bug#46609: Fix shell password prompt in minibuffer (bug 43302)

[Ryan Prior]

The current comint-password-prompt-regexp does not tolerate newlines at
the end of the prompt, so a string like "Password:\n" will not be
recognized as a password prompt in shell-mode. Before Emacs 27
(74277b0e881) newlines were tolerated here, so this is a regression, and
as a result I would sometimes echo my password in plain text where
previously it would be hidden.

The first patch in this series updates the regexp to use the :space:
Unicode character class for trailing space characters instead of
:blank:, which includes /only/ horizontal whitespace.

The second patch updates comint-watch-for-password-prompt to trim
trailing newlines from the ~string~ argument, which avoids showing the
user a fat password prompt with newlines in the middle.

I am not a Unicode expert and don't know if there might be undesirable
side-effects from using :space: instead of :blank:. However, in my
manual testing these change give me the exact behavior I'm after.

I pair-programmed with Nick Drozd to diagnose and fix this issue. Thanks
Nick!


===File
/home/ryan/dev/emacs/patches/0001-lisp-comint.el-comint-password-prompt-regexp-Allow-e.patch===
>From 6c9aa1f08b215abfb69f4f53f622289494588eea Mon Sep 17 00:00:00 2001
From: Ryan Prior <ryanprior@hey.com>
Subject: [PATCH 1/2] lisp/comint.el (comint-password-prompt-regexp): Allow
 ending newline.

---
 lisp/comint.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/comint.el b/lisp/comint.el
index 57df6bfb19..0bc358bf51 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -378,7 +378,7 @@ This variable is buffer-local."
    "\\(?:" (regexp-opt password-word-equivalents) "\\|Response\\)"
    "\\(?:\\(?:, try\\)? *again\\| (empty for no passphrase)\\| (again)\\)?"
    ;; "[[:alpha:]]" used to be "for", which fails to match non-English.
-   "\\(?: [[:alpha:]]+ .+\\)?[[:blank:]]*[:：៖][[:blank:]]*\\'")
+   "\\(?: [[:alpha:]]+ .+\\)?[[:blank:]]*[:：៖][[:space:]]*\\'")
   "Regexp matching prompts for passwords in the inferior process.
 This is used by `comint-watch-for-password-prompt'."
   :version "27.1"
--
2.30.1

============================================================


===File
/home/ryan/dev/emacs/patches/0002-lisp-comint.el-comint-watch-for-password-prompt-Trim.patch===
>From a9260384dfc0ced53d88380724c899f295ce0944 Mon Sep 17 00:00:00 2001
From: Ryan Prior <ryanprior@hey.com>
Subject: [PATCH 2/2] lisp/comint.el (comint-watch-for-password-prompt): Trim
 trailing newline(s)

---
 lisp/comint.el | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lisp/comint.el b/lisp/comint.el
index 0bc358bf51..c2942a13da 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -2432,6 +2432,8 @@ This function could be in the list 
`comint-output-filter-functions'."
                         (replace-regexp-in-string "\r" "" string)))
     (when (string-match "^[ \n\r\t\v\f\b\a]+" string)
       (setq string (replace-match "" t t string)))
+    (when (string-match "[\n]+$" string)
+      (setq string (replace-match "" t t string)))
     (let ((comint--prompt-recursion-depth (1+ comint--prompt-recursion-depth)))
       (if (> comint--prompt-recursion-depth 10)
           (message "Password prompt recursion too deep")
--
2.30.1

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