Respect global-eldoc-mode in minibuffers (Bug#36886)

* lisp/emacs-lisp/easy-mmode.el (define-globalized-minor-mode): Accept
a BODY parameter.
* doc/lispref/modes.texi (Defining Minor Modes): Document new
parameter.
* etc/NEWS: Announce it.

* lisp/simple.el (read--expression): Move eldoc-mode setup to...
* lisp/emacs-lisp/eldoc.el (eldoc--eval-expression-setup): ... here,
new function.
(global-eldoc-mode): Add or remove it to
eval-expression-minibuffer-setup-hook when enabling or disabling
global-eldoc-mode.  This enables eldoc in the minibuffer (solving
Bug#27202), only when global-eldoc-mode is enabled.

2 files changed, 40 insertions, 17 deletions

diff --git a/lisp/emacs-lisp/easy-mmode.el b/lisp/emacs-lisp/easy-mmode.el
index be531aab849..bbc3a27504c 100644
--- a/lisp/emacs-lisp/easy-mmode.el
+++ b/lisp/emacs-lisp/easy-mmode.el
@@ -363,18 +363,21 @@ No problems result if this variable is not bound.
 ;;;###autoload
 (defalias 'define-global-minor-mode 'define-globalized-minor-mode)
 ;;;###autoload
-(defmacro define-globalized-minor-mode (global-mode mode turn-on &rest keys)
+(defmacro define-globalized-minor-mode (global-mode mode turn-on &rest body)
   "Make a global mode GLOBAL-MODE corresponding to buffer-local minor MODE.
 TURN-ON is a function that will be called with no args in every buffer
   and that should try to turn MODE on if applicable for that buffer.
-KEYS is a list of CL-style keyword arguments.  As the minor mode
-  defined by this function is always global, any :global keyword is
-  ignored.  Other keywords have the same meaning as in `define-minor-mode',
-  which see.  In particular, :group specifies the custom group.
-  The most useful keywords are those that are passed on to the
-  `defcustom'.  It normally makes no sense to pass the :lighter
-  or :keymap keywords to `define-globalized-minor-mode', since these
-  are usually passed to the buffer-local version of the minor mode.
+Each of KEY VALUE is a pair of CL-style keyword arguments.  As
+  the minor mode defined by this function is always global, any
+  :global keyword is ignored.  Other keywords have the same
+  meaning as in `define-minor-mode', which see.  In particular,
+  :group specifies the custom group.  The most useful keywords
+  are those that are passed on to the `defcustom'.  It normally
+  makes no sense to pass the :lighter or :keymap keywords to
+  `define-globalized-minor-mode', since these are usually passed
+  to the buffer-local version of the minor mode.
+BODY contains code to execute each time the mode is enabled or disabled.
+  It is executed after toggling the mode, and before running GLOBAL-MODE-hook.
 
 If MODE's set-up depends on the major mode in effect when it was
 enabled, then disabling and reenabling MODE should make MODE work
@@ -384,7 +387,9 @@ call another major mode in their body.
 
 When a major mode is initialized, MODE is actually turned on just
 after running the major mode's hook.  However, MODE is not turned
-on if the hook has explicitly disabled it."
+on if the hook has explicitly disabled it.
+
+\(fn GLOBAL-MODE MODE TURN-ON [KEY VALUE]... BODY...)"
   (declare (doc-string 2))
   (let* ((global-mode-name (symbol-name global-mode))
 	 (mode-name (symbol-name mode))
@@ -404,12 +409,12 @@ on if the hook has explicitly disabled it."
 	 keyw)
 
     ;; Check keys.
-    (while (keywordp (setq keyw (car keys)))
-      (setq keys (cdr keys))
+    (while (keywordp (setq keyw (car body)))
+      (pop body)
       (pcase keyw
-	(:group (setq group (nconc group (list :group (pop keys)))))
-	(:global (setq keys (cdr keys)))
-	(_ (push keyw extra-keywords) (push (pop keys) extra-keywords))))
+        (:group (setq group (nconc group (list :group (pop body)))))
+        (:global (pop body))
+        (_ (push keyw extra-keywords) (push (pop body) extra-keywords))))
 
     `(progn
        (progn
@@ -446,7 +451,8 @@ See `%s' for more information on %s."
 	 ;; Go through existing buffers.
 	 (dolist (buf (buffer-list))
 	   (with-current-buffer buf
-	     (if ,global-mode (funcall #',turn-on) (when ,mode (,mode -1))))))
+             (if ,global-mode (funcall #',turn-on) (when ,mode (,mode -1)))))
+         ,@body)
 
        ;; Autoloading define-globalized-minor-mode autoloads everything
        ;; up-to-here.
diff --git a/lisp/emacs-lisp/eldoc.el b/lisp/emacs-lisp/eldoc.el
index 16b58632099..2892faae21d 100644
--- a/lisp/emacs-lisp/eldoc.el
+++ b/lisp/emacs-lisp/eldoc.el
@@ -207,7 +207,24 @@ expression point is on."
 (define-globalized-minor-mode global-eldoc-mode eldoc-mode turn-on-eldoc-mode
   :group 'eldoc
   :initialize 'custom-initialize-delay
-  :init-value t)
+  :init-value t
+  ;; For `read--expression', the usual global mode mechanism of
+  ;; `change-major-mode-hook' runs in the minibuffer before
+  ;; `eldoc-documentation-function' is set, so `turn-on-eldoc-mode'
+  ;; does nothing.  Configure and enable eldoc from
+  ;; `eval-expression-minibuffer-setup-hook' instead.
+  (if global-eldoc-mode
+      (add-hook 'eval-expression-minibuffer-setup-hook
+                #'eldoc--eval-expression-setup)
+    (remove-hook 'eval-expression-minibuffer-setup-hook
+                 #'eldoc--eval-expression-setup)))
+
+(defun eldoc--eval-expression-setup ()
+  ;; Setup `eldoc', similar to `emacs-lisp-mode'.  FIXME: Call
+  ;; `emacs-lisp-mode' itself?
+  (add-function :before-until (local 'eldoc-documentation-function)
+                #'elisp-eldoc-documentation-function)
+  (eldoc-mode +1))
 
 ;;;###autoload
 (defun turn-on-eldoc-mode ()