root/trunk/twisted/python/reflect.py

# -*- test-case-name: twisted.test.test_reflect -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Standardized versions of various cool and/or strange things that you can do
with Python's reflection capabilities.
"""

import sys
import os
import types
import pickle
import traceback
import weakref
import re
import warnings

try:
    from collections import deque
except ImportError:
    deque = list

RegexType = type(re.compile(""))


try:
    from cStringIO import StringIO
except ImportError:
    from StringIO import StringIO

from twisted.python.util import unsignedID
from twisted.python.deprecate import deprecated, deprecatedModuleAttribute
from twisted.python.deprecate import _fullyQualifiedName as fullyQualifiedName
from twisted.python.versions import Version



class Settable:
    """
    A mixin class for syntactic sugar.  Lets you assign attributes by
    calling with keyword arguments; for example, C{x(a=b,c=d,y=z)} is the
    same as C{x.a=b;x.c=d;x.y=z}.  The most useful place for this is
    where you don't want to name a variable, but you do want to set
    some attributes; for example, C{X()(y=z,a=b)}.
    """

    deprecatedModuleAttribute(
        Version("Twisted", 12, 1, 0),
        "Settable is old and untested. Please write your own version of this "
        "functionality if you need it.", "twisted.python.reflect", "Settable")

    def __init__(self, **kw):
        self(**kw)

    def __call__(self,**kw):
        for key,val in kw.items():
            setattr(self,key,val)
        return self


class AccessorType(type):
    """
    Metaclass that generates properties automatically.

    This is for Python 2.2 and up.

    Using this metaclass for your class will give you explicit accessor
    methods; a method called set_foo, will automatically create a property
    'foo' that uses set_foo as a setter method. Same for get_foo and del_foo.

    Note that this will only work on methods that are present on class
    creation. If you add methods after the class is defined they will not
    automatically become properties. Likewise, class attributes will only
    be used if they are present upon class creation, and no getter function
    was set - if a getter is present, the class attribute will be ignored.

    This is a 2.2-only alternative to the Accessor mixin - just set in your
    class definition::

        __metaclass__ = AccessorType

    """

    deprecatedModuleAttribute(
        Version("Twisted", 12, 1, 0),
        "AccessorType is old and untested. Please write your own version of "
        "this functionality if you need it.", "twisted.python.reflect",
        "AccessorType")

    def __init__(self, name, bases, d):
        type.__init__(self, name, bases, d)
        accessors = {}
        prefixs = ["get_", "set_", "del_"]
        for k in d.keys():
            v = getattr(self, k)
            for i in range(3):
                if k.startswith(prefixs[i]):
                    accessors.setdefault(k[4:], [None, None, None])[i] = v
        for name, (getter, setter, deler) in accessors.items():
            # create default behaviours for the property - if we leave
            # the getter as None we won't be able to getattr, etc..
            if getter is None:
                if hasattr(self, name):
                    value = getattr(self, name)
                    def getter(this, value=value, name=name):
                        if name in this.__dict__:
                            return this.__dict__[name]
                        else:
                            return value
                else:
                    def getter(this, name=name):
                        if name in this.__dict__:
                            return this.__dict__[name]
                        else:
                            raise AttributeError("no such attribute %r" % name)
            if setter is None:
                def setter(this, value, name=name):
                    this.__dict__[name] = value
            if deler is None:
                def deler(this, name=name):
                    del this.__dict__[name]
            setattr(self, name, property(getter, setter, deler, ""))


class PropertyAccessor(object):
    """
    A mixin class for Python 2.2 that uses AccessorType.

    This provides compatability with the pre-2.2 Accessor mixin, up
    to a point.

    Extending this class will give you explicit accessor methods; a
    method called set_foo, for example, is the same as an if statement
    in __setattr__ looking for 'foo'.  Same for get_foo and del_foo.

    There are also reallyDel and reallySet methods, so you can
    override specifics in subclasses without clobbering __setattr__
    and __getattr__, or using non-2.1 compatible code.

    There is are incompatibilities with Accessor - accessor
    methods added after class creation will *not* be detected. OTOH,
    this method is probably way faster.

