Add SET ... WITH COMPONENTS ... ASN.1 construct support (#171)

Added `WithComponentsConstraint` along with related
`ComponentPresentConstraint` and `ComponentAbsentConstraint` classes
to be used with `Sequence`/`Set` types representing
`SET ... WITH COMPONENTS ...` like ASN.1 constructs.

CHANGES.rst

@@ -16,6 +16,10 @@ Revision 0.4.7, released XX-09-2019
   objects as the type in field definition. When a bare Python value is
   assigned, then field type object is cloned and initialized with the
   bare value (constraints verificaton would run at this moment).
+- Added `WithComponentsConstraint` along with related
+  `ComponentPresentConstraint` and `ComponentAbsentConstraint` classes
+  to be used with `Sequence`/`Set` types representing
+  `SET ... WITH COMPONENTS ...` like ASN.1 constructs.
 
 Revision 0.4.6, released 31-07-2019
 -----------------------------------

docs/source/pyasn1/type/base/constructedasn1type.rst

@@ -7,4 +7,4 @@
 ------------
 
 .. autoclass:: pyasn1.type.base.ConstructedAsn1Type(tagSet=TagSet(), subtypeSpec=ConstraintsIntersection(), componentType=None)
-   :members: isSameTypeWith, isSuperTypeOf, tagSet, effectiveTagSet, tagMap, subtypeSpec, isInconsistent
+   :members: isSameTypeWith, isSuperTypeOf, tagSet, effectiveTagSet, tagMap, subtypeSpec

docs/source/pyasn1/type/constraint/contents.rst

@@ -32,6 +32,7 @@ they get attached to ASN.1 type object at a *.subtypeSpec* attribute.
    /pyasn1/type/constraint/valuerange
    /pyasn1/type/constraint/valuesize
    /pyasn1/type/constraint/permittedalphabet
+   /pyasn1/type/constraint/withcomponents
 
 
 Logic operations on constraints

docs/source/pyasn1/type/constraint/withcomponents.rst

@@ -0,0 +1,16 @@
+
+.. _constrain.WithComponentsConstraint:
+
+.. |Constraint| replace:: WithComponentsConstraint
+
+WITH COMPONENTS constraint
+--------------------------
+
+.. autoclass:: pyasn1.type.constraint.WithComponentsConstraint(*fields)
+   :members:
+
+.. autoclass:: pyasn1.type.constraint.ComponentPresentConstraint()
+   :members:
+
+.. autoclass:: pyasn1.type.constraint.ComponentAbsentConstraint()
+   :members:

pyasn1/type/base.py

@@ -677,24 +677,6 @@ class takes on instantiation except that all parameters
 
         return clone
 
-    @property
-    def isInconsistent(self):
-        """Run necessary checks to ensure object consistency.
-
-        Default action is to verify |ASN.1| object against constraints imposed
-        by `subtypeSpec`.
-
-        Raises
-        ------
-        :py:class:`~pyasn1.error.PyAsn1tError` on any inconsistencies found
-        """
-        try:
-            self.subtypeSpec(self)
-
-        except error.PyAsn1Error:
-            exc = sys.exc_info()[1]
-            return exc
-
     def getComponentByPosition(self, idx):
         raise error.PyAsn1Error('Method not implemented')
 

pyasn1/type/constraint.py

@@ -342,6 +342,139 @@ def _testValue(self, value, idx):
             raise error.ValueConstraintError(value)
 
