5.28 Forgets or reverts identifiers

[Disabled Reader]

Calibre 5.28
Windows 11

I use the Goodreads Sync plugin to download the identifier links but calibre forgets or reverts when switching libraries.

1) Goodreads plugin: Link to Goodreads
2) Select from options show
3) Goodreads plugin: Switch Goodreads Edition
4) Identifiers are correct
5) Switch to another library and then switch back
6) The identifiers info is lost

Re-installed 5.27 and everything is fine.

[Kovid Goyal (kovid)]

Changing the component for this bug.

 assignee cbhaley
 status triaged

[Kovid Goyal (kovid)]

@charles: I am guessing this is caused by your changes to avoid writing
unchanged values, it's probably the plugin doing something unexpected
with the API, but...

[Charles Haley (cbhaley)]

@kovid: the root cause of the problem is that cache.field_for('identifiers') returns the dict from the table without making a copy. Thus when legacy.set_identifier() adds a new identifier to the dict it is changing base calibre data.

I can fix this by making legacy.set_identifier() make a copy of the dict before modifying it. However, that won't fix anywhere else that does field_for(), modify dict, set_field(). Note that if someone does a field_for() then modifies the dict then calibre will show modified values even if they were never written.

Seems to me that the right fix is to make a shallow copy in fields.IdentifiersField.for_book(). A deep copy isn't needed because the dict contains strings that are (I think) immutable. Are you OK with this or would your rather I change legacy.set_identifier()?

[Charles Haley (cbhaley)]

I submitted a PR with the copy in IdentifiersField.for_book() in case you are OK with that.

[Charles Haley (cbhaley)]

Also, as far as I can tell core calibre doesn't use legacy.set_identifer(). The problem is restricted to plugins.

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased

[Kovid Goyal (kovid)]

Yes, I agree this is restricted to plugins.