AIP-79 Generate assets for Flask application in FAB provider (#44744)

[vincbeck]

Revert the revert #45057 of #44744.

It failed because of:

Traceback (most recent call last):
  File "/opt/airflow/./scripts/ci/pre_commit/compile_www_assets.py", line 86, in <module>
    if is_fab_provider_installed():
  File "/opt/airflow/./scripts/ci/pre_commit/compile_www_assets.py", line 79, in is_fab_provider_installed
    return importlib.util.find_spec("airflow.providers.fab") is not None
  File "/usr/local/lib/python3.9/importlib/util.py", line 94, in find_spec
    parent = __import__(parent_name, fromlist=['__path__'])
ModuleNotFoundError: No module named 'airflow'

I updated the function is_fab_provider_installed and check if airflow is installed first. I ran breeze release-management prepare-airflow-package --package-format wheel and it succeeds (but fails without the fix).

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[vincbeck]

Running all tests just to be sure

[jscheffl]

I am not sure whether this will work. because airflow and providers are not installed in pre-commit.

But as you can be sure the source tree is checked-out, how about checking if source tree is available?

[vincbeck]

But when you install, the sources are not available, are not they? So is_fab_provider_installed will return False in this case? Although we wan do want to generate assets for FAB as well. As for the pre-commit, since Airflow is not installed, is_fab_provider_installed will return False.

I am not 100% sure I understand everything correctly here so I might be wrong :)

EDIT: what I meant is, it is okay to not generate the assets for FAB in the CI, however, when Airflow is installed, we definitely should generate them

[jscheffl]

I thought from the point of lifecycle. The pre-commit hook will be called in CI and locally... at build time. Source tree will be there. And it needs to be called at build-time to create the static JS content as dist folder to be packaged into the wheel.

The check you are referring to is at runtime At pip install apache-airflow-providers-fab time the wheel is only un-packed to site-packages. There will no pre-commit be executed as well as you need to assume that at point of install no yarn will be available (might be the user installing is even offline w/o internet).
Otherwise - not being an expert - if the wheel install need to compile/bind/do something at point of install you need to define this in package meta data - not in a pre-commit script that is not available at install time.

You can see this also for airflow/www - the pre-commit is making the package before the sdist/wheel is built and then the dist is packed into the wheel.

So if the check now makes it more safe... I assume the dist will just not be created during build then and only the TS/TSX source tree will be packaged into the wheel.

[vincbeck]

Alright. Following this approach I am at the exact same point as in #45058. I dont quite get the error. Will re-try later

[jscheffl]

@bbovenzi or @pierrejeambrun can you help here? yarn is not really successfully compiling www assets. I assume the yarn lock file is somewhat "different" but I am not an expert why the compile fails. (Still I suspect that loading airflow a Py module is not correct because at CI/compile time the packahe is not installed (chicken+egg))