Fastapi: [BUG] Broken against latest release of Starlette

[Chippiewill]

Describe the bug
The latest release of Starlette 0.12.13 introduced a breaking change to the way it initialises the core Starlette class which is incompatible with FastAPI's use (lack of use of super()). Introduced by this change: https://github.com/encode/starlette/commit/91eefb2af3940364b051138bed47319e189d31be

To Reproduce
Steps to reproduce the behavior:

1. Install Starlette 0.12.13 and FastAPI
2. Attempt to start a FastAPI server

Expected behavior
Fast API server starts

Screenshots
If applicable, add screenshots to help explain your problem.

Environment:

• OS: Linux
  
  
  
  • FastAPI version: 0.42.0, but problem exists in master
  
  
  • Python version: 3.8.0
  
  

[prostomarkeloff]

Now in fastapi pinned the 0.12.9 version. I think it isn't bug (at least in current release).

[florimondmanca]

The latest release of Starlette 0.12.13

I think the breakage is happening on v0.13, not v0.12.13. Here's the traceback I've got on Starlette v0.13 / FastAPI v0.42:

# app.py
from fastapi import FastAPI

app = FastAPI()

$ python app.py 
email-validator not installed, email fields will be treated as str.
To install, run: pip install email-validator
Traceback (most recent call last):
  File "app.py", line 3, in <module>
    app = FastAPI()
  File "/Users/florimond/Developer/datadog-projects/ddtrace-asgi/venv/lib/python3.8/site-packages/fastapi/applications.py", line 78, in __init__
    self.setup()
  File "/Users/florimond/Developer/datadog-projects/ddtrace-asgi/venv/lib/python3.8/site-packages/fastapi/applications.py", line 130, in setup
    self.add_exception_handler(HTTPException, http_exception_handler)
  File "/Users/florimond/Developer/datadog-projects/ddtrace-asgi/venv/lib/python3.8/site-packages/starlette/applications.py", line 124, in add_exception_handler
    self.exception_handlers[exc_class_or_status_code] = handler
AttributeError: 'FastAPI' object has no attribute 'exception_handlers'

But I agree with @prostomarkeloff — FastAPI v0.42 seems to be pinned to Starlette v0.12.9, so I'm not getting this error unless I forcefully install Starlette v0.13.

[tiangolo]

Thanks @prostomarkeloff and @florimondmanca for the help! :bowing_man: :clap:

Yeah @Chippiewill , that would be a feature request to update FastAPI to support the latest Starlette (that I will) rather than a bug.

[sm-Fifteen]

Starlette 0.12.12 is safe to use with FastAPI, this bug only occurs under 0.12.13 and latter.

[tiangolo]

Now that FastAPI supports the latest Starlette (since version 0.50.0), may we close this issue @Chippiewill ?

[github-actions[bot]]

Assuming the original issue was solved, it will be automatically closed now. But feel free to add more comments or create new issues.