feat: add GOOGLE_SSO_PRE_VALIDATE_CALLBACK option.

Fixes #43

django_google_sso/conf.py

@@ -34,6 +34,11 @@
 GOOGLE_SSO_AUTHENTICATION_BACKEND = getattr(
     settings, "GOOGLE_SSO_AUTHENTICATION_BACKEND", None
 )
+GOOGLE_SSO_PRE_VALIDATE_CALLBACK = getattr(
+    settings,
+    "GOOGLE_SSO_PRE_VALIDATE_CALLBACK",
+    "django_google_sso.hooks.pre_validate_user",
+)
 GOOGLE_SSO_PRE_CREATE_CALLBACK = getattr(
     settings,
     "GOOGLE_SSO_PRE_CREATE_CALLBACK",

django_google_sso/hooks.py

@@ -23,3 +23,16 @@ def pre_create_user(google_user_info: dict, request: HttpRequest) -> dict | None
             is always the user email.
     """
     return {}
+
+
+def pre_validate_user(google_user_info: dict, request: HttpRequest) -> bool:
+    """
+    Callback function called before user is validated.
+
+    Must return a boolean to indicate if user is valid to login.
+
+    params:
+        google_user_info: dict containing user info received from Google.
+        request: HttpRequest object.
+    """
+    return True

django_google_sso/tests/conftest.py

@@ -94,6 +94,9 @@ def client_with_session(client, settings, mocker, google_response):
     settings.GOOGLE_SSO_ALLOWABLE_DOMAINS = ["example.com"]
     settings.GOOGLE_SSO_PRE_LOGIN_CALLBACK = "django_google_sso.hooks.pre_login_user"
     settings.GOOGLE_SSO_PRE_CREATE_CALLBACK = "django_google_sso.hooks.pre_create_user"
+    settings.GOOGLE_SSO_PRE_VALIDATE_CALLBACK = (
+        "django_google_sso.hooks.pre_validate_user"
+    )
     importlib.reload(conf)
     session = client.session
     session.update({"sso_state": "foo", "sso_next_url": SECRET_PATH})

django_google_sso/views.py

@@ -89,8 +89,14 @@ def callback(request: HttpRequest) -> HttpResponseRedirect:
     google_user_data = google.get_user_info()
     user_helper = UserHelper(google_user_data, request)
 
+    # Run Pre-Validate Callback
+    module_path = ".".join(conf.GOOGLE_SSO_PRE_VALIDATE_CALLBACK.split(".")[:-1])
+    pre_validate_fn = conf.GOOGLE_SSO_PRE_VALIDATE_CALLBACK.split(".")[-1]
+    module = importlib.import_module(module_path)
+    user_is_valid = getattr(module, pre_validate_fn)(google_user_data, request)
+
     # Check if User Info is valid to login
-    if not user_helper.email_is_valid:
+    if not user_helper.email_is_valid or not user_is_valid:
         send_message(
             request,
             _(

docs/users.md

@@ -47,6 +47,21 @@ For staff user creation _only_, you can add all users using "*" as the value:
 GOOGLE_SSO_STAFF_LIST = ["*"]
 ```
 
+## Fine-tuning validation before user creation
+
+If you need to do some custom validation _before_ user is created, you can set the
+`GOOGLE_SSO_PRE_VALIDATE_CALLBACK` setting to import a custom function that will be called before the user is created.
+This function will receive two arguments: the `google_user_info` dict from Google User API and `request` objects.
+
+```python
+# myapp/hooks.py
+def pre_validate_user(google_info, request):
+    # Check some info from google_info and/or request
+    return True  # The user can be created
+```
+
+Please note, even if this function returns `True`, the user can be denied if their email is not valid.
+
 ## Fine-tuning users before creation
 
 If you need to do some processing _before_ user is created, you can set the
@@ -106,6 +121,11 @@ GOOGLE_SSO_PRE_LOGIN_CALLBACK = "myapp.hooks.pre_login_user"
 Please remember this function will be invoked only if user exists, and if it is active.
 In other words, if the user is eligible for login.
 
+!!! tip "You can add your hooks to customize all steps:"
+    * `GOOGLE_SSO_PRE_VALIDATE_CALLBACK`: Run before the user is validated.
+    * `GOOGLE_SSO_PRE_CREATE_CALLBACK`: Run before the user is created.
+    * `GOOGLE_SSO_PRE_LOGIN_CALLBACK`: Run before the user is logged in.
+
 
 !!! warning "Be careful with these options"
     The idea here is to make your life easier, especially when testing. But if you are not careful, you can give

example_google_app/backend.py

@@ -90,3 +90,18 @@ def pre_create_callback(google_info, request) -> dict:
         "username": f"{user_key}_{user_id}",
         "date_joined": arrow.utcnow().shift(days=-1).datetime,
     }
+
+
+def pre_validate_callback(google_info, request) -> bool:
+    """Callback function called before user is validated.
+
+    Must return a boolean to indicate if user is valid to login.
+
+    params:
+        google_info: dict containing user info received from Google.
+        request: HttpRequest object.
+    """
+    messages.info(
+        request, f"Running Pre-Validate callback for email: {google_info.get('email')}."
+    )
+    return True

example_google_app/settings.py

@@ -198,6 +198,9 @@
 # Optional: Change default login text
 # GOOGLE_SSO_TEXT = "Login using Google Account"
 
+# Optional: Add pre-validate logic
+GOOGLE_SSO_PRE_VALIDATE_CALLBACK = "backend.pre_validate_callback"
+
 # Optional: Add pre-create logic
 GOOGLE_SSO_PRE_CREATE_CALLBACK = "backend.pre_create_callback"