Implement custom functions. Resolves #13.

[asottile]

So Yelp only really needs custom functions for strings, but I decided to implement all of the types.

This is my first attempt at writing CPython code so I'm probably doing a bunch of things wrong. Advice would be great here :)

I had a lot of fun writing this and took a lot of inspiration from https://github.com/sass/perl-libsass/blob/master/lib/CSS/Sass.xs

[coveralls]

Coverage increased (+3.06%) to 76.04% when pulling 4227f4f on asottile:custom_functions into b043a03 on dahlia:python.

[coveralls]

Coverage increased (+3.06%) to 76.04% when pulling 2c41388 on asottile:custom_functions into b043a03 on dahlia:python.

[coveralls]

Coverage increased (+3.06%) to 76.04% when pulling 2c41388 on asottile:custom_functions into b043a03 on dahlia:python.

[dahlia]

It would be better if there is a type for custom function. The type could have explicit fields about sass function: its name, parameter names, and an arbitrary callable. It also could have a method that returns its signature string. I wonder what’s your thought about this idea.

[dahlia]

I don’t think data types have to be defined in a separated module. They could be placed in sass.py together.

[dahlia]

It seems to segfault during CustomFunctionsTest.test_error on Windows.

[dahlia]

Is it good idea to subclass dict to define a immutable mapping type? How about subclassing collections.Mapping?

[dahlia]

Anyway I really appreciate you! It would be the killer feature of the next release.

[asottile]

I'll respond all at once instead of a bunch of comments so it's easier:

• custom function map
  So I actually went back and forth a bunch on this :/ My initial implementation mapped signature to function, but that duplicates all of the information that we can just derive from the function itself (and then we have to do a bunch of validation). This also seems to have a nice balance between ease of use to callers and correctness.
• sassutils.sass_types: I initially put them in sassutils because I was worried about circular imports. However that's not really a problem in c-api, I'll move them to the sass module instead!
• Hmm, I'll try and fix windows when I get home.
• I can change it to Mapping pretty easily, I'll do that.

[coveralls]

Coverage increased (+2.48%) to 75.47% when pulling 0a9e498 on asottile:custom_functions into b043a03 on dahlia:python.

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling 8a6f37d on asottile:custom_functions into b043a03 on dahlia:python.

[asottile]

I'm having a really hard time debugging the windows errors :( It would seem it only happens in release mode as well so I lose most of the debugger symbols.

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling 2dda11f on asottile:custom_functions into b043a03 on dahlia:python.

[dahlia]

I think these _immutable/__setitem__/__delitem__ methods don’t have to be overridden anymore, because they actually aren’t defined by collections.Mapping! It is immutable by default, and there’s collections.MutableMapping instead for additional mutability.

[asottile]

Yeah I thought these were better error messages, I can remove however

[dahlia]

My initial implementation mapped signature to function, but that duplicates all of the information that we can just derive from the function itself (and then we have to do a bunch of validation). This also seems to have a nice balance between ease of use to callers and correctness.

I am almost with you. For ease of use I think we can make compile() function possible to take multiple types e.g.:

def func_name():
    pass

# The most general form: passing a set of SassFunctions.
# It can take any kind of callables, but pretty verbose.
compile(
    custom_functions={  # I just suggest this more general parameter name instead
        SassFunction('func_name', (), func_name)
    }
)

# Less general, but easier-to-use form: passing a mapping.
# Although it cannot take any kind of callables, it can take any kind of *functions*
#   defined using `def`/`lambda` syntax.
# It cannot take callables other than them since inspecting arguments is not
#   always available for every kind of callables.
compile(
    custom_functions={
        'func_name': lambda: ...
    }
)

# Not general, but the easiest-to-use form for *named* functions:
#   passing a set of named functions.
# It can take only named functions which mean defined using `def`.
# It cannot take lambdas since names are unavailable for them.
compile(
    custom_functions={func_name}
)

[asottile]

That's a lot of complexity imo. I can take a stab at it however

[dahlia]

Okay, so let’s keep the current implementation. How about the parameter name I suggested?

[asottile]

Name works for me, I'll change it :)

[asottile]

So I've determined the windows issue is actually a problem with upstream. Would it be acceptable to simply disable the error-handling tests under windows?

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling e3c3f57 on asottile:custom_functions into b043a03 on dahlia:python.

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling e3c3f57 on asottile:custom_functions into b043a03 on dahlia:python.

[dahlia]

Would it be acceptable to simply disable the error-handling tests under windows?

That would be fine if it’s marked as FIXME.

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling efa2b9f on asottile:custom_functions into b043a03 on dahlia:python.

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling efa2b9f on asottile:custom_functions into b043a03 on dahlia:python.

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling 82655fa on asottile:custom_functions into b043a03 on dahlia:python.

[asottile]

\o/ I got windows to pass \o/

one stupid compile flag was missing >.<

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling b5faf60 on asottile:custom_functions into b043a03 on dahlia:python.

[coveralls]

Coverage increased (+3.31%) to 76.3% when pulling b5faf60 on asottile:custom_functions into b043a03 on dahlia:python.

[dahlia]

Thanks for you again. 😄

[dahlia]

I am going to release the next version (probably 0.7.0) which includes this.

[asottile]

Thanks!