bug#81514: 32.0.50; Eglot messages progress reporter shows errors

I can reproduce it with clangd on the following C++ repository:
https://github.com/rui314/mold. It doesn't happen every time but often 
enough:

Debugger entered--Lisp error: (wrong-type-argument sequencep 100)
   ((20 . [1785337541.907988 nil nil "[eglot] mold 
backgroundIndexProgress: indexing..." 1 0.2 nil nil]) 20 100)
   progress-reporter-do-update((20 . [1785337541.907988 nil nil "[eglot] 
mold backgroundIndexProgress: indexing..." 1 0.2 nil nil]) 100 nil)
   eglot--reporter-update((20 . [1785337541.907988 nil nil "[eglot] mold 
backgroundIndexProgress: indexing..." 1 0.2 nil nil]) 100 nil)
   #f(compiled-function (arg1 arg2 arg3 arg4 &rest rest) #<bytecode 
0xa1216d65848076a>)(#<eglot-lsp-server 1022b7360904> 
"backgroundIndexProgress" 100 nil)
   #f(compiled-function (arg1 arg2 &rest rest) "Handle $/progress 
notification identified by TOKEN from SERVER." #<bytecode 
-0xf68beacb9f43862>)(#<eglot-lsp-server 1022b7360904> $/progress :token 
"backgroundIndexProgress" :value (:kind "end"))
   apply(#f(compiled-function (arg1 arg2 &rest rest) "Handle $/progress 
notification identified by TOKEN from SERVER." #<bytecode 
-0xf68beacb9f43862>) #<eglot-lsp-server 1022b7360904> $/progress (:token 
"backgroundIndexProgress" :value (:kind "end")))
   eglot-handle-notification(#<eglot-lsp-server 1022b7360904> $/progress 
:token "backgroundIndexProgress" :value (:kind "end"))
   apply(eglot-handle-notification #<eglot-lsp-server 1022b7360904> 
$/progress (:token "backgroundIndexProgress" :value (:kind "end")))
   #f(compiled-function (server method params) #<bytecode 
0x1f1b657efb0838aa>)(#<eglot-lsp-server 1022b7360904> $/progress (:token 
"backgroundIndexProgress" :value (:kind "end")))
   jsonrpc-connection-receive(#<eglot-lsp-server 1022b7360904> (:jsonrpc 
"2.0" :method "$/progress" :params (:token "backgroundIndexProgress" 
:value (:kind "end"))))
   #f(compiled-function (conn msg) #<bytecode 
0x4e6153735258fd3>)(#<eglot-lsp-server 1022b7360904> (:jsonrpc "2.0" 
:method "$/progress" :params (:token "backgroundIndexProgress" :value 
(:kind "end"))))
   apply(#f(compiled-function (conn msg) #<bytecode 0x4e6153735258fd3>) 
(#<eglot-lsp-server 1022b7360904> (:jsonrpc "2.0" :method "$/progress" 
:params (:token "backgroundIndexProgress" :value (:kind "end")))))
   timer-event-handler([t 27242 5829 902968 nil #f(compiled-function 
(conn msg) #<bytecode 0x4e6153735258fd3>) (#<eglot-lsp-server 
1022b7360904> (:jsonrpc "2.0" :method "$/progress" :params (:token 
"backgroundIndexProgress" :value (:kind "end")))) nil 894000 nil])

The LSP message that causes it looks like this from the 
(eglot-events-buffer):
<-- $/progress 
{"jsonrpc":"2.0","method":"$/progress","params":{"token":"backgroundIndexProgress","value":{"kind":"end"}}}

Based on my understanding of Eglot code, Eglot creates a non-numeric 
progress
reporter because MIN-VALUE and MAX-VALUE arguments are not provided. 
However, it
looks like Eglot updates the created progress reporter as it were numeric:
(eglot--reporter-update pr pcnt msg)

For the {"kind": "end"} notification, pcnt is set to 100 and msg is nil. 
After
commit b6849229003, the pulsing reporter forwards (or update-text value) as
UPDATE-TEXT. That evaluates to 100. Then progress-reporter-echo-area tries
(concat (if update-text " " "") update-text) which triggers the shown error.

