Support read-only address-books

[AutoImport-MarcelWaldvogel]

(#126 is a similar issue, but related to calendars, instead of address books. However, it seems that address books do not seem to have a read-only flag in Android, so this needs to be solved differently.)

When adding an address book, DAVdroid can identify whether it is read-only or read-write. However, it seems to be unable to make this clear to Android (it seems there is no support for a read-only flag there).

Changing contacts from this read-only address book results in the problem described in #126: DAVdroid tries to write the changes back and fails with HTTP 403. This is repeated at every sync attempt, resulting every time in an error message the user can do nothing about.

It also seems that the (automatic or manual) merging of contacts changes them, probably setting some relationship attributes. So having related contacts in read-only address books seems to be an automatic cause for persistent sync errors.

My suggestion to fix this is as follows.

1. Try to convey the read-only flag to Android (this is probably not possible; in this case: skip this).
2. When a 403 occurs when writing to a read-only address book, handle it as follows.
3. Display the error message, with a clear description of what has caused this and what this means.
4. Set a flag, causing further writes to the address book to fail silently.
5. Display this flag in the sync options for this address book to remind the user.

I do not yet know what is the best way to deal with the changed contacts. I would suggest just to revert them back to the server version on sync. However, if there is some automatically updated linking information, that would need to be preserved in order to avoid an endless syncing loop.

[AutoImport-jkufner]

Davdroid should offer storing modified contact in another addressbook
and merge the contacts. If the difference is only in some safely
discardable metadata (like timestamp of last modification), then
Davdroid should ignore it during sync.

One way or another, Davdrodid must make a backup copy (dump vcard file
somewhere or at least into log) and warn user (and include info about
backup).

Marcel Waldvogel wrote, on 24.1.2015 16:59:

(#126 https://github.com/bitfireAT/davdroid/issues/126 is a similar
issue, but related to calendars, instead of address books. However, it
seems that address books do not seem to have a read-only flag in
Android, so this needs to be solved differently.)

When adding an address book, DAVdroid can identify whether it is
read-only or read-write. However, it seems to be unable to make this
clear to Android (it seems there is no support for a read-only flag there).

Changing contacts from this read-only address book results in the
problem described in #126
https://github.com/bitfireAT/davdroid/issues/126: DAVdroid tries to
write the changes back and fails with HTTP 403. This is repeated at
every sync attempt, resulting every time in an error message the user
can do nothing about.

It also seems that the (automatic or manual) merging of contacts changes
them, probably setting some relationship attributes. So having related
contacts in read-only address books seems to be an automatic cause for
persistent sync errors.

My suggestion to fix this is as follows.

1. Try to convey the read-only flag to Android (this is probably not
   possible; in this case: skip this).
2. When a 403 occurs when writing to a read-only address book, handle
   it as follows.
   1. Display the error message, with a clear description of what has
      caused this and what this means.
   2. Set a flag, causing further writes to the address book to fail
      silently.
   3. Display this flag in the sync options for this address book to
      remind the user.

I do not yet know what is the best way to deal with the changed
contacts. I would suggest just to revert them back to the server version
on sync. However, if there is some automatically updated linking
information, that would need to be preserved in order to avoid an
endless syncing loop.

—
Reply to this email directly or view it on GitHub
https://github.com/bitfireAT/davdroid/issues/434.

[rfc2822]

I wonder whether syncing read-only address books is in the scope of DAVdroid, especially when considering that Android doesn’t provide such a facility (read-only address book).

I’ll leave this issue open as enhancement for further exploration.

[rfc2822]

It seems like there is a possibility to mark contacts as read-only (RAW_CONTACT_IS_READ_ONLY). As far as I have read, there’s a sync-adapter called “Facebook” which creates read-only contacts using this field.

So if the DAVdroid address book is read-only on the server, DAVdroid could also mark all contact as read-only locally.

[AutoImport-benoiton]

DAVdroid knows that the address-book is read-only. It should avoid trying to upload any change to remote server, and just raise a warning “local modification of a read-only address-book”.
Even better: an option to discard local changes and revert to unmodified remote data.