Postcss plugin sets inappropriate working directory

[dwt]

While trying to get postcss to work the way we want, we noticed that

webassets/src/webassets/filter/postcss.py

Line 57 in e3e8211

with working_directory(filename=source_path):

seems to be wrong / not functional.

The problem is that when you use the filter to build a file that is outside the source tree of the main project (e.g. provided by a plugin) then the source path will also be outside the project, therefore preventing postcss from finding its config file.

We have replaced that line with this:

        with working_directory(directory=self.ctx.directory):

which allows us to configure the working directory with the directory path from the Environment.

What do you think?