/usr/lib/python3/dist-packages/plainbox/impl/unit/validators.py is in python3-plainbox 0.25-1.
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#
# Copyright 2012-2014 Canonical Ltd.
# Written by:
# Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
#
# Checkbox is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 3,
# as published by the Free Software Foundation.
#
# Checkbox is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Checkbox. If not, see <http://www.gnu.org/licenses/>.
"""
:mod:`plainbox.impl.unit` -- unit definition
============================================
"""
import abc
import inspect
import itertools
import logging
import os
import shlex
import sys
from plainbox.i18n import gettext as _
from plainbox.i18n import ngettext
from plainbox.impl import pod
from plainbox.abc import IProvider1
from plainbox.impl.unit import get_accessed_parameters
from plainbox.impl.validation import Issue
from plainbox.impl.validation import Problem
from plainbox.impl.validation import Severity
__all__ = [
'CorrectFieldValueValidator',
'DeprecatedFieldValidator',
'FieldValidatorBase',
'IFieldValidator',
'PresentFieldValidator',
'TemplateInvariantFieldValidator',
'TemplateVariantFieldValidator',
'TranslatableFieldValidator',
'UniqueValueValidator',
'UnitReferenceValidator',
'UntranslatableFieldValidator',
]
logger = logging.getLogger("plainbox.unit")
def field2prop(field):
"""
Convert a field to the property that is used to access that field
:param field:
A string or Symbol that represents the field
:returns:
Name of the property to access on the unit.
"""
return str(field).replace('-', '_')
class UnitValidationContext(pod.POD):
"""
Helper class for validating units in a bigger context
This class has two purposes:
1) to allow the validated object to see "everything" (other units)
2) to allow validators to share temporary data structures
and to prevent O(N**2) complexity of some checks.
"""
provider_list = pod.Field(
"list of all the providers", list, pod.MANDATORY,
assign_filter_list=[pod.typed, pod.typed.sequence(IProvider1)])
shared_cache = pod.Field(
"cached computations", dict, initial_fn=dict,
assign_filter_list=[pod.typed])
def compute_shared(self, cache_key, func, *args, **kwargs):
"""
Compute a shared helper.
:param cache_key:
Key to use to lookup the helper value
:param func:
Function that computes the helper value. The function is called
with the context as the only argument
:returns:
Return value of func(self, *args, **kwargs) (possibly computed
earlier).
Compute something that can be shared by all the validation classes
and units within one context. This allows certain validators to
only compute expensive 'global' transformations of the context at most
once.
.. note::
The caller is responsible for ensuring that ``args`` and ``kwargs``
match the `cache_key` each time this function is called.
"""
if cache_key not in self.shared_cache:
self.shared_cache[cache_key] = func(*args, **kwargs)
return self.shared_cache[cache_key]
class UnitFieldIssue(Issue):
"""
Issue specific to a field of an Unit
:attr unit:
Name of the unit that the issue relates to
:attr field:
Name of the field within the unit
"""
def __init__(self, message, severity, kind, origin, unit, field):
super().__init__(message, severity, kind, origin)
self.unit = unit
self.field = field
def __repr__(self):
return (
"{}(message={!r}, severity={!r}, kind={!r}, origin={!r}"
" unit={!r}, field={!r})"
).format(
self.__class__.__name__,
self.message, self.severity, self.kind, self.origin,
self.unit, self.field)
class MultiUnitFieldIssue(Issue):
"""
Issue involving multiple units.
:attr unit_list:
Name of the unit that the issue relates to
:attr field:
Name of the field within the unit
"""
def __init__(self, message, severity, kind, origin, unit_list, field):
super().__init__(message, severity, kind, origin)
self.unit_list = unit_list
self.field = field
def __repr__(self):
return (
"{}(message={!r}, severity={!r}, kind={!r}, origin={!r}"
" unit_list={!r}, field={!r})"
).format(
self.__class__.__name__,
self.message, self.severity, self.kind, self.origin,
self.unit_list, self.field)
class IFieldValidator(metaclass=abc.ABCMeta):
"""
Interface for all :class:`Unit` field validators.
Instances of this class participate in the validation process.
"""
@abc.abstractmethod
def __init__(self, **kwargs):
"""
Initialize the validator to check the specified field.
