feat: add a flask_context_manager. (#21061)
Signed-off-by: -LAN- <laipz8200@outlook.com>pull/21120/head
-LAN-
8 months ago
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GitHub
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7a2a8a2ffd
commit
0dcacdf83d
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import contextvars
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from collections.abc import Iterator
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from contextlib import contextmanager
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from typing import TypeVar
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from flask import Flask, g, has_request_context
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T = TypeVar("T")
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@contextmanager
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def preserve_flask_contexts(
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flask_app: Flask,
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context_vars: contextvars.Context,
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) -> Iterator[None]:
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"""
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A context manager that handles:
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1. flask-login's UserProxy copy
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2. ContextVars copy
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3. flask_app.app_context()
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This context manager ensures that the Flask application context is properly set up,
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the current user is preserved across context boundaries, and any provided context variables
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are set within the new context.
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Note:
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This manager aims to allow use current_user cross thread and app context,
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but it's not the recommend use, it's better to pass user directly in parameters.
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Args:
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flask_app: The Flask application instance
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context_vars: contextvars.Context object containing context variables to be set in the new context
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Yields:
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None
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Example:
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```python
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with preserve_flask_contexts(flask_app, context_vars=context_vars):
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# Code that needs Flask app context and context variables
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# Current user will be preserved if available
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```
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"""
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# Set context variables if provided
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if context_vars:
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for var, val in context_vars.items():
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var.set(val)
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# Save current user before entering new app context
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saved_user = None
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if has_request_context() and hasattr(g, "_login_user"):
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saved_user = g._login_user
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# Enter Flask app context
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with flask_app.app_context():
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try:
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# Restore user in new app context if it was saved
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if saved_user is not None:
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g._login_user = saved_user
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# Yield control back to the caller
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yield
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finally:
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# Any cleanup can be added here if needed
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pass
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@ -0,0 +1,124 @@
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import contextvars
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import threading
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from typing import Optional
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import pytest
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from flask import Flask
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from flask_login import LoginManager, UserMixin, current_user, login_user
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from libs.flask_utils import preserve_flask_contexts
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class User(UserMixin):
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"""Simple User class for testing."""
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def __init__(self, id: str):
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self.id = id
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def get_id(self) -> str:
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return self.id
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@pytest.fixture
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def login_app(app: Flask) -> Flask:
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"""Set up a Flask app with flask-login."""
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# Set a secret key for the app
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app.config["SECRET_KEY"] = "test-secret-key"
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login_manager = LoginManager()
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login_manager.init_app(app)
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@login_manager.user_loader
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def load_user(user_id: str) -> Optional[User]:
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if user_id == "test_user":
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return User("test_user")
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return None
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return app
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@pytest.fixture
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def test_user() -> User:
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"""Create a test user."""
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return User("test_user")
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def test_current_user_not_accessible_across_threads(login_app: Flask, test_user: User):
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"""
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Test that current_user is not accessible in a different thread without preserve_flask_contexts.
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This test demonstrates that without the preserve_flask_contexts, we cannot access
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current_user in a different thread, even with app_context.
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"""
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# Log in the user in the main thread
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with login_app.test_request_context():
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login_user(test_user)
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assert current_user.is_authenticated
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assert current_user.id == "test_user"
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# Store the result of the thread execution
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result = {"user_accessible": True, "error": None}
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# Define a function to run in a separate thread
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def check_user_in_thread():
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try:
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# Try to access current_user in a different thread with app_context
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with login_app.app_context():
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# This should fail because current_user is not accessible across threads
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# without preserve_flask_contexts
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result["user_accessible"] = current_user.is_authenticated
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except Exception as e:
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result["error"] = str(e) # type: ignore
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# Run the function in a separate thread
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thread = threading.Thread(target=check_user_in_thread)
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thread.start()
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thread.join()
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# Verify that we got an error or current_user is not authenticated
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assert result["error"] is not None or (result["user_accessible"] is not None and not result["user_accessible"])
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def test_current_user_accessible_with_preserve_flask_contexts(login_app: Flask, test_user: User):
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"""
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Test that current_user is accessible in a different thread with preserve_flask_contexts.
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This test demonstrates that with the preserve_flask_contexts, we can access
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current_user in a different thread.
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"""
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# Log in the user in the main thread
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with login_app.test_request_context():
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login_user(test_user)
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assert current_user.is_authenticated
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assert current_user.id == "test_user"
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# Save the context variables
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context_vars = contextvars.copy_context()
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# Store the result of the thread execution
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result = {"user_accessible": False, "user_id": None, "error": None}
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# Define a function to run in a separate thread
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def check_user_in_thread_with_manager():
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try:
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# Use preserve_flask_contexts to access current_user in a different thread
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with preserve_flask_contexts(login_app, context_vars):
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from flask_login import current_user
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if current_user:
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result["user_accessible"] = True
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result["user_id"] = current_user.id
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else:
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result["user_accessible"] = False
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except Exception as e:
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result["error"] = str(e) # type: ignore
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# Run the function in a separate thread
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thread = threading.Thread(target=check_user_in_thread_with_manager)
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thread.start()
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thread.join()
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# Verify that current_user is accessible and has the correct ID
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assert result["error"] is None
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assert result["user_accessible"] is True
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assert result["user_id"] == "test_user"
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