symlink-related asset 404 error will be introduced under pypi installation with uv

[MagicFrogSJTU]

Apache Airflow version

3.0.2

If "Other Airflow 2 version" selected, which one?

No response

What happened?

# Install airflow via uv
uv pip install "apache-airflow[celery]==3.0.2" --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-3.0.2/constraints-3.10.txt"

# run airflow locally
airflow standalone

# when visiting the web ui, 404 is returned.
api-server | INFO:     127.0.0.1:58002 - "GET /api/v2/static/assets/index-QiQVuLYY.js HTTP/1.1" 404 Not Found

# direct curling also return 404
curl http://127.0.0.1:8080/static/assets/index-QiQVuLYY.js

What you think should happen instead?

should be 200 OK like the other installation method.

This is because uv default link-mode is link rather than copy, and StaticFiles default follow_symlink is False.

default symlink:

>> ll /mnt/cat/yzchen/code/cog_fusion/airflow/.venv/lib/python3.10/site-packages/airflow/ui/dist
total 28K
drwxrwxr-x 4 yzchen yzchen 4.0K Jul  1 11:30 ./
drwxrwxr-x 8 yzchen yzchen 4.0K Jul  1 11:30 ../
drwxrwxr-x 2 yzchen yzchen 4.0K Jul  1 11:30 assets/
lrwxrwxrwx 1 yzchen yzchen   82 Jul  1 11:30 index.html -> /home/yzchen/.cache/uv/archive-v0/D9UWS7CGfe4U_6ms45U3B/airflow/ui/dist/index.html
lrwxrwxrwx 1 yzchen yzchen   83 Jul  1 11:30 pin_100.png -> /home/yzchen/.cache/uv/archive-v0/D9UWS7CGfe4U_6ms45U3B/airflow/ui/dist/pin_100.png
lrwxrwxrwx 1 yzchen yzchen   82 Jul  1 11:30 pin_32.png -> /home/yzchen/.cache/uv/archive-v0/D9UWS7CGfe4U_6ms45U3B/airflow/ui/dist/pin_32.png
drwxrwxr-x 2 yzchen yzchen 4.0K Jul  1 11:30 .vite/

one of the airflow code that introduces the bug.

# airflow/api_fastapi/core_api/app.py
    app.mount(
        "/static",
        StaticFiles(
            directory=directory,
            html=True,
        ),
        name="webapp_static_folder",
    )

Thus,
follow_symlink=True should be added to StaticFiles().

How to reproduce

# Install airflow via uv
uv pip install "apache-airflow[celery]==3.0.2" --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-3.0.2/constraints-3.10.txt"

# Install airflow via uv
airflow standalone
```bash

### Operating System

ubuntu24.04

### Versions of Apache Airflow Providers

_No response_

### Deployment

Virtualenv installation

### Deployment details

_No response_

### Anything else?

_No response_

### Are you willing to submit PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

[boring-cyborg]

Thanks for opening your first issue here! Be sure to follow the issue template! If you are willing to raise PR to address this issue please do so, no need to wait for approval.

[potiuk]

Just to clarify - this should not happen when you install "airflow" from package - but when you install it in editable mode from sources ? The repro steps are not exact and I was surprised to see from "package" installation - but it would be explained if source installation and editable mode is used.

[MagicFrogSJTU]

Just to clarify - this should not happen when you install "airflow" from package - but when you install it in editable mode from sources ? The repro steps are not exact and I was surprised to see from "package" installation - but it would be explained if source installation and editable mode is used.

not source installation in editable mode. Just ordinary installation.
uv is a new and flashing-quick tool, and symlinking package installing is one of the reason why it is fast.

# to reproduce
rm -r .venv || true
echo 3.10.6> .python-version
uv venv
UV_PYTHON=.venv/bin/python uv pip install "apache-airflow[celery]==3.0.2" --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-3.0.2/constraints-3.10.txt"
airflow standalone

# open another terminal
curl http://127.0.0.1:8080/static/assets/index-QiQVuLYY.js

[potiuk]

Cannot reproduce.

You are likely running DIFFERENT airflow (one that you have on the PATH - and likely coming from editable installation) than the one installed from package - because you have not activated the environment.

You should either:

. ./.venv/bin/activate 

Before running airflow standalone

Or do

uv run airflow standalone

Without activation of the env or uv run - you are running whatever airflow can be found in the PATH first - and it can be literally anything.

[potiuk]

BTW. It's literally impossible to have symbolic links in your package installed from .whl file, unless the symbolic links are part of the package. No uv symbolic linking changes that.

BTW2. uv is fast for multiple reasons, but one of reasons is that it uses HARD links not SYMBOLIC links. Symbolic links that you observe is a standard way how editable packages works - it has nothing to do with uv optimisations.

[potiuk]

And yes - airflow is one of the first uv users. We started using it a day after it's been officially released and we know it intimately well - including the fact that uv is the default development tool and you cannot develop airflow without it.

[potiuk]

Please - makes sure to reproduce this issue "precisely" - and attempt to fix it when you know the exact problem you have - I reverted the original fix as it was causing issues - broke main. But please make sure you have a verifiable and reproducible scenario you want to fix.

[MagicFrogSJTU]

my bad.
I found there exists a pyproject.toml in the upper directory. which specifies: link-mode = symlink.

Thus, to reproduce, should be:

uv pip install --link-mode symlink

I wonder why follow-symlink would break the main. follow_symlink should introduce no harm.
@potiuk do you think whether it is worth fixing the possible link-mode-symlink case?

BTW, uv is a wonderful tool and I am heavily using uv workspace in my own project.