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[EDIT] FILE: engines.py

# testing/engines.py
# Copyright (C) 2005-2021 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

from __future__ import absolute_import

import re
import warnings
import weakref

from . import config
from . import uses_deprecated
from .util import decorator
from .. import event
from .. import pool

class ConnectionKiller(object):
    def __init__(self):
        self.proxy_refs = weakref.WeakKeyDictionary()
        self.testing_engines = weakref.WeakKeyDictionary()
        self.conns = set()

def add_engine(self, engine):
        self.testing_engines[engine] = True

def connect(self, dbapi_conn, con_record):
        self.conns.add((dbapi_conn, con_record))

def checkout(self, dbapi_con, con_record, con_proxy):
        self.proxy_refs[con_proxy] = True

def invalidate(self, dbapi_con, con_record, exception):
        self.conns.discard((dbapi_con, con_record))

def _safe(self, fn):
        try:
            fn()
        except Exception as e:
            warnings.warn(
                "testing_reaper couldn't " "rollback/close connection: %s" % e
            )

def rollback_all(self):
        for rec in list(self.proxy_refs):
            if rec is not None and rec.is_valid:
                self._safe(rec.rollback)

def close_all(self):
        for rec in list(self.proxy_refs):
            if rec is not None and rec.is_valid:
                self._safe(rec._close)

def _after_test_ctx(self):
        # this can cause a deadlock with pg8000 - pg8000 acquires
        # prepared statement lock inside of rollback() - if async gc
        # is collecting in finalize_fairy, deadlock.
        # not sure if this should be if pypy/jython only.
        # note that firebird/fdb definitely needs this though
        for conn, rec in list(self.conns):
            if rec.connection is None:
                # this is a hint that the connection is closed, which
                # is causing segfaults on mysqlclient due to
                # https://github.com/PyMySQL/mysqlclient-python/issues/270;
                # try to work around here
                continue
            self._safe(conn.rollback)

def _stop_test_ctx(self):
        if config.options.low_connections:
            self._stop_test_ctx_minimal()
        else:
            self._stop_test_ctx_aggressive()

@uses_deprecated()
    def _stop_test_ctx_minimal(self):
        self.close_all()

self.conns = set()

for rec in list(self.testing_engines):
            if rec is not config.db:
                rec.dispose()

@uses_deprecated()
    def _stop_test_ctx_aggressive(self):
        self.close_all()
        for conn, rec in list(self.conns):
            self._safe(conn.close)
            rec.connection = None

self.conns = set()
        for rec in list(self.testing_engines):
            rec.dispose()

def assert_all_closed(self):
        for rec in self.proxy_refs:
            if rec.is_valid:
                assert False

testing_reaper = ConnectionKiller()

def drop_all_tables(metadata, bind):
    testing_reaper.close_all()
    if hasattr(bind, "close"):
        bind.close()

if not config.db.dialect.supports_alter:
        from . import assertions

with assertions.expect_warnings("Can't sort tables", assert_=False):
            metadata.drop_all(bind)
    else:
        metadata.drop_all(bind)

@decorator
def assert_conns_closed(fn, *args, **kw):
    try:
        fn(*args, **kw)
    finally:
        testing_reaper.assert_all_closed()

@decorator
def rollback_open_connections(fn, *args, **kw):
    """Decorator that rolls back all open connections after fn execution."""

try:
        fn(*args, **kw)
    finally:
        testing_reaper.rollback_all()

@decorator
def close_first(fn, *args, **kw):
    """Decorator that closes all connections before fn execution."""

testing_reaper.close_all()
    fn(*args, **kw)

@decorator
def close_open_connections(fn, *args, **kw):
    """Decorator that closes all connections after fn execution."""
    try:
        fn(*args, **kw)
    finally:
        testing_reaper.close_all()

def all_dialects(exclude=None):
    import sqlalchemy.databases as d

for name in d.__all__:
        # TEMPORARY
        if exclude and name in exclude:
            continue
        mod = getattr(d, name, None)
        if not mod:
            mod = getattr(
                __import__("sqlalchemy.databases.%s" % name).databases, name
            )
        yield mod.dialect()

class ReconnectFixture(object):
    def __init__(self, dbapi):
        self.dbapi = dbapi
        self.connections = []
        self.is_stopped = False

def __getattr__(self, key):
        return getattr(self.dbapi, key)

def connect(self, *args, **kwargs):

conn = self.dbapi.connect(*args, **kwargs)
        if self.is_stopped:
            self._safe(conn.close)
            curs = conn.cursor()  # should fail on Oracle etc.
            # should fail for everything that didn't fail
            # above, connection is closed
            curs.execute("select 1")
            assert False, "simulated connect failure didn't work"
        else:
            self.connections.append(conn)
            return conn

