From 9d8e1af6f41bf11704c00cc5f6fdbc5eb52ed2d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20T=C3=A1vora?= <joaotavora@gmail.com>
Date: Wed, 21 Jan 2026 11:57:38 +0000
Subject: [PATCH] Eglot: fix textDocument/prepareRename support

Can't send prepareRename requests willy-nilly.

See https://github.com/joaotavora/eglot/issues/1554.

* lisp/progmodes/eglot.el (eglot--rename-interactive): Fix.
(eglot-client-capabilities): Advertise "prepareSupport".

* etc/EGLOT-NEWS: Mention change.
---
 etc/EGLOT-NEWS          |  5 +++++
 lisp/progmodes/eglot.el | 38 +++++++++++++++++++++++---------------
 2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/etc/EGLOT-NEWS b/etc/EGLOT-NEWS
index 201d782575f..89870c64641 100644
--- a/etc/EGLOT-NEWS
+++ b/etc/EGLOT-NEWS
@@ -50,6 +50,11 @@ beneficial and helps servers avoid costly useless work.
 Eglot now sets 'imenu-create-index-function' directly without using
 advice, making the integration cleaner and more predictable.
 
+** Fixed textDocument/prepareRename support (github#1554)
+
+Eglot now properly checks server capabilities before sending
+prepareRename requests.
+
 
 * Changes in Eglot 1.21 (11/1/2026)
 
diff --git a/lisp/progmodes/eglot.el b/lisp/progmodes/eglot.el
index 10a58c57989..b418bfdedc8 100644
--- a/lisp/progmodes/eglot.el
+++ b/lisp/progmodes/eglot.el
@@ -1139,7 +1139,8 @@ object."
                                   :isPreferredSupport t)
              :formatting         `(:dynamicRegistration :json-false)
              :rangeFormatting    `(:dynamicRegistration :json-false)
-             :rename             `(:dynamicRegistration :json-false)
+             :rename             `(:dynamicRegistration :json-false
+                                   :prepareSupport t)
              :semanticTokens     `(:dynamicRegistration :json-false
                                    :requests (:full (:delta t))
                                    :overlappingTokenSupport t
@@ -4489,20 +4490,27 @@ the edit was attempted and optionally why not."
           (if (user-accepts-p) (apply-all) `(nil "decision to decline")))
          ((apply-all)))))))
 
-(cl-defun eglot--rename-interactive (&aux region)
-  (eglot-server-capable-or-lose :renameProvider)
-  (let* ((probe (eglot--request (eglot--current-server-or-lose)
-                                :textDocument/prepareRename
-                                (eglot--TextDocumentPositionParams)))
-         (def
-          (cond ((null probe) (user-error "[eglot] Can't rename here"))
-                ((plist-get probe :placeholder))
-                ((plist-get probe :defaultBehavior) (thing-at-point 'symbol t))
-                ((setq region (eglot-range-region probe))
-                 (buffer-substring-no-properties (car region) (cdr region))))))
-    (list (read-from-minibuffer
-           (format "Rename `%s' to: " (or def "unknown symbol"))
-           nil nil nil nil def))))
+(cl-defun eglot--rename-interactive
+    (&aux
+     def region
+     (rename-support (eglot-server-capable-or-lose :renameProvider))
+     (prepare-support (and (listp rename-support)
+                           (plist-get rename-support :prepareProvider))))
+  (setq
+   def
+   (cond (prepare-support
+          (let ((x (eglot--request (eglot--current-server-or-lose)
+                                   :textDocument/prepareRename
+                                   (eglot--TextDocumentPositionParams))))
+            (cond ((null x) (user-error "[eglot] Can't rename here"))
+                  ((plist-get x :placeholder))
+                  ((plist-get x :defaultBehavior) (thing-at-point 'symbol t))
+                  ((setq region (eglot-range-region x))
+                   (buffer-substring-no-properties (car region) (cdr region))))))
+         (t (thing-at-point 'symbol t))))
+  (list (read-from-minibuffer
+         (format "Rename `%s' to: " (or def "unknown symbol"))
+         nil nil nil nil def)))
 
 (defun eglot-rename (newname)
   "Rename the current symbol to NEWNAME."