sqlobject/sqlobject/events.py at master · sqlobject/sqlobject · GitHub

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from __future__ import print_function

import sys

import types

from pydispatch import dispatcher

from weakref import ref

from .compat import class_types

subclassClones = {}

def listen(receiver, soClass, signal, alsoSubclasses=True, weak=True):

"""

Listen for the given ``signal`` on the SQLObject subclass

``soClass``, calling ``receiver()`` when ``send(soClass, signal,

...)`` is called.

If ``alsoSubclasses`` is true, receiver will also be called when

an event is fired on any subclass.

"""

dispatcher.connect(receiver, signal=signal, sender=soClass, weak=weak)

weakReceiver = ref(receiver)

subclassClones.setdefault(soClass, []).append((weakReceiver, signal))

# We export this function:

send = dispatcher.send

class Signal(object):

"""

Base event for all SQLObject events.

In general the sender for these methods is the class, not the

instance.

"""

class ClassCreateSignal(Signal):

"""

Signal raised after class creation. The sender is the superclass

(in case of multiple superclasses, the first superclass). The

arguments are ``(new_class_name, bases, new_attrs, post_funcs,

early_funcs)``. ``new_attrs`` is a dictionary and may be modified

(but ``new_class_name`` and ``bases`` are immutable).

``post_funcs`` is an initially-empty list that can have callbacks

appended to it.

Note: at the time this event is called, the new class has not yet

been created. The functions in ``post_funcs`` will be called

after the class is created, with the single arguments of

``(new_class)``. Also, ``early_funcs`` will be called at the

soonest possible time after class creation (``post_funcs`` is

called after the class's ``__classinit__``).

"""

def _makeSubclassConnections(new_class_name, bases, new_attrs,

post_funcs, early_funcs):

early_funcs.insert(0, _makeSubclassConnectionsPost)

def _makeSubclassConnectionsPost(new_class):

for cls in new_class.__bases__:

for weakReceiver, signal in subclassClones.get(cls, []):

receiver = weakReceiver()

if not receiver:

continue

listen(receiver, new_class, signal)

dispatcher.connect(_makeSubclassConnections, signal=ClassCreateSignal)

# @@: Should there be a class reload event? This would allow modules

# to be reloaded, possibly. Or it could even be folded into

# ClassCreateSignal, since anything that listens to that needs to pay

# attention to reloads (or else it is probably buggy).

class RowCreateSignal(Signal):

"""

Called before an instance is created, with the class as the

sender. Called with the arguments ``(instance, kwargs, post_funcs)``.

There may be a ``connection`` argument. ``kwargs``may be usefully

modified. ``post_funcs`` is a list of callbacks, intended to have

functions appended to it, and are called with the arguments

``(new_instance)``.

Note: this is not called when an instance is created from an

existing database row.

"""

class RowCreatedSignal(Signal):

"""

Called after an instance is created, with the class as the

sender. Called with the arguments ``(instance, kwargs, post_funcs)``.

There may be a ``connection`` argument. ``kwargs``may be usefully

modified. ``post_funcs`` is a list of callbacks, intended to have

functions appended to it, and are called with the arguments

``(new_instance)``.

Note: this is not called when an instance is created from an

existing database row.

"""

# @@: An event for getting a row? But for each row, when doing a

# select? For .sync, .syncUpdate, .expire?

class RowDestroySignal(Signal):

"""

Called before an instance is deleted. Sender is the instance's

class. Arguments are ``(instance, post_funcs)``.

``post_funcs`` is a list of callbacks, intended to have

functions appended to it, and are called with arguments ``(instance)``.

If any of the post_funcs raises an exception, the deletion is only

affected if this will prevent a commit.

You cannot cancel the delete, but you can raise an exception (which will

probably cancel the delete, but also cause an uncaught exception if not

expected).

Note: this is not called when an instance is destroyed through

garbage collection.

@@: Should this allow ``instance`` to be a primary key, so that a

row can be deleted without first fetching it?

"""

class RowDestroyedSignal(Signal):

"""

Called after an instance is deleted. Sender is the instance's

class. Arguments are ``(instance)``.

This is called before the post_funcs of RowDestroySignal

Note: this is not called when an instance is destroyed through

garbage collection.

"""

class RowUpdateSignal(Signal):

"""

Called when an instance is updated through a call to ``.set()``

(or a column attribute assignment). The arguments are

``(instance, kwargs)``. ``kwargs`` can be modified. This is run

*before* the instance is updated; if you want to look at the

current values, simply look at ``instance``.

"""

class RowUpdatedSignal(Signal):

"""

Called when an instance is updated through a call to ``.set()``

(or a column attribute assignment). The arguments are

``(instance, post_funcs)``. ``post_funcs`` is a list of callbacks,

intended to have functions appended to it, and are called with the

arguments ``(new_instance)``. This is run *after* the instance is

updated; Works better with lazyUpdate = True.

"""

class AddColumnSignal(Signal):

"""

Called when a column is added to a class, with arguments ``(cls,

connection, column_name, column_definition, changeSchema,

post_funcs)``. This is called *after* the column has been added,

and is called for each column after class creation.

post_funcs are called with ``(cls, so_column_obj)``

"""

class DeleteColumnSignal(Signal):

"""

Called when a column is removed from a class, with the arguments

``(cls, connection, column_name, so_column_obj, post_funcs)``.

