Re: [PATCH v3] RFC: eldoc-documentation-functions hook

[Mark Oteiza <mvoteiza@udel.edu>]

---
On 13/06/16 at 05:17pm, Mark Oteiza wrote:
> On 12/06/16 at 02:24pm, Mark Oteiza wrote:
> > On 12/06/16 at 10:09am, Eli Zaretskii wrote:
> > > > Date: Sun, 12 Jun 2016 02:12:29 -0400
> > > > From: Mark Oteiza <mvoteiza@udel.edu>
> > > > 
> > > > This is a draft patch changing eldoc-documentation-function into a hook
> > > > variable, so instead of using add-function, one can instead use add-hook
> > > > to control the behavior of eldoc.  It is backwards compatible.
> > > 
> > > Thanks.  Please be sure to update the ELisp manual accordingly.
> > 
> > <snip> changed the default value back to nil, since this isn't being
> > unconditionally funcall'd anymore.
> 
> Ah, this was a mistake wrt backwards compatibility.  The default can be
> changed sometime in the future, I suppose.
> 
> Also had to fix eldoc-supported-p...
> 
> > In the manual, it appears that the -functions suffix is to be used for
> > abnormal hooks; however this is a normal hook, so it would seem the name
> > should use the -hook suffix.
> 
> ... but I'll wait for some judgement on this before sending another
> patch.

Nevermind, I missed the part of the manual that says -functions is used
when a hooks result is used.

Here is the patch that I have been using.  No problems encountered.

diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi
index 7b76e6a..b5d07da 100644
--- a/doc/lispref/modes.texi
+++ b/doc/lispref/modes.texi
@@ -417,7 +417,7 @@ Major Mode Conventions
 
 @item
 The mode can specify a local value for
-@code{eldoc-documentation-function} to tell ElDoc mode how to handle
+@code{eldoc-documentation-functions} to tell ElDoc mode how to handle
 this mode.
 
 @item
diff --git a/etc/NEWS b/etc/NEWS
index e2c99a1..92bf8e4 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -212,6 +212,11 @@ viewing HTML files and the like.
 breakpoint (e.g. with "f" and "o") by customizing the new option
 'edebug-sit-on-break'.
 
+** ElDoc
+
++++
+*** 'eldoc-documentation-functions' replaces 'eldoc-documentation-function'.
+
 ** eww
 
 +++
diff --git a/lisp/emacs-lisp/eldoc.el b/lisp/emacs-lisp/eldoc.el
index 6c2f869..67d0a9e 100644
--- a/lisp/emacs-lisp/eldoc.el
+++ b/lisp/emacs-lisp/eldoc.el
@@ -43,7 +43,7 @@
 
 ;; Major modes for other languages may use ElDoc by defining an
 ;; appropriate function as the buffer-local value of
-;; `eldoc-documentation-function'.
+;; `eldoc-documentation-functions'.
 
 ;;; Code:
 
@@ -80,7 +80,7 @@ eldoc-argument-case
 returns another string is acceptable.
 
 Note that this variable has no effect, unless
-`eldoc-documentation-function' handles it explicitly."
+`eldoc-documentation-functions' handle it explicitly."
   :type '(radio (function-item upcase)
 		(function-item downcase)
                 function)
@@ -103,7 +103,7 @@ eldoc-echo-area-use-multiline-p
 truncated to make more of the arglist or documentation string visible.
 
 Note that this variable has no effect, unless
-`eldoc-documentation-function' handles it explicitly."
+`eldoc-documentation-functions' handle it explicitly."
   :type '(radio (const :tag "Always" t)
                 (const :tag "Never" nil)
                 (const :tag "Yes, but truncate symbol names if it will\
@@ -113,8 +113,8 @@ eldoc-echo-area-use-multiline-p
 (defface eldoc-highlight-function-argument
   '((t (:inherit bold)))
   "Face used for the argument at point in a function's argument list.
-Note that this face has no effect unless the `eldoc-documentation-function'
-handles it explicitly."
+Note that this face has no effect unless the `eldoc-documentation-functions'
+handle it explicitly."
   :group 'eldoc)
 
