String values cannot contain $

[MartinBernstorff]

Minimal example:

from confection import Config

config_str = """[section]
value='^test$'
"""

Config().from_str(config_str)

Would love to be able to have regex strings in my config, e.g. for using polars.exclude to filter columns.

Raises:

InterpolationSyntaxError
'$' must be followed by '$' or '{', found: '$'
  File "C:\Users\adminmanber\Desktop\psycop-common\psycop\common\model_training_v2\config\config_utils.py", line 33, in <module>
    Config().from_str(config_str)
configparser.InterpolationSyntaxError: '$' must be followed by '$' or '{', found: '$'

[adrianeboyd]

Thanks for the report!

If it worked as intended, I think that $$ should work here as the escaped form of $ in the configparser format.

I haven't looked into the gory details, but it initially looks like it's being interpolated more than once, which causes problems with $$.

A terrible hacky workaround for this one specific problem:

[section]
value="^test$$$$"

The interpolated config then looks like this, where this string does still work as the intended regex:

[section]
value = "^test$$"

[MartinBernstorff]

Ah, I see, thanks! Hadn't noticed that configparser was part of stdlib, glad to see it!

This appears to be a bug in configparser, then?

[adrianeboyd]

No, we've overridden some of the interpolation with custom methods, so I think it's a bug in confection.

[adrianeboyd]

Ah, the problem isn't directly in the parsing/interpolation, it's in the to_str conversion that doesn't re-escape $ in its own output.