Completion stops working intermittently with lsp-mode

[lassemaatta]

Problem

Sometimes completing a symbol with corfu gets stuck returning "No match", even though everything worked fine a moment ago.

Setup

I use corfu with lsp-mode as the LSP client and clojure-lsp as the LSP server. Emacs is compiled from the 29 branch (GNU Emacs 29.1.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38, cairo version 1.18.0) of 2023-09-30). My emacs config, which should hopefully follow the corfu+lsp-mode instructions from the wiki.

Disclaimer: I'm very much a emacs-beginner, so it's more than likely that this is just some user error or problem in my emacs configuration.

How to reproduce and/or resolve

When testing this I tried to completions on the following Clojure form (http/|), where http is an symbolic alias for a HTTP library namespace and | represents the cursor position. The expected result is seeing something like:

Unfortunately I don't have a fool-proof way to reproduce this nor how to fix it once it happens.

It feels like there's some kind of caching issue. For example, if completion for some form (e.g. (http/|)) gets stuck returning "No match" then attempting completion for another form might work fine. Sometimes doing stuff like changing the alias (e.g. rename http to https and then completing on (https/|)) or modifying the file and saving it seems to fix the problem. At least for a while.

I tried playing around with the cape-capf-buster in a very "I have no idea what I'm doing" sort of way, but it did not appear to affect the situation.

Debugging

At first I looked at the communication between the LSP client and the server. I have no idea how the LSP protocol and the completion system in emacs interact, but from what I've deducted: something (corfu, lsp-mode?) will fetch completions from LSP server and cache them. That is, when everything is working fine attempting completion may or may not ask completions from the LSP server.

To debug corfu, I used the cape-capf-debug thing to wrap lsp-completion-at-point.

Log - Completion success

lsp-completion-at-point@126 => input=223:228:"http/" table=(#("http/*current-middleware*" 0 25 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/*current-middleware*" 0 25 ...) "kind" 6 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "*current-middleware*" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 1119 "name-col" 3))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/accept-encoding-value" 0 26 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/accept-encoding-value" 0 26 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "accept-encoding-value" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 732 "name-col" 7))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/basic-auth-value" 0 21 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/basic-auth-value" 0 21 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "basic-auth-value" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 821 "name-col" 7))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/check-url!" 0 15 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/check-url!" 0 15 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "check-url!" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 1163 "name-col" 12))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/client-error?" 0 18 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/client-error?" 0 18 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "client-error?" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 224 "name-col" 7))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) ...) annotation-function=lsp-completion--annotate company-kind=lsp-completion--candidate-kind company-deprecated=lsp-completion--candidate-deprecated company-require-match=never company-prefix-length=t company-match=lsp-completion--company-match company-doc-buffer=# exit-function=#
lsp-completion-at-point@126(action=metadata input=223:228:"http/" prefix="http/" ignore-case=nil) => (metadata (category . lsp-capf) (display-sort-function . identity) (cycle-sort-function . identity))
lsp-completion-at-point@126(action=(boundaries . "") input=223:228:"http/" prefix="http/" ignore-case=nil predicate=#) => nil
lsp-completion-at-point@126(action=metadata input=223:228:"http/" prefix="http/" ignore-case=nil) => (metadata (category . lsp-capf) (display-sort-function . identity) (cycle-sort-function . identity))
lsp-completion-at-point@126(action=(boundaries . "") input=223:228:"http/" prefix="http/" ignore-case=nil) => nil [2 times]
lsp-completion-at-point@126(action=all input=223:228:"http/" prefix="" ignore-case=t regexp=("\\(?:http/\\)")) => (#("http/*current-middleware*" 0 25 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/*current-middleware*" 0 25 ...) "kind" 6 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "*current-middleware*" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 1119 "name-col" 3))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/accept-encoding-value" 0 26 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/accept-encoding-value" 0 26 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "accept-encoding-value" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 732 "name-col" 7))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/basic-auth-value" 0 21 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/basic-auth-value" 0 21 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "basic-auth-value" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 821 "name-col" 7))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/check-url!" 0 15 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/check-url!" 0 15 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "check-url!" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 1163 "name-col" 12))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) #("http/client-error?" 0 18 (lsp-completion-item #s(hash-table size 6 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("label" #("http/client-error?" 0 18 ...) "kind" 3 "data" #s(hash-table size 1 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("unresolved" [["documentation" #s(hash-table size 4 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("name" "client-error?" "uri" "file:///home/lassemaatta/.emacs.d/workspace/.cache/clj_http.client.clj" "name-row" 224 "name-col" 7))] ["alias" #s(hash-table size 3 test equal rehash-size 1.5 rehash-threshold 0.8125 data ("ns-to-add" "clj-http.client" "alias-to-add" "http" "uri" "file:///home/lassemaatta/work/uimaranta_basis/src/uimaranta_basis/core.clj"))]])) "score" 8 "_emacsStartPoint" 223)) lsp-sort-text nil lsp-completion-start-point 223 lsp-completion-markers ... lsp-completion-prefix "http/" match-data ...)) ...)
lsp-completion-at-point@126(action=(boundaries . "") input=223:228:"http/" prefix="http/" ignore-case=nil) => nil

