wrap.py

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#
# LSST Data Management System
# Copyright 2008, 2009, 2010 LSST Corporation.
#
# This product includes software developed by the
# LSST Project (http://www.lsst.org/).
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the LSST License Statement and
# the GNU General Public License along with this program.  If not,
# see <http://www.lsstcorp.org/LegalNotices/>.
#
__all__ = ("wrap", "makeConfigClass")

import inspect
import re
import importlib

from .config import Config, Field
from .listField import ListField, List
from .configField import ConfigField
from .callStack import getCallerFrame, getCallStack

_dtypeMap = {
    "bool": bool,
    "int": int,
    "double": float,
    "float": float,
    "std::int64_t": int,
    "std::string": str
}
"""Mapping from C++ types to Python type (`dict`)

Tassumes we can round-trip between these using the usual pybind11 converters,
but doesn't require they be binary equivalent under-the-hood or anything.
"""

_containerRegex = re.compile(r"(std::)?(vector|list)<\s*(?P<type>[a-z0-9_:]+)\s*>")


def makeConfigClass(ctrl, name=None, base=Config, doc=None, module=0, cls=None):
    """Create a `~lsst.pex.config.Config` class that matches a  C++ control
    object class.

    See the `wrap` decorator as a convenient interface to ``makeConfigClass``.

    Parameters
    ----------
    ctrl : class
        C++ control class to wrap.
    name : `str`, optional
        Name of the new config class; defaults to the ``__name__`` of the
        control class with ``'Control'`` replaced with ``'Config'``.
    base : `lsst.pex.config.Config`-type, optional
        Base class for the config class.
    doc : `str`, optional
        Docstring for the config class.
    module : object, `str`, or `int`, optional
        Either a module object, a string specifying the name of the module, or
        an integer specifying how far back in the stack to look for the module
        to use: 0 is the immediate caller of `~lsst.pex.config.wrap`. This will
        be used to set ``__module__`` for the new config class, and the class
        will also be added to the module. Ignored if `None` or if ``cls`` is
        not `None`, but note that the default is to use the callers' module.
    cls : class
        An existing config class to use instead of creating a new one; name,
        base doc, and module will be ignored if this is not `None`.

    Notes
    -----
    To use ``makeConfigClass``, write a control object in C++ using the
    ``LSST_CONTROL_FIELD`` macro in ``lsst/pex/config.h`` (note that it must
    have sensible default constructor):

    .. code-block:: cpp

       // myHeader.h

       struct InnerControl {
           LSST_CONTROL_FIELD(wim, std::string, "documentation for field 'wim'");
       };

       struct FooControl {
           LSST_CONTROL_FIELD(bar, int, "documentation for field 'bar'");
           LSST_CONTROL_FIELD(baz, double, "documentation for field 'baz'");
           LSST_NESTED_CONTROL_FIELD(zot, myWrappedLib, InnerControl, "documentation for field 'zot'");

           FooControl() : bar(0), baz(0.0) {}
       };

    You can use ``LSST_NESTED_CONTROL_FIELD`` to nest control objects. Wrap
    those control objects as you would any other C++ class, but make sure you
    include ``lsst/pex/config.h`` before including the header file where
    the control object class is defined.

    Next, in Python:

    .. code-block:: py

       import lsst.pex.config
       import myWrappedLib

       InnerConfig = lsst.pex.config.makeConfigClass(myWrappedLib.InnerControl)
       FooConfig = lsst.pex.config.makeConfigClass(myWrappedLib.FooControl)

    This does the following things:

    - Adds ``bar``, ``baz``, and ``zot`` fields to ``FooConfig``.
    - Set ``FooConfig.Control`` to ``FooControl``.
    - Adds ``makeControl`` and ``readControl`` methods to create a
      ``FooControl`` and set the ``FooConfig`` from the ``FooControl``,
      respectively.
    - If ``FooControl`` has a ``validate()`` member function,
      a custom ``validate()`` method will be added to ``FooConfig`` that uses
      it.

    All of the above are done for ``InnerConfig`` as well.

    Any field that would be injected that would clash with an existing
    attribute of the class is be silently ignored. This allows you to
    customize fields and inherit them from wrapped control classes. However,
    these names are still be processed when converting between config and
    control classes, so they should generally be present as base class fields
    or other instance attributes or descriptors.

    While ``LSST_CONTROL_FIELD`` will work for any C++ type, automatic
    `~lsst.pex.config.Config` generation only supports ``bool``, ``int``,
    ``std::int64_t``, ``double``, and ``std::string`` fields, along with
    ``std::list`` and ``std::vectors`` of those types.

