Spencer Baugh <sbaugh@janestreet.com> writes:
>>>                   (funcall visit bbeg bend)))))
>>> +      (setq next-error-buffer diagnostics-buffer
>>> +            next-error-last-buffer diagnostics-buffer)
>
> Setting next-error-last-buffer makes sense and matches other buffers
> which set next-error-function (e.g. xref-goto-xref), but do we need to
> set next-error-buffer?  It seems like setting that is managed by
> next-error itself.

I think you're right.  That should be removed.

>>>  (define-derived-mode flymake-diagnostics-buffer-mode tabulated-list-mode
>>>    "Flymake diagnostics"
>>>    "A mode for listing Flymake diagnostics."
>>> @@ -2015,6 +2040,9 @@ flymake-diagnostics-buffer-mode
>>>    (setq tabulated-list-format flymake--diagnostics-base-tabulated-list-format)
>>>    (setq tabulated-list-entries
>>>          'flymake--diagnostics-buffer-entries)
>>> +
>>> +  (setq-local next-error-function #'flymake--diagnostics-next-error)
>>> +
>
> This should be set in the major mode initialization (the body of the
> define-derived-mode).

It is set in the body of the define-derived-mode.

>>> @@ -2085,6 +2114,9 @@ flymake-project-diagnostics-mode
>>>    (setq tabulated-list-format
>>>          (vconcat [("File" 25 t)]
>>>                   flymake--diagnostics-base-tabulated-list-format))
>>> +
>>> +  (setq-local next-error-function #'flymake--diagnostics-next-error)
>>> +
>
> Likewise, this should be set in the major mode initialization (the body
> of the define-derived-mode).

Ditto here.

See this patch for changes: