master 9093834d0b5: Eglot: unbreak activation/management of derived modes (bug#62907)

[João Távora]

branch: master
commit 9093834d0b590bc15ed994bd62f18f7b47a48f55
Author: João Távora <joaotavora@gmail.com>
Commit: João Távora <joaotavora@gmail.com>

    Eglot: unbreak activation/management of derived modes (bug#62907)
    
    After recent changes to how LSP "languageId" is computed from major
    modes and stored in the eglot-lsp-server object, the activation of the
    'eglot--managed-mode' minor mode in modes _derived_ from some
    major-mode mentioned in 'eglot-server-programs' was broken.
    
    This commit restores that by introducing a new helper which uses the
    same logic to provide the current-buffer's "languageId" to the server
    and to discover if the server should manage the mode at all.  This
    ensures the two things stay in sync.
    
    Also, this helper uses the function 'provided-mode-derived-p' to fix
    this bug#62907.
    
    * lisp/progmodes/eglot.el (eglot--languageId): New helper.
    (eglot-current-server, eglot--TextDocumentItem): Use it.
---
 lisp/progmodes/eglot.el | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/lisp/progmodes/eglot.el b/lisp/progmodes/eglot.el
index 7ad33fa3786..fe0c986d746 100644
--- a/lisp/progmodes/eglot.el
+++ b/lisp/progmodes/eglot.el
@@ -1935,10 +1935,9 @@ Use `eglot-managed-p' to determine if current buffer is 
managed.")
   "Return logical Eglot server for current buffer, nil if none."
   (setq eglot--cached-server
         (or eglot--cached-server
-            (cl-find major-mode
-                     (gethash (eglot--current-project) 
eglot--servers-by-project)
-                     :key #'eglot--major-modes
-                     :test #'memq)
+            (cl-find-if #'eglot--languageId
+                        (gethash (eglot--current-project)
+                                 eglot--servers-by-project))
             (and eglot-extend-to-xref
                  buffer-file-name
                  (gethash (expand-file-name buffer-file-name)
@@ -2360,12 +2359,20 @@ THINGS are either registrations or unregisterations 
(sic)."
   (append (eglot--TextDocumentIdentifier)
           `(:version ,eglot--versioned-identifier)))
 
+(cl-defun eglot--languageId (&optional (server 
(eglot--current-server-or-lose)))
+  "Compute LSP \\='languageId\\=' string for current buffer.
+Doubles as an predicate telling if SERVER can manage current
+buffer."
+  (cl-loop for (mode . languageid) in
+           (eglot--languages server)
+           when (provided-mode-derived-p major-mode mode)
+           return languageid))
+
 (defun eglot--TextDocumentItem ()
   "Compute TextDocumentItem object for current buffer."
   (append
    (eglot--VersionedTextDocumentIdentifier)
-   (list :languageId
-         (alist-get major-mode (eglot--languages 
(eglot--current-server-or-lose)))
+   (list :languageId (eglot--languageId)
          :text
          (eglot--widening
           (buffer-substring-no-properties (point-min) (point-max))))))