:param kwargs:
Any additional arguments associated with the validator
that were defined on the UnitValidator
"""
def check(self, parent, unit, field):
"""
Perform the check associated with a specific field
:param parent:
The :class:`UnitValidator` that this validator cooperates with
:param unit:
The :class:`Unit` to validate
:param field:
The field to check, this may be a Symbol
:returns:
None
This method doesn't raise any exceptions nor returns error values.
Instead it is expected to use the :meth:`UnitValidator.report_issue()`
family of methods (including error, warning and advice) to report
detected problems
"""
def check_in_context(self, parent, unit, field, context):
"""
Perform the check associated with a specific field in a known context
:param parent:
The :class:`UnitValidator` that this validator cooperates with
:param unit:
The :class:`Unit` to validate
:param field:
The field to check, this may be a Symbol
:param context:
The :class:`UnitValidationContext` to use
:returns:
None
This method doesn't raise any exceptions nor returns error values.
Instead it is expected to use the :meth:`UnitValidator.report_issue()`
family of methods (including error, warning and advice) to report
detected problems
"""
class FieldValidatorBase(IFieldValidator):
"""
Base validator that implements no checks of any kind
"""
def __init__(self, message=None):
self.message = message
def check(self, parent, unit, field):
return ()
def check_in_context(self, parent, unit, field, context):
return ()
class CorrectFieldValueValidator(FieldValidatorBase):
"""
Validator ensuring that a field value is correct according to some criteria
This validator simply ensures that a value of a field (as accessed through
a field-property) matches a predefined criteria. The criteria can
be specified externally which makes this validator very flexible.
"""
default_severity = Severity.error
default_kind = Problem.wrong
def __init__(self, correct_fn, kind=None, severity=None, message=None,
onlyif=None):
"""
correct_fn:
A function that checks if the value is correct or not. If it
returns False then an issue is reported in accordance with other
arguments. It is called either as ``correct_fn(value)`` or
``correct_fn(value, unit)`` based on the number of accepted
arguments.
kind:
Kind of issue to report. By default this is Problem.wrong
severity:
Severity of the issue to report. By default this is Severity.error
message:
Customized error message. This message will be used to report the
issue if the validation fails. By default it is derived from the
specified issue ``kind`` by :meth:`UnitValidator.explain()`.
onlyif:
An optional function that checks if this validator should be
applied or not. The function is called with the `unit` as the only
argument. If it returns True then the validator proceeds to
perform its check.
"""
super().__init__(message)
if sys.version_info[:2] >= (3, 5):
has_two_args = len(inspect.signature(correct_fn).parameters) == 2
else:
has_two_args = len(inspect.getargspec(correct_fn).args) == 2
self.correct_fn = correct_fn
self.correct_fn_needs_unit = has_two_args
self.kind = kind or self.default_kind
self.severity = severity or self.default_severity
self.onlyif = onlyif
def check(self, parent, unit, field):
# Skip this validator if onlyif says we should do so
if self.onlyif is not None and not self.onlyif(unit):
return
# Look up the value
value = getattr(unit, field2prop(field))
try:
if self.correct_fn_needs_unit:
is_correct = self.correct_fn(value, unit)
else:
is_correct = self.correct_fn(value)
except Exception as exc:
yield parent.report_issue(
unit, field, self.kind, self.severity,
self.message or str(exc))
else:
# Report an issue if the correctness check failed
if not is_correct:
yield parent.report_issue(
unit, field, self.kind, self.severity, self.message)
class PresentFieldValidator(CorrectFieldValueValidator):
"""
Validator ensuring that a field has a value
This validator simply ensures that a value of a field (as accessed through
a field-property) is not None. It is useful for simple checks for required
fields.
"""
default_kind = Problem.missing
def __init__(self, kind=None, severity=None, message=None, onlyif=None):
"""
correct_fn:
A function that checks if the value is correct or not. If it
returns False then an issue is reported in accordance with other
arguments
kind:
Kind of issue to report. By default this is Problem.missing
severity:
Severity of the issue to report. By default this is Severity.error
message:
Customized error message. This message will be used to report the
issue if the validation fails. By default it is derived from the
specified issue ``kind`` by :meth:`UnitValidator.explain()`.
"""
correct_fn = lambda value: value is not None
super().__init__(correct_fn, kind, severity, message, onlyif)
class UselessFieldValidator(CorrectFieldValueValidator):
"""
Validator ensuring that no value is specified to a field in certain context
The context should be encoded by passing the onlyif argument which can
inspect the unit and determine if a field is useless or not.