On 7/29/26 3:21 PM, Stéphane Marks wrote:
> On Wed, Jul 29, 2026 at 7:37 AM Eli Zaretskii <[email protected]> wrote:
>
>     > From: "Jacek Świerk" <[email protected]>
>     > Date: Wed, 29 Jul 2026 09:41:39 +0200
>     >
>     > When Eglot is configured with `eglot-report-progress` set to
>     `messages`, it
>     > reports an error while trying to use the progress reporter in a
>     nontrivial
>     > project.
>     >
>     > Reproduction using rust-analyzer:
>     > 1. Clone https://github.com/BurntSushi/ripgrep
>     > 2. Open ripgrep/crates/core/main.rs
>     > 3. M-: (setopt eglot-report-progress 'messages)
>     > 4. M-x toggle-debug-on-error
>     > 5. M-x eglot
>     >
>     > Debugger entered--Lisp error: (wrong-type-argument sequencep 100)
>     >    progress-reporter-echo-area((7 . [1785304002.532535 nil nil
>     "[eglot]
>     > ripgrep rustAnalyzer/Building compile-time-deps: Building
>     > compile-time-deps..." 1 0.2 nil nil]) 7 100)
>     >    progress-reporter-do-update((7 . [1785304002.532535 nil nil
>     "[eglot]
>     > ripgrep rustAnalyzer/Building compile-time-deps: Building
>     > compile-time-deps..." 1 0.2 nil nil]) 100 nil)
>     >    eglot--reporter-update((7 . [1785304002.532535 nil nil "[eglot]
>     > ripgrep rustAnalyzer/Building compile-time-deps: Building
>     > compile-time-deps..." 1 0.2 nil nil]) 100 nil)
>     >    #f(compiled-function (arg1 arg2 arg3 arg4 &rest rest) #<bytecode
>     > 0x1c7b74ccff3232d6>)(#<eglot-lsp-server 1008c31da7cc>
>     > "rustAnalyzer/Building compile-time-deps" 100 nil)
>     >    #f(compiled-function (arg1 arg2 &rest rest) "Handle $/progress
>     > notification identified by TOKEN from SERVER." #<bytecode
>     > -0x35b89fe1a323862>)(#<eglot-lsp-server 1008c31da7cc> $/progress
>     :token
>     > "rustAnalyzer/Building compile-time-deps" :value (:kind "end"))
>     >    apply(#f(compiled-function (arg1 arg2 &rest rest) "Handle
>     $/progress
>     > notification identified by TOKEN from SERVER." #<bytecode
>     > -0x35b89fe1a323862>) #<eglot-lsp-server 1008c31da7cc> $/progress
>     (:token
>     > "rustAnalyzer/Building compile-time-deps" :value (:kind "end")))
>     >    eglot-handle-notification(#<eglot-lsp-server 1008c31da7cc>
>     $/progress
>     > :token "rustAnalyzer/Building compile-time-deps" :value (:kind
>     "end"))
>     >    apply(eglot-handle-notification #<eglot-lsp-server 1008c31da7cc>
>     > $/progress (:token "rustAnalyzer/Building compile-time-deps" :value
>     > (:kind "end")))
>     >    #f(compiled-function (server method params) #<bytecode
>     > 0x1f1068c682e838aa>)(#<eglot-lsp-server 1008c31da7cc> $/progress
>     (:token
>     > "rustAnalyzer/Building compile-time-deps" :value (:kind "end")))
>     >    jsonrpc-connection-receive(#<eglot-lsp-server 1008c31da7cc>
>     (:jsonrpc
>     > "2.0" :method "$/progress" :params (:token "rustAnalyzer/Building
>     > compile-time-deps" :value (:kind "end"))))
>     >    #f(compiled-function (conn msg) #<bytecode
>     > 0x1bafe9b6d4ce09dc>)(#<eglot-lsp-server 1008c31da7cc> (:jsonrpc
>     "2.0"
>     > :method "$/progress" :params (:token "rustAnalyzer/Building
>     > compile-time-deps" :value (:kind "end"))))
>     >    apply(#f(compiled-function (conn msg) #<bytecode
>     0x1bafe9b6d4ce09dc>)
>     > (#<eglot-lsp-server 1008c31da7cc> (:jsonrpc "2.0" :method
>     "$/progress"
>     > :params (:token "rustAnalyzer/Building compile-time-deps" :value
>     (:kind
>     > "end")))))
>     >    timer-event-handler([t 27241 37827 781121 nil
>     #f(compiled-function
>     > (conn msg) #<bytecode 0x1bafe9b6d4ce09dc>) (#<eglot-lsp-server
>     > 1008c31da7cc> (:jsonrpc "2.0" :method "$/progress" :params (:token
>     > "rustAnalyzer/Building compile-time-deps" :value (:kind
>     "end")))) nil
>     > 734000 nil])
>     >
>     > This seems to be introduced by the following commit
>     >
>     https://github.com/emacs-mirror/emacs/commit/b6849229003f214570acedfa7e2755051c0e4305
>     > and most likely affects Emacs 31 as well.
>
>     Thanks.
>
>     Stéphane, please look into fixing this.
>
>
> I don't use rust so I don't have that toolchain installed.  I tried to 
> trigger this condition using clangd on src/emacs.c and it works fine.  
> Perhaps my clangd configuration does not emit the asynchronous 
> notifications that touch that eglot code path.  If we can create a 
> recipe that works with clangd that would be ideal.