Fixed anonymous layer import

lib/mayaUsd/commands/baseImportCommand.cpp

@@ -124,7 +124,8 @@ MStatus MayaUSDImportCommand::doIt(const MArgList& args)
         mFileName = UsdMayaUtil::convert(tmpVal);
 
         // Use the usd resolver for validation (but save the unresolved)
-        if (ArGetResolver().Resolve(mFileName).empty()) {
+        if (ArGetResolver().Resolve(mFileName).empty()
+            && !SdfLayer::IsAnonymousLayerIdentifier(mFileName)) {
             TF_RUNTIME_ERROR(
                 "File '%s' does not exist, or could not be resolved. "
                 "Exiting.",

test/lib/usd/translators/CMakeLists.txt

@@ -44,6 +44,7 @@ set(TEST_SCRIPT_FILES
     testUsdExportStroke.py
     testUsdExportUserTaggedAttributes.py
     testUsdExportVisibilityDefault.py
+    testUsdImportAnonymousLayer.py
     testUsdImportCamera.py
     testUsdImportColorSets.py
     testUsdImportDisplacement.py

test/lib/usd/translators/testUsdImportAnonymousLayer.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env mayapy
+#
+# Copyright 2021 Autodesk
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import os
+import unittest
+
+from pxr import Usd, Sdf
+
+from maya import cmds
+from maya import standalone
+
+import fixturesUtils
+
+class testUsdImportSessionLayer(unittest.TestCase):
+
+    @classmethod
+    def tearDownClass(cls):
+        standalone.uninitialize()
+
+    @classmethod
+    def setUpClass(cls):
+        cls.inputPath = fixturesUtils.readOnlySetUpClass(__file__)
+
+    def testUsdImport(self):
+        """
+        This test executes import from an anonymous layer as per GitHub Discussion
+        https://github.com/Autodesk/maya-usd/discussions/1069
+        """
+
+        layer = Sdf.Layer.CreateAnonymous()
+        stage = Usd.Stage.Open(layer)
+        stage.DefinePrim('/Foo', 'Xform')
+
+        cmds.mayaUSDImport(f=layer.identifier, primPath='/')
+
+        expectedMayaNodesSet = set([
+            '|Foo'])
+        mayaNodesSet = set(cmds.ls('|Foo*', long=True))
+        self.assertEqual(expectedMayaNodesSet, mayaNodesSet)
+
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)