Extend translations to generate log entries for missing translations.

app/Providers/AppServiceProvider.php

@@ -3,6 +3,7 @@
 namespace App\Providers;
 
 use Illuminate\Support\ServiceProvider;
+use Illuminate\Translation\Translator;
 
 class AppServiceProvider extends ServiceProvider
 {
@@ -14,6 +15,12 @@ class AppServiceProvider extends ServiceProvider
         if ($this->app->environment() === 'local') {
             $this->app->register(\Laravel\Telescope\TelescopeServiceProvider::class);
             $this->app->register(TelescopeServiceProvider::class);
+
+            $this->app->extend('translator', function (Translator $translator) {
+                $trans = new \App\Translator($translator->getLoader(), $translator->getLocale());
+                $trans->setFallback($translator->getFallback());
+                return $trans;
+            });
         }
     }
 

app/Translator.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App;
+
+use Illuminate\Support\Facades\Log;
+use Illuminate\Translation\Translator as BaseTranslator;
+class Translator extends BaseTranslator
+{
+    /**
+     * @param string $key
+     * @param array $replace
+     * @param null $locale
+     * @param bool $fallback
+     *
+     * @return array|null|string|void
+     */
+    public function get($key, array $replace = [], $locale = null, $fallback = true)
+    {
+        $translation = parent::get($key, $replace, $locale, $fallback);
+
+        if ($translation === $key) {
+            Log::warning('Language item could not be found.', [
+                'language' => $locale ?? config('app.locale'),
+                'id' => $key,
+                'url' => config('app.url')
+            ]);
+        }
+
+        return $translation;
+    }
+}