ElDoc: make eldoc-display-in-echo-are useful from M-x eldoc

M-x eldoc is ElDoc's interactive entry point for on-demand
documentation for users that don't want the behind-the-scenes idle
timer behaviour.

However, eldoc-display-in-echo-area, a member of
eldoc-display-functions, refused to do anything because it thought it
didn't have permission to use the echo area, which isn't true
in interactive use cases.  Fix that.

See also: https://github.com/joaotavora/eglot/discussions/1328

* lisp/emacs-lisp/eldoc.el (eldoc-display-in-echo-area): Use
INTERACTIVE argument.  Rework comments.
(Version): Bump to 1.15.0

1 files changed, 18 insertions, 14 deletions

diff --git a/lisp/emacs-lisp/eldoc.el b/lisp/emacs-lisp/eldoc.el
index 22144ed7c18..e28d73c3555 100644
--- a/lisp/emacs-lisp/eldoc.el
+++ b/lisp/emacs-lisp/eldoc.el
@@ -5,7 +5,7 @@
 ;; Author: Noah Friedman <friedman@splode.com>
 ;; Keywords: extensions
 ;; Created: 1995-10-06
-;; Version: 1.14.0
+;; Version: 1.15.0
 ;; Package-Requires: ((emacs "26.3"))
 
 ;; This is a GNU ELPA :core package.  Avoid functionality that is not
@@ -605,25 +605,29 @@ known to be truncated."
                     'maybe)))
        (get-buffer-window eldoc--doc-buffer t)))
 
-(defun eldoc-display-in-echo-area (docs _interactive)
+(defun eldoc-display-in-echo-area (docs interactive)
   "Display DOCS in echo area.
-Honor `eldoc-echo-area-use-multiline-p' and
+INTERACTIVE is non-nil if user explictly invoked ElDoc.  Honor
+`eldoc-echo-area-use-multiline-p' and
 `eldoc-echo-area-prefer-doc-buffer'."
   (cond
-   (;; Check if we have permission to mess with echo area at all.  For
-    ;; example, if this-command is non-nil while running via an idle
-    ;; timer, we're still in the middle of executing a command, e.g. a
-    ;; query-replace where it would be annoying to overwrite the echo
-    ;; area.
-    (or
-     (not (eldoc-display-message-no-interference-p))
-     this-command
-     (not (eldoc--message-command-p last-command))))
-   (;; If we do but nothing to report, clear the echo area.
+   ((and (not interactive)
+         ;; When called non-interactively, check if we have permission
+         ;; to mess with echo area at all.  For example, if
+         ;; this-command is non-nil while running via an idle timer,
+         ;; we're still in the middle of executing a command, e.g. a
+         ;; query-replace where it would be annoying to overwrite the
+         ;; echo area.
+         (or
+          (not (eldoc-display-message-no-interference-p))
+          this-command
+          (not (eldoc--message-command-p last-command)))))
+   (;; If nothing to report, clear the echo area.
     (null docs)
     (eldoc--message nil))
    (t
-    ;; Otherwise, establish some parameters.
+    ;; Otherwise, proceed to change the echo area.  Start by
+    ;; establishing some parameters.
     (let*
         ((width (1- (window-width (minibuffer-window))))
          (val (if (and (symbolp eldoc-echo-area-use-multiline-p)