 ;;; No user options below here.
@@ -186,7 +186,7 @@ eldoc-mode
   :group 'eldoc :lighter eldoc-minor-mode-string
   (setq eldoc-last-message nil)
   (cond
-   ((memq eldoc-documentation-function '(nil ignore))
+   ((not (eldoc-supported-p))
     (message "There is no ElDoc support in this buffer")
     (setq eldoc-mode nil))
    (eldoc-mode
@@ -211,7 +211,7 @@ global-eldoc-mode
 
 If Global Eldoc mode is on, `eldoc-mode' will be enabled in all
 buffers where it's applicable.  These are buffers that have modes
-that have enabled eldoc support.  See `eldoc-documentation-function'."
+that have enabled eldoc support.  See `eldoc-documentation-functions'."
   :group 'eldoc
   :global t
   :initialize 'custom-initialize-delay
@@ -236,9 +236,7 @@ eldoc-schedule-timer
 	     eldoc-idle-delay nil
 	     (lambda ()
                (when (or eldoc-mode
-                         (and global-eldoc-mode
-                              (not (memq eldoc-documentation-function
-                                         '(nil ignore)))))
+                         (and global-eldoc-mode (eldoc-supported-p)))
                  (eldoc-print-current-symbol-info))))))
 
   ;; If user has changed the idle delay, update the timer.
@@ -334,26 +332,29 @@ eldoc-display-message-no-interference-p
 
 \f
 ;;;###autoload
-(defvar eldoc-documentation-function #'ignore
-  "Function to call to return doc string.
-The function of no args should return a one-line string for displaying
-doc about a function etc. appropriate to the context around point.
-It should return nil if there's no doc appropriate for the context.
-Typically doc is returned if point is on a function-like name or in its
-arg list.
+(defvar eldoc-documentation-functions #'ignore
+  "Hook to run to obtain doc string.
+Each element of this variable should be a function of no args
+that returns a one-line string for displaying doc about a
+function etc. appropriate to the context around point.  It should
+return nil if there is no doc appropriate for the context.
+Typically, doc is returned if point is on a function-like name or
+in its arg list.
 
 The result is used as is, so the function must explicitly handle
 the variables `eldoc-argument-case' and `eldoc-echo-area-use-multiline-p',
 and the face `eldoc-highlight-function-argument', if they are to have any
 effect.
 
-Major modes should modify this variable using `add-function', for example:
-  (add-function :before-until (local \\='eldoc-documentation-function)
-                #\\='foo-mode-eldoc-function)
+Major modes should modify this variable using `add-hook', for example:
+  (add-hook \\='eldoc-documentation-functions #\\='foo-eldoc nil t)
 so that the global documentation function (i.e. the default value of the
 variable) is taken into account if the major mode specific function does not
 return any documentation.")
 
+(define-obsolete-variable-alias 'eldoc-documentation-function
+  'eldoc-documentation-functions "25.2")
+
 (defun eldoc-print-current-symbol-info ()
   ;; This is run from post-command-hook or some idle timer thing,
   ;; so we need to be careful that errors aren't ignored.
@@ -363,7 +364,20 @@ eldoc-print-current-symbol-info
              (when eldoc-last-message
                (eldoc-message nil)
                nil))
-	 (eldoc-message (funcall eldoc-documentation-function)))))
+	 (eldoc-message
+          (run-hook-with-args-until-success 'eldoc-documentation-functions)))))
+
+(defun eldoc-supported-p ()
+  "Return t if `eldoc-documentation-functions' has non-null elements."
+  (if (listp eldoc-documentation-functions)
+      (catch :eldoc-supported
+        (mapc
+         (lambda (fun)
+           (when (not (memq fun '(nil ignore)))
+             (throw :eldoc-supported t)))
+         eldoc-documentation-functions)
+        nil)
+    (not (memq eldoc-documentation-functions '(nil ignore)))))
 
 ;; If the entire line cannot fit in the echo area, the symbol name may be
 ;; truncated or eliminated entirely from the output to make room for the