Jinja/Flask get_flashed_messages fails #82

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1. NoRePercussions commented on Jul 12, 2023

   

   NoRePercussions

   on Jul 12, 2023

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   If I disable auto_bind:

   [2023-07-12 17:54:14,660] ERROR in app: Exception on / [GET]
   Traceback (most recent call last):
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/injector/__init__.py", line 1047, in args_to_inject
       instance: Any = self.get(interface)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/injector/__init__.py", line 932, in get
       binding, binder = self.binder.get_binding(interface)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/injector/__init__.py", line 650, in get_binding
       raise UnsatisfiedRequirement(None, interface)
   injector.UnsatisfiedRequirement: unsatisfied requirement on bool
   
   During handling of the above exception, another exception occurred:
   
   Traceback (most recent call last):
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/flask/app.py", line 2073, in wsgi_app
       response = self.full_dispatch_request()
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/flask/app.py", line 1519, in full_dispatch_request
       rv = self.handle_user_exception(e)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/flask/app.py", line 1517, in full_dispatch_request
       rv = self.dispatch_request()
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/flask/app.py", line 1503, in dispatch_request
       return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/app.py", line 9, in hello_world
       return render_template("helloworld.html")
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/flask/templating.py", line 154, in render_template
       return _render(
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/flask/templating.py", line 128, in _render
       rv = template.render(context)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/jinja2/environment.py", line 1301, in render
       self.environment.handle_exception()
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/jinja2/environment.py", line 936, in handle_exception
       raise rewrite_traceback_stack(source=source)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/templates/helloworld.html", line 1, in top-level template code
       <!DOCTYPE html>
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/flask_injector/__init__.py", line 89, in wrapper
       return injector.call_with_injection(callable=fun, args=args, kwargs=kwargs)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/injector/__init__.py", line 999, in call_with_injection
       dependencies = self.args_to_inject(
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/injector/__init__.py", line 91, in wrapper
       return function(*args, **kwargs)
     File "/Users/-/Projects/PycharmProjects/FlaskInjectorError/venv/lib/python3.9/site-packages/injector/__init__.py", line 1051, in args_to_inject
       raise e
   injector.UnsatisfiedRequirement: flask.helpers has an unsatisfied requirement on bool
   

   However, the app runs fine if Flask-Injector is not installed.

   So far I haven't found any other methods in my actual web app with this issue.

   👍React with 👍1Reacted by olehkodak
2. olehkodak commented on Aug 11, 2023

   

   olehkodak

   on Aug 11, 2023

   Last edited by olehkodak

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   It's because:
   Flask-Injector lets you inject dependencies into Jinja environment globals functions
   (And I would even say it obliges them to be introduced into the Standard Context.)

   and,

   The following global variables are available within Jinja2 templates by default in the Standard Context
   (by the way, the "url_for()" is there, too)

   So,

   # Somewhere in imports
   ....
   from injector import Module, provider
   from typing import Iterable
   ....
   
   # flask.get_flashed_messages(with_categories=False, category_filter=())
   # Parameters:
   # with_categories ([bool])– set to True to also receive categories.
   # category_filter (Iterable][str]) – filter of categories to limit return values. Only categories in the list will be returned.
   
   class GetFlashModule(Module):
       def configure(self, binder):
           binder.bind(bool, to=False)  # provide with_categories
   
       @provider
       def category_filter(self) -> Iterable[str]:
           return ()
   
   FlaskInjector(app=app, modules=[GetFlashModule])
   ...
   

   Or, the best solution, in my opinion:

   # Somewhere in imports
   ...
   from flask.helpers import get_flashed_messages
   .
   .
   .
   FlaskInjector(app=app, modules=[])
   
   # after init the FlaskInjector
   app.jinja_env.globals.update({'url_for': app.url_for, 'get_flashed_messages': get_flashed_messages})
   
   # or, use 'context_processor' 
   # @app.context_processor
   # def noninject_ctx_processor():  
   #    return dict(url_for=app.url_for, get_flashed_messages=get_flashed_messages)
   
   ...
   

   I can't imagine a single use case where dependencies must be injected into the Standard template context. It's annoying and painful.
3. jstasiak commented on Sep 5, 2023

   

   jstasiak

   on Sep 5, 2023

   Last edited by jstasiak

   Collaborator

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   I think the conclusion here would be the "inject in many places even if they don't declare they need injection" aspect of Flask-Injector's behavior is problematic.

   It'd be a breaking change but I'm open to changing that.