Emacs freezes, seemingly when attempting to send data to HLS

[byorgey]

I am having an issue where for certain .hs files, emacs consistently freezes after they have been open for a few seconds. I cannot get emacs unstuck with Ctrl-G; the only way to get it unstuck is to kill it or at least send it a SIGUSR2.

• Examples of files that consistently cause the freeze:
  • https://github.com/swarm-game/swarm/blob/main/src/swarm-lang/Swarm/Language/Types.hs
  • https://github.com/swarm-game/swarm/blob/main/src/swarm-lang/Swarm/Language/Typecheck.hs
  • Unfortunately I am not sure how to make smaller examples reproducing the issue. The freeze does not seem to happen when there are type errors, or if I just start editing a small .hs file from scratch.
• I tried running haskell-language-server-wrapper manually from the command line; it completes successfully on these files.
• So the problem is either in lsp-haskell or in lsp-mode. I do not know for sure where the problem is but I am nearing the limits of my ability to debug this on my own. Any help or insights are appreciated, even if the problem does not end up being in lsp-haskell.

When emacs freezes, sending it SIGUSR2 produces a trace like the following (the trace always looks very similar to this). Happy to provide any additional information or carry out any recommended debugging steps.

  process-send-string(#<process lsp-haskell> "Content-Length: 64\15\n\15\n{\"jsonrpc\":\"2.0\",\"method\":\"$...")
  #f(compiled-function (process message) #<bytecode 0x1fd20b4909e61763>)(#<process lsp-haskell> (:jsonrpc "2.0" :method "$/cancelRequest" :params (:id 45)))
  apply(#f(compiled-function (process message) #<bytecode 0x1fd20b4909e61763>) #<process lsp-haskell> (:jsonrpc "2.0" :method "$/cancelRequest" :params (:id 45)))
  lsp-process-send(#<process lsp-haskell> (:jsonrpc "2.0" :method "$/cancelRequest" :params (:id 45)))
  lsp--send-no-wait((:jsonrpc "2.0" :method "$/cancelRequest" :params (:id 45)) #<process lsp-haskell>)
  #f(compiled-function (it) #<bytecode -0x1b141d6c1beff8af>)(#s(lsp--workspace :ewoc nil :server-capabilities #<hash-table equal 21/21 0x18eee560b415> :registered-server-capabilities nil :root "/home/brent/projects/swarm" :client #s(lsp--client :language-id "haskell" :add-on? nil :new-connection (:connect #f(compiled-function (filter sentinel name environment-fn workspace) #<bytecode -0x21d182a32f08a07>) :test? #f(compiled-function () #<bytecode 0x18182831b02c6d09>)) :ignore-regexps nil :ignore-messages nil :notification-handlers #<hash-table equal 0/65 0x18eee52170f1> :request-handlers #<hash-table equal 0/65 0x18eee521731f> :response-handlers #<hash-table eql 3/65 0x18eee5218a9b> :prefix-function nil :uri-handlers #<hash-table equal 0/65 0x18eee5218abb> :action-handlers #<hash-table equal 0/65 0x18eee5218f0d> :action-filter lsp-haskell--action-filter :major-modes (haskell-mode haskell-literate-mode haskell-tng-mode haskell-cabal-mode haskell-ts-mode) :activation-fn nil :priority 0 :server-id lsp-haskell :multi-root nil :initialization-options nil :semantic-tokens-faces-overrides nil :custom-capabilities nil :library-folders-fn nil :before-file-open-fn nil :initialized-fn nil :remote? nil :completion-in-comments? t :path->uri-fn nil :uri->path-fn nil :environment-fn nil :after-open-fn nil :async-request-handlers #<hash-table equal 0/65 0x18eee5219323> :download-server-fn nil :download-in-progress? nil :buffers nil :synchronize-sections ("haskell")) :host-root nil :proc #<process lsp-haskell> :cmd-proc #<process lsp-haskell> :buffers (#<buffer Types.hs> #<buffer Context.hs>) :semantic-tokens-faces nil :semantic-tokens-modifier-faces nil :extra-client-capabilities nil :status initialized :metadata #<hash-table equal 0/65 0x18eee54ab767> :watches #<hash-table equal 0/65 0x18eee54ab995> :workspace-folders nil :last-id 0 :status-string nil :shutdown-action nil :diagnostics #<hash-table equal 0/65 0x18eee54ab9b5> :work-done-tokens #<hash-table equal 0/65 0x18eee550586b>))