    In addition, class attributes will only be used if no getter
    was defined, and instance attributes will not override getter methods
    whereas in original Accessor the class attribute or instance attribute
    would override the getter method.
    """
    # addendum to above:
    # The behaviour of Accessor is wrong IMHO, and I've found bugs
    # caused by it.
    #  -- itamar

    deprecatedModuleAttribute(
        Version("Twisted", 12, 1, 0),
        "PropertyAccessor is old and untested. Please write your own version "
        "of this functionality if you need it.", "twisted.python.reflect",
        "PropertyAccessor")
    __metaclass__ = AccessorType

    def reallySet(self, k, v):
        self.__dict__[k] = v

    def reallyDel(self, k):
        del self.__dict__[k]


class Accessor:
    """
    Extending this class will give you explicit accessor methods; a
    method called C{set_foo}, for example, is the same as an if statement
    in L{__setattr__} looking for C{'foo'}.  Same for C{get_foo} and
    C{del_foo}.  There are also L{reallyDel} and L{reallySet} methods,
    so you can override specifics in subclasses without clobbering
    L{__setattr__} and L{__getattr__}.

    This implementation is for Python 2.1.
    """

    deprecatedModuleAttribute(
        Version("Twisted", 12, 1, 0),
        "Accessor is an implementation for Python 2.1 which is no longer "
        "supported by Twisted.", "twisted.python.reflect", "Accessor")

    def __setattr__(self, k,v):
        kstring='set_%s'%k
        if hasattr(self.__class__,kstring):
            return getattr(self,kstring)(v)
        else:
            self.reallySet(k,v)

    def __getattr__(self, k):
        kstring='get_%s'%k
        if hasattr(self.__class__,kstring):
            return getattr(self,kstring)()
        raise AttributeError("%s instance has no accessor for: %s" % (qual(self.__class__),k))

    def __delattr__(self, k):
        kstring='del_%s'%k
        if hasattr(self.__class__,kstring):
            getattr(self,kstring)()
            return
        self.reallyDel(k)

    def reallySet(self, k,v):
        """
        *actually* set self.k to v without incurring side-effects.
        This is a hook to be overridden by subclasses.
        """
        if k == "__dict__":
            self.__dict__.clear()
            self.__dict__.update(v)
        else:
            self.__dict__[k]=v

    def reallyDel(self, k):
        """
        *actually* del self.k without incurring side-effects.  This is a
        hook to be overridden by subclasses.
        """
        del self.__dict__[k]

# just in case
OriginalAccessor = Accessor
deprecatedModuleAttribute(
    Version("Twisted", 12, 1, 0),
    "OriginalAccessor is a reference to class twisted.python.reflect.Accessor "
    "which is deprecated.", "twisted.python.reflect", "OriginalAccessor")


class Summer(Accessor):
    """
    Extend from this class to get the capability to maintain 'related
    sums'.  Have a tuple in your class like the following::

        sums=(('amount','credit','credit_total'),
              ('amount','debit','debit_total'))

    and the 'credit_total' member of the 'credit' member of self will
    always be incremented when the 'amount' member of self is
    incremented, similiarly for the debit versions.
    """

    deprecatedModuleAttribute(
        Version("Twisted", 12, 1, 0),
        "Summer is a child class of twisted.python.reflect.Accessor which is " 
        "deprecated.", "twisted.python.reflect", "Summer")

    def reallySet(self, k,v):
        "This method does the work."
        for sum in self.sums:
            attr=sum[0]
            obj=sum[1]
            objattr=sum[2]
            if k == attr:
                try:
                    oldval=getattr(self, attr)
                except:
                    oldval=0
                diff=v-oldval
                if hasattr(self, obj):
                    ob=getattr(self,obj)
                    if ob is not None:
                        try:oldobjval=getattr(ob, objattr)
                        except:oldobjval=0.0
                        setattr(ob,objattr,oldobjval+diff)

