poky/meta/lib/oe/maketype.py

#
# Copyright OpenEmbedded Contributors
#
# SPDX-License-Identifier: GPL-2.0-only
#
"""OpenEmbedded variable typing support

Types are defined in the metadata by name, using the 'type' flag on a
variable.  Other flags may be utilized in the construction of the types.  See
the arguments of the type's factory for details.
"""

import inspect
import oe.types as types
from collections.abc import Callable

available_types = {}

class MissingFlag(TypeError):
    """A particular flag is required to construct the type, but has not been
    provided."""
    def __init__(self, flag, type):
        self.flag = flag
        self.type = type
        TypeError.__init__(self)

    def __str__(self):
        return "Type '%s' requires flag '%s'" % (self.type, self.flag)

def factory(var_type):
    """Return the factory for a specified type."""
    if var_type is None:
        raise TypeError("No type specified. Valid types: %s" %
                        ', '.join(available_types))
    try:
        return available_types[var_type]
    except KeyError:
        raise TypeError("Invalid type '%s':\n  Valid types: %s" %
                        (var_type, ', '.join(available_types)))

def create(value, var_type, **flags):
    """Create an object of the specified type, given the specified flags and
    string value."""
    obj = factory(var_type)
    objflags = {}
    for flag in obj.flags:
        if flag not in flags:
            if flag not in obj.optflags:
                raise MissingFlag(flag, var_type)
        else:
            objflags[flag] = flags[flag]

    return obj(value, **objflags)

def get_callable_args(obj):
    """Grab all but the first argument of the specified callable, returning
    the list, as well as a list of which of the arguments have default
    values."""
    if type(obj) is type:
        obj = obj.__init__

    sig = inspect.signature(obj)
    args = list(sig.parameters.keys())
    defaults = list(s for s in sig.parameters.keys() if sig.parameters[s].default != inspect.Parameter.empty)
    flaglist = []
    if args:
        if len(args) > 1 and args[0] == 'self':
            args = args[1:]
        flaglist.extend(args)

    optional = set()
    if defaults:
        optional |= set(flaglist[-len(defaults):])
    return flaglist, optional

def factory_setup(name, obj):
    """Prepare a factory for use."""
    args, optional = get_callable_args(obj)
    extra_args = args[1:]
    if extra_args:
        obj.flags, optional = extra_args, optional
        obj.optflags = set(optional)
    else:
        obj.flags = obj.optflags = ()

    if not hasattr(obj, 'name'):
        obj.name = name

def register(name, factory):
    """Register a type, given its name and a factory callable.

    Determines the required and optional flags from the factory's
    arguments."""
    factory_setup(name, factory)
    available_types[factory.name] = factory


# Register all our included types
for name in dir(types):
    if name.startswith('_'):
        continue

    obj = getattr(types, name)
    if not isinstance(obj, Callable):
        continue

    register(name, obj)