Consistently wrap two context managers in parens (in --preview).

[yilei]

Description

Fixes #3572

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[yilei]

Attaching a diff-shades result: 3589.diff.zip

This is from running:

diff-shades analyze base.json --work-dir projects-cache --force-preview-style -- --target-version=py39
diff-shades analyze new.json --work-dir projects-cache --force-preview-style -- --target-version=py39
diff-shades compare base.json new.json --diff

[yilei]

Ah, the diff-shades check on CI is broken?

[ichard26]

Yup. 🙃

[JelleZijlstra]

Two nits, and a question about async with.

[JelleZijlstra]

Does this also cover async with? We should treat both of these the same.

[yilei]

Good catch! Turns out async with isn't handled at all in #3489. It has a different code path here so the code I'm touching in this PR isn't called at all.

I filed #3591, will address separately.

[yilei]

@ichard26 FYI I just sent ichard26/diff-shades#11 to fix diff-shades

[JelleZijlstra]

Thanks @yilei! I merged the diff-shades change, let's see if that's enough.

[ichard26]

The workflow pulls from the stable branch which was admittedly bad design on my part (I'll rename the default branch on ichard26/diff-shades to avoid disrupting this repo). I updated it and triggered a rerun although it seems to be stuck? Let's try this again.

[github-actions]

diff-shades reports zero changes comparing this PR (e8f81c9) to main (4a063a9).

---

What is this? | Workflow run | diff-shades documentation

[yilei]

Success!

[yilei]

Kindly ping @JelleZijlstra?

[yilei]

Ah sorry, I'll resolve the merge conflicts.