storage/v2: refactor partition format/mount attrs

Cleanup some duplicated logic.

subiquity/common/filesystem/labels.py

@@ -275,13 +275,6 @@ def _for_client_disk(disk, *, min_size=0):
 
 @for_client.register(Partition)
 def _for_client_partition(partition, *, min_size=0):
-    format = ''
-    mount = ''
-    if partition._fs:
-        format = partition._fs.fstype
-        if partition._fs._mount:
-            mount = partition._fs._mount.path
-
     return types.Partition(
         size=partition.size,
         number=partition._number,
@@ -290,5 +283,5 @@ def _for_client_partition(partition, *, min_size=0):
         grub_device=partition.grub_device,
         boot=partition.boot,
         annotations=annotations(partition) + usage_labels(partition),
-        mount=mount,
+        mount=partition.mount,
-        format=format)
+        format=partition.format)

subiquity/models/filesystem.py

@@ -454,6 +454,18 @@ class _Formattable(ABC):
         else:
             return cd
 
+    @property
+    def format(self):
+        if not self._fs:
+            return None
+        return self._fs.fstype
+
+    @property
+    def mount(self):
+        if not self._fs or not self._fs._mount:
+            return None
+        return self._fs._mount.path
+
     @property
     @abstractmethod
     def ok_for_raid(self):

subiquity/server/controllers/filesystem.py

@@ -374,15 +374,9 @@ class FilesystemController(SubiquityController, FilesystemManipulator):
         if data.partition.boot is not None \
                 and data.partition.boot != partition.boot:
             raise ValueError('edit_partition does not support changing boot')
-        existing_format = ''
-        existing_mount = ''
-        if partition._fs:
-            existing_format = partition._fs.fstype
-            if partition._fs._mount:
-                existing_mount = partition._fs._mount.path
         spec = {
-            'fstype': data.partition.format or existing_format,
+            'fstype': data.partition.format or partition.format,
-            'mount': data.partition.mount or existing_mount,
+            'mount': data.partition.mount or partition.mount,
         }
         self.partition_disk_handler(disk, partition, spec)
         return await self.v2_GET()