ob-shell: Fix output containing strings matching `comint-prompt-regexp'

* lisp/ob-comint.el (org-babel-comint-wait-for-output): Do not rely on
`face-at-point' returning non-nil.
* lisp/ob-shell.el (org-babel-shell-set-prompt-commands): New constant
holding shell-specific commands to change prompt.
(org-babel-prompt-command): New variable holding command to be user to
set distinguishable prompt.
(org-babel-shell-initialize): Set `org-babel-prompt-command' according
to shell name.
(org-babel-sh-prompt): New variable holding default shell prompt.
(org-babel-sh-initiate-session): Change the default prompt to
`org-babel-sh-prompt' and alter `comint-prompt-regexp' to match it
tightly.

Fixes https://list.orgmode.org/CKK9TULBP2BG.2UITT31YJV03J@laptop/T/#mc8e3ca2f5f1b9a94040a68b4c6201234b209041c

lisp/ob-comint.el

@@ -124,9 +124,7 @@ statement (not large blocks of code)."
     (while (progn
              (goto-char comint-last-input-end)
              (not (and (re-search-forward comint-prompt-regexp nil t)
-                       (goto-char (match-beginning 0))
-                       (string= (face-name (face-at-point))
-                                "comint-highlight-prompt"))))
+                     (goto-char (match-beginning 0)))))
       (accept-process-output (get-buffer-process buffer)))))
 
 (defun org-babel-comint-eval-invisibly-and-wait-for-file

lisp/ob-shell.el

@@ -42,6 +42,23 @@
 (defvar org-babel-default-header-args:shell '())
 (defvar org-babel-shell-names)
 
+(defconst org-babel-shell-set-prompt-commands
+  '(("fish" . "function fish_prompt\n\techo \"%s\"\nend")
+    ("csh" . "set prompt=\"%s\"")
+    ("posh" . "function prompt { \"%s\" }")
+    (t . "PS1=\"%s\""))
+  "Alist assigning shells with their prompt setting command.
+
+Each element of the alist associates a shell type from
+`org-babel-shell-names' with a template used to create a command to
+change the default prompt.  The template is an argument to `format'
+that will be called with a single additional argument: prompt string.
+
+The fallback association template is defined in (t . \"template\")
+alist element.")
+
+(defvar org-babel-prompt-command)
+
 (defun org-babel-shell-initialize ()
   "Define execution functions associated to shell names.
 This function has to be called whenever `org-babel-shell-names'
@@ -51,7 +68,10 @@ is modified outside the Customize interface."
     (eval `(defun ,(intern (concat "org-babel-execute:" name))
 	       (body params)
 	     ,(format "Execute a block of %s commands with Babel." name)
-	     (let ((shell-file-name ,name))
+	     (let ((shell-file-name ,name)
+                   (org-babel-prompt-command
+                    (or (alist-get ,name org-babel-shell-set-prompt-commands)
+                        (alist-get t org-babel-shell-set-prompt-commands))))
 	       (org-babel-execute:shell body params))))
     (eval `(defalias ',(intern (concat "org-babel-variable-assignments:" name))
 	     'org-babel-variable-assignments:shell
@@ -206,6 +226,13 @@ var of the same value."
       (mapconcat echo-var var "\n"))
      (t (funcall echo-var var)))))
 
+(defvar org-babel-sh-eoe-indicator "echo 'org_babel_sh_eoe'"
+  "String to indicate that evaluation has completed.")
+(defvar org-babel-sh-eoe-output "org_babel_sh_eoe"
+  "String to indicate that evaluation has completed.")
+(defvar org-babel-sh-prompt "org_babel_sh_prompt> "
+  "String to set prompt in session shell.")
+
 (defun org-babel-sh-initiate-session (&optional session _params)
   "Initiate a session named SESSION according to PARAMS."
   (when (and session (not (string= session "none")))
@@ -213,17 +240,20 @@ var of the same value."
       (or (org-babel-comint-buffer-livep session)
           (progn
 	    (shell session)
+            ;; Set unique prompt for easier analysis of the output.
+            (org-babel-comint-wait-for-output (current-buffer))
+            (org-babel-comint-input-command
+             (current-buffer)
+             (format org-babel-prompt-command org-babel-sh-prompt))
+            (setq-local comint-prompt-regexp
+                        (concat "^" (regexp-quote org-babel-sh-prompt)
+                                " *"))
 	    ;; Needed for Emacs 23 since the marker is initially
 	    ;; undefined and the filter functions try to use it without
 	    ;; checking.
 	    (set-marker comint-last-output-start (point))
 	    (get-buffer (current-buffer)))))))
 
-(defvar org-babel-sh-eoe-indicator "echo 'org_babel_sh_eoe'"
-  "String to indicate that evaluation has completed.")
-(defvar org-babel-sh-eoe-output "org_babel_sh_eoe"
-  "String to indicate that evaluation has completed.")
-
 (defun org-babel-sh-evaluate (session body &optional params stdin cmdline)
   "Pass BODY to the Shell process in BUFFER.
 If RESULT-TYPE equals `output' then return a list of the outputs