Description

sobolevn

opened on Jul 4, 2023

Issue body actions

3.11:

>>> import ast
>>> print(ast.dump(ast.parse("""f'"{var:}"'"""), indent=2))
Module(
  body=[
    Expr(
      value=JoinedStr(
        values=[
          Constant(value='"'),
          FormattedValue(
            value=Name(id='var', ctx=Load()),
            conversion=-1,
            format_spec=JoinedStr(values=[])),
          Constant(value='"')]))],
  type_ignores=[])

3.12:

>>> import ast
>>> print(ast.dump(ast.parse("""f'"{var:}"'"""), indent=2))
Module(
  body=[
    Expr(
      value=JoinedStr(
        values=[
          Constant(value='"'),
          FormattedValue(
            value=Name(id='var', ctx=Load()),
            conversion=-1,
            format_spec=JoinedStr(
              values=[
                Constant(value='')])),
          Constant(value='"')]))],
  type_ignores=[])

This affects several linters:

1. Fix parse test case on Python 3.12 mypy#15577
2. B907 crashes when bugbear is run on Python 3.12 PyCQA/flake8-bugbear#393

Is this a bug? Or is it a feature?

Linked PRs

• gh-106396: Special-case empty format spec to gen empty JoinedStr node #106401
• [3.12] gh-106396: Special-case empty format spec to gen empty JoinedStr node (GH-106401) #106416

Reacted by sunmy2019

Activity

1. sobolevn

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   3.12only security fixesonly security fixes

   on Jul 4, 2023
2. AlexWaygood

   assigned

   pablogsal

   and

   lysnikolaou

   on Jul 4, 2023
3. AlexWaygood

   added

   3.13only security fixesonly security fixes

   on Jul 4, 2023
4. sunmy2019 commented on Jul 4, 2023

   

   sunmy2019

   on Jul 4, 2023

   Member

   More actions

   First of all, it is not wrong. We do have an empty format spec string here.

   Fixing it for compatibility reasons is also acceptable to me. I am 60-40 towards fixing it.
5. lysnikolaou commented on Jul 4, 2023

   

   lysnikolaou

   on Jul 4, 2023

   Member

   More actions

   I'd say let's fix it both for compatibility and for consistency with things like an empty f-string, which is also a JoinedStr with an empty values array.

   cpython on main via C v14.0.3-clang via 🐍 pyenv 3.11.3 
   ❯ ./python.exe           
   Python 3.13.0a0 (heads/main:6c60684bf5, Jul  4 2023, 11:09:56) [Clang 14.0.3 (clang-1403.0.22.14.1)] on darwin
   Type "help", "copyright", "credits" or "license" for more information.
   >>> import ast
   >>> print(ast.dump(ast.parse("""f''"""), indent=2))
   Module(
     body=[
       Expr(
         value=JoinedStr(values=[]))],
     type_ignores=[])
   >>> print(ast.dump(ast.parse("""f'"{var:}"'"""), indent=2))
   Module(
     body=[
       Expr(
         value=JoinedStr(
           values=[
             Constant(value='"'),
             FormattedValue(
               value=Name(id='var', ctx=Load()),
               conversion=-1,
               format_spec=JoinedStr(
                 values=[
                   Constant(value='')])),
             Constant(value='"')]))],
     type_ignores=[])

   Reacted by Alex Waygood
6. lysnikolaou

   added 2 commits that reference this issue on Jul 4, 2023

   pythongh-106396: Special-case empty format spec to gen empty JoinedSt…

   a6152ae

   gh-106396: Special-case empty format spec to gen empty JoinedStr node (…

   dfe4de2
7. miss-islington

   added a commit that references this issue on Jul 4, 2023

   pythongh-106396: Special-case empty format spec to gen empty JoinedSt…

   741e919
8. lysnikolaou

   closed this as completedon Jul 4, 2023
9. lysnikolaou

   added a commit that references this issue on Jul 4, 2023

   [3.12] gh-106396: Special-case empty format spec to gen empty JoinedS…

   930df7b
10. carljm

    added a commit that references this issue on Jul 5, 2023

    Merge branch 'main' into modulelocals

    4c59e51

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