repl stays in pending state after clojurescript jack in if there's some buffer with an invalid ns declaration

[Andre0991]

This error occurs when there's some buffer in clojure-mode with an invalid ns declaration (such as (ns ).

It seems that the culprit is clojure-find-ns (see the stacktrace below), which does not fail gracefully if it can't identify the ns in a buffer. It's not clear from its docstring if throwing an error is its expected behaviour when the ns form is invalid. That's why I'm opening the bug in this repo - I'm not sure if this situation should be handled by cider or clojure-mode, but it does affect cider.

I use Spacemacs, if that's relevant.

Expected behavior

Cider would jack in without errors.

Actual behavior

I got this error (I'm using toggle-debug-on-error):

Debugger entered--Lisp error: (scan-error "Containing expression ends prematurely" 5 6)
  scan-sexps(5 1)
  forward-sexp(1)
  clojure-forward-logical-sexp()
  clojure--find-ns-in-direction(backward)
  clojure-find-ns()
  cider-current-ns()
  cider-refresh-dynamic-font-lock()
  cider-mode(1)
  cider-enable-on-existing-clojure-buffers()
  #f(compiled-function () #<bytecode 0x477bb459>)()
  #f(compiled-function (buffer) #<bytecode 0x4770c08d>)(#<buffer *cider-repl nu/timeline:localhost:63972(pending-cljs)*>)
  #f(compiled-function (response) #<bytecode 0x4770c109>)((dict "id" "4" "session" "f0733cfc-31b2-4759-bb10-2416c787fa6f" "status" ("done")))
  #f(compiled-function (response) #<bytecode 0x4770c151>)((dict "id" "4" "session" "f0733cfc-31b2-4759-bb10-2416c787fa6f" "status" ("done")))
  nrepl--dispatch-response((dict "id" "4" "session" "f0733cfc-31b2-4759-bb10-2416c787fa6f" "status" ("done")))
  nrepl-client-filter(#<process nrepl-connection> "d2:id1:47:session36:f0733cfc-31b2-4759-bb10-2416c787fa6f5:value3:niled2:id1:42:ns11:shadow.user7:session36:f0733cfc-31b2-4759-bb10-2416c787fa6fed2:id1:47:session36:f0733cfc-31b2-4759-bb10-2416c787fa6f6:statusl4:doneee")

Steps to reproduce the problem

• Create a clojure buffer with the following content: (ns ).
• Use cider-jack-in-cljs in a shadow project (I don't know if shadow is relevant for the issue)
• Select shadow and the app profile

Environment & Version information

CIDER version information

Include here the version string displayed when CIDER's REPL is launched. Here's an example:

;; CIDER 0.25.0snapshot (package: 20200521.627), nREPL 0.7.0
;; Clojure 1.10.0, Java 13.0.1

Emacs version

GNU Emacs 26.3 (build 1, x86_64-apple-darwin18.5.0, NS appkit-1671.40 Version 10.14.4 (Build 18E226)) of 2019-08-30

Operating system

Mac OS 10.15.4

[dpsutton]

The simplest repro is to have a buffer with a simple (ns ) form and call clojure-find-ns.

Seems like this should be fixed in clojure-mode and perhaps also CIDER?

[bbatsov]

I was also thinking that probably this should be fixed in clojure-mode, e.g. cider-find-ns could return nil in such cases.