Log - Completion failure

lsp-completion-at-point@93 => input=223:228:"http/" table=nil annotation-function=lsp-completion--annotate company-kind=lsp-completion--candidate-kind company-deprecated=lsp-completion--candidate-deprecated company-require-match=never company-prefix-length=t company-match=lsp-completion--company-match company-doc-buffer=# exit-function=#
lsp-completion-at-point@93(action=metadata input=223:228:"http/" prefix="http/" ignore-case=nil) => (metadata (category . lsp-capf) (display-sort-function . identity) (cycle-sort-function . identity))
lsp-completion-at-point@93(action=(boundaries . "") input=223:228:"http/" prefix="http/" ignore-case=nil predicate=#) => nil
lsp-completion-at-point@93(action=all input=223:228:"http/" prefix="" ignore-case=t regexp=("\\(?:http/\\)") predicate=#) => nil
lsp-completion-at-point@93(action=(boundaries . "") input=223:228:"http/" prefix="http/" ignore-case=nil) => nil
lsp-completion-at-point@93(action=try input=223:228:"http/" prefix="http/" ignore-case=nil) => nil
lsp-completion-at-point@93(action=(boundaries . "") input=223:228:"http/" prefix="http/" ignore-case=nil) => nil
lsp-completion-at-point@93(action=all input=223:228:"http/" prefix="http" ignore-case=nil regexp=("\\`http.*?/")) => nil

Comparing the two I can see that the success case has an entry with a bunch of results:

• (action=all input=223:228:"http/" prefix="" ignore-case=t regexp=("\\(?:http/\\)"))
  while the problematic case as a similarish looking row with an extra predicate (no idea if this is relevant)
• (action=all input=223:228:"http/" prefix="" ignore-case=t regexp=("\\(?:http/\\)") predicate=#)

[minad]

Do you use https://github.com/minad/corfu/wiki#configuring-corfu-for-lsp-clients?

[lassemaatta]

I believe so. The relevant parts of my config:

(use-package corfu
  :init
  (global-corfu-mode)
  (corfu-popupinfo-mode)
  (corfu-history-mode -1)
  (add-to-list 'savehist-additional-variables 'corfu-history)
  :custom
  (corfu-auto nil)
  (corfu-preselect 'prompt)
  (corfu-popupinfo-delay '(0.5 . 1.0))
  (corfu-cycle t)
  (corfu-on-exact-match nil)
  (corfu-quit-no-match nil)
  (corfu-preview-current nil)
  (corfu-min-width 70)
  (corfu-count 20))

(use-package orderless
  :demand t
  :after vertico
  :custom
  (completion-styles '(basic orderless partial-completion))
  (completion-category-defaults nil)
  (completion-category-overrides '((file (styles basic partial-completion)))))

(use-package cape
  :demand t
  :after vertico)

(use-package lsp-mode
  :custom
  (lsp-completion-provider :none)
  (lsp-completion-sort-initial-results nil)
  ;; set prefix for lsp-command-keymap (few alternatives - "C-l", "C-c l")
  (lsp-keymap-prefix "C-f l")
  (lsp-idle-delay 0.5)
  (lsp-eldoc-enable-hover t)
  (lsp-lens-enable t)
  (lsp-headerline-breadcrumb-enable nil)
  ;; Close LSP server when last buffer closed
  (lsp-keep-workspace-alive nil)
  ;; Don't include the var/function declaration itself when listing references to a var/function
  (lsp-references-exclude-definition t)
  ;; We use yasnippet, but not through LSP
  (lsp-enable-snippet nil)
  ;; Prefer clojure-mode indentation
  (lsp-enable-indentation nil)
  (lsp-modeline-code-actions-enable nil)
  (lsp-imenu-index-function #'lsp-imenu-create-categorized-index)
  ;; For logging IO between client and server
  (lsp-log-io nil)
  ;(lsp-clojure-custom-server-command '("bash" "-c" "/home/lassemaatta/Lataukset/clojure-lsp"))
  :init
  (defun my/lsp-mode-setup-completion ()
    (setf (alist-get 'styles (alist-get 'lsp-capf completion-category-defaults))
          '(orderless)))
  :hook (;; replace XXX-mode with concrete major-mode(e. g. python-mode)
         (clojure-mode . lsp)
         (clojurescript-mode . lsp)
         (clojurec-mode . lsp)
         (js-mode . lsp)
         (typescript-mode . lsp)
         ;; if you want which-key integration
         (lsp-mode . lsp-enable-which-key-integration)
         (lsp-completion-mode . my/lsp-mode-setup-completion)
         (lsp-after-apply-edits . (lambda (op)
                                    (save-some-buffers t))))
  :bind (("<C-return>" . lsp-find-definition)
         ("<C-.>" . lsp-find-definition)
         ("<C-M-return>" . lsp-describe-thing-at-point))
  :commands (lsp lsp-deferred))

[lassemaatta]

I did a bit more testing. I disabled corfu and used the default completion method (not sure what it's called, the *Completions* buffer thing) and the same problem still occurs. Also, starting a "plain LSP" instance with lsp-start-plain also exhibits this issue. Therefore, I think I'll raise this issue over at lsp-mode and see if they have any ideas what's going on.

[minad]

Thanks. Yes, reporting this to lsp-mode with a self-contained recipe would be good.

[emagieika]

Hey @lassemaatta, I've just encountered something similar and in my case this was(corfu-quit-no-match nil) that I accidentally enabled and after typing something like a single letter, lsp wouldn't return a match, because of minimum length required and after I finished typing what I needed "No Match" persisted.
Not sure if this is expected or not (from the variable name it kind of sounds like it is), but leaving (corfu-quit-no-match t) solved the problem for me.