view mercurial/thirdparty/attr/_funcs.py @ 38486:4c0683655599

namespaces: let namespaces override singlenode() definition

Some namespaces have multiple nodes per name (meaning that their
namemap() returns multiple nodes). One such namespace is the "topics"
namespace (from the evolve repo). We also have our own internal
namespace at Google (for review units) that has multiple nodes per
name. These namespaces may not want to use the default "pick highest
revnum" resolution that we currently use when resolving a name to a
single node. As an example, they may decide that `hg co <name>` should
check out a commit that's last in some sense even if an earlier commit
had just been amended and thus had a higher revnum [1]. This patch
gives the namespace the option to continue to return multiple nodes
and to override how the best node is picked. Allowing namespaces to
override that may also be useful as an optimization (it may be cheaper
for the namespace to find just that node).

I have been arguing (in D3715) for using all the nodes returned from
namemap() when resolving the symbol to a revset, so e.g. `hg log -r
stable` would resolve to *all* nodes on stable, not just the one with
the highest revnum (except that I don't actually think we should
change it for the branch namespace because of BC). Most people seem
opposed to that. If we decide not to do it, I think we can deprecate
the namemap() function in favor of the new singlenode() (I find it
weird to have namespaces, like the branch namespace, where namemap()
isn't nodemap()'s inverse). I therefore think this patch makes sense
regardless of what we decide on that issue.


 [1] Actually, even the branch namespace would have wanted to override
     singlenode() if it had supported multiple nodes. That's because
     closes branch heads are mostly ignored, so "hg co default" will
     not check out the highest-revnum node if that's a closed head.

Differential Revision: https://phab.mercurial-scm.org/D3852

from __future__ import absolute_import, division, print_function

import copy

from ._compat import iteritems
from ._make import NOTHING, fields, _obj_setattr
from .exceptions import AttrsAttributeNotFoundError


def asdict(inst, recurse=True, filter=None, dict_factory=dict,
           retain_collection_types=False):
    """
    Return the ``attrs`` attribute values of *inst* as a dict.

    Optionally recurse into other ``attrs``-decorated classes.

    :param inst: Instance of an ``attrs``-decorated class.
    :param bool recurse: Recurse into classes that are also
        ``attrs``-decorated.
    :param callable filter: A callable whose return code deteremines whether an
        attribute or element is included (``True``) or dropped (``False``).  Is
        called with the :class:`attr.Attribute` as the first argument and the
        value as the second argument.
    :param callable dict_factory: A callable to produce dictionaries from.  For
        example, to produce ordered dictionaries instead of normal Python
        dictionaries, pass in ``collections.OrderedDict``.
    :param bool retain_collection_types: Do not convert to ``list`` when
        encountering an attribute whose type is ``tuple`` or ``set``.  Only
        meaningful if ``recurse`` is ``True``.

    :rtype: return type of *dict_factory*

    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  versionadded:: 16.0.0 *dict_factory*
    ..  versionadded:: 16.1.0 *retain_collection_types*
    """
    attrs = fields(inst.__class__)
    rv = dict_factory()
    for a in attrs:
        v = getattr(inst, a.name)
        if filter is not None and not filter(a, v):
            continue
        if recurse is True:
            if has(v.__class__):
                rv[a.name] = asdict(v, recurse=True, filter=filter,
                                    dict_factory=dict_factory)
            elif isinstance(v, (tuple, list, set)):
                cf = v.__class__ if retain_collection_types is True else list
                rv[a.name] = cf([
                    asdict(i, recurse=True, filter=filter,
                           dict_factory=dict_factory)
                    if has(i.__class__) else i
                    for i in v
                ])
            elif isinstance(v, dict):
                df = dict_factory
                rv[a.name] = df((
                    asdict(kk, dict_factory=df) if has(kk.__class__) else kk,
                    asdict(vv, dict_factory=df) if has(vv.__class__) else vv)
                    for kk, vv in iteritems(v))
            else:
                rv[a.name] = v
        else:
            rv[a.name] = v
    return rv


def astuple(inst, recurse=True, filter=None, tuple_factory=tuple,
            retain_collection_types=False):
    """
    Return the ``attrs`` attribute values of *inst* as a tuple.

