ApplyPatches - Moving Shadow copy to Shadow Backup

[Patrick Burrows]

In mobwrite_core.py in the function applyPatches at lines 309 - 313, there is this code:

    # First, update the client's shadow.

    viewobj.shadow = DMP.diff_text2(diffs)

    viewobj.backup_shadow = viewobj.shadow

    viewobj.backup_shadow_server_version = viewobj.shadow_server_version

    viewobj.changed = True

shouldn't this code instead be:

    # First, update the client's shadow.

    viewobj.backup_shadow = viewobj.shadow

    viewobj.backup_shadow_server_version = viewobj.shadow_server_version

    viewobj.shadow = DMP.diff_text2(diffs)

    viewobj.changed = True

Otherwise the backup_shadow is always equal to the shadow. My understanding is that the backup shadow should be a backup in case of a duplicate packet or some other rollback scenario.

[Patrick Burrows]

(I mean, obviously the unit tests pass with the code the way it is, and they don't if they make the change I just mentioned -- so it is obviously this way for a reason).

[Patrick Burrows]

FWIW, I was wrong about how this worked. The Backup_Shadow is only used in the event that the client did not receive a response. Applying the patch to both the shadow and backup is appropriate here (which is after receiving diffs and applying patches from the client side -- the backup check was already passed).