            elif k == obj:
                if hasattr(self, attr):
                    x=getattr(self,attr)
                    setattr(self,attr,0)
                    y=getattr(self,k)
                    Accessor.reallySet(self,k,v)
                    setattr(self,attr,x)
                    Accessor.reallySet(self,y,v)
        Accessor.reallySet(self,k,v)


class QueueMethod:
    """
    I represent a method that doesn't exist yet.
    """
    def __init__(self, name, calls):
        self.name = name
        self.calls = calls
    def __call__(self, *args):
        self.calls.append((self.name, args))


def funcinfo(function):
    """
    this is more documentation for myself than useful code.
    """
    warnings.warn(
        "[v2.5] Use inspect.getargspec instead of twisted.python.reflect.funcinfo",
        DeprecationWarning,
        stacklevel=2)
    code=function.func_code
    name=function.func_name
    argc=code.co_argcount
    argv=code.co_varnames[:argc]
    defaults=function.func_defaults

    out = []

    out.append('The function %s accepts %s arguments' % (name ,argc))
    if defaults:
        required=argc-len(defaults)
        out.append('It requires %s arguments' % required)
        out.append('The arguments required are: %s' % argv[:required])
        out.append('additional arguments are:')
        for i in range(argc-required):
            j=i+required
            out.append('%s which has a default of' % (argv[j], defaults[i]))
    return out


ISNT=0
WAS=1
IS=2


def fullFuncName(func):
    qualName = (str(pickle.whichmodule(func, func.__name__)) + '.' + func.__name__)
    if namedObject(qualName) is not func:
        raise Exception("Couldn't find %s as %s." % (func, qualName))
    return qualName


def qual(clazz):
    """
    Return full import path of a class.
    """
    return clazz.__module__ + '.' + clazz.__name__


def getcurrent(clazz):
    assert type(clazz) == types.ClassType, 'must be a class...'
    module = namedModule(clazz.__module__)
    currclass = getattr(module, clazz.__name__, None)
    if currclass is None:
        return clazz
    return currclass


def getClass(obj):
    """
    Return the class or type of object 'obj'.
    Returns sensible result for oldstyle and newstyle instances and types.
    """
    if hasattr(obj, '__class__'):
        return obj.__class__
    else:
        return type(obj)

# class graph nonsense

# I should really have a better name for this...
def isinst(inst,clazz):
    if type(inst) != types.InstanceType or type(clazz)!= types.ClassType:
        return isinstance(inst,clazz)
    cl = inst.__class__
    cl2 = getcurrent(cl)
    clazz = getcurrent(clazz)
    if issubclass(cl2,clazz):
        if cl == cl2:
            return WAS
        else:
            inst.__class__ = cl2
            return IS
    else:
        return ISNT


def namedModule(name):
    """
    Return a module given its name.
    """
    topLevel = __import__(name)
    packages = name.split(".")[1:]
    m = topLevel
    for p in packages:
        m = getattr(m, p)
    return m


def namedObject(name):
    """
    Get a fully named module-global object.
    """
    classSplit = name.split('.')
    module = namedModule('.'.join(classSplit[:-1]))
    return getattr(module, classSplit[-1])

namedClass = namedObject # backwards compat



class _NoModuleFound(Exception):
    """
    No module was found because none exists.
    """


class InvalidName(ValueError):
    """
    The given name is not a dot-separated list of Python objects.
    """


class ModuleNotFound(InvalidName):
    """
    The module associated with the given name doesn't exist and it can't be
    imported.
    """


class ObjectNotFound(InvalidName):
    """
    The object associated with the given name doesn't exist and it can't be
    imported.
    """


def _importAndCheckStack(importName):
    """
    Import the given name as a module, then walk the stack to determine whether
    the failure was the module not existing, or some code in the module (for
    example a dependent import) failing.  This can be helpful to determine
    whether any actual application code was run.  For example, to distiguish
    administrative error (entering the wrong module name), from programmer
    error (writing buggy code in a module that fails to import).

    @raise Exception: if something bad happens.  This can be any type of
    exception, since nobody knows what loading some arbitrary code might do.

