def set_default_attrs(
obj, **kws
): # e if this was general, we could refile into py_utils, but it turns out it's not general enough
"""For each attr=val pair in **kws, if attr is not set in obj, set it, without doing usage or change tracking.
If obj supports __setattr_default__ (not a special name to Python itself), use that, otherwise use hasattr and setattr
(with a temporary dynamic suppression of usage or change tracking, if possible -- nim for now except as an assertion).
Note: this is not very efficient (or self-contained) for general use, for which pure hasattr/setattr would be sufficient.
"""
# Note about why we disable tracking: hasattr itself does legitimately track use of the attr,
# since testing thereness does use its "value" in a general sense (as if value was _UNSET_ when not there).
# But, in this specific code, we don't want client (caller) to see us using attr,
# since from client POV, all we're doing is changing _UNSET_ to v, which are equivalent values
# (as client is declaring by calling us).
# So we need to discard tracked usage of attr here.
# We also need to discard any change from the set to default value,
# except that we can probably ignore that issue for now (due to an accident of how current code uses this),
# since if the attr is unset, it was never yet used, so invalidating it should have no effect.
if 1:
from exprs.Exprs import is_pure_expr
if is_pure_expr(obj):
assert 0, (
"set_default_attrs called on pure_expr %r is almost surely a bug; normally do it in _init_instance"
% (obj,)
)
import foundation.changes as changes
try:
method = obj.__setattr_default__
except AttributeError:
## print "fyi: set_default_attrs using general case for",obj,kws.keys() # this happens for all non-tracked StatePlaces
# general case - let's hope the object doesn't have tracked attrs; the temporary assertion here might not catch this
###e instead, we should actively suppress usage/change tracking, so we can permit it in obj
# (tho careless uses of that would lead to bugs)
mc = changes.begin_disallowing_usage_tracking("set_default_attrs (hasattr/setattr) for %r" % obj)
# note: the argument is just an explanation for use in error messages ##e OPTIM: don't precompute that arg
try:
for k, v in kws.iteritems():
if not hasattr(obj, k):
setattr(obj, k, v)
finally:
changes.end_disallowing_usage_tracking(mc)
else:
# use the special method
mc = changes.begin_disallowing_usage_tracking("set_default_attrs (__setattr_default__) for %r" % obj)
# e optim: remove this check; it only catches usage tracking, not change tracking (ie inval of something by this), anyway
try:
for k, v in kws.iteritems():
method(
k, v
) # does its own usage/change-tracking suppression (we assume); this is partially checked (for now)
finally:
changes.end_disallowing_usage_tracking(mc)
return # from set_default_attrs
def set_default_attrs(
obj, **kws
): #e if this was general, we could refile into py_utils, but it turns out it's not general enough
"""For each attr=val pair in **kws, if attr is not set in obj, set it, without doing usage or change tracking.
If obj supports __setattr_default__ (not a special name to Python itself), use that, otherwise use hasattr and setattr
(with a temporary dynamic suppression of usage or change tracking, if possible -- nim for now except as an assertion).
Note: this is not very efficient (or self-contained) for general use, for which pure hasattr/setattr would be sufficient.
"""
