bug#71823: 31.0.50; project-mode-line and eglot duplicate project-name in mode-line

[Spencer Baugh <sbaugh@janestreet.com>]

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Patch fixing this:


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From 928101e122725866ee95172730ebff03f4d54d5a Mon Sep 17 00:00:00 2001
From: Spencer Baugh <sbaugh@janestreet.com>
Date: Fri, 28 Jun 2024 10:00:10 -0400
Subject: [PATCH] Skip eglot project-name when project-mode-line=t

Both the eglot mode line entry and project-mode-line add
project-name to the modeline.  When both of them are enabled,
this is unnecessary duplication.

To fix, add the customization eglot-mode-line-project-name to
allow disabling the project-name in eglot's mode-line entry.

Furthermore, by default, set this customization so that eglot
will check project-mode-line and omit the project-name if
project-mode-line is non-nil.  This allows a user to just set
project-mode-line without having to separately customize eglot.

* lisp/progmodes/eglot.el (eglot-mode-line-project-name): Add.
(eglot--mode-line-format): Check
eglot-mode-line-project-name. (bug#71823)
---
 lisp/progmodes/eglot.el | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/eglot.el b/lisp/progmodes/eglot.el
index df4cbe50dc0..60e68b323f6 100644
--- a/lisp/progmodes/eglot.el
+++ b/lisp/progmodes/eglot.el
@@ -2237,10 +2237,29 @@ eglot--mode-line-props
                                          keymap ,map help-echo ,(concat prepend blurb)
                                          mouse-face mode-line-highlight))))
 
+(defcustom eglot-mode-line-project-name
+  (if (version< "30" emacs-version)
+      ;; The project mode-line entry was added to `mode-line-format' in
+      ;; Emacs 30; before that, `project-mode-line' has no effect.
+      'unless-project-mode-line
+    nil)
+  "If non-nil, the eglot mode-line entry may contain `project-name'.
+
+If t, the eglot mode-line entry always contains `project-name'; if nil,
+it never contains `project-name'.
+
+If the symbol `unless-project-mode-line', the eglot mode-line entry only
+contains `project-name' if `project-mode-line' is nil.  (This avoids
+showing `project-name' in the modeline twice.)")
+
 (defun eglot--mode-line-format ()
   "Compose Eglot's mode-line."
   (let* ((server (eglot-current-server))
          (nick (and server (eglot-project-nickname server)))
+         (use-nick (cl-case eglot-mode-line-project-name
+                 (nil nil)
+                 (unless-project-mode-line (not (bound-and-true-p project-mode-line)))
+                 (t t)))
          (pending (and server (jsonrpc-continuation-count server)))
          (last-error (and server (jsonrpc-last-error server))))
     (append
@@ -2253,9 +2272,9 @@ eglot--mode-line-format
                    (define-key map [mode-line down-mouse-1] eglot-menu)
                    map)))
      (when nick
-       `(":"
+       `(,(if use-nick ":" "")
          ,(propertize
-           nick
+           (if use-nick nick ":")
            'face 'eglot-mode-line
            'mouse-face 'mode-line-highlight
            'help-echo (format "Project '%s'\nmouse-1: LSP server control menu" nick)
-- 
2.39.3