From 8817e8e010e4227547dd3bea79f76c7b12f83ad9 Mon Sep 17 00:00:00 2001
From: Vladimir Razuvaev <vladimir.razuvaev@gmail.com>
Date: Wed, 22 Aug 2018 18:53:25 +0700
Subject: [PATCH] Throws descriptive error when non-type used instead of
 interface

---
 src/Type/Schema.php                  |  4 +++-
 src/Type/SchemaValidationContext.php | 21 ++++++++++++---------
 tests/Type/ValidationTest.php        | 22 ++++++++++++++++++++++
 3 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/src/Type/Schema.php b/src/Type/Schema.php
index a2ac20d..cb74d03 100644
--- a/src/Type/Schema.php
+++ b/src/Type/Schema.php
@@ -297,7 +297,9 @@ class Schema
             foreach ($this->getTypeMap() as $type) {
                 if ($type instanceof ObjectType) {
                     foreach ($type->getInterfaces() as $interface) {
-                        $this->possibleTypeMap[$interface->name][$type->name] = $type;
+                        if ($interface instanceof InterfaceType) {
+                            $this->possibleTypeMap[$interface->name][$type->name] = $type;
+                        }
                     }
                 } else if ($type instanceof UnionType) {
                     foreach ($type->getTypes() as $innerType) {
diff --git a/src/Type/SchemaValidationContext.php b/src/Type/SchemaValidationContext.php
index 7a02ff3..d1d587d 100644
--- a/src/Type/SchemaValidationContext.php
+++ b/src/Type/SchemaValidationContext.php
@@ -278,6 +278,18 @@ class SchemaValidationContext
     {
         $implementedTypeNames = [];
         foreach($object->getInterfaces() as $iface) {
+            if (! $iface instanceof InterfaceType) {
+                $this->reportError(
+                    sprintf(
+                        'Type %s must only implement Interface types, ' .
+                        'it cannot implement %s.',
+                        $object->name,
+                        Utils::printSafe($iface)
+                    ),
+                    $this->getImplementsInterfaceNode($object, $iface)
+                );
+                continue;
+            }
             if (isset($implementedTypeNames[$iface->name])) {
                 $this->reportError(
                     "Type {$object->name} can only implement {$iface->name} once.",
@@ -296,15 +308,6 @@ class SchemaValidationContext
      */
     private function validateObjectImplementsInterface(ObjectType $object, $iface)
     {
-        if (!$iface instanceof InterfaceType) {
-            $this->reportError(
-                "Type {$object->name} must only implement Interface types, " .
-                "it cannot implement ". Utils::printSafe($iface) . ".",
-                $this->getImplementsInterfaceNode($object, $iface)
-            );
-            return;
-        }
-
         $objectFieldMap = $object->getFields();
         $ifaceFieldMap = $iface->getFields();
 
diff --git a/tests/Type/ValidationTest.php b/tests/Type/ValidationTest.php
index f5e2176..3481e15 100644
--- a/tests/Type/ValidationTest.php
+++ b/tests/Type/ValidationTest.php
@@ -974,6 +974,28 @@ class ValidationTest extends TestCase
 
     // DESCRIBE: Type System: Objects can only implement unique interfaces
 
+    /**
+     * @it rejects an Object implementing a non-type values
+     */
+    public function testRejectsAnObjectImplementingANonTypeValues()
+    {
+        $schema = new Schema([
+            'query' => new ObjectType([
+                'name' => 'BadObject',
+                'interfaces' => [null],
+                'fields' => ['a' => Type::string()]
+            ]),
+        ]);
+        $expected = [
+            'message' => 'Type BadObject must only implement Interface types, it cannot implement null.'
+        ];
+
+        $this->assertContainsValidationMessage(
+            $schema->validate(),
+            [$expected]
+        );
+    }
+
     /**
      * @it rejects an Object implementing a non-Interface type
      */