Why is the register being cleared after ejc-sql initialization?

[madorian]

I've encountered an issue where one of my Emacs registers (specifically register 'e') is being cleared shortly after ejc-sql initializes. I've narrowed down the timing to about 7 seconds after Emacs init, which coincides with the nREPL server starting up.

Here's what I've observed:

1. The register is correctly set during Emacs initialization.
2. It maintains its value for about 6 seconds after init.
3. At around 7 seconds, coinciding with nREPL server startup, the register suddenly becomes empty.
4. It remains empty for all subsequent checks.

I've added debug statements to track the register's content, and here's a snippet of the output:

Register 'e' at 6 seconds after init: (file . "~/ds/platform/conf/home.dot.emacs.dot.d.emacsen.org")
[nREPL] server started on 39169
[nREPL] Establishing direct connection to localhost:39169 ...
[nREPL] Direct connection to localhost:39169 established
Connected! Programmers know the benefits of everything and the tradeoffs of nothing. -Rich Hickey
Register 'e' at 7 seconds after init: ""

I've reviewed the ejc-sql source code but couldn't find any direct manipulation of registers. However, I suspect there might be some indirect effect causing this issue.

Has anyone encountered similar behavior or have insights into what might be causing this? Any suggestions for further debugging or potential fixes would be greatly appreciated.

[kostafey]

This is a CIDER bug, not ejc-sql.

cider-eval-register defaults to ?e, and on connection setup CIDER sends
its out-subscribe op through the interactive eval handler. That op returns
no value, so the handler ends up doing (set-register ?e "") - which is why
your register turns into "" exactly when the connection comes up. CIDER's own
source has a ;; TODO: Use some null handler here right above that call.

Workaround:

(setq cider-eval-register nil)

(or just move your file register to another letter). Verified: with this,
register e survives the connection and subsequent queries.

I'll open an issue against CIDER - a plain cider-jack-in should reproduce it
too, ejc-sql just brings CIDER up automatically at startup.

[kostafey]

Filed upstream: clojure-emacs/cider#4182