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//usr/lib64/python2.7/site-packages/sqlalchemy/testing/util.py

# testing/util.py
# Copyright (C) 2005-2020 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

import decimal
import gc
import random
import sys
import time
import types

from ..util import decorator
from ..util import defaultdict
from ..util import inspect_getfullargspec
from ..util import jython
from ..util import py2k
from ..util import pypy

if jython:

def jython_gc_collect(*args):
        """aggressive gc.collect for tests."""
        gc.collect()
        time.sleep(0.1)
        gc.collect()
        gc.collect()
        return 0

# "lazy" gc, for VM's that don't GC on refcount == 0
    gc_collect = lazy_gc = jython_gc_collect
elif pypy:

def pypy_gc_collect(*args):
        gc.collect()
        gc.collect()

gc_collect = lazy_gc = pypy_gc_collect
else:
    # assume CPython - straight gc.collect, lazy_gc() is a pass
    gc_collect = gc.collect

def lazy_gc():
        pass

def picklers():
    picklers = set()
    if py2k:
        try:
            import cPickle

picklers.add(cPickle)
        except ImportError:
            pass

import pickle

picklers.add(pickle)

# yes, this thing needs this much testing
    for pickle_ in picklers:
        for protocol in range(-2, pickle.HIGHEST_PROTOCOL):
            yield pickle_.loads, lambda d: pickle_.dumps(d, protocol)

def round_decimal(value, prec):
    if isinstance(value, float):
        return round(value, prec)

# can also use shift() here but that is 2.6 only
    return (value * decimal.Decimal("1" + "0" * prec)).to_integral(
        decimal.ROUND_FLOOR
    ) / pow(10, prec)

class RandomSet(set):
    def __iter__(self):
        l = list(set.__iter__(self))
        random.shuffle(l)
        return iter(l)

def pop(self):
        index = random.randint(0, len(self) - 1)
        item = list(set.__iter__(self))[index]
        self.remove(item)
        return item

def union(self, other):
        return RandomSet(set.union(self, other))

def difference(self, other):
        return RandomSet(set.difference(self, other))

def intersection(self, other):
        return RandomSet(set.intersection(self, other))

def copy(self):
        return RandomSet(self)

def conforms_partial_ordering(tuples, sorted_elements):
    """True if the given sorting conforms to the given partial ordering."""

deps = defaultdict(set)
    for parent, child in tuples:
        deps[parent].add(child)
    for i, node in enumerate(sorted_elements):
        for n in sorted_elements[i:]:
            if node in deps[n]:
                return False
    else:
        return True

def all_partial_orderings(tuples, elements):
    edges = defaultdict(set)
    for parent, child in tuples:
        edges[child].add(parent)

def _all_orderings(elements):

if len(elements) == 1:
            yield list(elements)
        else:
            for elem in elements:
                subset = set(elements).difference([elem])
                if not subset.intersection(edges[elem]):
                    for sub_ordering in _all_orderings(subset):
                        yield [elem] + sub_ordering

return iter(_all_orderings(elements))

def function_named(fn, name):
    """Return a function with a given __name__.

Will assign to __name__ and return the original function if possible on
    the Python implementation, otherwise a new function will be constructed.

This function should be phased out as much as possible
    in favor of @decorator.   Tests that "generate" many named tests
    should be modernized.

"""
    try:
        fn.__name__ = name
    except TypeError:
        fn = types.FunctionType(
            fn.__code__, fn.__globals__, name, fn.__defaults__, fn.__closure__
        )
    return fn

def run_as_contextmanager(ctx, fn, *arg, **kw):
    """Run the given function under the given contextmanager,
    simulating the behavior of 'with' to support older
    Python versions.

This is not necessary anymore as we have placed 2.6
    as minimum Python version, however some tests are still using
    this structure.

"""

obj = ctx.__enter__()
    try:
        result = fn(obj, *arg, **kw)
        ctx.__exit__(None, None, None)
        return result
    except:
        exc_info = sys.exc_info()
        raise_ = ctx.__exit__(*exc_info)
        if not raise_:
            raise
        else:
            return raise_

def rowset(results):
    """Converts the results of sql execution into a plain set of column tuples.

