[mu4e rfe] Query API for third-party extensions

[xzz53]

Is your feature request related to a problem? Please describe. Since mu 1.6, mu4e-alert turned effectively unusable, because query results obtained by calling mu executable and those reported in mu4e fell out of sync (at least read/unread status).

Describe the solution you'd like It would be good to have an API for executing queries which could be used by third-party extensions. Basically something along the lines of mu4e~headers-search-execute, but passing results to a user-provided callback instead of displaying them in a buffer.

Describe alternatives you've considered At present a gross hack is used: mu4e~proc-find is called directly and handlers are overridden for the duration of the call. This is obviously far from ideal.

[djcb]

I'll consider it, but I'm reluctant to do so, since it makes future development much harder (having to consider third-party packages and whatever details they depend on).

[djcb]

Note, at least mu4e (10.x) has much of the mu4e-alert functionality built-in now. Anyway, such an API is not planned for the foreseeable future, so closing this.