Revert "Remove interface and check method/property instead"

This reverts commit bc45489.

src/Illuminate/Contracts/Queue/UniqueJob.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Illuminate\Contracts\Queue;
+
+interface UniqueJob
+{
+    //
+}

src/Illuminate/Foundation/Bus/PendingDispatch.php

@@ -5,6 +5,7 @@
 use Illuminate\Container\Container;
 use Illuminate\Contracts\Bus\Dispatcher;
 use Illuminate\Contracts\Cache\Repository as Cache;
+use Illuminate\Contracts\Queue\UniqueJob;
 
 class PendingDispatch
 {
@@ -130,8 +131,7 @@ public function afterResponse()
      */
     protected function shouldDispatch()
     {
-        if (! method_exists($this->job, 'uniqueId')
-            && ! property_exists($this->job, 'uniqueId')) {
+        if (! ($this->job instanceof UniqueJob)) {
             return true;
         }
 

src/Illuminate/Foundation/Console/stubs/job.queued.stub

@@ -4,6 +4,7 @@ namespace {{ namespace }};
 
 use Illuminate\Bus\Queueable;
 use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Contracts\Queue\UniqueJob;
 use Illuminate\Foundation\Bus\Dispatchable;
 use Illuminate\Queue\InteractsWithQueue;
 use Illuminate\Queue\SerializesModels;

src/Illuminate/Queue/CallQueuedHandler.php

@@ -8,6 +8,7 @@
 use Illuminate\Contracts\Cache\Repository as Cache;
 use Illuminate\Contracts\Container\Container;
 use Illuminate\Contracts\Queue\Job;
+use Illuminate\Contracts\Queue\UniqueJob;
 use Illuminate\Database\Eloquent\ModelNotFoundException;
 use Illuminate\Pipeline\Pipeline;
 use ReflectionClass;
@@ -166,8 +167,7 @@ protected function ensureSuccessfulBatchJobIsRecorded($command)
      */
     protected function ensureUniqueJobLockIsReleased($command)
     {
-        if (method_exists($command, 'uniqueId')
-            || property_exists($command, 'uniqueId')) {
+        if ($command instanceof UniqueJob) {
             $uniqueId = method_exists($command, 'uniqueId')
                         ? $command->uniqueId()
                         : ($command->uniqueId ?? '');

tests/Integration/Queue/UniqueJobTest.php

@@ -5,6 +5,7 @@
 use Illuminate\Bus\Queueable;
 use Illuminate\Contracts\Cache\Repository as Cache;
 use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Contracts\Queue\UniqueJob;
 use Illuminate\Database\Schema\Blueprint;
 use Illuminate\Foundation\Bus\Dispatchable;
 use Illuminate\Queue\InteractsWithQueue;
@@ -145,28 +146,24 @@ protected function getLockKey($job)
     }
 }
 
-class UniqueTestJob implements ShouldQueue
+class UniqueTestJob implements ShouldQueue, UniqueJob
 {
     use InteractsWithQueue, Queueable, Dispatchable;
 
     public static $handled = false;
 
-    public $uniqueId = '';
-
     public function handle()
     {
         static::$handled = true;
     }
 }
 
-class UniqueTestFailJob implements ShouldQueue
+class UniqueTestFailJob implements ShouldQueue, UniqueJob
 {
     use InteractsWithQueue, Queueable, Dispatchable;
 
     public $tries = 1;
 
-    public $uniqueId = '';
-
     public static $handled = false;
 
     public function handle()