feat: Implement new Namespace-based class discovery

This commit reworks the discovery of metamodel classes and namespaces.
It introduces the `Namespace` object, whose instances keep track of the
contained classes. Namespace objects are discovered through the Python
entrypoint system. This makes extending the metamodel significantly
easier. It's no longer necessary to add weirdly formatted entries into
barely documented dictionaries, with errors only appearing at some
arbitrary later point.

Discovery of classes now happens via a custom metaclass by simply
inheriting from `ModelElement`. This also allows additional metadata to
be specified at subclassing time, which is especially relevant for
namespace versioning. Due to this, the following decorators are now no
longer needed and have been deprecated:

- `@xtype_handler`: Was used to register classes for discovery, which is
  now done by the metaclass.
- `@attr_equal`: This overwrites the `__eq__` method to compare against
  an attribute. Now handled by the `eq=...` class keyword argument.

capellambse/extensions/filtering.py

@@ -20,16 +20,20 @@
 import capellambse.model as m
 from capellambse import _native, helpers
 
-VIEWPOINT: t.Final = "org.polarsys.capella.filtering"
-NAMESPACE: t.Final = "http://www.polarsys.org/capella/filtering/6.0.0"
-SYMBOLIC_NAME: t.Final = "filtering"
-
 _LOGGER = logging.getLogger(__name__)
 
-m.XTYPE_ANCHORS[__name__] = SYMBOLIC_NAME
+NS = m.Namespace(
+    "http://www.polarsys.org/capella/filtering/{VERSION}",
+    "filtering",
+    "org.polarsys.capella.filtering",
+    "7.0.0",
+)
+
+VIEWPOINT: t.Final = NS.viewpoint
+NAMESPACE: t.Final = NS.uri.format(VERSION="6.0.0")
+SYMBOLIC_NAME: t.Final = NS.alias
 
 
-@m.xtype_handler(None)
 class FilteringCriterion(m.ModelElement):
     """A single filtering criterion."""
 
@@ -40,17 +44,15 @@ class FilteringCriterion(m.ModelElement):
     )
 
 
-@m.xtype_handler(None)
 class FilteringCriterionPkg(m.ModelElement):
     """A package containing multiple filtering criteria."""
 
     _xmltag = "ownedFilteringCriterionPkgs"
 
     criteria = m.DirectProxyAccessor(FilteringCriterion, aslist=m.ElementList)
-    packages: m.Accessor[FilteringCriterionPkg]
+    packages: m.Accessor[m.ElementList[FilteringCriterionPkg]]
 
 
-@m.xtype_handler(None)
 class FilteringModel(m.ModelElement):
     """A filtering model containing criteria to filter by."""
 
@@ -83,7 +85,7 @@ def __get__(
 
         loader = obj._model._loader
         try:
-            xt_critset = f"{SYMBOLIC_NAME}:AssociatedFilteringCriterionSet"
+            xt_critset = f"{NS.alias}:AssociatedFilteringCriterionSet"
             critset = next(loader.iterchildren_xt(obj._element, xt_critset))
         except StopIteration:
             elems = []
@@ -94,32 +96,26 @@ def __get__(
         return self._make_list(obj, elems)
 
 
-@m.xtype_handler(None)
 class FilteringResult(m.ModelElement):
     """A filtering result."""
 
 
-@m.xtype_handler(None)
 class ComposedFilteringResult(m.ModelElement):
     """A composed filtering result."""
 
 
 def init() -> None:
-    m.set_accessor(
-        mm.capellamodeller.SystemEngineering,
-        "filtering_model",
-        m.DirectProxyAccessor(FilteringModel),
+    mm.capellamodeller.SystemEngineering.filtering_model = (
+        m.DirectProxyAccessor(FilteringModel)
     )
     m.MelodyModel.filtering_model = property(  # type: ignore[attr-defined]
         operator.attrgetter("project.model_root.filtering_model")
     )
-    m.set_accessor(
-        m.ModelElement, "filtering_criteria", AssociatedCriteriaAccessor()
-    )
+    m.ModelElement.filtering_criteria = AssociatedCriteriaAccessor()
 
 
-m.set_self_references(
-    (FilteringCriterionPkg, "packages"),
+FilteringCriterionPkg.packages = m.DirectProxyAccessor(
+    FilteringCriterionPkg, aslist=m.ElementList
 )
 
 try:

capellambse/extensions/pvmt/__init__.py

@@ -31,7 +31,7 @@ def _get_pvmt_configuration(model: m.MelodyModel) -> PVMTConfiguration:
 def init() -> None:
     """Initialize the PVMT extension."""
     m.MelodyModel.pvmt = property(_get_pvmt_configuration)  # type: ignore[attr-defined]
-    m.set_accessor(m.ModelElement, "pvmt", m.AlternateAccessor(ObjectPVMT))
+    m.ModelElement.pvmt = m.AlternateAccessor(ObjectPVMT)
 
 
 if not t.TYPE_CHECKING:

capellambse/extensions/pvmt/_config.py

@@ -52,6 +52,11 @@
     r"(?m)\[(?P<key>\w+)\]\s*(?P<value>.+?)\s*\[/(?P=key)\]"
 )
 
