Simplify erc-button movement commands

* etc/ERC-NEWS: Mention TAB being bound to new command `erc-tab' and
`erc-previous-button' now stopping at the start of buttons.
* lisp/erc/erc-button.el (erc-button-mode, erc-button-enable,
erc-button-disable): Add and remove `erc-button-next' to
`erc--tab-functions' hook, which is tantamount to binding the command
in the read-only area of an ERC buffer.
(erc-button-next-function): Deprecate and remove from client code path
because this module doesn't concern itself with prompt input and thus
no longer needs to conform to the `completion-at-point-functions'
interface.
(erc-button--prev-next-predicate-functions): New variable, a hook to
determine whether to continue searching for a button.  Other modules
should utilize this as needed.
(erc-button--end-of-button-p): Add function to serve as default value
for `erc-button--continue-predicate'.
(erc--button-next): Add generalized button-movement function.
(erc-button-next, erc-button-previous): Make `erc-button-previous'
behave more predictably by having it land at the beginning of buttons.
And remove roundabout appeal to HOF in `erc-button-next'.
(erc-button-previous-of-nick): New command to jump to previous
appearance of nick at point.
* lisp/erc/erc-fill.el (erc-fill-wrap, erc-fill-wrap-enable,
erc-fill-wrap-disable): Add and remove merge-related hookee from
`erc-button--prev-next-predicate-functions'.
(erc-fill--wrap-merged-button-p): New function to detect redundant
speakers.
* lisp/erc/erc.el (erc-complete-functions): Quote TAB in doc string.
(erc-mode-map): Bind `erc-tab' to TAB.
(erc--tab-functions, erc-tab): Add new command and hook to serve as
unified dispatch for TAB-related operations.  It calls `c-a-p' in the
input area and defers to module code in the read-only message area.
* test/lisp/erc/erc-button-tests.el: New file.
* test/lisp/erc/erc-fill-tests.el (erc-fill-tests--wrap-populate): Run
finalizer for transient keymap timer.
* test/lisp/erc/erc-tests.el
(erc-button--display-error-notice-with-keys): Move to new dedicated
test file for erc-button and fix expected behavior of
`erc-button-previous'.  (Bug#62834)

1 files changed, 15 insertions, 2 deletions

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 05b6b5bfd21..a439e2438b0 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -354,7 +354,7 @@ simply because we do not necessarily receive the QUIT event."
   :type 'hook)
 
 (defcustom erc-complete-functions nil
-  "These functions get called when the user hits TAB in ERC.
+  "These functions get called when the user hits \\`TAB' in ERC.
 Each function in turn is called until one returns non-nil to
 indicate it has handled the input."
   :group 'erc-hooks
@@ -1231,7 +1231,7 @@ which the local user typed."
     (define-key map "\C-c\C-u" #'erc-kill-input)
     (define-key map "\C-c\C-x" #'erc-quit-server)
     (define-key map "\M-\t" #'ispell-complete-word)
-    (define-key map "\t" #'completion-at-point)
+    (define-key map "\t" #'erc-tab)
 
     ;; Suppress `font-lock-fontify-block' key binding since it
     ;; destroys face properties.
@@ -4675,6 +4675,19 @@ This places `point' just after the prompt, or at the beginning of the line."
         (setq erc-input-ring-index nil))
     (kill-line)))
 
+(defvar erc--tab-functions nil
+  "Functions to try when user hits \\`TAB' outside of input area.
+Called with a numeric prefix arg.")
+
+(defun erc-tab (&optional arg)
+  "Call `completion-at-point' when typing in the input area.
+Otherwise call members of `erc--tab-functions' with raw prefix
+ARG until one of them returns non-nil."
+  (interactive "P")
+  (if (>= (point) erc-input-marker)
+      (completion-at-point)
+    (run-hook-with-args-until-success 'erc--tab-functions arg)))
+
 (defun erc-complete-word-at-point ()
   (run-hook-with-args-until-success 'erc-complete-functions))