    See also
    --------
    wrap
    """
    if name is None:
        if "Control" not in ctrl.__name__:
            raise ValueError("Cannot guess appropriate Config class name for %s." % ctrl)
        name = ctrl.__name__.replace("Control", "Config")
    if cls is None:
        cls = type(name, (base,), {"__doc__": doc})
        if module is not None:
            # Not only does setting __module__ make Python pretty-printers more useful,
            # it's also necessary if we want to pickle Config objects.
            if isinstance(module, int):
                frame = getCallerFrame(module)
                moduleObj = inspect.getmodule(frame)
                moduleName = moduleObj.__name__
            elif isinstance(module, str):
                moduleName = module
                moduleObj = __import__(moduleName)
            else:
                moduleObj = module
                moduleName = moduleObj.__name__
            cls.__module__ = moduleName
            setattr(moduleObj, name, cls)
    if doc is None:
        doc = ctrl.__doc__
    fields = {}
    # loop over all class attributes, looking for the special static methods that indicate a field
    # defined by one of the macros in pex/config.h.
    for attr in dir(ctrl):
        if attr.startswith("_type_"):
            k = attr[len("_type_"):]
            getDoc = "_doc_" + k
            getModule = "_module_" + k
            getType = attr
            if hasattr(ctrl, k) and hasattr(ctrl, getDoc):
                doc = getattr(ctrl, getDoc)()
                ctype = getattr(ctrl, getType)()
                if hasattr(ctrl, getModule):  # if this is present, it's a nested control object
                    nestedModuleName = getattr(ctrl, getModule)()
                    if nestedModuleName == moduleName:
                        nestedModuleObj = moduleObj
                    else:
                        nestedModuleObj = importlib.import_module(nestedModuleName)
                    try:
                        dtype = getattr(nestedModuleObj, ctype).ConfigClass
                    except AttributeError:
                        raise AttributeError("'%s.%s.ConfigClass' does not exist" % (moduleName, ctype))
                    fields[k] = ConfigField(doc=doc, dtype=dtype)
                else:
                    try:
                        dtype = _dtypeMap[ctype]
                        FieldCls = Field
                    except KeyError:
                        dtype = None
                        m = _containerRegex.match(ctype)
                        if m:
                            dtype = _dtypeMap.get(m.group("type"), None)
                            FieldCls = ListField
                    if dtype is None:
                        raise TypeError("Could not parse field type '%s'." % ctype)
                    fields[k] = FieldCls(doc=doc, dtype=dtype, optional=True)

    # Define a number of methods to put in the new Config class.  Note that these are "closures";
    # they have access to local variables defined in the makeConfigClass function (like the fields dict).
    def makeControl(self):
        """Construct a C++ Control object from this Config object.

        Fields set to `None` will be ignored, and left at the values defined
        by the Control object's default constructor.
        """
        r = self.Control()
        for k, f in fields.items():
            value = getattr(self, k)
            if isinstance(f, ConfigField):
                value = value.makeControl()
            if value is not None:
                if isinstance(value, List):
                    setattr(r, k, value._list)
                else:
                    setattr(r, k, value)
        return r

    def readControl(self, control, __at=None, __label="readControl", __reset=False):
        """Read values from a C++ Control object and assign them to self's
        fields.

        Parameters
        ----------
        control
            C++ Control object.

        Notes
        -----
        The ``__at``, ``__label``, and ``__reset`` arguments are for internal
        use only; they are used to remove internal calls from the history.
        """
        if __at is None:
            __at = getCallStack()
        values = {}
        for k, f in fields.items():
            if isinstance(f, ConfigField):
                getattr(self, k).readControl(getattr(control, k),
                                             __at=__at, __label=__label, __reset=__reset)
            else:
                values[k] = getattr(control, k)
        if __reset:
            self._history = {}
        self.update(__at=__at, __label=__label, **values)

    def validate(self):
        """Validate the config object by constructing a control object and
        using a C++ ``validate()`` implementation.
        """
        super(cls, self).validate()
        r = self.makeControl()
        r.validate()

    def setDefaults(self):
        """Initialize the config object, using the Control objects default ctor
        to provide defaults.
        """
        super(cls, self).setDefaults()
        try:
            r = self.Control()
            # Indicate in the history that these values came from C++, even if we can't say which line
            self.readControl(r, __at=[(ctrl.__name__ + " C++", 0, "setDefaults", "")], __label="defaults",
                             __reset=True)
        except Exception:
            pass  # if we can't instantiate the Control, don't set defaults

    ctrl.ConfigClass = cls
    cls.Control = ctrl
    cls.makeControl = makeControl
    cls.readControl = readControl
    cls.setDefaults = setDefaults
    if hasattr(ctrl, "validate"):
        cls.validate = validate
    for k, field in fields.items():
        if not hasattr(cls, k):
            setattr(cls, k, field)
    return cls


def wrap(ctrl):
    """Decorator that adds fields from a C++ control class to a
    `lsst.pex.config.Config` class.

    Parameters
    ----------
    ctrl : object
        The C++ control class.

    Notes
    -----
    See `makeConfigClass` for more information. This `wrap` decorator is
    equivalent to calling `makeConfigClass` with the decorated class as the
    ``cls`` argument.

    Examples
    --------
    Use `wrap` like this::

        @wrap(MyControlClass)
        class MyConfigClass(Config):
            pass

    See also
    --------
    makeConfigClass
    """
    def decorate(cls):
        return makeConfigClass(ctrl, cls=cls)
    return decorate