[8.x] Add App::isDebug() method to detect debug mode (#39755)

* add App::isDebug() method to detect debug mode

Like App::isLocal(), isProduction(), runningInConsole(), isLocale(), etc. it makes sense to have a method on the Container to detect debug mode.

I struggled with the method name, but isDebug() sort of matches most of the methods with similar functionality. I also like:

* debugMode()
* debugEnabled()
* debugModeEnabled()
* inDebugMode()

* add isDebug() unit test

* Update Application.php

* Update FoundationApplicationTest.php

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Foundation/Application.php

@@ -631,6 +631,16 @@ public function runningUnitTests()
         return $this->bound('env') && $this['env'] === 'testing';
     }
 
+    /**
+     * Determine if the application is running with debug mode enabled.
+     *
+     * @return bool
+     */
+    public function hasDebugModeEnabled()
+    {
+        return (bool) $this['config']->get('app.debug');
+    }
+
     /**
      * Register all of the configured providers.
      *

tests/Foundation/FoundationApplicationTest.php

@@ -2,6 +2,7 @@
 
 namespace Illuminate\Tests\Foundation;
 
+use Illuminate\Config\Repository;
 use Illuminate\Contracts\Support\DeferrableProvider;
 use Illuminate\Foundation\Application;
 use Illuminate\Foundation\Bootstrap\RegisterFacades;
@@ -239,6 +240,19 @@ public function testEnvironmentHelpers()
         $this->assertFalse($testing->isProduction());
     }
 
+    public function testDebugHelper()
+    {
+        $debugOff = new Application;
+        $debugOff['config'] = new Repository(['app' => ['debug' => false]]);
+
+        $this->assertFalse($debugOff->hasDebugModeEnabled());
+
+        $debugOn = new Application;
+        $debugOn['config'] = new Repository(['app' => ['debug' => true]]);
+
+        $this->assertTrue($debugOn->hasDebugModeEnabled());
+    }
+
     public function testMethodAfterLoadingEnvironmentAddsClosure()
     {
         $app = new Application;