cider-eldoc try to display doc when point on weird symbols like on image content-type

[stardiviner]

When use cider display image content-type. I move point backward, then CIDER REPL can't evaluate sexp anymore.

Steps to reproduce:
Toggle nrepl log messaging.
Disable eldoc-mode in CIDER REPL buffer, then display image, then movie point backward around, on the image etc. All things fine, no weird symbol in nrepl log.
Enable eldoc-mode in CIDER REPL buffer, then move point backward around, on the image, then nrepl log displays those weird symbols. then input (+ 1 1) does not work any more. even though I disable eldoc-mode again.
Here is the nrepl log:

(-->
  id         "25"
  op         "eldoc"
  session    "07c655d4-444b-43c4-a695-43a9da90104e"
  time-stamp "2018-05-08 11:42:29.972220486"
  ns         "user"
  symbol     "\266J\206\306\251\347\355"
)
(-->
  id         "26"
  op         "eldoc"
  time-stamp "2018-05-08 11:42:35.941183374"
  ns         "user"
  symbol     "\266J\206\306\251\347\355"
)
(-->
  id           "27"
  op           "eval"
  time-stamp   "2018-05-08 11:42:41.580182208"
  code         "(print \"hi\")"
  column       7
  content-type "true"
  file         "*cider-repl localhost*"
  line         335
  ns           "user"
)

This weird symbol is from display image which eldoc try to get doc for them.

Guess might cider-eldoc need to filter on non-standard symbols?
With reference as background to original issue: #2277

[bbatsov]

I can't test/fix this, as the image display doesn't work for me at all as mentioned in #2277.

I'm also puzzled how the two can be related at all. I'd expect that eldoc simply won't work, but it should not break eval.

[stardiviner]

I guess because cider-eldoc send cider/nrepl request to REPL code. This request not finished or other reasons, then CIDER is blocked. further sexp are not evaluated anymore.

[stardiviner]

You can test with a simple call:

(cider-sync-request:eldoc "\266J\206\306\251\347\355")

P.S I just copied the weird text, but it might direct copy is not original weird character.

[stardiviner]

About upper cider-eldoc op cause nrepl connection crash problem. I found why now. Because the funciton cider-repl--display-image pass image and image data (should be string) to function insert-image. I will send a PR ASAP.