"""
default_kind = Problem.useless
default_severity = Severity.warning
def __init__(self, kind=None, severity=None, message=None, onlyif=None):
"""
correct_fn:
A function that checks if the value is correct or not. If it
returns False then an issue is reported in accordance with other
arguments
kind:
Kind of issue to report. By default this is Problem.useless
severity:
Severity of the issue to report. By default this is
Severity.warning
message:
Customized error message. This message will be used to report the
issue if the validation fails. By default it is derived from the
specified issue ``kind`` by :meth:`UnitValidator.explain()`.
"""
correct_fn = lambda value: value is None
super().__init__(correct_fn, kind, severity, message, onlyif)
class DeprecatedFieldValidator(FieldValidatorBase):
"""
Validator ensuring that deprecated field is not used (passed a value)
"""
def check(self, parent, unit, field):
# This is not a using a property so that we can remove the property but
# still check that the field is not being used.
if unit.get_record_value(field) is not None:
yield parent.report_issue(
unit, field, Problem.deprecated, Severity.advice, self.message)
class TranslatableFieldValidator(FieldValidatorBase):
"""
Validator ensuring that a field is marked as translatable
The validator can be customized by passing the following keyword arguments:
message:
Customized error message. This message will be used to report the
issue if the validation fails. By default it is derived from
``Problem.expected_i18n`` by :meth:`UnitValidator.explain()`.
"""
def check(self, parent, unit, field):
if (unit.virtual is False
and unit.get_record_value(field) is not None
and not unit.is_translatable_field(field)):
yield parent.warning(unit, field, Problem.expected_i18n)
class UntranslatableFieldValidator(FieldValidatorBase):
"""
Validator ensuring that a field is not marked as translatable
The validator can be customized by passing the following keyword arguments:
message:
Customized error message. This message will be used to report the
issue if the validation fails. By default it is derived from
``Problem.unexpected_i18n`` by :meth:`UnitValidator.explain()`.
"""
def check(self, parent, unit, field):
if (unit.get_record_value(field)
and unit.is_translatable_field(field)):
yield parent.warning(unit, field, Problem.unexpected_i18n)
class TemplateInvariantFieldValidator(FieldValidatorBase):
"""
Validator ensuring that a field value doesn't depend on a template resource
"""
def check(self, parent, unit, field):
# Non-parametric units are always valid
if unit.is_parametric:
value = unit._data.get(field)
# No value? No problem!
if value is None:
return
param_set = get_accessed_parameters(value)
# Invariant fields cannot depend on any parameters
if len(param_set) != 0:
yield parent.error(unit, field, Problem.variable, self.message)
class TemplateVariantFieldValidator(FieldValidatorBase):
"""
Validator ensuring that a field value does depend on a template resource
In addition, the actual value template is checked to ensure that each
parameter it references is defined in the particular unit being validated.
"""
def check(self, parent, unit, field):
# Non-parametric units are always valid
if unit.is_parametric:
value = unit._data.get(field)
# No value? No problem!
if value is not None:
param_set = get_accessed_parameters(value)
# Variant fields must depend on some parameters
if len(param_set) == 0:
yield parent.error(
unit, field, Problem.constant, self.message)
# Each parameter must be present in the unit
for param_name in param_set:
if param_name not in unit.parameters:
message = _(
"reference to unknown parameter {!r}"
).format(param_name)
yield parent.error(
unit, field, Problem.unknown_param, message)
class ShellProgramValidator(FieldValidatorBase):
"""
Validator ensuring that a field value looks like a valid shell program
This validator can help catch simple mistakes detected by a
shell-compatible lexer. It doesn't support the heredoc syntax and it
silently ignores fields that have '<<' anywhere in the value.
"""
def check(self, parent, unit, field):
# Look up the value
value = getattr(unit, field2prop(field))
if value is not None:
if '<<' in value:
# TODO: implement heredoc-aware shlex parser
# and use it to validate the input
pass
else:
lex = shlex.shlex(value, posix=True)
token = None
try:
for token in lex:
pass
except ValueError as exc:
if token is not None:
yield parent.error(
unit, field, Problem.syntax_error,
"{}, near {!r}".format(exc, token),
offset=lex.lineno - 1)
else:
yield parent.error(
unit, field, Problem.syntax_error, str(exc),
offset=lex.lineno - 1)
def compute_value_map(context, field):
"""
Compute support data structure
:param context:
The :class:`UnitValidationContext` instance that this data is computed
for. It is used to discover a list of providers
:returns:
A dictionary mapping from all the existing values of a specific field
(that is being validated) to a list of units that have that value in
that field.
