ashb commented on code in PR #53149:
URL: https://github.com/apache/airflow/pull/53149#discussion_r2202540161


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shared/README.md:
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+
+# Shared Python Code for Airflow Components
+
+This folder contains code that is shared across two or more of the Airflow 
distributions.
+
+## Be Thoughtful about what you add under here
+
+Not every piece of code that is used in two distributions should be 
automatically placed in one of the shared libraries, and sometimes "just 
duplicate it" is the right approach to take. For example if it's just a 5 or 10 
line function and it's used in two places, it might be easier to future 
developers to understand if the function is in two places.
+
+There is no hard rules about what should or shouldn't be in these libraries, 
so try to apply your best judgement.
+
+## Vendoring process
+
+i.e. how this code ends up in distributions
+
+One of the desires we had when setting up this shared code process was to only 
have one copy of the source in the repo; while we could have used a pre-commit 
check to ensure that other copies were kept up to date, and that approach would 
have worked, it is "a bit messier" and makes PRs look scarier, so we have an 
process that has only a single copy of the code in the repo.
+
+### In built distributions
+
+We make use of [hatch-build-time-vendoring] to automatically run [vendoring] 
for us when the `sdist` is built (and then the wheel is automatically built 
using that already vendored sdist).
+
+`vendoring` is a project from the pip maintainers and is how pip vendors code 
into it's tree. Now the eagle-eyed amongst you will notice that the project 
description essentially says "do not use this if you aren't pip", but in this 
specific case (of vendoring in _our own code_) none of the specific warnings or 
caveats apply to us.
+
+The main thing the vendoring tool does for us is that it will copy all of the 
python code out of the source distribution (i.e. 
`shared/core-and-tasksdk/src/airlfow_shared/*.py`), place it in the target 
namespace (i.e. `task-sdk/src/airflow/sdk/_vendor/airflow_shared/`) and then 
most usefully, it will automatically re-write the imports so they use the new 
names.

Review Comment:
   Yes, I hadn't adjusted anything to reflect the latest discussion on the dev 
list yet, hence why this is still WIP



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