+NS = m.Namespace(
+    m.VIRTUAL_NAMESPACE_PREFIX + "pvmt",
+    "capellambse.virtual.pvmt",
+)
+
 
 class ScopeError(m.InvalidModificationError):
     """Raised when trying to apply a PVMT group to an out-of-scope element."""
@@ -173,13 +178,40 @@ def _to_xml(self, value: SelectorRules | str, /) -> str:
         return value
 
 
-class ManagedGroup(m.ModelElement):
+class _PVMTBase:
+    _model: capellambse.MelodyModel
+    _element: etree._Element
+
+    uuid = m.StringPOD("id")
+    name = m.StringPOD("name")
+    parent = m.ParentAccessor()
+    property_values: m.Accessor[m.ElementList[mm.capellacore.PropertyValue]]
+
+    def __init__(self, *_args, **_kw) -> None:
+        raise TypeError("Use 'model.pvmt' to access PVMT configuration")
+
+    @classmethod
+    def from_model(
+        cls, model: capellambse.MelodyModel, element: etree._Element
+    ) -> te.Self:
+        self = cls.__new__(cls)
+        self._model = model
+        self._element = element
+        return self
+
+    def _short_repr_(self) -> str:
+        return f"<{type(self).__name__} {self.name!r}>"
+
+
+_PVMTBase.property_values = mm.modellingcore.ModelElement.property_values
+
+
+class ManagedGroup(mm.capellacore.PropertyValueGroup):
     """A managed group of property values."""
 
     _required_attrs = frozenset({"name"})
 
     selector = PVMTDescriptionProperty("description")
-    description = m.Alias("selector", dirhide=True)  # type: ignore[assignment]
 
     @property
     def fullname(self) -> str:
@@ -236,7 +268,9 @@ def apply(self, obj: m.ModelObject) -> mm.capellacore.PropertyValueGroup:
 
         groupobj = obj.property_value_groups.create(
             name=groupname,
-            applied_property_value_groups=[self],
+            applied_property_value_groups=[
+                m.wrap_xml(self._model, self._element)
+            ],
         )
         for propdef in self.property_values:
             pv = groupobj.property_values.create(
@@ -259,7 +293,7 @@ def _short_html_(self) -> markupsafe.Markup:
         )
 
 
-class ManagedDomain(m.ModelElement):
+class ManagedDomain(mm.capellacore.PropertyValuePkg):
     """A "domain" in the property value management extension."""
 
     _required_attrs = frozenset({"name"})
@@ -272,18 +306,12 @@ class ManagedDomain(m.ModelElement):
         mm.capellacore.EnumerationPropertyType,
         aslist=m.ElementList,
     )
-    groups = m.Containment(
+    groups = m.Containment[mm.capellacore.PropertyValueGroup](
         "ownedPropertyValueGroups",
         mm.capellacore.PropertyValueGroup,
-        aslist=m.ElementList,
         mapkey="name",
         alternate=ManagedGroup,
     )
-    enumeration_property_types = m.Containment(
-        "ownedEnumerationPropertyTypes",
-        mm.capellacore.EnumerationPropertyType,
-        aslist=m.ElementList,
-    )
 
     def __init__(
         self,
@@ -300,7 +328,7 @@ def __init__(
     def from_model(
         cls, model: capellambse.MelodyModel, element: etree._Element
     ) -> te.Self:
-        self = super().from_model(model, element)
+        self = m.wrap_xml(model, element, cls)
         try:
             version = self.property_values.by_name("version").value
         except Exception:
@@ -316,16 +344,12 @@ def from_model(
         return self
 
 
-class PVMTConfiguration(m.ModelElement):
+class PVMTConfiguration(mm.capellacore.PropertyValuePkg):
     """Provides access to the model-wide PVMT configuration."""
 
