`Feature` | App Config System Checks

[masterPiece93]

App Config System Checks

• Session Middleware Check
• Required Settings Check
  • System check warning raising for non conforming settings
  • info raising for faulty settings
• add error code description in docs/
• [ ]

Our package is dependent on session middleware , hence the client django project must have it added .
So, our app package must raise errors to client for on configuration .

Our package is dependent on certain settings , hence the client django project must have them set .
So, our app package must raise warning to client on system start .

---

RnD

• how to apply system checks

Important Takeaways ^LEARNING

• Applying System Checks in Django

[masterPiece93]

Applying System Checks in Django

• master guide
• stackoverflow answer

Check if a specific middleware exists

    ```python
        from django.conf import settings
        
        def check_middleware_exists(middleware_path):
            """
            Checks if a specific middleware is present in the Django settings.
            """
            return middleware_path in settings.MIDDLEWARE
        
        # Example usage:
        if check_middleware_exists('django.contrib.auth.middleware.AuthenticationMiddleware'):
            print("AuthenticationMiddleware is present.")
        else:
            print("AuthenticationMiddleware is NOT present.")
        
        if check_middleware_exists('my_app.middleware.MyCustomMiddleware'):
            print("MyCustomMiddleware is present.")
        else:
            print("MyCustomMiddleware is NOT present.")
    ```

Simple approach on applying system checks

Django's AppConfig provides a structured way to configure applications and integrate system checks within them. The ready() method of an AppConfig subclass is a suitable place to register these checks.
Registering System Checks in AppConfig.ready():

• Define your check function: Create a function that performs the desired check and returns a list of Error or Warning objects if issues are found. This function typically accepts app_configs and **kwargs as arguments.

  Python

      # myapp/checks.py
      from django.core.checks import Error
  
      def check_my_setting(app_configs, **kwargs):
          errors = []
          if not hasattr(app_configs[0].app_module.settings, 'MY_CUSTOM_SETTING'):
              errors.append(
                  Error(
                      'MY_CUSTOM_SETTING is not defined in settings.',
                      hint='Define MY_CUSTOM_SETTING in your project settings.py',
                      id='myapp.E001',
                  )
              )
          return errors

• Register the check in AppConfig.ready(): Import the register decorator from django.core.checks and apply it to your check function within the ready() method of your app's AppConfig subclass.

  Python

      # myapp/apps.py
      from django.apps import AppConfig
      from django.core.checks import register, Tags
      from .checks import check_my_setting
  
      class MyappConfig(AppConfig):
          name = 'myapp'
          verbose_name = 'My Application'
  
          def ready(self):
              register(Tags.compatibility)(check_my_setting)
              # You can also use it as a decorator directly on the check function
              # if the check function is defined within the AppConfig class.

• Ensure INSTALLED_APPS points to your AppConfig: Your settings.py should include the dotted path to your AppConfig subclass in INSTALLED_APPS.

  Python

      # project/settings.py
      INSTALLED_APPS = [
          # ...
          'myapp.apps.MyappConfig',
          # ...
      ]

Running the Checks:

Django's system checks are automatically run during various management commands, including runserver, migrate, and check. You can also explicitly run them using:

Code

python manage.py check

To run only specific checks based on their tags (e.g., compatibility checks):
Code

python manage.py check --tag compatibility

To run deployment checks (checks registered with deploy=True):
Code

python manage.py check --deploy