Keep parens around lambda iterables in comprehensions (preview)#5176
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wrap_comprehension_in made the visible parens around the iterable after `in` invisible whenever the inner expression was a low-precedence test, but the guard that preserves them for ternaries only checked for syms.test. A lambda iterable such as `[x for x in (lambda: 0) if x]` fell through, so the parens were dropped and the trailing comprehension clauses were swallowed into the lambda body, producing unparsable output and an ASTSafetyError crash. Extend the guard to syms.lambdef as well.
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…view) `wrap_comprehension_in` keeps the parentheses around a lambda or conditional expression used as a comprehension's iterable, otherwise the trailing `for`/`if` clauses get absorbed into it and the result is invalid. psf#5176 handled the single-paren case, but `maybe_make_parens_invisible_in_atom` recurses through the atom, so a redundantly nested pair like `[x for x in ((lambda: 0))]` still had *both* layers stripped, producing `[x for x in lambda: 0]` and crashing with an ASTSafetyError. Look through redundant nested parens before deciding whether the atom wraps a lambda or ternary, so at least one pair is kept.
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Description
On
--preview, this code crashes Black with anASTSafetyError:wrap_comprehension_inmakes the parens around a comprehension's iterableinvisible when the inner expression is low-precedence. There's already a guard
that keeps them for ternaries, but it only checks for
syms.test, so a lambdaiterable slips through. Dropping the parens lets the trailing
if/forclausesget parsed as part of the lambda body (
lambda: 0 if x), which isn't valid, soBlack emits unparsable output and bails out with an internal error. A bare
[x for x in (lambda y: y)]is broken the same way.The fix extends the existing guard to also cover
syms.lambdef. Long lambdaiterables still get wrapped, just with the parens kept. Hit a few comprehension
shapes (list/set/dict/genexpr, trailing
ifandfor) while checking it.Checklist - did you ...
--previewstyle, following the stability policy?CHANGES.mdif necessary?