[9.x] Show error if key:generate artisan command fails (#44927)

* Show error when key:generate artisan command fails

* Update KeyGenerateCommand.php

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

src/Illuminate/Foundation/Console/KeyGenerateCommand.php

@@ -90,7 +90,9 @@ protected function setKeyInEnvironmentFile($key)
  return false;
  }
 
- $this->writeNewEnvironmentFileWith($key);
+ if (! $this->writeNewEnvironmentFileWith($key)) {
+ return false;
+ }
 
  return true;
  }
@@ -99,15 +101,25 @@ protected function setKeyInEnvironmentFile($key)
  * Write a new environment file with the given key.
  *
  * @param string $key
- * @return void
+ * @return bool
  */
  protected function writeNewEnvironmentFileWith($key)
  {
- file_put_contents($this->laravel->environmentFilePath(), preg_replace(
+ $replaced = preg_replace(
  $this->keyReplacementPattern(),
  'APP_KEY='.$key,
- file_get_contents($this->laravel->environmentFilePath())
- ));
+ $input = file_get_contents($this->laravel->environmentFilePath())
+ );
+
+ if ($replaced === $input || $replaced === null) {
+ $this->error('Unable to set application key. No APP_KEY variable was found in the .env file.');
+
+ return false;
+ }
+
+ file_put_contents($this->laravel->environmentFilePath(), $replaced);
+
+ return true;
  }
 
  /**