    @raise _NoModuleFound: if no module was found.
    """
    try:
        try:
            return __import__(importName)
        except ImportError:
            excType, excValue, excTraceback = sys.exc_info()
            while excTraceback:
                execName = excTraceback.tb_frame.f_globals["__name__"]
                if (execName is None or # python 2.4+, post-cleanup
                    execName == importName): # python 2.3, no cleanup
                    raise excType, excValue, excTraceback
                excTraceback = excTraceback.tb_next
            raise _NoModuleFound()
    except:
        # Necessary for cleaning up modules in 2.3.
        sys.modules.pop(importName, None)
        raise



def namedAny(name):
    """
    Retrieve a Python object by its fully qualified name from the global Python
    module namespace.  The first part of the name, that describes a module,
    will be discovered and imported.  Each subsequent part of the name is
    treated as the name of an attribute of the object specified by all of the
    name which came before it.  For example, the fully-qualified name of this
    object is 'twisted.python.reflect.namedAny'.

    @type name: L{str}
    @param name: The name of the object to return.

    @raise InvalidName: If the name is an empty string, starts or ends with
        a '.', or is otherwise syntactically incorrect.

    @raise ModuleNotFound: If the name is syntactically correct but the
        module it specifies cannot be imported because it does not appear to
        exist.

    @raise ObjectNotFound: If the name is syntactically correct, includes at
        least one '.', but the module it specifies cannot be imported because
        it does not appear to exist.

    @raise AttributeError: If an attribute of an object along the way cannot be
        accessed, or a module along the way is not found.

    @return: the Python object identified by 'name'.
    """
    if not name:
        raise InvalidName('Empty module name')

    names = name.split('.')

    # if the name starts or ends with a '.' or contains '..', the __import__
    # will raise an 'Empty module name' error. This will provide a better error
    # message.
    if '' in names:
        raise InvalidName(
            "name must be a string giving a '.'-separated list of Python "
            "identifiers, not %r" % (name,))

    topLevelPackage = None
    moduleNames = names[:]
    while not topLevelPackage:
        if moduleNames:
            trialname = '.'.join(moduleNames)
            try:
                topLevelPackage = _importAndCheckStack(trialname)
            except _NoModuleFound:
                moduleNames.pop()
        else:
            if len(names) == 1:
                raise ModuleNotFound("No module named %r" % (name,))
            else:
                raise ObjectNotFound('%r does not name an object' % (name,))

    obj = topLevelPackage
    for n in names[1:]:
        obj = getattr(obj, n)

    return obj



def _determineClass(x):
    try:
        return x.__class__
    except:
        return type(x)



def _determineClassName(x):
    c = _determineClass(x)
    try:
        return c.__name__
    except:
        try:
            return str(c)
        except:
            return '<BROKEN CLASS AT 0x%x>' % unsignedID(c)



def _safeFormat(formatter, o):
    """
    Helper function for L{safe_repr} and L{safe_str}.
    """
    try:
        return formatter(o)
    except:
        io = StringIO()
        traceback.print_exc(file=io)
        className = _determineClassName(o)
        tbValue = io.getvalue()
        return "<%s instance at 0x%x with %s error:\n %s>" % (
            className, unsignedID(o), formatter.__name__, tbValue)



def safe_repr(o):
    """
    safe_repr(anything) -> string

    Returns a string representation of an object, or a string containing a
    traceback, if that object's __repr__ raised an exception.
    """
    return _safeFormat(repr, o)



def safe_str(o):
    """
    safe_str(anything) -> string

    Returns a string representation of an object, or a string containing a
    traceback, if that object's __str__ raised an exception.
    """
    return _safeFormat(str, o)



## the following were factored out of usage

@deprecated(Version("Twisted", 11, 0, 0), "inspect.getmro")
def allYourBase(classObj, baseClass=None):
    """
    allYourBase(classObj, baseClass=None) -> list of all base
    classes that are subclasses of baseClass, unless it is None,
    in which case all bases will be added.
    """
    l = []
    _accumulateBases(classObj, l, baseClass)
    return l


