## Summary
Adds a new ecosystem-analyzer workflow with a similar purpose to the
mypy-primer workflow. It creates a richer ecosystem diff report using
[ecosystem-analyzer](https://github.com/astral-sh/ecosystem-analyzer/)
([example
report](https://shark.fish/diff-attr-subscript-narrowing.html)). This is
still experimental and also quite a bit slower than mypy_primer, so I
chose to make this opt-in for now via a `ecosystem-analyzer` label. This
would give us a way to play with this while still evaluating if we
should further invest in this or not.
Advantages over the mypy_primer diff output:
- Interactive filtering of diagnostics
- Statistics overview which breaks down added/removed/changed
diagnostics across lint rules
- Has the concept of "changed" diagnostics, which makes it easier to
review changes where diagnostic messages have changed (along with other
changes).
- Compute diff based on old and new project-lists (`good.txt`). This
allows us to diff changes to the project list itself. This has caused
confusion in the past where we tried to add new projects to `good.txt`,
but then ran the `main`-branch version of ty on that new list (where the
bug was not yet fixed)
Disadvantages:
- The report currently needs to be downloaded from the workflow run, as
I don't know if we have a way of deploying HTML files like this
temporarily to some hosted infrastructure.
## Summary
I think `division-by-zero` is a low-value diagnostic in general; most
real division-by-zero errors (especially those that are less obvious to
the human eye) will occur on values typed as `int`, in which case we
don't issue the diagnostic anyway. Mypy and pyright do not emit this
diagnostic.
Currently the diagnostic is prone to false positives because a) we do
not silence it in unreachable code, and b) we do not implement narrowing
of literals from inequality checks. We will probably fix (a) regardless,
but (b) is low priority apart from division-by-zero.
I think we have many more important things to do and should not allow
false positives on a low-value diagnostic to be a distraction. Not
opposed to re-enabling this diagnostic in future when we can prioritize
reducing its false positives.
References https://github.com/astral-sh/ty/issues/443
## Test Plan
Existing tests.
First take on a contributing guide for `ty`. Lots of it is copied from
the existing Ruff contribution guide.
I've put this in Ruff repo, since I think a contributing guide belongs
where the code is. I also updated the Ruff contributing guide to link to
the `ty` one.
Once this is merged, we can also add a link from the `CONTRIBUTING.md`
in ty repo (which focuses on making contributions to things that are
actually in the ty repo), to this guide.
I also updated the pull request template to mention that it might be a
ty PR, and mention the `[ty]` PR title prefix.
Feel free to update/modify/merge this PR before I'm awake tomorrow.
---------
Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>
Co-authored-by: David Peter <mail@david-peter.de>
