Add option to disable help completion autoloading (Bug#28607)

* lisp/help-fns.el (help-enable-completion-auto-load): New option.
(help--symbol-completion-table): Consult it.
* doc/emacs/building.texi (Lisp Libraries): Document it.
* etc/NEWS: Announce it.
* doc/lispref/loading.texi (Autoload by Prefix): New section.
(Autoload): Reference it.

diff --git a/doc/emacs/building.texi b/doc/emacs/building.texi
index 31acfc827bf00390ffc31b6bb7f0afbd6072314e..246a04c28246962930be5d06f8c2bae7b11ba3e9 100644 (file)
--- a/doc/emacs/building.texi
+++ b/doc/emacs/building.texi
@@ -1499,6 +1499,12 @@ library lets Emacs properly set up the hyperlinks in the @file{*Help*}
 buffer).  To disable this feature, change the variable
 @code{help-enable-auto-load} to @code{nil}.
 
+@vindex help-enable-completion-auto-load
+Automatic loading also occurs when completing names for
+@code{describe-variable} and @code{describe-function}, based on the
+prefix being completed.  To disable this feature, change the variable
+@code{help-enable-completion-auto-load} to @code{nil}.
+
 @vindex load-dangerous-libraries
 @cindex Lisp files byte-compiled by XEmacs
   By default, Emacs refuses to load compiled Lisp files which were

diff --git a/doc/lispref/loading.texi b/doc/lispref/loading.texi
index f0cc689d1f6ee7a4c904605811914ddaae8f3e32..fa6b301bb0f9a8096260b7f15c0b7a733bbc6b6c 100644 (file)
--- a/doc/lispref/loading.texi
+++ b/doc/lispref/loading.texi
@@ -466,9 +466,11 @@ first call to the function automatically loads the proper library, in
 order to install the real definition and other associated code, then
 runs the real definition as if it had been loaded all along.
 Autoloading can also be triggered by looking up the documentation of
-the function or macro (@pxref{Documentation Basics}).
+the function or macro (@pxref{Documentation Basics}), and completion
+of variable and function names (@pxref{Autoload by Prefix} below).
 
 @menu
+* Autoload by Prefix:: Autoload by Prefix.
 * When to Autoload::   When to Use Autoload.
 @end menu
 
@@ -703,6 +705,25 @@ symbol's new function value.  If the value of the optional argument
 function, only a macro.
 @end defun
 
+@node Autoload by Prefix
+@subsection Autoload by Prefix
+@cindex autoload by prefix
+
+@vindex definition-prefixes
+@findex register-definition-prefixes
+@vindex autoload-compute-prefixes
+During completion for the commands @code{describe-variable} and
+@code{describe-function}, Emacs will try to load files which may
+contain definitions matching the prefix being completed.  The variable
+@code{definition-prefixes} holds a hashtable which maps a prefix to
+the corresponding list of files to load for it.  Entries to this
+mapping are added by calls to @code{register-definition-prefixes}
+which are generated by @code{update-file-autoloads}
+(@pxref{Autoload}).  Files which don't contain any definitions worth
+loading (test files, for examples), should set
+@code{autoload-compute-prefixes} to @code{nil} as a file-local
+variable.
+
 @node When to Autoload
 @subsection When to Use Autoload
 @cindex autoload, when to use

diff --git a/etc/NEWS b/etc/NEWS
index 573c8236b23c1c55d261c170f4c3ae1d3dd184c6..1b668628413dde17c92f1d2097945ba44aa2471d 100644 (file)
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -24,6 +24,12 @@ with a prefix argument or by typing 'C-u C-h C-n'.
 \f
 * Changes in Emacs 26.3
 
++++
+** New option 'help-enable-completion-auto-load'.
+This allows disabling the new feature introduced in Emacs 26.1 which
+loads files during completion of 'C-h f' and 'C-h v' according to
+'definition-prefixes'.
+
 \f
 * Editing Changes in Emacs 26.3
 

diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index a7812e3b4b5b1f52621695a19236f3a29762064d..8684a853af2967a177b4d4a5d65128fe9d57b66c 100644 (file)
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -89,11 +89,23 @@ The functions will receive the function name as argument.")
       (unless (help--loaded-p file)
         (load file 'noerror 'nomessage)))))
 
+(defcustom help-enable-completion-auto-load t
+  "Whether completion for Help commands can perform autoloading.
+If non-nil, whenever invoking completion for `describe-function'
+or `describe-variable' load files that might contain definitions
+with the current prefix.  The files are chosen according to
+`definition-prefixes'."
+  :type 'boolean
+  :group 'help
+  :version "26.3")
+
 (defun help--symbol-completion-table (string pred action)
-  (let ((prefixes (radix-tree-prefixes (help-definition-prefixes) string)))
-    (help--load-prefixes prefixes))
+  (when help-enable-completion-auto-load
+    (let ((prefixes (radix-tree-prefixes (help-definition-prefixes) string)))
+      (help--load-prefixes prefixes)))
   (let ((prefix-completions
-         (mapcar #'intern (all-completions string definition-prefixes))))
+         (and help-enable-completion-auto-load
+              (mapcar #'intern (all-completions string definition-prefixes)))))
     (complete-with-action action obarray string
                           (if pred (lambda (sym)
                                      (or (funcall pred sym)