On Wed, May 19, 2021 at 7:28 PM Pablo Galindo Salgado
<pablogsal@gmail.com> wrote:
>>
>> Excellent point! Do you know how reliable this is in practice, i.e.
>> what proportion of bytecode source spans are something you can
>> successfully pass to ast.parse? If it works it's obviously nicer, but
>> I can't tell how often it works. E.g. anything including
>> return/break/continue/yield/await will fail, since those require an
>> enclosing context to be legal. I doubt return/break/continue will
>> raise exceptions often, but yield/await do all the time.
>
>
> All those limitations are compiler-time limitations because they imply
> scoping. A valid AST is any piece of a converted parse tree, or a piece
> of the PEG sub grammar:
>
> >>> ast.dump(ast.parse("yield"))
> 'Module(body=[Expr(value=Yield())], type_ignores=[])'
> >>> ast.dump(ast.parse("return"))
> 'Module(body=[Return()], type_ignores=[])'
> >>> ast.dump(ast.parse("continue"))
> 'Module(body=[Continue()], type_ignores=[])'
> >>> ast.dump(ast.parse("await x"))
> "Module(body=[Expr(value=Await(value=Name(id='x', ctx=Load())))], type_ignores=[])"

Ah, nice! I guess I was confused by memories of the behavior in 3.6
and earlier, where 'await' was a pseudokeyword:

❯ docker run -it --rm python:3.6-alpine
>>> import ast
>>> ast.parse("await f()")
SyntaxError: invalid syntax

Hopefully if we add more pseudokeywords in the future it won't break
the ability to parse traceback spans.

-n

--
Nathaniel J. Smith -- https://vorpus.org