-    def __init__(self, *_args, **_kw) -> None:
-        raise TypeError("Use 'model.pvmt' to access PVMT configuration")
-
-    domains = m.Containment(
+    domains = m.Containment[mm.capellacore.PropertyValuePkg](
         "ownedPropertyValuePkgs",
         mm.capellacore.PropertyValuePkg,
-        aslist=m.ElementList,
         mapkey="name",
         alternate=ManagedDomain,
     )

capellambse/extensions/pvmt/_objects.py

@@ -17,6 +17,7 @@
 from capellambse.metamodel import capellacore
 
 from . import _config
+from ._config import NS as NS
 
 e = markupsafe.escape
 
@@ -142,6 +143,7 @@ def __repr__(self) -> str:
                 for prop in group.property_values:
                     fragments.append(f"\n  - {prop.name}: ")
                     if hasattr(prop.value, "_short_repr_"):
+                        assert prop.value is not None
                         fragments.append(prop.value._short_repr_())
                     else:
                         fragments.append(repr(prop.value))
@@ -181,6 +183,7 @@ def __html__(self) -> markupsafe.Markup:
                     else:
                         actual = e(actual_val)
                 if hasattr(prop.value, "_short_html_"):
+                    assert prop.value is not None
                     default = prop.value._short_html_()
                 else:
                     default = e(prop.value)

capellambse/extensions/reqif/__init__.py

@@ -11,10 +11,18 @@
 from ._glue import *
 from ._requirements import *
 
+from ._capellareq import NS as CapellaRequirementsNS  # isort: skip
+from ._requirements import NS as RequirementsNS  # isort: skip
+
 if not t.TYPE_CHECKING:
     from ._capellareq import __all__ as _cr_all
     from ._requirements import __all__ as _rq_all
 
-    __all__ = [*_cr_all, *_rq_all]
+    __all__ = [
+        "CapellaRequirementsNS",
+        "RequirementsNS",
+        *_cr_all,
+        *_rq_all,
+    ]
     del _cr_all, _rq_all
 del t

capellambse/extensions/reqif/_capellareq.py

@@ -27,18 +27,21 @@
 from . import _requirements as rq
 from . import exporter
 
-m.XTYPE_ANCHORS[__name__] = "CapellaRequirements"
+NS = m.Namespace(
+    "http://www.polarsys.org/capella/requirements",
+    "CapellaRequirements",
+    "org.polarsys.capella.vp.requirements",
+)
 
 
-@m.xtype_handler(None)
 class CapellaModule(rq.ReqIFElement):
     """A ReqIF Module that bundles multiple Requirement folders."""
 
     _xmltag = "ownedExtensions"
 
     folders = m.DirectProxyAccessor(rq.Folder, aslist=m.ElementList)
     requirements = m.DirectProxyAccessor(rq.Requirement, aslist=m.ElementList)
-    type = m.Association(rq.ModuleType, "moduleType")
+    type = m.Single(m.Association(rq.ModuleType, "moduleType"))
     attributes = rq.AttributeAccessor()
 
     def to_reqif(
@@ -81,24 +84,21 @@ def to_reqif(
         )
 
 
-@m.xtype_handler(None)
 class CapellaIncomingRelation(rq.AbstractRequirementsRelation):
     """A Relation between a requirement and an object."""
 
     _xmltag = "ownedRelations"
 
 
-@m.xtype_handler(None)
 class CapellaOutgoingRelation(rq.AbstractRequirementsRelation):
     """A Relation between an object and a requirement."""
 
     _xmltag = "ownedExtensions"
 
-    source = m.Association(rq.Requirement, "target")
-    target = m.Association(m.ModelElement, "source")
+    source = m.Single(m.Association(rq.Requirement, "target"))
+    target = m.Single(m.Association(m.ModelElement, "source"))
 
 
-@m.xtype_handler(None)
 class CapellaTypesFolder(rq.ReqIFElement):
     _xmltag = "ownedExtensions"
 
@@ -214,6 +214,11 @@ def insert(
             raise NotImplementedError("Cannot insert new objects yet")
 
         if isinstance(value, CapellaOutgoingRelation):
+            if not value.target:
+                raise RuntimeError(
+                    "Cannot insert outgoing relation without target:"
+                    f" {value._short_repr_()}"
+                )
             parent = value.target._element
         else:
             assert isinstance(
@@ -262,7 +267,7 @@ def __init__(
         source: m.ModelObject,
     ) -> None:
         del elemclass
-        super().__init__(model, elements, rq.AbstractRequirementsRelation)
+        super().__init__(model, elements)
         self._source = source
 
     @t.overload
@@ -364,5 +369,5 @@ def _make_list(self, parent_obj, elements):
         )
 
 
-m.set_accessor(rq.Requirement, "relations", RequirementsRelationAccessor())
-m.set_accessor(rq.Requirement, "related", ElementRelationAccessor())
+rq.Requirement.relations = RequirementsRelationAccessor()
+rq.Requirement.related = ElementRelationAccessor()