elfeed-db-load: Wrong type argument: avl-tree-, nil with Emacs 29.3 and no upgrade

[al3xandru]

By searching old issues, I have found similar issues (listed below).
The majority of these are not marked as solved and they refer to upgrading Emacs versions. The latter condition does not apply in this case at all: I'm using Emacs 29.3 on macOS.

The errror is the one in the subject: elfeed-db-load: Wrong type argument: avl-tree-, nil

Possibly related issues:

• After update to Emacs 26: elfeed-db-load: Wrong type argument: avl-tree- #340
• let: Wrong type argument: hash-table-p, nil #466
• (wrong-type-argument avl-tree- #s(avl-tree- ... #284

[al3xandru]

Every usage of elfeed results in this error next try I try to load it.

I tried:

1. use elfeed-search-quit-window
2. use elfeed-search-quit-window followed by elfeed-db-unload
3. use elfeed-db-unload
4. not doing anything

In all these cases the next invocation of elfeed results in this error.

[al3xandru]

I have compared index and index.backup: the files are identical. I assume elfeed reports an error simply by checking there's an index.backup file?

[al3xandru]

I am using the patch described in this comment #466 (comment) and I haven't seen the issue since. I believe this would indicate this is a bug. I don't know how to fix this in elfeed and I see no activity on the project.

[BenediktBroich]

Same here on nixos:
Commit: bbb3cac

GNU Emacs v30.2
Doom core v2.1.0
Doom modules v26.05.0-pre

elfeed-db-load: Wrong type argument: avl-tree-, nil

The patch does not work for me.

[minad]

@BenediktBroich It looks as if the database is corrupted and the elfeed-db-index is nil. This could happen when the database is unloaded and still saved. Could you check your database if the elfeed-db-index is nil, or the :index plist value in the file is nil? Alternatively could you share your database privately with me or the other Elfeed co-maintainers to check?