@deprecated(Version("Twisted", 11, 0, 0), "inspect.getmro")
def accumulateBases(classObj, l, baseClass=None):
    _accumulateBases(classObj, l, baseClass)


def _accumulateBases(classObj, l, baseClass=None):
    for base in classObj.__bases__:
        if baseClass is None or issubclass(base, baseClass):
            l.append(base)
        _accumulateBases(base, l, baseClass)


def prefixedMethodNames(classObj, prefix):
    """
    A list of method names with a given prefix in a given class.
    """
    dct = {}
    addMethodNamesToDict(classObj, dct, prefix)
    return dct.keys()


def addMethodNamesToDict(classObj, dict, prefix, baseClass=None):
    """
    addMethodNamesToDict(classObj, dict, prefix, baseClass=None) -> dict
    this goes through 'classObj' (and its bases) and puts method names
    starting with 'prefix' in 'dict' with a value of 1. if baseClass isn't
    None, methods will only be added if classObj is-a baseClass

    If the class in question has the methods 'prefix_methodname' and
    'prefix_methodname2', the resulting dict should look something like:
    {"methodname": 1, "methodname2": 1}.
    """
    for base in classObj.__bases__:
        addMethodNamesToDict(base, dict, prefix, baseClass)

    if baseClass is None or baseClass in classObj.__bases__:
        for name, method in classObj.__dict__.items():
            optName = name[len(prefix):]
            if ((type(method) is types.FunctionType)
                and (name[:len(prefix)] == prefix)
                and (len(optName))):
                dict[optName] = 1


def prefixedMethods(obj, prefix=''):
    """
    A list of methods with a given prefix on a given instance.
    """
    dct = {}
    accumulateMethods(obj, dct, prefix)
    return dct.values()


def accumulateMethods(obj, dict, prefix='', curClass=None):
    """
    accumulateMethods(instance, dict, prefix)
    I recurse through the bases of instance.__class__, and add methods
    beginning with 'prefix' to 'dict', in the form of
    {'methodname':*instance*method_object}.
    """
    if not curClass:
        curClass = obj.__class__
    for base in curClass.__bases__:
        accumulateMethods(obj, dict, prefix, base)

    for name, method in curClass.__dict__.items():
        optName = name[len(prefix):]
        if ((type(method) is types.FunctionType)
            and (name[:len(prefix)] == prefix)
            and (len(optName))):
            dict[optName] = getattr(obj, name)


def accumulateClassDict(classObj, attr, adict, baseClass=None):
    """
    Accumulate all attributes of a given name in a class hierarchy into a single dictionary.

    Assuming all class attributes of this name are dictionaries.
    If any of the dictionaries being accumulated have the same key, the
    one highest in the class heirarchy wins.
    (XXX: If \"higest\" means \"closest to the starting class\".)

    Ex::

      class Soy:
        properties = {\"taste\": \"bland\"}
    
      class Plant:
        properties = {\"colour\": \"green\"}
    
      class Seaweed(Plant):
        pass
    
      class Lunch(Soy, Seaweed):
        properties = {\"vegan\": 1 }
    
      dct = {}
    
      accumulateClassDict(Lunch, \"properties\", dct)
    
      print dct

    {\"taste\": \"bland\", \"colour\": \"green\", \"vegan\": 1}
    """
    for base in classObj.__bases__:
        accumulateClassDict(base, attr, adict)
    if baseClass is None or baseClass in classObj.__bases__:
        adict.update(classObj.__dict__.get(attr, {}))


def accumulateClassList(classObj, attr, listObj, baseClass=None):
    """
    Accumulate all attributes of a given name in a class heirarchy into a single list.

    Assuming all class attributes of this name are lists.
    """
    for base in classObj.__bases__:
        accumulateClassList(base, attr, listObj)
    if baseClass is None or baseClass in classObj.__bases__:
        listObj.extend(classObj.__dict__.get(attr, []))


def isSame(a, b):
    return (a is b)


def isLike(a, b):
    return (a == b)


def modgrep(goal):
    return objgrep(sys.modules, goal, isLike, 'sys.modules')


def isOfType(start, goal):
    return ((type(start) is goal) or
            (isinstance(start, types.InstanceType) and
             start.__class__ is goal))


def findInstances(start, t):
    return objgrep(start, t, isOfType)