 
+class ComponentPresentConstraint(AbstractConstraint):
+    """Create a ComponentPresentConstraint object.
+
+    The ComponentPresentConstraint is only satisfied when the value
+    is not `None`.
+
+    The ComponentPresentConstraint object is typically used with
+    `WithComponentsConstraint`.
+
+    Examples
+    --------
+    .. code-block:: python
+
+        present = ComponentPresentConstraint()
+
+        # this will succeed
+        present('whatever')
+
+        # this will raise ValueConstraintError
+        present(None)
+    """
+    def _setValues(self, values):
+        self._values = ('<must be present>',)
+
+        if values:
+            raise error.PyAsn1Error('No arguments expected')
+
+    def _testValue(self, value, idx):
+        if value is None:
+            raise error.ValueConstraintError(
+                'Component is not present:')
+
+
+class ComponentAbsentConstraint(AbstractConstraint):
+    """Create a ComponentAbsentConstraint object.
+
+    The ComponentAbsentConstraint is only satisfied when the value
+    is `None`.
+
+    The ComponentAbsentConstraint object is typically used with
+    `WithComponentsConstraint`.
+
+    Examples
+    --------
+    .. code-block:: python
+
+        absent = ComponentAbsentConstraint()
+
+        # this will succeed
+        absent(None)
+
+        # this will raise ValueConstraintError
+        absent('whatever')
+    """
+    def _setValues(self, values):
+        self._values = ('<must be absent>',)
+
+        if values:
+            raise error.PyAsn1Error('No arguments expected')
+
+    def _testValue(self, value, idx):
+        if value is not None:
+            raise error.ValueConstraintError(
+                'Component is not absent: %r' % value)
+
+
+class WithComponentsConstraint(AbstractConstraint):
+    """Create a WithComponentsConstraint object.
+
+    The WithComponentsConstraint satisfies any mapping object that has
+    constrained fields present or absent, what is indicated by
+    `ComponentPresentConstraint` and `ComponentAbsentConstraint`
+    objects respectively.
+
+    The WithComponentsConstraint object is typically applied
+    to  :class:`~pyasn1.type.univ.Set` or
+    :class:`~pyasn1.type.univ.Sequence` types.
+
+    Parameters
+    ----------
+    *fields: :class:`tuple`
+        Zero or more tuples of (`field`, `constraint`) indicating constrained
+        fields.
+
+    Examples
+    --------
+
+    .. code-block:: python
+
+        class Item(Sequence):  #  Set is similar
+            '''
+            ASN.1 specification:
+
+            Item ::= SEQUENCE {
+                id    INTEGER OPTIONAL,
+                name  OCTET STRING OPTIONAL
+            } WITH COMPONENTS id PRESENT, name ABSENT | id ABSENT, name PRESENT
+            '''
+            componentType = NamedTypes(
+                OptionalNamedType('id', Integer()),
+                OptionalNamedType('name', OctetString())
+            )
+            withComponents = ConstraintsIntersection(
+                WithComponentsConstraint(
+                    ('id', ComponentPresentConstraint()),
+                    ('name', ComponentAbsentConstraint())
+                ),
+                WithComponentsConstraint(
+                    ('id', ComponentAbsentConstraint()),
+                    ('name', ComponentPresentConstraint())
+                )
+            )
+
+        item = Item()
+
+        # This will succeed
+        item['id'] = 1
+
+        # This will succeed
+        item['name'] = 'John'
+
+        # This will fail on encoding
+        descr['id'] = 1
+        descr['name'] = 'John'
+    """
+    def _testValue(self, value, idx):
+        for field, constraint in self._values:
+            constraint(value.get(field))
+
+    def _setValues(self, values):
+        AbstractConstraint._setValues(self, values)
+
+
 # This is a bit kludgy, meaning two op modes within a single constraint
 class InnerTypeConstraint(AbstractConstraint):
     """Value must satisfy the type and presence constraints"""

pyasn1/type/univ.py

@@ -2042,6 +2042,41 @@ def isValue(self):
 
