Custom parser for environment variable

[bnjjj]

Hello I'm trying to use environment variable or cli flags by specifying a field in my struct like this:

#[clap(long, env, multiple_occurrences(true))]
endpoints: Option<Vec<Url>>,

But in the environment variables I would like to have a comma separated list of urls to specify several urls. Do you have a feature to provide our own env parser from a string to convert it to the right type ?

What could be the best solution in that case ?

[epage]

At the moment, we do not have env-specific parsing.

In master (soon to be 3.2), we have added value_parser which allows customizing the parser behavior for both arguments and env variables. You could make that support a delimiter. We could also look at our native delimiter support being extended to environment variables.

All of those are for sharing between arguments and env. As for adding env specific parsing in the future, I think I'd like to wait on moving env support out of the core of clap (see #3476). This will more easily allow env support to evolve on its own without adding to the core complexity of clap or its size.

[henryiii]

Note that this would be very useful for uv pip, which needs to behave like pip, and pip supports -c file1 -c file2 or PIP_CONSTRAINT="file1 file2", with spaces allowed in filenames for the command-line version only. (This is true for pretty much all it's filenames by options) astral-sh/uv#12639