prompt_pwd: strip control characters

If a directory has a control sequence in it, then prompt_pwd (used in
the default prompt) would emit it to the console, which could cause
the terminal to interpret the escape sequence.

Strip control sequences from within prompt_pwd, in the same way as
we do in __fish_paste.fish, to sanitize it.

Closes #12629

CHANGELOG.rst

@@ -17,6 +17,7 @@ Other improvements
 ------------------
 - History is no longer corrupted with NUL bytes when fish receives SIGTERM or SIGHUP (:issue:`10300`).
 - ``fish_update_completions`` now handles groff ``\X'...'`` device control escapes, fixing completion generation for man pages produced by help2man 1.50 and later (such as coreutils 9.10).
+- ``prompt_pwd`` now strips control characters.
 
 For distributors and developers
 -------------------------------

share/functions/prompt_pwd.fish

@@ -26,7 +26,8 @@ function prompt_pwd --description 'short CWD for the prompt'
     or set -l fish_prompt_pwd_full_dirs 1
 
     for path in $argv
-        set -l tmp (__fish_unexpand_tilde $path)
+        # Strip control characters to avoid injecting terminal escape sequences into the prompt.
+        set -l tmp (__fish_unexpand_tilde $path | string replace -ra '[[:cntrl:]]' '')
 
         if test "$fish_prompt_pwd_dir_length" -eq 0
             echo $tmp

tests/checks/prompt.fish

@@ -14,3 +14,7 @@ prompt_pwd -D 0 /usr/share/fish/prompts
 
 prompt_pwd -d1 -D 3 /usr/local/share/fish/prompts
 # CHECK: /u/l/share/fish/prompts
+
+# Ensure control characters in paths are stripped
+prompt_pwd -d 0 /foo/(printf '\e]0;OHNO\a')bar
+# CHECK: /foo/]0;OHNObar