Ruud
82 lines
2.8 KiB
Python
82 lines
2.8 KiB
Python
"""Defines `FunctionLibrary`, a class that collects functions to be exposed to
|
|
SCSS during compilation.
|
|
"""
|
|
|
|
# TODO the constant versions of this should be frozen
|
|
class FunctionLibrary(object):
|
|
"""Contains a set of functions to be exposed to SCSS.
|
|
|
|
Functions are keyed by both their name _and_ arity; this allows for
|
|
function overloading somewhat beyond what Python easily allows, and is
|
|
required for several functions in the standard Sass library.
|
|
|
|
Functions may also have arbitrary arity, in which case they accept any
|
|
number of arguments, though a function of the same name with a specific
|
|
arity takes precedence.
|
|
"""
|
|
|
|
def __init__(self):
|
|
self._functions = {}
|
|
|
|
def derive(self):
|
|
"""Returns a new registry object, pre-populated with all the functions
|
|
in this registry.
|
|
"""
|
|
new = type(self)()
|
|
new.inherit(self)
|
|
return new
|
|
|
|
def inherit(self, *other_libraries):
|
|
"""Import all the functions from the given other libraries into this one.
|
|
|
|
Note that existing functions ARE NOT replaced -- which also means that
|
|
functions from the first library take precedence over functions from
|
|
the second library, etc.
|
|
"""
|
|
new_functions = dict()
|
|
|
|
# dict.update replaces keys; go through the other libraries in reverse,
|
|
# so the first one wins
|
|
for library in reversed(other_libraries):
|
|
new_functions.update(library._functions)
|
|
|
|
new_functions.update(self._functions)
|
|
self._functions = new_functions
|
|
|
|
def register(self, name, argc=None):
|
|
"""Decorator for adding a function to this library."""
|
|
# XXX: this should allow specifying names of keyword arguments, as
|
|
# well. currently none of these functions support kwargs, i think.
|
|
# XXX automatically inferring the name and args would be...
|
|
# interesting
|
|
# XXX also it would be nice if a function which EXISTS but has the
|
|
# wrong number of args threw a useful error; atm i think it'll become
|
|
# literal (yikes!)
|
|
|
|
key = (name, argc)
|
|
|
|
def decorator(f):
|
|
self._functions[key] = f
|
|
return f
|
|
|
|
return decorator
|
|
|
|
def add(self, function, name, argc=None):
|
|
"""Add a function to this library imperatively."""
|
|
|
|
key = (name, argc)
|
|
self._functions[key] = function
|
|
|
|
def lookup(self, name, argc=None):
|
|
"""Find a function given its name and the number of arguments it takes.
|
|
Falls back to a function with the same name that takes any number of
|
|
arguments.
|
|
"""
|
|
# Try the given arity first
|
|
key = name, argc
|
|
if key in self._functions:
|
|
return self._functions[key]
|
|
|
|
# Fall back to arbitrary-arity (or KeyError if neither exists)
|
|
return self._functions[name, None]
|