Bug 781875 – sys-apps/portage: improve make.conf parser

• Product: Portage Development
• Status: CONFIRMED ---

[Description Zac Medico 2021-04-09 21:41:31 UTC]

The variable expansion support in this library could be useful:

https://github.com/sloria/environs#variable-expansion

We can use it when available, and otherwise fallback to our existing portage.util.getconfig() implementation.

[Comment 1 Zac Medico 2021-04-09 22:05:41 UTC]

(In reply to Zac Medico from comment #0)
> The variable expansion support in this library could be useful:
> 
> https://github.com/sloria/environs#variable-expansion

I've checked the code, and it actually uses this regular expression to search for variable references and expand them on-demand (portage can't use it):

_EXPANDED_VAR_PATTERN = re.compile(r"(?<!\\)\$\{([A-Za-z0-9_]+)(:-[^\}:]*)?\}")

[Comment 2 Zac Medico 2021-04-09 22:11:05 UTC]

python-dotenv might be usable, and supports default values with this regex:

_posix_variable = re.compile(
    r"""
    \$\{
        (?P<name>[^\}:]*)
        (?::-
            (?P<default>[^\}]*)
        )?
    \}
    """,
    re.VERBOSE,
)  # type: Pattern[Text]

https://github.com/theskumar/python-dotenv/blob/master/src/dotenv/variables.py

[Comment 3 Zac Medico 2021-04-09 22:19:35 UTC]

Since python-dotenv requires { and } to surround variables names, it's only useful in the sense that we can copy and modify its _posix_variable regex.