use JSON_PARTIAL_OUTPUT_ON_ERROR for json_decode()

ApiProblem was not able to render exceptions when the option
ApiProblem::detailIncludesStackTrace was true and the exception contained
PHP streams in the arguments of the traces ("args" key in
Exception::getTraces()). For example: GuzzleHttp works internally with
streams which meant that some exceptions raised from GuzzleHttp didn't
result in a ApiProblem response but in an empty 500 response because
json_encode() failed.

Author: Michael Kühn

src/ApiProblemResponse.php

@@ -23,7 +23,7 @@ class ApiProblemResponse extends Response
      *
      * @var int
      */
-    protected $jsonFlags = 0;
+    protected $jsonFlags = JSON_PARTIAL_OUTPUT_ON_ERROR;
 
     /**
      * @param ApiProblem $apiProblem
@@ -35,7 +35,7 @@ public function __construct(ApiProblem $apiProblem)
         $this->setReasonPhrase($apiProblem->title);
 
         if (defined('JSON_UNESCAPED_SLASHES')) {
-            $this->jsonFlags = constant('JSON_UNESCAPED_SLASHES');
+            $this->jsonFlags |= constant('JSON_UNESCAPED_SLASHES');
         }
     }
 

test/ApiProblemResponseTest.php

@@ -32,9 +32,21 @@ public function testApiProblemResponseSetsStatusCodeAndReasonPhrase()
 
     public function testApiProblemResponseBodyIsSerializedApiProblem()
     {
-        $apiProblem = new ApiProblem(400, 'Random error');
+        $additional = [
+            'foo' => fopen('php://memory', 'r')
+        ];
+
+        $expected = [
+            'foo' => null,
+            'type' => 'http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html',
+            'title' => 'Bad Request',
+            'status' => 400,
+            'detail' => 'Random error',
+        ];
+
+        $apiProblem = new ApiProblem(400, 'Random error', null, null, $additional);
         $response   = new ApiProblemResponse($apiProblem);
-        $this->assertEquals($apiProblem->toArray(), json_decode($response->getContent(), true));
+        $this->assertEquals($expected, json_decode($response->getContent(), true));
     }
 
     /**