Like ``AddColumnSignal`` this is called after the action has been

performed, and is called for subclassing (when a column is

implicitly removed by setting it to ``None``).

post_funcs are called with ``(cls, so_column_obj)``

"""

# @@: Signals for indexes and joins? These are mostly event consumers,

# though.

class CreateTableSignal(Signal):

"""

Called when a table is created. If ``ifNotExists==True`` and the

table exists, this event is not called.

Called with ``(cls, connection, extra_sql, post_funcs)``.

``extra_sql`` is a list (which can be appended to) of extra SQL

statements to be run after the table is created. ``post_funcs``

functions are called with ``(cls, connection)`` after the table

has been created. Those functions are *not* called simply when

constructing the SQL.

"""

class DropTableSignal(Signal):

"""

Called when a table is dropped. If ``ifExists==True`` and the

table doesn't exist, this event is not called.

Called with ``(cls, connection, extra_sql, post_funcs)``.

``post_funcs`` functions are called with ``(cls, connection)``

after the table has been dropped.

"""

class CommitSignal(Signal):

"""

Called on transaction commit

"""

class RollbackSignal(Signal):

"""

Called on transaction rollback

"""

############################################################

# Event Debugging

############################################################

def summarize_events_by_sender(sender=None, output=None, indent=0):

"""

Prints out a summary of the senders and listeners in the system,

for debugging purposes.

"""

if output is None:

output = sys.stdout

leader = ' ' * indent

if sender is None:

send_list = [

(deref(dispatcher.senders.get(sid)), listeners)

for sid, listeners in dispatcher.connections.items()

if deref(dispatcher.senders.get(sid))]

for sender, listeners in sorted_items(send_list):

real_sender = deref(sender)

if not real_sender:

continue

header = 'Sender: %r' % real_sender

print(leader + header, file=output)

print(leader + ('=' * len(header)), file=output)

summarize_events_by_sender(real_sender, output=output,

indent=indent + 2)

else:

for signal, receivers in \

sorted_items(dispatcher.connections.get(id(sender), [])):

receivers = [deref(r) for r in receivers if deref(r)]

header = 'Signal: %s (%i receivers)' % (sort_name(signal),

len(receivers))

print(leader + header, file=output)

print(leader + ('-' * len(header)), file=output)

for receiver in sorted(receivers, key=sort_name):

print(leader + ' ' + nice_repr(receiver), file=output)

def deref(value):

if isinstance(value, dispatcher.WEAKREF_TYPES):

return value()

else:

return value

def sorted_items(a_dict):

if isinstance(a_dict, dict):

a_dict = a_dict.items()

return sorted(a_dict, key=lambda t: sort_name(t[0]))

def sort_name(value):

if isinstance(value, type):

return value.__name__

elif isinstance(value, types.FunctionType):

return value.__name__

else:

return str(value)

_real_dispatcher_send = dispatcher.send

_real_dispatcher_sendExact = dispatcher.sendExact

_real_dispatcher_connect = dispatcher.connect

_real_dispatcher_disconnect = dispatcher.disconnect

_debug_enabled = False

def debug_events():

global _debug_enabled, send

if _debug_enabled:

return

_debug_enabled = True

dispatcher.send = send = _debug_send

dispatcher.sendExact = _debug_sendExact

dispatcher.disconnect = _debug_disconnect

dispatcher.connect = _debug_connect

def _debug_send(signal=dispatcher.Any, sender=dispatcher.Anonymous,

*arguments, **named):

print("send %s from %s: %s" % (

nice_repr(signal), nice_repr(sender),

fmt_args(*arguments, **named)))

return _real_dispatcher_send(signal, sender, *arguments, **named)

def _debug_sendExact(signal=dispatcher.Any, sender=dispatcher.Anonymous,

*arguments, **named):

print("sendExact %s from %s: %s" % (

nice_repr(signal), nice_repr(sender), fmt_args(*arguments, **name)))

return _real_dispatcher_sendExact(signal, sender, *arguments, **named)

def _debug_connect(receiver, signal=dispatcher.Any, sender=dispatcher.Any,

weak=True):

print("connect %s to %s signal %s" % (

nice_repr(receiver), nice_repr(signal), nice_repr(sender)))

return _real_dispatcher_connect(receiver, signal, sender, weak)

def _debug_disconnect(receiver, signal=dispatcher.Any, sender=dispatcher.Any,

weak=True):

print("disconnecting %s from %s signal %s" % (

nice_repr(receiver), nice_repr(signal), nice_repr(sender)))

return _real_dispatcher_disconnect(receiver, signal, sender, weak)

def fmt_args(*arguments, **name):

args = [repr(a) for a in arguments]

args.extend([

'%s=%r' % (n, v) for n, v in sorted(name.items())])

return ', '.join(args)

def nice_repr(v):

"""

Like repr(), but nicer for debugging here.

"""

if isinstance(v, class_types):

return v.__module__ + '.' + v.__name__

elif isinstance(v, types.FunctionType):

if '__name__' in v.__globals__:

if getattr(sys.modules[v.__globals__['__name__']],

v.__name__, None) is v:

return '%s.%s' % (v.__globals__['__name__'], v.__name__)

return repr(v)

elif isinstance(v, types.MethodType):

return '%s.%s of %s' % (

nice_repr(v.__self__.__class__), v.__func__.__name__,

nice_repr(v.__self__))

else:

return repr(v)

__all__ = ['listen', 'send']

# Use copy() to avoid 'dictionary changed' issues on python 3

for name, value in globals().copy().items():

if isinstance(value, type) and issubclass(value, Signal):

__all__.append(name)

sqlobject/sqlobject/events.py at master · sqlobject/sqlobject · GitHub

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