Add job context parameter to USD publisher

E.g. You can now directly export with a `Arnold` job context (if it's registered) so that the USD export is Arnold supported and directly renderable with shaders/render attributes by Arnold renderer.

openpype/hosts/maya/plugins/create/create_maya_usd.py

@@ -5,6 +5,8 @@ from openpype.lib import (
     TextDef
 )
 
+from maya import cmds
+
 
 class CreateMayaUsd(plugin.MayaCreator):
     """Create Maya USD Export"""
@@ -15,11 +17,28 @@ class CreateMayaUsd(plugin.MayaCreator):
     icon = "cubes"
     description = "Create Maya USD Export"
 
+    cache = {}
+
     def get_publish_families(self):
         return ["usd", "mayaUsd"]
 
     def get_instance_attr_defs(self):
 
+        if "jobContextItems" not in self.cache:
+            # Query once instead of per instance
+            job_context_items = {}
+            try:
+                cmds.loadPlugin("mayaUsdPlugin", quiet=True)
+                job_context_items = {
+                    cmds.mayaUSDListJobContexts(jobContext=name): name
+                    for name in cmds.mayaUSDListJobContexts(export=True)
+                }
+            except RuntimeError:
+                # Likely `mayaUsdPlugin` plug-in not available
+                self.log.warning("Unable to retrieve available job "
+                                 "contexts for `mayaUsdPlugin` exports")
+            self.cache["jobContextItems"] = job_context_items
+
         defs = lib.collect_animation_defs()
         defs.extend([
             EnumDef("defaultUSDFormat",
@@ -45,7 +64,11 @@ class CreateMayaUsd(plugin.MayaCreator):
             TextDef("attrPrefix",
                     label="Custom Attributes Prefix",
                     default="",
-                    placeholder="prefix1, prefix2")
+                    placeholder="prefix1, prefix2"),
+            EnumDef("jobContext",
+                    label="Job Context",
+                    items=self.cache["jobContextItems"],
+                    multiselection=True),
         ])
 
         return defs

openpype/hosts/maya/plugins/publish/extract_maya_usd.py

@@ -148,6 +148,7 @@ class ExtractMayaUsd(publish.Extractor):
             "exportRefsAsInstanceable": bool,
             "eulerFilter": bool,
             "renderableOnly": bool,
+            "jobContext": (list, None)  # optional list
             # "worldspace": bool,
         }
 
@@ -169,6 +170,7 @@ class ExtractMayaUsd(publish.Extractor):
             "exportRefsAsInstanceable": False,
             "eulerFilter": True,
             "renderableOnly": False,
+            "jobContext": None
             # "worldspace": False
         }