Optionally allow substitution patterns in erc-prompt

* etc/ERC-NEWS: Add entry for `erc-prompt-format'.
* lisp/erc/erc-compat.el (erc-compat--defer-format-spec-in-buffer):
New macro to wrap `format-spec' specification values in functions that
run in the current buffer and fall back to the empty string.
* lisp/erc/erc.el (erc-prompt): Add predefined Custom choice for
function type in `erc-prompt-format'.
(erc--prompt-format-face-example): New "pre-propertized" value for
option `erc-prompt-format'.
(erc-prompt-format): New companion option for `erc-prompt' choice
`erc-prompt-format'.  New function of the same name to perform format
substitutions and serve as a Custom choice value for `erc-prompt'.
Based on work and ideas originally proposed by Stefan Kangas.
(erc--away-indicator, erc-away-status-indicator,
erc--format-away-indicator): New formatting function and helper
variables for displaying short away status.
(erc--user-modes-indicator): New variable.
(erc--format-user-modes): New function.
(erc--format-channel-status-prefix): New function.
(erc--format-modes): New function.
* test/lisp/erc/erc-scenarios-prompt-format.el: New file.  (Bug#51082)

Co-authored-by: Stefan Kangas <stefankangas@gmail.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/test/lisp/erc/erc-scenarios-prompt-format.el b/test/lisp/erc/erc-scenarios-prompt-format.el
new file mode 100644
index 00000000000..7eccb859dbc
--- /dev/null
+++ b/test/lisp/erc/erc-scenarios-prompt-format.el
@@ -0,0 +1,117 @@
+;;; erc-scenarios-prompt-format.el --- erc-prompt-format-mode -*- lexical-binding: t -*-
+
+;; Copyright (C) 2023 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(require 'ert-x)
+(eval-and-compile
+  (let ((load-path (cons (ert-resource-directory) load-path)))
+    (require 'erc-scenarios-common)))
+
+(defvar erc-fill-wrap-align-prompt)
+(defvar erc-fill-wrap-use-pixels)
+
+(defun erc-scenarios-prompt-format--assert (needle &rest props)
+  (save-excursion
+    (goto-char erc-insert-marker)
+    (should (search-forward needle nil t))
+    (pcase-dolist (`(,k . ,v) props)
+      (should (equal (get-text-property (point) k) v)))))
+
+;; This makes assertions about the option `erc-fill-wrap-align-prompt'
+;; as well as the standard value of `erc-prompt-format'.  One minor
+;; omission is that this doesn't check behavior in query buffers.
+(ert-deftest erc-scenarios-prompt-format ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-scenarios-common-dialog "base/modes")
+       (erc-server-flood-penalty 0.1)
+       (dumb-server (erc-d-run "localhost" t 'chan-changed))
+       (erc-modules (cons 'fill-wrap erc-modules))
+       (erc-fill-wrap-align-prompt t)
+       (erc-fill-wrap-use-pixels nil)
+       (erc-prompt #'erc-prompt-format)
+       (erc-autojoin-channels-alist '((Libera.Chat "#chan")))
+       (expect (erc-d-t-make-expecter))
+       ;; Collect samples of `line-prefix' to verify deltas as the
+       ;; prompt grows and shrinks.
+       (line-prefixes nil)
+       (stash-pfx (lambda ()
+                    (pcase (get-text-property erc-insert-marker 'line-prefix)
+                      (`(space :width (- erc-fill--wrap-value ,n))
+                       (car (push n line-prefixes)))))))
+
+    (ert-info ("Connect to Libera.Chat")
+      (with-current-buffer (erc :server "127.0.0.1"
+                                :port (process-contact dumb-server :service)
+                                :nick "tester"
+                                :full-name "tester")
+        (funcall expect 5 "Welcome to the Libera.Chat")
+        (funcall stash-pfx)
+        (funcall expect 5 "changed mode")
+        ;; New prompt is shorter than default with placeholders, like
+        ;; "(foo?)(bar?)" (assuming we win the inherent race).
+        (should (>= (car line-prefixes) (funcall stash-pfx)))
+        (erc-scenarios-prompt-format--assert "user-" '(display . ("Ziw")))))
+
+    (with-current-buffer (erc-d-t-wait-for 5 (get-buffer "#chan"))
+      (should-not erc-channel-key)
+      (should-not erc-channel-user-limit)
+
+      (ert-info ("Receive notice that mode has changed")
+        (erc-d-t-wait-for 10 (equal erc-channel-modes '("n" "t")))
+        (funcall stash-pfx)
+        (erc-scenarios-common-say "ready before")
+        (funcall expect 10 " has changed mode for #chan to +Qu")
+        (erc-d-t-wait-for 10 (equal erc-channel-modes '("Q" "n" "t" "u")))
+        ;; Prompt is longer now, so too is the `line-prefix' subtrahend.
+        (should (< (car line-prefixes) (funcall stash-pfx)))
+        (erc-scenarios-prompt-format--assert "Qntu")
+        (erc-scenarios-prompt-format--assert "#chan>"))
+
+      (ert-info ("Key stored locally")
+        (erc-scenarios-common-say "ready key")
+        (funcall expect 10 " has changed mode for #chan to +k hunter2")
+        ;; Prompt has grown by 1.
+        (should (< (car line-prefixes) (funcall stash-pfx)))
+        (erc-scenarios-prompt-format--assert "Qkntu"))
+
+      (ert-info ("Limit stored locally")
+        (erc-scenarios-common-say "ready limit")
+        (funcall expect 10 " has changed mode for #chan to +l 3")
+        (erc-d-t-wait-for 10 (eql erc-channel-user-limit 3))
+        (should (equal erc-channel-modes '("Q" "n" "t" "u")))
+        ;; Prompt has grown by 1 again.
+        (should (< (car line-prefixes) (funcall stash-pfx)))
+        (erc-scenarios-prompt-format--assert "Qklntu"))
+
+      (ert-info ("Modes removed and local state deletion succeeds")
+        (erc-scenarios-common-say "ready drop")
+        (funcall expect 10 " has changed mode for #chan to -lu")
+        (funcall expect 10 " has changed mode for #chan to -Qk *")
+        (erc-d-t-wait-for 10 (equal erc-channel-modes '("n" "t")))
+        ;; Prompt has shrunk.
+        (should (> (car line-prefixes) (funcall stash-pfx)))
+        (erc-scenarios-prompt-format--assert "nt"))
+
+      (should-not erc-channel-key)
+      (should-not erc-channel-user-limit)
+      (funcall expect 10 "<Chad> after"))))
+
+;;; erc-scenarios-prompt-format.el ends here