# Note about why we disable tracking: hasattr itself does legitimately track use of the attr,
# since testing thereness does use its "value" in a general sense (as if value was _UNSET_ when not there).
# But, in this specific code, we don't want client (caller) to see us using attr,
# since from client POV, all we're doing is changing _UNSET_ to v, which are equivalent values
# (as client is declaring by calling us).
# So we need to discard tracked usage of attr here.
# We also need to discard any change from the set to default value,
# except that we can probably ignore that issue for now (due to an accident of how current code uses this),
# since if the attr is unset, it was never yet used, so invalidating it should have no effect.
if 1:
from exprs.Exprs import is_pure_expr
if is_pure_expr(obj):
assert 0, "set_default_attrs called on pure_expr %r is almost surely a bug; normally do it in _init_instance" % (
obj, )
import foundation.changes as changes
try:
method = obj.__setattr_default__
except AttributeError:
## print "fyi: set_default_attrs using general case for",obj,kws.keys() # this happens for all non-tracked StatePlaces
# general case - let's hope the object doesn't have tracked attrs; the temporary assertion here might not catch this
###e instead, we should actively suppress usage/change tracking, so we can permit it in obj
# (tho careless uses of that would lead to bugs)
mc = changes.begin_disallowing_usage_tracking(
'set_default_attrs (hasattr/setattr) for %r' % obj)
# note: the argument is just an explanation for use in error messages ##e OPTIM: don't precompute that arg
try:
for k, v in kws.iteritems():
if not hasattr(obj, k):
setattr(obj, k, v)
finally:
changes.end_disallowing_usage_tracking(mc)
else:
# use the special method
mc = changes.begin_disallowing_usage_tracking(
'set_default_attrs (__setattr_default__) for %r' % obj)
#e optim: remove this check; it only catches usage tracking, not change tracking (ie inval of something by this), anyway
try:
for k, v in kws.iteritems():
method(
k, v
) # does its own usage/change-tracking suppression (we assume); this is partially checked (for now)
finally:
changes.end_disallowing_usage_tracking(mc)
return # from set_default_attrs
def __getitem__(self, key):
try:
return dict.__getitem__(self, key)
except KeyError:
import foundation.changes as changes
mc = changes.begin_disallowing_usage_tracking(self) # note: argument is just explanation for use in error messages
try:
val = self._way(key)
# note, it needs to be legal for something during this to reallow using tracking for itself, locally
except:
# try not to hurt this object for use at other keys, but good to reraise exception to whoever accessed this key
# (maybe something's wrong with this key, but good even if not, i think [061121])
# Note: the exception might be an error being reported by begin_disallowing_usage_tracking!
# So we should do the ending of that disallowing -- the initial raising of that exception should not do it.
changes.end_disallowing_usage_tracking(mc)
raise
else:
changes.end_disallowing_usage_tracking(mc)
dict.__setitem__(self, key, val)
return val
pass
def __getitem__(self, key):
try:
return dict.__getitem__(self, key)
except KeyError:
import foundation.changes as changes
mc = changes.begin_disallowing_usage_tracking(self) # note: argument is just explanation for use in error messages
try:
val = self._way(key)
# note, it needs to be legal for something during this to reallow using tracking for itself, locally
except:
# try not to hurt this object for use at other keys, but good to reraise exception to whoever accessed this key
# (maybe something's wrong with this key, but good even if not, i think [061121])
# Note: the exception might be an error being reported by begin_disallowing_usage_tracking!
# So we should do the ending of that disallowing -- the initial raising of that exception should not do it.
changes.end_disallowing_usage_tracking(mc)
raise
else:
changes.end_disallowing_usage_tracking(mc)
dict.__setitem__(self, key, val)
return val
pass
def _set_defaultValue(self, defaultValue):
"""If attr is not set, set it to defaultValue; never do any usage or change tracking.
(WARNING: This will cause bugs unless all providers of access to a given attribute-instance
use this consistently (same default value, and all of them using this rather than some of
them providing access to the attr with no default value); they must all use it before
providing access to that attr to any client object.)
"""
# see comments in set_default_attrs about why we need this to do no usage or change tracking
if self.valid:
return # easy case
# Dilemma: we might have no value, or we might have one computable by an initial-value compute method...
# or we might have such a method which will raise LvalError_ValueIsUnset when we try it
# (e.g. valfunc method in some client code). The only way to find out is to use that method,
# but what if doing so tracked some usage? I think it's normal for that to happen...
# OTOH, it's not correct, I think, to have two inconsistent ways of setting a default value --
# code that calls this, vs. code that supplies an initial-value compute method that actually works.
# So, maybe we should be able to ask the method which kind it is... but for now, assume it could
# be either. If it computes a real value, we better not run it now, since usage would get tracked...
# though that's an error... one way to detect is to return now and let it run, but that led to infrecur
# in self.delegate in If.cond (don't know why). But setting defaultValue now risks hiding bugs.
# That leaves: run it now, asserting no usage tracking. [Note: current calling code redundantly asserts the same thing. #e]
#
# One case which is not covered: something asked if we were set, was told "we're unset", and tracked its usage of us.
# Ideally we'd assert right here that we have no current inval-subscribers. ####e DOIT
# (For now, if we *do* have subscribers who learned we were unset, and if we leave them untouched,
# it's indeed a bug that they asked that before we were initialized, but it's not so bad that they'll
# get invalled when something changes us later.)
printnim("assert no current inval-subscribers")
mc = changes.begin_disallowing_usage_tracking('_set_defaultValue in %r' % self)
# note: the argument is just an explanation for use in error messages ##e OPTIM: don't precompute that arg
try:
try:
val = self._compute_value() # don't call get_value since it calls track_use
except LvalError_ValueIsUnset:
