Don't create folder structure on Cloud when pulling settings.

Instead, an error is shown that there are no synced settings. This will
have to be replaced, allowing the user to select from settings that
are available for other Blender versions.

blender_cloud/settings_sync.py

@@ -74,6 +74,10 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
                                                description='Blender version to sync for',
                                                default='%i.%i' % bpy.app.version[:2])
 
+    home_project_id = None
+    sync_group_id = None  # top-level sync group node ID
+    sync_group_versioned_id = None  # sync group node ID for the given Blender version.
+
     def invoke(self, context, event):
         if not self.blender_version:
             self.report({'ERROR'}, 'No Blender version to sync for was given.')
@@ -143,15 +147,22 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
                 self._state = 'QUIT'
                 return
 
+            # Only create the folder structure if we're pushing.
+            may_create = self.action == 'PUSH'
             try:
-                self.sync_group_id = await self.find_sync_group_id()
+                gid, subgid = await self.find_sync_group_id(may_create=may_create)
-                self.log.info('Found group node ID: %s', self.sync_group_id)
+                self.sync_group_id = gid
+                self.sync_group_versioned_id = subgid
+                self.log.info('Found top-level group node ID: %s', self.sync_group_id)
+                self.log.info('Found group node ID for %s: %s',
+                              self.blender_version, self.sync_group_versioned_id)
             except sdk_exceptions.ForbiddenAccess:
                 self.log.exception('Unable to find Group ID')
                 self.report({'ERROR'}, 'Unable to find sync folder.')
                 self._state = 'QUIT'
                 return
 
+            # Perform the requested action.
             action = {
                 'PUSH': self.action_push,
                 'PULL': self.action_pull,
@@ -198,6 +209,16 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
                                    ' settings from the Blender Cloud.')
             return
 
+        # If the sync group node doesn't exist, offer a list of groups that do.
+        if self.sync_group_id is None:
+            self.report({'ERROR'}, 'There are no synced Blender settings in your home project.')
+            return
+
+        if self.sync_group_versioned_id is None:
+            self.report({'ERROR'}, 'Therre are no synced Blender settings for version %s' %
+                        self.blender_version)
+            return
+
         self.report({'INFO'}, 'Pulling settings from Blender Cloud')
         with tempfile.TemporaryDirectory(prefix='bcloud-sync') as tempdir:
             for fname in SETTINGS_FILES_TO_UPLOAD:
@@ -215,7 +236,7 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
         # Get the asset node
         node_props = {'project': self.home_project_id,
                       'node_type': 'asset',
-                      'parent': self.sync_group_id,
+                      'parent': self.sync_group_versioned_id,
                       'name': fname}
         node = await pillar_call(pillarsdk.Node.find_first, {
             'where': node_props,
@@ -301,7 +322,8 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
     async def find_or_create_node(self,
                                   where: dict,
                                   additional_create_props: dict,
-                                  projection: dict = None) -> (pillarsdk.Node, bool):
+                                  projection: dict = None,
+                                  may_create: bool = True) -> (pillarsdk.Node, bool):
         """Finds a node by the `filter_props`, creates it using the additional props.
 
         :returns: tuple (node, created), where 'created' is a bool indicating whether
@@ -318,6 +340,9 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
 
         created = False
         if found_node is None:
+            if not may_create:
+                return None, False
+
             log.info('Creating new sync group node')
 
             # Augment the node properties to form a complete node.
@@ -333,10 +358,10 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
 
         return found_node, created
 
-    async def find_sync_group_id(self) -> str:
+    async def find_sync_group_id(self, may_create=True) -> str:
         """Finds the group node in which to store sync assets.
 
-        If the group node doesn't exist, it creates it.
+        If the group node doesn't exist and may_create=True, it creates it.
         """
 
         # Find/create the top-level sync group node.
@@ -351,10 +376,15 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
                     'description': SYNC_GROUP_NODE_DESC,
                     'properties': {'status': 'published'},
                 },
-                projection={'_id': 1})
+                projection={'_id': 1},
+                may_create=may_create)
         except pillar.PillarError:
             raise pillar.PillarError('Unable to create sync folder on the Cloud')
 
+        if not may_create and sync_group is None:
+            log.info("Sync folder doesn't exist, and not creating it either.")
+            return None, None
+
         # Find/create the sub-group for the requested Blender version
         try:
             sub_sync_group, created = await self.find_or_create_node(
@@ -367,11 +397,17 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
                     'description': 'Sync folder for Blender %s' % self.blender_version,
                     'properties': {'status': 'published'},
                 },
-                projection={'_id': 1})
+                projection={'_id': 1},
+                may_create=may_create)
         except pillar.PillarError:
             raise pillar.PillarError('Unable to create sync folder on the Cloud')
 
-        return sub_sync_group['_id']
+        if not may_create and sub_sync_group is None:
+            log.info("Sync folder for Blender version %s doesn't exist, "
+                     "and not creating it either.", self.blender_version)
+            return sync_group['_id'], None
+
+        return sync_group['_id'], sub_sync_group['_id']
 
     async def attach_file_to_group(self, file_path: pathlib.Path) -> pillarsdk.Node:
         """Creates an Asset node and attaches a file document to it."""
@@ -385,7 +421,7 @@ class PILLAR_OT_sync(async_loop.AsyncModalOperatorMixin, bpy.types.Operator):
             where={
                 'project': self.home_project_id,
                 'node_type': 'asset',
-                'parent': self.sync_group_id,
+                'parent': self.sync_group_versioned_id,
                 'name': file_path.name,
                 'user': self.user_id},
             additional_create_props={