Useful for asserting the results of an unordered query.
    """

return {tuple(row) for row in results}

def fail(msg):
    assert False, msg

@decorator
def provide_metadata(fn, *args, **kw):
    """Provide bound MetaData for a single test, dropping afterwards."""

from . import config
    from . import engines
    from sqlalchemy import schema

metadata = schema.MetaData(config.db)
    self = args[0]
    prev_meta = getattr(self, "metadata", None)
    self.metadata = metadata
    try:
        return fn(*args, **kw)
    finally:
        engines.drop_all_tables(metadata, config.db)
        self.metadata = prev_meta

def flag_combinations(*combinations):
    """A facade around @testing.combinations() oriented towards boolean
    keyword-based arguments.

Basically generates a nice looking identifier based on the keywords
    and also sets up the argument names.

E.g.::

@testing.flag_combinations(
            dict(lazy=False, passive=False),
            dict(lazy=True, passive=False),
            dict(lazy=False, passive=True),
            dict(lazy=False, passive=True, raiseload=True),
        )

would result in::

@testing.combinations(
            ('', False, False, False),
            ('lazy', True, False, False),
            ('lazy_passive', True, True, False),
            ('lazy_passive', True, True, True),
            id_='iaaa',
            argnames='lazy,passive,raiseload'
        )

"""

from . import config

keys = set()

for d in combinations:
        keys.update(d)

keys = sorted(keys)

return config.combinations(
        *[
            ("_".join(k for k in keys if d.get(k, False)),)
            + tuple(d.get(k, False) for k in keys)
            for d in combinations
        ],
        id_="i" + ("a" * len(keys)),
        argnames=",".join(keys)
    )

def resolve_lambda(__fn, **kw):
    """Given a no-arg lambda and a namespace, return a new lambda that
    has all the values filled in.

This is used so that we can have module-level fixtures that
    refer to instance-level variables using lambdas.

"""

pos_args = inspect_getfullargspec(__fn)[0]
    pass_pos_args = {arg: kw.pop(arg) for arg in pos_args}
    glb = dict(__fn.__globals__)
    glb.update(kw)
    new_fn = types.FunctionType(__fn.__code__, glb)
    return new_fn(**pass_pos_args)

def metadata_fixture(ddl="function"):
    """Provide MetaData for a pytest fixture."""

from . import config

def decorate(fn):
        def run_ddl(self):
            from sqlalchemy import schema

metadata = self.metadata = schema.MetaData()
            try:
                result = fn(self, metadata)
                metadata.create_all(config.db)
                # TODO:
                # somehow get a per-function dml erase fixture here
                yield result
            finally:
                metadata.drop_all(config.db)

return config.fixture(scope=ddl)(run_ddl)

return decorate

def force_drop_names(*names):
    """Force the given table names to be dropped after test complete,
    isolating for foreign key cycles

"""
    from . import config
    from sqlalchemy import inspect

@decorator
    def go(fn, *args, **kw):

try:
            return fn(*args, **kw)
        finally:
            drop_all_tables(config.db, inspect(config.db), include_names=names)

return go

class adict(dict):
    """Dict keys available as attributes.  Shadows."""

def __getattribute__(self, key):
        try:
            return self[key]
        except KeyError:
            return dict.__getattribute__(self, key)

def __call__(self, *keys):
        return tuple([self[key] for key in keys])

get_all = __call__

def drop_all_tables(engine, inspector, schema=None, include_names=None):
    from sqlalchemy import (
        Column,
        Table,
        Integer,
        MetaData,
        ForeignKeyConstraint,
    )
    from sqlalchemy.schema import DropTable, DropConstraint

if include_names is not None:
        include_names = set(include_names)

with engine.connect() as conn:
        for tname, fkcs in reversed(
            inspector.get_sorted_table_and_fkc_names(schema=schema)
        ):
            if tname:
                if include_names is not None and tname not in include_names:
                    continue
                conn.execute(
                    DropTable(Table(tname, MetaData(), schema=schema))
                )
            elif fkcs:
                if not engine.dialect.supports_alter:
                    continue
                for tname, fkc in fkcs:
                    if (
                        include_names is not None
                        and tname not in include_names
                    ):
                        continue
                    tb = Table(
                        tname,
                        MetaData(),
                        Column("x", Integer),
                        Column("y", Integer),
                        schema=schema,
                    )
                    conn.execute(
                        DropConstraint(
                            ForeignKeyConstraint([tb.c.x], [tb.c.y], name=fkc)
                        )
                    )

def teardown_events(event_cls):
    @decorator
    def decorate(fn, *arg, **kw):
        try:
            return fn(*arg, **kw)
        finally:
            event_cls._clear()

return decorate