def objgrep(start, goal, eq=isLike, path='', paths=None, seen=None, showUnknowns=0, maxDepth=None):
    """
    An insanely CPU-intensive process for finding stuff.
    """
    if paths is None:
        paths = []
    if seen is None:
        seen = {}
    if eq(start, goal):
        paths.append(path)
    if id(start) in seen:
        if seen[id(start)] is start:
            return
    if maxDepth is not None:
        if maxDepth == 0:
            return
        maxDepth -= 1
    seen[id(start)] = start
    if isinstance(start, types.DictionaryType):
        for k, v in start.items():
            objgrep(k, goal, eq, path+'{'+repr(v)+'}', paths, seen, showUnknowns, maxDepth)
            objgrep(v, goal, eq, path+'['+repr(k)+']', paths, seen, showUnknowns, maxDepth)
    elif isinstance(start, (list, tuple, deque)):
        for idx in xrange(len(start)):
            objgrep(start[idx], goal, eq, path+'['+str(idx)+']', paths, seen, showUnknowns, maxDepth)
    elif isinstance(start, types.MethodType):
        objgrep(start.im_self, goal, eq, path+'.im_self', paths, seen, showUnknowns, maxDepth)
        objgrep(start.im_func, goal, eq, path+'.im_func', paths, seen, showUnknowns, maxDepth)
        objgrep(start.im_class, goal, eq, path+'.im_class', paths, seen, showUnknowns, maxDepth)
    elif hasattr(start, '__dict__'):
        for k, v in start.__dict__.items():
            objgrep(v, goal, eq, path+'.'+k, paths, seen, showUnknowns, maxDepth)
        if isinstance(start, types.InstanceType):
            objgrep(start.__class__, goal, eq, path+'.__class__', paths, seen, showUnknowns, maxDepth)
    elif isinstance(start, weakref.ReferenceType):
        objgrep(start(), goal, eq, path+'()', paths, seen, showUnknowns, maxDepth)
    elif (isinstance(start, types.StringTypes+
                    (types.IntType, types.FunctionType,
                     types.BuiltinMethodType, RegexType, types.FloatType,
                     types.NoneType, types.FileType)) or
          type(start).__name__ in ('wrapper_descriptor', 'method_descriptor',
                                   'member_descriptor', 'getset_descriptor')):
        pass
    elif showUnknowns:
        print 'unknown type', type(start), start
    return paths


def filenameToModuleName(fn):
    """
    Convert a name in the filesystem to the name of the Python module it is.

    This is agressive about getting a module name back from a file; it will
    always return a string.  Agressive means 'sometimes wrong'; it won't look
    at the Python path or try to do any error checking: don't use this method
    unless you already know that the filename you're talking about is a Python
    module.
    """
    fullName = os.path.abspath(fn)
    base = os.path.basename(fn)
    if not base:
        # this happens when fn ends with a path separator, just skit it
        base = os.path.basename(fn[:-1])
    modName = os.path.splitext(base)[0]
    while 1:
        fullName = os.path.dirname(fullName)
        if os.path.exists(os.path.join(fullName, "__init__.py")):
            modName = "%s.%s" % (os.path.basename(fullName), modName)
        else:
            break
    return modName



__all__ = [
    'InvalidName', 'ModuleNotFound', 'ObjectNotFound',

    'ISNT', 'WAS', 'IS',

    'Settable', 'AccessorType', 'PropertyAccessor', 'Accessor', 'Summer',
    'QueueMethod', 'OriginalAccessor',

    'funcinfo', 'fullFuncName', 'qual', 'getcurrent', 'getClass', 'isinst',
    'namedModule', 'namedObject', 'namedClass', 'namedAny',
    'safe_repr', 'safe_str', 'allYourBase', 'accumulateBases',
    'prefixedMethodNames', 'addMethodNamesToDict', 'prefixedMethods',
    'accumulateClassDict', 'accumulateClassList', 'isSame', 'isLike',
    'modgrep', 'isOfType', 'findInstances', 'objgrep', 'filenameToModuleName',
    'fullyQualifiedName']