gh-129515: Clarify syntax error messages for conditional expressions #129880

sergey-miryanov · 2025-02-09T06:14:08Z

Issue: Syntax error on '{z} if z is not None else pass' #129515

Along the suggestion from the original issue, I have added the following rules and messages:
The following expressions will be handled by a=disjunction 'if' b=disjunction 'else' c=invalid_ifexp_orelse_stmt and generate the message "Syntax Error: statement given where 'orelse' expression required" instead of just "Syntax Error: invalid syntax":

1 if True else pass
1 if True else return
1 if True else raise Exception('test')
1 if True else del smth
1 if True else yield 2
1 if True else assert False
1 if True else break
1 if True else continue

The following expressions will be handled by a=invalid_ifexp_body_stmt 'if' b=disjunction 'else' c=expression and generate the message "Syntax Error: statement given where 'body' expression required":

pass if True else 1
break if True else 1
continue if True else 1

The followingexpressions will be handled by a=invalid_ifexp_body_stmt 'if' b=disjunction 'else' c=invalid_ifexp_orelse_stmt and generate the message "Syntax Error: statement given where 'body' expression required":

pass if True else pass
break if True else continue

…sions

Grammar/python.gram

sergey-miryanov · 2025-02-09T06:55:51Z

test_fstring fails, will dig

Grammar/python.gram

Lib/test/test_ast/test_ast.py

…y-miryanov/cpython into pythongh-129515-ifexp-syntax-error

pablogsal

Left some new comments

bedevere-app · 2025-02-12T23:30:56Z

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

- also reword error messages - move tests to test_syntax - update whatsnew and news

sergey-miryanov · 2025-02-13T19:43:03Z

I have made the requested changes; please review again

bedevere-app · 2025-02-13T19:43:08Z

Thanks for making the requested changes!

@pablogsal: please review the changes made to this pull request.

Doc/whatsnew/3.14.rst

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

pablogsal

Ah, this looks MUCH better. Really well done @sergey-miryanov! 👍

Grammar/python.gram

Doc/whatsnew/3.14.rst

Lib/test/test_syntax.py

Misc/NEWS.d/next/Core_and_Builtins/2025-02-09-11-30-38.gh-issue-129515.3L3vmo.rst

…e-129515.3L3vmo.rst Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

…y-miryanov/cpython into pythongh-129515-ifexp-syntax-error

sergey-miryanov · 2025-02-17T14:07:43Z

Thank you all for your review! I made the suggested changes, and it is ready now.

pablogsal · 2025-02-18T21:43:41Z

Excellent job @sergey-miryanov!

Thanks for your contribution 👌

sergey-miryanov · 2025-02-19T12:43:38Z

Thanks!

pythongh-129515: Clarify syntax error messages for conditional expres…

4dbba6b

…sions

sergey-miryanov requested review from Eclips4, pablogsal and lysnikolaou as code owners February 9, 2025 06:14

bedevere-app bot added the awaiting review label Feb 9, 2025

bedevere-app bot mentioned this pull request Feb 9, 2025

Syntax error on '{z} if z is not None else pass' #129515

Closed

sergey-miryanov commented Feb 9, 2025

View reviewed changes