  lsp--send-notification((:jsonrpc "2.0" :method "$/cancelRequest" :params (:id 45)))
  lsp-notify("$/cancelRequest" (:id 45))
  #f(compiled-function (it) #<bytecode 0x8a1908cc2553771>)(#s(lsp--workspace :ewoc nil :server-capabilities #<hash-table equal 21/21 0x18eee560b415> :registered-server-capabilities nil :root "/home/brent/projects/swarm" :client #s(lsp--client :language-id "haskell" :add-on? nil :new-connection (:connect #f(compiled-function (filter sentinel name environment-fn workspace) #<bytecode -0x21d182a32f08a07>) :test? #f(compiled-function () #<bytecode 0x18182831b02c6d09>)) :ignore-regexps nil :ignore-messages nil :notification-handlers #<hash-table equal 0/65 0x18eee52170f1> :request-handlers #<hash-table equal 0/65 0x18eee521731f> :response-handlers #<hash-table eql 3/65 0x18eee5218a9b> :prefix-function nil :uri-handlers #<hash-table equal 0/65 0x18eee5218abb> :action-handlers #<hash-table equal 0/65 0x18eee5218f0d> :action-filter lsp-haskell--action-filter :major-modes (haskell-mode haskell-literate-mode haskell-tng-mode haskell-cabal-mode haskell-ts-mode) :activation-fn nil :priority 0 :server-id lsp-haskell :multi-root nil :initialization-options nil :semantic-tokens-faces-overrides nil :custom-capabilities nil :library-folders-fn nil :before-file-open-fn nil :initialized-fn nil :remote? nil :completion-in-comments? t :path->uri-fn nil :uri->path-fn nil :environment-fn nil :after-open-fn nil :async-request-handlers #<hash-table equal 0/65 0x18eee5219323> :download-server-fn nil :download-in-progress? nil :buffers nil :synchronize-sections ("haskell")) :host-root nil :proc #<process lsp-haskell> :cmd-proc #<process lsp-haskell> :buffers (#<buffer Types.hs> #<buffer Context.hs>) :semantic-tokens-faces nil :semantic-tokens-modifier-faces nil :extra-client-capabilities nil :status initialized :metadata #<hash-table equal 0/65 0x18eee54ab767> :watches #<hash-table equal 0/65 0x18eee54ab995> :workspace-folders nil :last-id 0 :status-string nil :shutdown-action nil :diagnostics #<hash-table equal 0/65 0x18eee54ab9b5> :work-done-tokens #<hash-table equal 0/65 0x18eee550586b>))
  lsp--cancel-request(45)
  lsp-cancel-request-by-token(:eldoc-hover)
  lsp--send-request-async((:jsonrpc "2.0" :method "textDocument/hover" :params (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4))) #f(compiled-function (input0) #<bytecode 0x12baa7473c34bcf9>) tick ignore nil nil :eldoc-hover)
  lsp-request-async("textDocument/hover" (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4)) #f(compiled-function (input0) #<bytecode 0x12baa7473c34bcf9>) :error-handler ignore :mode tick :cancel-token :eldoc-hover)
  lsp-eldoc-function(#f(compiled-function (string &rest plist) #<bytecode 0x138508dae21a79a6>))
  eldoc-documentation-default()
  eldoc--invoke-strategy(nil)
  eldoc-print-current-symbol-info()
  #<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_12>()
  apply(#<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_12> nil)
  timer-event-handler([t 0 0 500000 nil #<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_12> nil idle 0 nil])
  process-send-string(#<process lsp-haskell> "Content-Length: 214\15\n\15\n{\"jsonrpc\":\"2.0\",\"method\":\"...")
  #f(compiled-function (process message) #<bytecode 0x1fd20b4909e61763>)(#<process lsp-haskell> (:jsonrpc "2.0" :method "textDocument/documentHighlight" :params (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4)) :id 54))
  apply(#f(compiled-function (process message) #<bytecode 0x1fd20b4909e61763>) #<process lsp-haskell> (:jsonrpc "2.0" :method "textDocument/documentHighlight" :params (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4)) :id 54))
  lsp-process-send(#<process lsp-haskell> (:jsonrpc "2.0" :method "textDocument/documentHighlight" :params (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4)) :id 54))
