Add Falcon (ASGI) adapter

[sarayourfriend]

This PR adds an ASGI Falcon App adapter to complement the existing Falcon adapter for WSGI apps.

I wrote this code originally based on the existing adapter for https://git.sr.ht/~sara/openverse-slack-reaction.

The code I wrote there is copied almost directly here with some modifications to raise errors when an incompatible Falcon version is being used. You can see the original code here: https://git.sr.ht/~sara/openverse-slack-reaction/tree/main/item/falcon_adapter.py

It's deployed to production with https://openverse-slack.sarayourfriend.pictures.

Hope it's okay I didn't open an issue for this first, but I needed it for my own app one way or another and copying the file and adding tests was trivial so I didn't spend too much extra time on this compared to just writing a helpful issue describing the feature 🙂

Category (place an x in each of the [ ])

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others

Requirements (place an x in each [ ])

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.

[CLAassistant]

All committers have signed the CLA.

[seratch]

Thanks for the great addition! We are happy to have this enhancement but could you check my comments and update your branch?

[sarayourfriend]

Thanks for the quick review @seratch! I've updated the PR with your requested changes.

[seratch]

Can you update a few comments in the example apps?

[seratch]

@sarayourfriend Thanks for quick updates on the feedback! My last request is to update the examples a bit. Once the builds pass, we can merge this PR and release a new version by the end of this week.

[sarayourfriend]

Hmm, it seems like there's an issue with the fact that there are tests that expect Falcon 2 instead of 3... is there some way to exclude the async Falcon tests when the falcon version is 2.x?

I suppose the module level skip could do it?

https://docs.pytest.org/en/latest/how-to/skipping.html#skipping-test-functions

[seratch]

@sarayourfriend Can you add unvicorn to requirements.txt in the same directory?

[sarayourfriend]

Sure thing. I'm not sure what version range to pin it to. The project is still <1. Should I just use uvicorn>=0.17.6 (the currently released version)?

[seratch]

You can do the same with fastapi examples

[seratch]

@sarayourfriend You can change this line to use >=3,<4 instead: https://github.com/slackapi/bolt-python/blob/v1.11.6/setup.py#L82
Changing the part does not affect users.

[sarayourfriend]

@seratch should I also remove the conditional in the existing Falcon adapter tests? I've never worked with setup.py before so just want to make sure I'm understanding correctly that it will run the tests only with Falcon 3.x?

It could make this function unnecessary: https://github.com/sarayourfriend/bolt-python/blob/78b64878b692039e39530888a012bf738ca74058/tests/adapter_tests/falcon/test_falcon.py#L23

[seratch]

@sarayourfriend Ah, sorry - never mind my above comment. I totally forget what I did in the past 🤦 No need to modify setup.py.

Can you modify https://github.com/slackapi/bolt-python/blob/v1.11.6/.github/workflows/tests.yml#L73 to have pip install "falcon>=3,<4" before the pytest execution? It should resolve the issue.

[sarayourfriend]

@seratch just wanted to make sure, because I don't see any other explicit dependency installations in that workflow... would it make sense to add the falcon>=3 range in the async dependency list as that's already being installed in the tests.yml

This is the patch I would apply if that makes sense, but I don't know if "conflicting" arguments like this would cause pip to fail (it seems to work okay locally FWIW):

diff --git a/setup.py b/setup.py
index 6543529..9c92d94 100755
--- a/setup.py
+++ b/setup.py
@@ -68,6 +68,8 @@ setuptools.setup(
             "aiohttp>=3,<4",
             # Socket Mode 3rd party implementation
             "websockets>=8,<10",
+            # Falcon introduced ASGI support in v3
+            "falcon>=3,<4",
         ],
         # pip install -e ".[adapter]"
         # NOTE: any of async ones requires pip install -e ".[async]" too
@@ -79,7 +81,7 @@ setuptools.setup(
             "click>=7,<8",  # for chalice
             "CherryPy>=18,<19",
             "Django>=3,<5",
-            "falcon>=3,<4",
+            "falcon>=2,<4",
             "fastapi>=0.70.0,<1",
             "Flask>=1,<3",
             "Werkzeug>=2,<3",

If this doesn't work for some reason or you still prefer the explicit installation in the tests.yml script then let me know and I'll make the appropriate change.

[seratch]

@sarayourfriend this line manually installs v2: https://github.com/slackapi/bolt-python/blob/v1.11.6/.github/workflows/tests.yml#L56 this is necessary for v2 tests but it causes errors in the async tests you added.

[sarayourfriend]

Ah, I see. Makes sense, thanks for explaining. Pushed the update!

[seratch]

@sarayourfriend I found that your unit test properly detects a bug in your code. Can you check my comments?

[codecov]

Codecov Report

Merging #614 (efd3fb8) into main (837c773) will decrease coverage by 0.05%.
The diff coverage is 83.72%.

❗ Current head efd3fb8 differs from pull request most recent head 5a9cb0a. Consider uploading reports for the commit 5a9cb0a to get more accurate results

@@            Coverage Diff             @@
##             main     #614      +/-   ##
==========================================
- Coverage   91.52%   91.46%   -0.06%     
==========================================
  Files         169      170       +1     
  Lines        5723     5766      +43     
==========================================
+ Hits         5238     5274      +36     
- Misses        485      492       +7     

Impacted Files	Coverage Δ
slack_bolt/adapter/falcon/__init__.py	100.00% <ø> (ø)
slack_bolt/adapter/falcon/async_resource.py	83.72% <83.72%> (ø)

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[seratch]

LGTM