sphinx.pycode.ast.unparse does not understand operator precedence

[eric-wieser]

As an example:

>>> import sphinx.pycode.ast as ast
>>> ast.unparse(ast.parse("(1 + 2) * 3").body[0].value)
'1 + 2 * 3'
>>> ast.unparse(ast.parse("(1, 2) + (3, 4)").body[0].value)
'1, 2 + 3, 4'

Easiest way to fix this will be to copy some of the approach from the python 3.9 ast.unparse, which needs #7497 in order to keep track of the current precedence level.

[tk0miya]

Please mind we also need to support Callable[[str, str], str]. This type hint also uses a tuple without parenthesis.

[eric-wieser]

Indeed, the idea would be to add parentheses only where needed, like ast.unparse does

[eric-wieser]

Although note that Callable[([str, str], str)] is perfectly correct, it just is unfortunately also ugly.

[tk0miya]

It seems ast.unparse() uses items_view() to generate common part of sequences. It's cool.

[eric-wieser]

Copying the entirety of ast.unparse into sphinx may also be a sensible option.

[tk0miya]

Reasonable. But we should notice about license issue to copy it.

[tk0miya]

Fixed by #8265 now.