  lsp--send-no-wait((:jsonrpc "2.0" :method "textDocument/documentHighlight" :params (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4)) :id 54) #<process lsp-haskell>)
  #f(compiled-function (workspace) #<bytecode 0x6987de46e58b218>)(#s(lsp--workspace :ewoc nil :server-capabilities #<hash-table equal 21/21 0x18eee560b415> :registered-server-capabilities nil :root "/home/brent/projects/swarm" :client #s(lsp--client :language-id "haskell" :add-on? nil :new-connection (:connect #f(compiled-function (filter sentinel name environment-fn workspace) #<bytecode -0x21d182a32f08a07>) :test? #f(compiled-function () #<bytecode 0x18182831b02c6d09>)) :ignore-regexps nil :ignore-messages nil :notification-handlers #<hash-table equal 0/65 0x18eee52170f1> :request-handlers #<hash-table equal 0/65 0x18eee521731f> :response-handlers #<hash-table eql 3/65 0x18eee5218a9b> :prefix-function nil :uri-handlers #<hash-table equal 0/65 0x18eee5218abb> :action-handlers #<hash-table equal 0/65 0x18eee5218f0d> :action-filter lsp-haskell--action-filter :major-modes (haskell-mode haskell-literate-mode haskell-tng-mode haskell-cabal-mode haskell-ts-mode) :activation-fn nil :priority 0 :server-id lsp-haskell :multi-root nil :initialization-options nil :semantic-tokens-faces-overrides nil :custom-capabilities nil :library-folders-fn nil :before-file-open-fn nil :initialized-fn nil :remote? nil :completion-in-comments? t :path->uri-fn nil :uri->path-fn nil :environment-fn nil :after-open-fn nil :async-request-handlers #<hash-table equal 0/65 0x18eee5219323> :download-server-fn nil :download-in-progress? nil :buffers nil :synchronize-sections ("haskell")) :host-root nil :proc #<process lsp-haskell> :cmd-proc #<process lsp-haskell> :buffers (#<buffer Types.hs> #<buffer Context.hs>) :semantic-tokens-faces nil :semantic-tokens-modifier-faces nil :extra-client-capabilities nil :status initialized :metadata #<hash-table equal 0/65 0x18eee54ab767> :watches #<hash-table equal 0/65 0x18eee54ab995> :workspace-folders nil :last-id 0 :status-string nil :shutdown-action nil :diagnostics #<hash-table equal 0/65 0x18eee54ab9b5> :work-done-tokens #<hash-table equal 0/65 0x18eee550586b>))
  mapc(#f(compiled-function (workspace) #<bytecode 0x6987de46e58b218>) (#s(lsp--workspace :ewoc nil :server-capabilities #<hash-table equal 21/21 0x18eee560b415> :registered-server-capabilities nil :root "/home/brent/projects/swarm" :client #s(lsp--client :language-id "haskell" :add-on? nil :new-connection (:connect #f(compiled-function (filter sentinel name environment-fn workspace) #<bytecode -0x21d182a32f08a07>) :test? #f(compiled-function () #<bytecode 0x18182831b02c6d09>)) :ignore-regexps nil :ignore-messages nil :notification-handlers #<hash-table equal 0/65 0x18eee52170f1> :request-handlers #<hash-table equal 0/65 0x18eee521731f> :response-handlers #<hash-table eql 3/65 0x18eee5218a9b> :prefix-function nil :uri-handlers #<hash-table equal 0/65 0x18eee5218abb> :action-handlers #<hash-table equal 0/65 0x18eee5218f0d> :action-filter lsp-haskell--action-filter :major-modes (haskell-mode haskell-literate-mode haskell-tng-mode haskell-cabal-mode haskell-ts-mode) :activation-fn nil :priority 0 :server-id lsp-haskell :multi-root nil :initialization-options nil :semantic-tokens-faces-overrides nil :custom-capabilities nil :library-folders-fn nil :before-file-open-fn nil :initialized-fn nil :remote? nil :completion-in-comments? t :path->uri-fn nil :uri->path-fn nil :environment-fn nil :after-open-fn nil :async-request-handlers #<hash-table equal 0/65 0x18eee5219323> :download-server-fn nil :download-in-progress? nil :buffers nil :synchronize-sections ("haskell")) :host-root nil :proc #<process lsp-haskell> :cmd-proc #<process lsp-haskell> :buffers (#<buffer Types.hs> #<buffer Context.hs>) :semantic-tokens-faces nil :semantic-tokens-modifier-faces nil :extra-client-capabilities nil :status initialized :metadata #<hash-table equal 0/65 0x18eee54ab767> :watches #<hash-table equal 0/65 0x18eee54ab995> :workspace-folders nil :last-id 0 :status-string nil :shutdown-action nil :diagnostics #<hash-table equal 0/65 0x18eee54ab9b5> :work-done-tokens #<hash-table equal 0/65 0x18eee550586b>)))