"""
value_map = {}
all_units = itertools.chain(
*(provider.unit_list for provider in context.provider_list))
for unit in all_units:
try:
value = getattr(unit, field2prop(field))
except AttributeError:
continue
if value not in value_map:
value_map[value] = [unit]
else:
value_map[value].append(unit)
return value_map
class UniqueValueValidator(FieldValidatorBase):
"""
Validator that checks if a value of a specific field is unique
This validator only works in context mode where it ensures that all the
units in all providers present in the context have an unique value for a
specific field.
This is mostly applicable to the 'id' field but other fields may be used.
The algorithm has O(1) complexity (where N is the number of units) per unit
which translates to O(N) cost for the whole context.
"""
def check_in_context(self, parent, unit, field, context):
value_map = context.compute_shared(
"field_value_map[{}]".format(field),
compute_value_map, context, field)
value = getattr(unit, field2prop(field))
units_with_this_value = value_map[value]
n = len(units_with_this_value)
if n > 1:
# come up with unit_list where this unit is always at the front
unit_list = list(units_with_this_value)
unit_list = sorted(
unit_list,
key=lambda a_unit: 0 if a_unit is unit
else unit_list.index(a_unit) + 1)
yield parent.error(
unit_list, field, Problem.not_unique, ngettext(
"clashes with {0} other unit",
"clashes with {0} other units", n - 1
).format(n - 1) + ', look at: ' + ', '.join(
# XXX: the relative_to is a hack, ideally we would
# allow the UI to see the fine structure of the error
# message and pass appropriate path to relative_to()
str(other_unit.origin.relative_to(os.getcwd()))
for other_unit in units_with_this_value
if other_unit is not unit))
class ReferenceConstraint:
"""
Description of a constraint on a unit reference
:attr constraint_fn:
A function fn(referrer, referee) that describes the constraint.
The function must return True in order for the constraint to hold.
:attr message:
Message that should be reported when the constraint fails to hold
:attr onlyif:
An (optional) function fn(referrer, referee) that checks if the
constraint should be checked or not. It must return True for the
``constraint_fn`` to make sense.
"""
def __init__(self, constraint_fn, message, *, onlyif=None):
self.constraint_fn = constraint_fn
self.onlyif = onlyif
self.message = message
class UnitReferenceValidator(FieldValidatorBase):
"""
Validator that checks if a field references another unit
This validator only works in context mode where it ensures that all the
units in all providers present in the context have an unique value for a
specific field.
The algorithm has O(1) complexity (where N is the number of units) per unit
which translates to O(N) cost for the whole context.
"""
def __init__(self, get_references_fn, constraints=None, message=None):
super().__init__(message)
self.get_references_fn = get_references_fn
if constraints is None:
constraints = ()
self.constraints = constraints
def check_in_context(self, parent, unit, field, context):
id_map = context.compute_shared(
"field_value_map[id]", compute_value_map, context, 'id')
try:
value_list = self.get_references_fn(unit)
except Exception as exc:
yield parent.error(unit, field, Problem.wrong, str(exc))
value_list = None
if value_list is None:
value_list = []
elif not isinstance(value_list, (list, tuple, set)):
value_list = [value_list]
for unit_id in value_list:
try:
units_with_this_id = id_map[unit_id]
except KeyError:
# zero is wrong, broken reference
yield parent.error(
unit, field, Problem.bad_reference,
self.message or _(
"unit {!a} is not available"
).format(unit_id))
continue
n = len(units_with_this_id)
if n == 1:
# one is exactly right, let's see if it's good
referrer = unit
referee = units_with_this_id[0]
for constraint in self.constraints:
if constraint.onlyif is not None and not constraint.onlyif(
referrer, referee):
continue
if not constraint.constraint_fn(referrer, referee):
yield parent.error(
unit, field, Problem.bad_reference,
self.message or constraint.message
or _("referee constraint failed"))
elif n > 1:
# more than one is also good, which one are we targeting?
yield parent.error(
unit, field, Problem.bad_reference,
self.message or _(
"multiple units with id {!a}: {}"
).format(
unit_id, ', '.join(
# XXX: the relative_to is a hack, ideally we would
# allow the UI to see the fine structure of the
# error message and pass appropriate path to
# relative_to()
str(other_unit.origin.relative_to(os.getcwd()))
for other_unit in units_with_this_id)))
|