def _safe(self, fn):
        try:
            fn()
        except Exception as e:
            warnings.warn(
                "ReconnectFixture couldn't " "close connection: %s" % e
            )

def shutdown(self, stop=False):
        # TODO: this doesn't cover all cases
        # as nicely as we'd like, namely MySQLdb.
        # would need to implement R. Brewer's
        # proxy server idea to get better
        # coverage.
        self.is_stopped = stop
        for c in list(self.connections):
            self._safe(c.close)
        self.connections = []

def restart(self):
        self.is_stopped = False

def reconnecting_engine(url=None, options=None):
    url = url or config.db.url
    dbapi = config.db.dialect.dbapi
    if not options:
        options = {}
    options["module"] = ReconnectFixture(dbapi)
    engine = testing_engine(url, options)
    _dispose = engine.dispose

def dispose():
        engine.dialect.dbapi.shutdown()
        engine.dialect.dbapi.is_stopped = False
        _dispose()

engine.test_shutdown = engine.dialect.dbapi.shutdown
    engine.test_restart = engine.dialect.dbapi.restart
    engine.dispose = dispose
    return engine

def testing_engine(url=None, options=None):
    """Produce an engine configured by --options with optional overrides."""

from sqlalchemy import create_engine
    from sqlalchemy.engine.url import make_url

if not options:
        use_reaper = True
    else:
        use_reaper = options.pop("use_reaper", True)

url = url or config.db.url

url = make_url(url)
    if options is None:
        if config.db is None or url.drivername == config.db.url.drivername:
            options = config.db_opts
        else:
            options = {}
    elif config.db is not None and url.drivername == config.db.url.drivername:
        default_opt = config.db_opts.copy()
        default_opt.update(options)

engine = create_engine(url, **options)
    engine._has_events = True  # enable event blocks, helps with profiling

if isinstance(engine.pool, pool.QueuePool):
        engine.pool._timeout = 0
        engine.pool._max_overflow = 0
    if use_reaper:
        event.listen(engine.pool, "connect", testing_reaper.connect)
        event.listen(engine.pool, "checkout", testing_reaper.checkout)
        event.listen(engine.pool, "invalidate", testing_reaper.invalidate)
        testing_reaper.add_engine(engine)

return engine

def mock_engine(dialect_name=None):
    """Provides a mocking engine based on the current testing.db.

This is normally used to test DDL generation flow as emitted
    by an Engine.

It should not be used in other cases, as assert_compile() and
    assert_sql_execution() are much better choices with fewer
    moving parts.

"""

from sqlalchemy import create_engine

if not dialect_name:
        dialect_name = config.db.name

buffer = []

def executor(sql, *a, **kw):
        buffer.append(sql)

def assert_sql(stmts):
        recv = [re.sub(r"[\n\t]", "", str(s)) for s in buffer]
        assert recv == stmts, recv

def print_sql():
        d = engine.dialect
        return "\n".join(str(s.compile(dialect=d)) for s in engine.mock)

engine = create_engine(
        dialect_name + "://", strategy="mock", executor=executor
    )
    assert not hasattr(engine, "mock")
    engine.mock = buffer
    engine.assert_sql = assert_sql
    engine.print_sql = print_sql
    return engine

class DBAPIProxyCursor(object):
    """Proxy a DBAPI cursor.

Tests can provide subclasses of this to intercept
    DBAPI-level cursor operations.

"""

def __init__(self, engine, conn, *args, **kwargs):
        self.engine = engine
        self.connection = conn
        self.cursor = conn.cursor(*args, **kwargs)

def execute(self, stmt, parameters=None, **kw):
        if parameters:
            return self.cursor.execute(stmt, parameters, **kw)
        else:
            return self.cursor.execute(stmt, **kw)

def executemany(self, stmt, params, **kw):
        return self.cursor.executemany(stmt, params, **kw)

def __getattr__(self, key):
        return getattr(self.cursor, key)

def __enter__(self):
        return self

def __exit__(self, *args):
        pass

class DBAPIProxyConnection(object):
    """Proxy a DBAPI connection.

Tests can provide subclasses of this to intercept
    DBAPI-level connection operations.

"""

def __init__(self, engine, cursor_cls):
        self.conn = self._sqla_unwrap = engine.pool._creator()
        self.engine = engine
        self.cursor_cls = cursor_cls

def cursor(self, *args, **kwargs):
        return self.cursor_cls(self.engine, self.conn, *args, **kwargs)

def close(self):
        self.conn.close()

def __getattr__(self, key):
        return getattr(self.conn, key)

def proxying_engine(
    conn_cls=DBAPIProxyConnection, cursor_cls=DBAPIProxyCursor
):
    """Produce an engine that provides proxy hooks for
    common methods.

"""

def mock_conn():
        return conn_cls(config.db, cursor_cls)

return testing_engine(options={"creator": mock_conn})

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