  seq-do(#f(compiled-function (workspace) #<bytecode 0x6987de46e58b218>) (#s(lsp--workspace :ewoc nil :server-capabilities #<hash-table equal 21/21 0x18eee560b415> :registered-server-capabilities nil :root "/home/brent/projects/swarm" :client #s(lsp--client :language-id "haskell" :add-on? nil :new-connection (:connect #f(compiled-function (filter sentinel name environment-fn workspace) #<bytecode -0x21d182a32f08a07>) :test? #f(compiled-function () #<bytecode 0x18182831b02c6d09>)) :ignore-regexps nil :ignore-messages nil :notification-handlers #<hash-table equal 0/65 0x18eee52170f1> :request-handlers #<hash-table equal 0/65 0x18eee521731f> :response-handlers #<hash-table eql 3/65 0x18eee5218a9b> :prefix-function nil :uri-handlers #<hash-table equal 0/65 0x18eee5218abb> :action-handlers #<hash-table equal 0/65 0x18eee5218f0d> :action-filter lsp-haskell--action-filter :major-modes (haskell-mode haskell-literate-mode haskell-tng-mode haskell-cabal-mode haskell-ts-mode) :activation-fn nil :priority 0 :server-id lsp-haskell :multi-root nil :initialization-options nil :semantic-tokens-faces-overrides nil :custom-capabilities nil :library-folders-fn nil :before-file-open-fn nil :initialized-fn nil :remote? nil :completion-in-comments? t :path->uri-fn nil :uri->path-fn nil :environment-fn nil :after-open-fn nil :async-request-handlers #<hash-table equal 0/65 0x18eee5219323> :download-server-fn nil :download-in-progress? nil :buffers nil :synchronize-sections ("haskell")) :host-root nil :proc #<process lsp-haskell> :cmd-proc #<process lsp-haskell> :buffers (#<buffer Types.hs> #<buffer Context.hs>) :semantic-tokens-faces nil :semantic-tokens-modifier-faces nil :extra-client-capabilities nil :status initialized :metadata #<hash-table equal 0/65 0x18eee54ab767> :watches #<hash-table equal 0/65 0x18eee54ab995> :workspace-folders nil :last-id 0 :status-string nil :shutdown-action nil :diagnostics #<hash-table equal 0/65 0x18eee54ab9b5> :work-done-tokens #<hash-table equal 0/65 0x18eee550586b>)))
  lsp--send-request-async((:jsonrpc "2.0" :method "textDocument/documentHighlight" :params (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4)) :id 54) lsp--document-highlight-callback tick nil nil nil :highlights)
  lsp-request-async("textDocument/documentHighlight" (:textDocument (:uri "file:///home/brent/projects/swarm/src/swarm-lang/S...") :position (:line 80 :character 4)) lsp--document-highlight-callback :mode tick :cancel-token :highlights)
  lsp--document-highlight()
  lsp--on-idle(#<buffer Types.hs>)
  apply(lsp--on-idle #<buffer Types.hs>)
  timer-event-handler([t 0 0 500000 nil lsp--on-idle (#<buffer Types.hs>) idle 0 nil])

[michaelpj]

Can you turn on lsp-mode's tracking of the messages it's sending to HLS and see if there's obviously anything that chokes it?

[byorgey]

I set lsp-log-io to true and was able to watch a bunch of messages going to and from HLS. Unfortunately, the problem is that when it hangs, I think it has not yet displayed the offending message in the log (if there is one), but emacs is completely frozen so I can't see what the last message was. If I send emacs a SIGUSR2 it gets unfrozen (temporarily) but the last message in the log window was some kind of cancelRequest.

[michaelpj]

Hmmm. Then I think you might need to raise this in the main lsp-mode repo if it's really on the emacs side.

I could see there being a bug if lsp-mode blocks on a cancellation happening?

[byorgey]

Yeah, I don't know, I'm just at a loss as to how to debug this or even figure out where the problem is. I'll try raising the issue in the lsp-mode repo, thanks.