    Optionally recurse into other ``attrs``-decorated classes.

    :param inst: Instance of an ``attrs``-decorated class.
    :param bool recurse: Recurse into classes that are also
        ``attrs``-decorated.
    :param callable filter: A callable whose return code determines whether an
        attribute or element is included (``True``) or dropped (``False``).  Is
        called with the :class:`attr.Attribute` as the first argument and the
        value as the second argument.
    :param callable tuple_factory: A callable to produce tuples from.  For
        example, to produce lists instead of tuples.
    :param bool retain_collection_types: Do not convert to ``list``
        or ``dict`` when encountering an attribute which type is
        ``tuple``, ``dict`` or ``set``.  Only meaningful if ``recurse`` is
        ``True``.

    :rtype: return type of *tuple_factory*

    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  versionadded:: 16.2.0
    """
    attrs = fields(inst.__class__)
    rv = []
    retain = retain_collection_types  # Very long. :/
    for a in attrs:
        v = getattr(inst, a.name)
        if filter is not None and not filter(a, v):
            continue
        if recurse is True:
            if has(v.__class__):
                rv.append(astuple(v, recurse=True, filter=filter,
                                  tuple_factory=tuple_factory,
                                  retain_collection_types=retain))
            elif isinstance(v, (tuple, list, set)):
                cf = v.__class__ if retain is True else list
                rv.append(cf([
                    astuple(j, recurse=True, filter=filter,
                            tuple_factory=tuple_factory,
                            retain_collection_types=retain)
                    if has(j.__class__) else j
                    for j in v
                ]))
            elif isinstance(v, dict):
                df = v.__class__ if retain is True else dict
                rv.append(df(
                        (
                            astuple(
                                kk,
                                tuple_factory=tuple_factory,
                                retain_collection_types=retain
                            ) if has(kk.__class__) else kk,
                            astuple(
                                vv,
                                tuple_factory=tuple_factory,
                                retain_collection_types=retain
                            ) if has(vv.__class__) else vv
                        )
                        for kk, vv in iteritems(v)))
            else:
                rv.append(v)
        else:
            rv.append(v)
    return rv if tuple_factory is list else tuple_factory(rv)


def has(cls):
    """
    Check whether *cls* is a class with ``attrs`` attributes.

    :param type cls: Class to introspect.
    :raise TypeError: If *cls* is not a class.

    :rtype: :class:`bool`
    """
    return getattr(cls, "__attrs_attrs__", None) is not None


def assoc(inst, **changes):
    """
    Copy *inst* and apply *changes*.

    :param inst: Instance of a class with ``attrs`` attributes.
    :param changes: Keyword changes in the new copy.

    :return: A copy of inst with *changes* incorporated.

    :raise attr.exceptions.AttrsAttributeNotFoundError: If *attr_name* couldn't
        be found on *cls*.
    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  deprecated:: 17.1.0
        Use :func:`evolve` instead.
    """
    import warnings
    warnings.warn("assoc is deprecated and will be removed after 2018/01.",
                  DeprecationWarning)
    new = copy.copy(inst)
    attrs = fields(inst.__class__)
    for k, v in iteritems(changes):
        a = getattr(attrs, k, NOTHING)
        if a is NOTHING:
            raise AttrsAttributeNotFoundError(
                "{k} is not an attrs attribute on {cl}."
                .format(k=k, cl=new.__class__)
            )
        _obj_setattr(new, k, v)
    return new


def evolve(inst, **changes):
    """
    Create a new instance, based on *inst* with *changes* applied.

    :param inst: Instance of a class with ``attrs`` attributes.
    :param changes: Keyword changes in the new copy.

    :return: A copy of inst with *changes* incorporated.

    :raise TypeError: If *attr_name* couldn't be found in the class
        ``__init__``.
    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  versionadded:: 17.1.0
    """
    cls = inst.__class__
    attrs = fields(cls)
    for a in attrs:
        if not a.init:
            continue
        attr_name = a.name  # To deal with private attributes.
        init_name = attr_name if attr_name[0] != "_" else attr_name[1:]
        if init_name not in changes:
            changes[init_name] = getattr(inst, attr_name)
    return cls(**changes)