lsp-sourcekit ;; completion stops working after lsp server returns an error

[wibed]

Thank you for the bug report

• I am using the latest version of lsp-mode related packages.
• I checked FAQ and Troubleshooting sections
• You may also try reproduce the issue using clean environment using the following command

emacs -q -l lsp-start-plain.el

where lsp-start-plain.el can be downloaded here.

Bug description

completion stopped working after receiving a completion error from the sourcekit-lsp

the completion stops working if one follows the reproduction right here:

func hello(na
------------^

and the following logs are produced. the communication with the sourcekit-lsp
continues, as the stacktrace shows, but completion stops working.

Steps to reproduce

1. open swift file
2. set the root path for the project
3. type "fun", select the proper ("func") selection from the dropdown
4. try typing out " hello(name: String)" after that

Expected behavior

the completion to work after receiving a completion error from the sourcekit-lsp

current behavior

completion stopped working after receiving a completion error from the sourcekit-lsp

Which Language Server did you use?

context

os: linux 5.12.19_1
emacs: 28.0.50 (x86_64)
language: swift (swift-mode)
lsp: lsp-mode, lsp-sourcekit

OS

Linux

Error callstack

- [company-diag](https://termbin.com/2oj0)
- [backtrace](https://termbin.com/so0c)
- [lsp-log](https://termbin.com/rzgk)
- [sourcekit-ls](https://termbin.com/s5ss)
- [stacktrace](https://termbin.com/1rqs)

Anything else?

• trying to clean the company cache manually had no effect
• adding (setq yas-inhibit-overlay-modification-protection t) had no effect

UPDATE:

• manually cleaning the cache with (lsp-completion--clear-cache t) had some effect, manual completion at point works. but even restarting swift-mode does not bring back expected functionality.
• disabling cache at startup setting (setq lsp-completion-no-cache t) had no effect.

[wibed]

@danielmartin i am fairly new to emacs. as far as i can tell sourcekit-lsp only establishes the connection to the lsp server

[wibed]

@yyoncho reading into #1853 and #1896

i found

(defun lsp-completion--clear-cache (&optional keep-last-result)
  "Clear completion caches.
KEEP-LAST-RESULT if specified."
  (-some-> lsp-completion--cache
    (cddr)
    (plist-get :markers)
    (cl-second)
    (set-marker nil))
  (setq lsp-completion--cache nil)
  (unless keep-last-result (setq lsp-completion--last-result nil)))

clearing the cache i got company to complete at point (company-complete) but it didnt fire automatically
is there a workaround, to keep company functionality? manually ask for completion kinda defeats the purpose

EDIT:
querying company-diag shows it runs in fundamental mode. changing its mode back (swift-mode) by restarting
the lsp-client, the company-diag shows
https://termbin.com/imhy

cleaning the cache again. makes the company work in swift mode, but only manually.
keeping the last result and without, didnt have any effect
restarting swift-mode, lsp interchangably, didnt have any effect

following response:

[Trace - 12:41:11 PM] Received response 'textDocument/completion - (685)' in 7ms.
Result: {
  "code": -32800,
  "message": "request cancelled"
}

results in the need to clear the cache again. without showing a stacktrace. so company crashes again silently

[kiennq]

@wibed Can you try to set lsp-completion-no-cache to t and retry?

[wibed]

@kiennq the error persists. resulting from the -32800, crashing completion.

[kiennq]

@wibed after the error is showing up, if you try to type more, is a new completion coming?

[wibed]

nope completion stops working after the error

• backtrace

EDIT
furthermore after using (lsp-completion--clear-cache t) and company-capf works again. manually that said and
having (setq lsp-completion-no-cache t) set on my .emacs (and starting emacs with such file)

[wibed]

@kiennq as linked above the problem is better explained in said words

The problem seems to be with lsp-completion--get-context that is used as a parameter to the completion request. 
For whatever reason, lsp-completion--cache gets set with an incomplete marker. 
The context sets specific :trigger-kind in this case which seems to break the completions.

Unfortunately, just deactivating caching with (setq lsp-completion-no-cache 't) doesn't seem to be enough, 
the :incomplete marker is still set.

[wibed]

this one seems related

#2970

[kiennq]

I think the problem here is that the server returns an error and it translated to Emacs user error, which will throw off the cache clearing part of lsp-mode's completion.
I will push a PR for this soon

[wibed]

@kiennq

I think the problem here is that the server returns an error and it translated to Emacs user error, which will throw off the cache clearing part of lsp-mode's completion.
I will push a PR for this soon

id say the completion message to the server is malformed triggering an error from the server blocking the completion from further actions. the lsp error states, that it received unexpected reference as completion request.

2021-09-19 05:52:44.639 sourcekit-lsp[48:5e34c700] triggerFromIncompleteCompletions with incompatible completion session; expected DocumentURI(storage: file:///work/test/swift/Package.swift)@153, but got DocumentURI(storage: file:///work/test/swift/Package.swift)@157

i recreated it for the log links above are dead