         return True
 
+    @property
+    def isInconsistent(self):
+        """Run necessary checks to ensure |ASN.1| object consistency.
+
+        Default action is to verify |ASN.1| object against constraints imposed
+        by `subtypeSpec`.
+
+        Raises
+        ------
+        :py:class:`~pyasn1.error.PyAsn1tError` on any inconsistencies found
+        """
+        if self.componentType is noValue or not self.subtypeSpec:
+            return False
+
+        if self._componentValues is noValue:
+            return True
+
+        mapping = {}
+
+        for idx, value in self._componentValues.items():
+            # Absent fields are not in the mapping
+            if value is noValue:
+                continue
+
+            mapping[idx] = value
+
+        try:
+            # Represent SequenceOf/SetOf as a bare dict to constraints chain
+            self.subtypeSpec(mapping)
+
+        except error.PyAsn1Error:
+            exc = sys.exc_info()[1]
+            return exc
+
+        return False
 
 class SequenceOf(SequenceOfAndSetOfBase):
     __doc__ = SequenceOfAndSetOfBase.__doc__
@@ -2637,6 +2672,44 @@ def isValue(self):
 
         return True
 
+    @property
+    def isInconsistent(self):
+        """Run necessary checks to ensure |ASN.1| object consistency.
+
+        Default action is to verify |ASN.1| object against constraints imposed
+        by `subtypeSpec`.
+
+        Raises
+        ------
+        :py:class:`~pyasn1.error.PyAsn1tError` on any inconsistencies found
+        """
+        if self.componentType is noValue or not self.subtypeSpec:
+            return False
+
+        if self._componentValues is noValue:
+            return True
+
+        mapping = {}
+
+        for idx, value in enumerate(self._componentValues):
+            # Absent fields are not in the mapping
+            if value is noValue:
+                continue
+
+            name = self.componentType.getNameByPosition(idx)
+
+            mapping[name] = value
+
+        try:
+            # Represent Sequence/Set as a bare dict to constraints chain
+            self.subtypeSpec(mapping)
+
+        except error.PyAsn1Error:
+            exc = sys.exc_info()[1]
+            return exc
+
+        return False
+
     def prettyPrint(self, scope=0):
         """Return an object representation string.
 

tests/type/test_constraint.py

@@ -128,6 +128,69 @@ def testBadVal(self):
             assert 0, 'constraint check fails'
 
 
+class WithComponentsConstraintTestCase(BaseTestCase):
+
+    def testGoodVal(self):
+        c = constraint.WithComponentsConstraint(
+            ('A', constraint.ComponentPresentConstraint()),
+            ('B', constraint.ComponentAbsentConstraint()))
+
+        try:
+            c({'A': 1})
+
+        except error.ValueConstraintError:
+            assert 0, 'constraint check fails'
+
+    def testGoodValWithExtraFields(self):
+        c = constraint.WithComponentsConstraint(
+            ('A', constraint.ComponentPresentConstraint()),
+            ('B', constraint.ComponentAbsentConstraint())
+        )
+
+        try:
+            c({'A': 1, 'C': 2})
+
+        except error.ValueConstraintError:
+            assert 0, 'constraint check fails'
+
+    def testEmptyConstraint(self):
+        c = constraint.WithComponentsConstraint()
+
+        try:
+            c({'A': 1})
+
+        except error.ValueConstraintError:
+            assert 0, 'constraint check fails'
+
+    def testBadVal(self):
+        c = constraint.WithComponentsConstraint(
+            ('A', constraint.ComponentPresentConstraint())
+        )
+
+        try:
+            c({'B': 2})
+
+        except error.ValueConstraintError:
+            pass
+
+        else:
+            assert 0, 'constraint check fails'
+
+    def testBadValExtraFields(self):
+        c = constraint.WithComponentsConstraint(
+            ('A', constraint.ComponentPresentConstraint())
+        )
+
+        try:
+            c({'B': 2, 'C': 3})
+
+        except error.ValueConstraintError:
+            pass
+
+        else:
+            assert 0, 'constraint check fails'
+
+
 class ConstraintsIntersectionTestCase(BaseTestCase):
     def setUp(self):
         BaseTestCase.setUp(self)