# this is the only non-error case!
# (the following just inlines self.set_constant_value(defaultValue):)
self._value = defaultValue
self.valid = True
## print "_set_defaultValue returning after set"
return
except:
# any other exception, including discovering usage tracking in that computation [once that works when it happens],
# should be reported, but then (I think) needn't prevent this from working.
print_compact_traceback("error: exception (ignored) in _set_defaultValue trying initval-computation in %r: " % self)
self._value = defaultValue
self.valid = True
return
else:
# If a value was computed, that conflicts with using this method... report that error (even if the values agree),
# but which value should we use? Let's use the computed one for now.
# NOTE: In present code [061121], this can also happen if usage tracking occurred, since it's not detected
# until the end_disallowing_usage_tracking call below (since begin_disallowing_usage_tracking is not fully
# implemented).
print "error: %r computed initial value %r (using it) but was also given an explicit _set_defaultValue(%r)" % \
(self, val, defaultValue)
self._value = val
self.valid = True
return
pass
finally:
changes.end_disallowing_usage_tracking(mc)
pass # end of method _set_defaultValue
def _set_defaultValue(self, defaultValue):
"""If attr is not set, set it to defaultValue; never do any usage or change tracking.
(WARNING: This will cause bugs unless all providers of access to a given attribute-instance
use this consistently (same default value, and all of them using this rather than some of
them providing access to the attr with no default value); they must all use it before
providing access to that attr to any client object.)
"""
# see comments in set_default_attrs about why we need this to do no usage or change tracking
if self.valid:
return # easy case
# Dilemma: we might have no value, or we might have one computable by an initial-value compute method...
# or we might have such a method which will raise LvalError_ValueIsUnset when we try it
# (e.g. valfunc method in some client code). The only way to find out is to use that method,
# but what if doing so tracked some usage? I think it's normal for that to happen...
# OTOH, it's not correct, I think, to have two inconsistent ways of setting a default value --
# code that calls this, vs. code that supplies an initial-value compute method that actually works.
# So, maybe we should be able to ask the method which kind it is... but for now, assume it could
# be either. If it computes a real value, we better not run it now, since usage would get tracked...
# though that's an error... one way to detect is to return now and let it run, but that led to infrecur
# in self.delegate in If.cond (don't know why). But setting defaultValue now risks hiding bugs.
# That leaves: run it now, asserting no usage tracking. [Note: current calling code redundantly asserts the same thing. #e]
#
# One case which is not covered: something asked if we were set, was told "we're unset", and tracked its usage of us.
# Ideally we'd assert right here that we have no current inval-subscribers. ####e DOIT
# (For now, if we *do* have subscribers who learned we were unset, and if we leave them untouched,
# it's indeed a bug that they asked that before we were initialized, but it's not so bad that they'll
# get invalled when something changes us later.)
printnim("assert no current inval-subscribers")
mc = changes.begin_disallowing_usage_tracking(
'_set_defaultValue in %r' % self)
# note: the argument is just an explanation for use in error messages ##e OPTIM: don't precompute that arg
try:
try:
val = self._compute_value(
) # don't call get_value since it calls track_use
except LvalError_ValueIsUnset:
# this is the only non-error case!
# (the following just inlines self.set_constant_value(defaultValue):)
self._value = defaultValue
self.valid = True
## print "_set_defaultValue returning after set"
return
except:
# any other exception, including discovering usage tracking in that computation [once that works when it happens],
# should be reported, but then (I think) needn't prevent this from working.
print_compact_traceback(
"error: exception (ignored) in _set_defaultValue trying initval-computation in %r: "
% self)
self._value = defaultValue
self.valid = True
return
else:
# If a value was computed, that conflicts with using this method... report that error (even if the values agree),
# but which value should we use? Let's use the computed one for now.
# NOTE: In present code [061121], this can also happen if usage tracking occurred, since it's not detected
# until the end_disallowing_usage_tracking call below (since begin_disallowing_usage_tracking is not fully
# implemented).
print "error: %r computed initial value %r (using it) but was also given an explicit _set_defaultValue(%r)" % \
(self, val, defaultValue)
self._value = val
self.valid = True
return
pass
finally:
changes.end_disallowing_usage_tracking(mc)
pass # end of method _set_defaultValue
