'OPTIONS');