[tahoe-lafs-trac-stream] [Tahoe-LAFS] #1634: TypeError due to "size" being None in pyfilesystem+dokan

[Tahoe-LAFS]

#1634: TypeError due to "size" being None in pyfilesystem+dokan
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     Reporter:  zooko    |      Owner:  Zancas
         Type:  defect   |     Status:  new
     Priority:  major    |  Milestone:  1.11.0
    Component:  code-    |    Version:  1.9.0
  frontend-web           |   Keywords:  pyfilesystem dokan error webapi
   Resolution:           |  docs mutable test-needed
Launchpad Bug:           |
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Comment (by warner):

 So mutable filenodes (SMDF or MDMF) are allowed to return None from
 `IFilesystemNode.get_size()` to indicate "I don't know yet". These mutable
 filenodes cache their size when it is fetched, so the first time you
 access them, you'll get None, and then if you look closely enough at them
 to warrant network traffic (i.e. you call `get_current_size()`), then
 you'll get real numbers from `get_size()` for as long as you hold onto
 that node (or it stays in the filenode cache).

 We can change the JSON return value from the WAPI independently. I'm still
 slightly in favor of value=null over omit-the-key, but either way is
 pretty easy.

 To use value=null, the tahoe code is already correct, and what needs to
 change is in pyfilesystem. In the code I've seen
 (https://code.google.com/p/pyfilesystem/source/browse/trunk/fs/contrib/tahoelafs/util.py#79),
 that `data.get('size', 0)` should be replaced with `data.get('size') or
 0`.

 To use omit-the-key, we must change tahoe's web/directory.py line 882 (in
 DirectoryJSONMetadata) to fetch `childnode.get_size()` but then only add
 it to `kiddata[1]['size']` if it's not None.

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1634#comment:13>
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