[Anandb71]

Description

IPython transforms an assignment magic that has a type annotation the same way as a plain one, so in a notebook cell

files: list[str] = !ls *.csv

runs as files: list[str] = get_ipython().getoutput('ls *.csv'). MagicFinder only visited ast.Assign nodes, so the magic in an annotated assignment was never masked, and Black wrote the transformed call back into the cell.

Reproduction on main (f74dfd7):

$ cat > repro.ipynb <<'NB'
{"cells":[{"cell_type":"code","execution_count":null,"metadata":{},"outputs":[],"source":["files: list[str] = !ls *.csv\n","print(files)"]}],"metadata":{"language_info":{"name":"python"}},"nbformat":4,"nbformat_minor":5}
NB
$ black repro.ipynb
reformatted repro.ipynb

The cell now reads files: list[str] = get_ipython().getoutput("ls *.csv"). The same happens for home: str = %env HOME. With this change the file is left unchanged.

The fix adds visit_AnnAssign to MagicFinder, reusing the visit_Assign logic (node.value is checked the same way).

Tests: new cases in test_magic (annotated ! and %env assignments) and in test_long_magic_assignment_is_not_wrapped_in_parentheses. They fail on main and pass here. tests/test_ipynb.py passes, and the full suite passes apart from the two *_diff_with_color tests, which fail the same way on main in my environment. pre-commit is clean.

Checklist - did you ...

• Implement any code style changes under the --preview style, following the stability policy?
• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[github-actions]

diff-shades results comparing this PR (e4edc88) to main (f74dfd7):

--preview style: no changes

--stable style: no changes

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