Implement MDGModifier::addAttribute binding

src/MDGModifier.inl

@@ -2,7 +2,27 @@ py::class_<MDGModifier>(m, "DGModifier")
     .def(py::init<>())
 
     .def("addAttribute", [](MDGModifier & self, MObject node, MObject attribute) {
-        throw std::logic_error{"Function not yet implemented."};
+        if (node.isNull()) 
+        {
+            throw std::invalid_argument("Cannot add attribute to a null object.");
+        } else if (!node.hasFn(MFn::kDependencyNode)) {
+            MString error_msg("Cannot add attribute - must specify a 'node' object, not a '^1s' object.");
+                    error_msg.format(error_msg, node.apiTypeStr());
+            throw pybind11::type_error(error_msg.asChar());
+        } 
+
+        if (attribute.isNull())
+        {
+            throw std::invalid_argument("Cannot add null attribute to an object.");
+        } else if (!node.hasFn(MFn::kAttribute)) {
+            MString error_msg("Cannot add attribute - must specify an 'attribute' object, not a(n) '^1s' object.");
+                    error_msg.format(error_msg, attribute.apiTypeStr());
+            throw pybind11::type_error(error_msg.asChar());
+        }
+
+        MStatus status = self.addAttribute(node, attribute);
+
+        CHECK_STATUS(status)
     }, 
 R"pbdoc(Adds an operation to the modifier to add a new dynamic attribute to the given dependency node. 
 If the attribute is a compound its children will ae added as well, so only the parent needs to be added using this method.)pbdoc")

tests/__init__.py

@@ -3,11 +3,28 @@
 import maya.standalone 
 from maya import cmds
 
+import cmdc
+
+
 def setup():
     maya.standalone.initialize()
 
+
 def new_scene():
     cmds.file(new=True, force=True)
 
+
 def teardown():
     maya.standalone.uninitialize()
+
+
+def as_obj(arg):
+    """Return the Maya Object for the given node."""
+
+    return cmdc.SelectionList().add(arg).getDependNode(0)
+
+
+def as_plug(arg):
+    """Return the Maya Plug for the given plug."""
+
+    return cmdc.SelectionList().add(arg).getPlug(0)

tests/test_MDGModifier.py

@@ -1,18 +1,42 @@
 import cmdc
 import nose
 
+from nose.plugins.skip import SkipTest
+
 from maya import cmds
 from maya.api import OpenMaya
 
-from . import new_scene
+from . import as_obj, as_plug, new_scene
 
 
-def _node_type_id():
-    node = cmds.createNode('network')
-    node = OpenMaya.MSelectionList().add(node).getDependNode(0)
-    type_id = OpenMaya.MFnDependencyNode(node).typeId.id()
+def test_addAttribute_pass(): 
+    raise SkipTest("Cannot test DGModifier.addAttribute until MFnAttribute classes are implemented.")
+
+
+def test_addAttribute_fail():
+    node = as_obj(cmds.createNode('network'))
+    null = cmdc.Object()
+
+    attr = as_plug('persp.message').attribute()
+
+    for exc, doc, node, attr in (
+        [ValueError, 'a null object', null, null],
+        [ValueError, 'a null attribute', node, null],
+        [TypeError, 'a non-node object', attr, null],
+        [TypeError, 'a non-attribute object', node, node],
+    ):
+        test_addAttribute_fail.__doc__ = """Test MDGModifier::addAttribute errors if passed {}.""".format(doc)
+
+        yield _addAttribute_fail, exc, node, attr 
+
+
+def _addAttribute_fail(exception, node, attr):    
+    nose.tools.assert_raises(
+        exception,
+        cmdc.DGModifier().addAttribute,
+        node, attr
+    )
 
-    return cmdc.TypeId(type_id)
 
 @nose.with_setup(teardown=new_scene)
 def test_createNode_pass():