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[3.11] gh-85267: Improvements to inspect.signature __text_signature__ handling (GH-98796) by hauntsaninja · Pull Request #100392 · python/cpython · GitHub
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[3.11] gh-85267: Improvements to inspect.signature __text_signature__ handling (GH-98796)#100392

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JelleZijlstra merged 1 commit into
python:3.11from
hauntsaninja:backport-79311cb-3.11
Dec 21, 2022
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[3.11] gh-85267: Improvements to inspect.signature __text_signature__ handling (GH-98796)#100392
JelleZijlstra merged 1 commit into
python:3.11from
hauntsaninja:backport-79311cb-3.11

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This makes a couple related changes to inspect.signature's behaviour when parsing a signature from __text_signature__.

First, inspect.signature is documented as only raising ValueError or TypeError. However, in some cases, we could raise RuntimeError. This PR changes that, thereby fixing GH-83685.

(Note that the new ValueErrors in RewriteSymbolics are caught and then reraised with a message)

Second, inspect.signature could randomly drop parameters that it didn't understand (corresponding to return None in the p function). This is the core issue in GH-85267. I think this is very surprising behaviour and it seems better to fail outright.

Third, adding this new failure broke a couple tests. To fix them (and to e.g. allow inspect.signature(select.epoll.register) as in GH-85267), I add constant folding of a couple binary operations to RewriteSymbolics.

(There's some discussion of making signature expression evaluation arbitrary powerful in GH-68155. I think that's out of scope. The additional constant folding here is pretty straightforward, useful, and not much of a slippery slope)

Fourth, while GH-85267 is incorrect about the cause of the issue, it turns out if you had consecutive newlines in text_signature, you'd get tokenize.TokenError.

Finally, the if name is invalid: code path was dead, since parse_name never returned invalid..
(cherry picked from commit 79311cb)

Co-authored-by: Shantanu 12621235+hauntsaninja@users.noreply.github.com

…ture__ handling (pythonGH-98796) This makes a couple related changes to inspect.signature's behaviour when parsing a signature from `__text_signature__`. First, `inspect.signature` is documented as only raising ValueError or TypeError. However, in some cases, we could raise RuntimeError. This PR changes that, thereby fixing pythonGH-83685. (Note that the new ValueErrors in RewriteSymbolics are caught and then reraised with a message) Second, `inspect.signature` could randomly drop parameters that it didn't understand (corresponding to `return None` in the `p` function). This is the core issue in pythonGH-85267. I think this is very surprising behaviour and it seems better to fail outright. Third, adding this new failure broke a couple tests. To fix them (and to e.g. allow `inspect.signature(select.epoll.register)` as in pythonGH-85267), I add constant folding of a couple binary operations to RewriteSymbolics. (There's some discussion of making signature expression evaluation arbitrary powerful in pythonGH-68155. I think that's out of scope. The additional constant folding here is pretty straightforward, useful, and not much of a slippery slope) Fourth, while pythonGH-85267 is incorrect about the cause of the issue, it turns out if you had consecutive newlines in __text_signature__, you'd get `tokenize.TokenError`. Finally, the `if name is invalid:` code path was dead, since `parse_name` never returned `invalid`.. (cherry picked from commit 79311cb) Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
JelleZijlstra merged commit bee9051 into python:3.11 Dec 21, 2022
hauntsaninja deleted the backport-79311cb-3.11 branch December 21, 2022 05:28
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