bug#65604: [PATCH] Display the exit code if the last command failed in Eshell

[Davide Masserut via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Jim Porter <jporterbugs@gmail.com> writes:

>> 2) It may require to update the regexp.
>
> The prompt regexp is (thankfully) almost irrelevant in Emacs 30
> now. It only matters for paragraph-movement commands, which we 
> could
> probably just remap to the actual Eshell-specific commands to 
> navigate
> forward and backward through the prompts. I should probably just 
> make
> a patch for this and finally get rid of that regexp entirely.

I didn't know that, thanks.

>> In this case I would add a small delay before signaling that
>> something is running.
>
> The delay isn't present in the current Eshell mode-line
> implementation, and I don't think anyone's raised an issue about
> that...

Sorry, I meant that if we decided to show a relative long message 
like "Running" in the mode-line, then we should show it only when 
it lasts for more than, let's say, 0.5s.  This would prevent the 
mode-line from moving to right for just a fraction of a second 
when running fast commands like cd or ls.

> ... in any case, maybe the simplest way forward here is to put 
> the
> (non-zero) exit status in the prompt like your original patch, 
> and
> then separately, I can try to improve the customizability of the
> prompt, as well as thinking about what to do with the mode-line.

I have updated the patch.


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From 83f716950a60ee64c49654033430f8e09d373f24 Mon Sep 17 00:00:00 2001
From: Davide Masserut <dm@mssdvd.com>
Date: Tue, 29 Aug 2023 22:33:48 +0200
Subject: [PATCH] Display the exit code if the last command failed in Eshell

* doc/misc/eshell.texi (Invocation): Document change.
* etc/NEWS: Announce change.
* lisp/eshell/em-prompt.el (eshell-prompt-function): Insert the exit
code if last command failed.
* lisp/eshell/esh-io.el (eshell-last-command-status): Make it
buffer-local.
* test/lisp/eshell/em-prompt-tests.el (em-prompt-test/after-failure)
(em-prompt-test/next-previous-prompt-with)
(em-prompt-test/forward-backward-matching-input-with): New tests.
---
 doc/misc/eshell.texi                |  3 +++
 etc/NEWS                            |  3 +++
 lisp/eshell/em-prompt.el            |  2 ++
 lisp/eshell/esh-io.el               |  2 +-
 test/lisp/eshell/em-prompt-tests.el | 37 +++++++++++++++++++++++++----
 5 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/doc/misc/eshell.texi b/doc/misc/eshell.texi
index 7a563bc794c..677bd0f3e3e 100644
--- a/doc/misc/eshell.texi
+++ b/doc/misc/eshell.texi
@@ -234,6 +234,9 @@ Invocation
 can be controlled the same way as any other background process in
 Emacs.
 
+If a command exits abnormally, Eshell displays the command's exit code
+in the prompt.
+
 @subsection Command form
 Command form looks much the same as in other shells.  A command
 consists of arguments separated by spaces; the first argument is the
diff --git a/etc/NEWS b/etc/NEWS
index 5c11b6b9ac7..7a9010a2a9a 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -370,6 +370,9 @@ to load the edited aliases.
 Running 'rgrep' in Eshell now uses the Emacs grep facility instead of
 calling external rgrep.
 
++++
+*** If a command exits abnormally, Eshell now displays the command's exit code in the prompt.
+
 ** Pcomplete
 
 ---
diff --git a/lisp/eshell/em-prompt.el b/lisp/eshell/em-prompt.el
index 42f8f273b52..692b579d02d 100644
--- a/lisp/eshell/em-prompt.el
+++ b/lisp/eshell/em-prompt.el
@@ -50,6 +50,8 @@ eshell-prompt-load-hook
 (defcustom eshell-prompt-function
   (lambda ()
     (concat (abbreviate-file-name (eshell/pwd))
+            (unless (eshell-exit-success-p)
+              (format " [%d]" eshell-last-command-status))
             (if (= (file-user-uid) 0) " # " " $ ")))
   "A function that returns the Eshell prompt string.
 Make sure to update `eshell-prompt-regexp' so that it will match your
diff --git a/lisp/eshell/esh-io.el b/lisp/eshell/esh-io.el
index c07f871dd37..cd0cee6e21d 100644
--- a/lisp/eshell/esh-io.el
+++ b/lisp/eshell/esh-io.el
@@ -170,7 +170,7 @@ eshell-redirection-operators-alist
 
 (defvar eshell-current-handles nil)
 
-(defvar eshell-last-command-status 0
+(defvar-local eshell-last-command-status 0
   "The exit code from the last command.  0 if successful.")
 
 (defvar eshell-last-command-result nil
diff --git a/test/lisp/eshell/em-prompt-tests.el b/test/lisp/eshell/em-prompt-tests.el
index 93bf9d84ab3..c90f417cefd 100644
--- a/test/lisp/eshell/em-prompt-tests.el
+++ b/test/lisp/eshell/em-prompt-tests.el
@@ -34,6 +34,25 @@
 
 ;;; Tests:
 
+(ert-deftest em-prompt-test/after-failure ()
+  "Check that current prompt shows the exit code of the last failed command."
+  (with-temp-eshell
+   (let ((debug-on-error nil))
+     (eshell-insert-command "(zerop \"foo\")"))
+   (let ((current-prompt (field-string (1- (point)))))
+     (should (equal-including-properties
+              current-prompt
+              (propertize
+               (concat (directory-file-name default-directory)
+                       (unless (eshell-exit-success-p)
+                         (format " [%d]" eshell-last-command-status))
+                       (if (= (file-user-uid) 0) " # " " $ "))
+               'read-only t
+               'field 'prompt
+               'font-lock-face 'eshell-prompt
+               'front-sticky '(read-only field font-lock-face)
+               'rear-nonsticky '(read-only field font-lock-face)))))))
+
 (ert-deftest em-prompt-test/field-properties ()
   "Check that field properties are properly set on Eshell output/prompts."
   (with-temp-eshell
@@ -88,6 +107,8 @@ em-prompt-test--with-multiline
 (defun em-prompt-test/next-previous-prompt-with ()
   "Helper for checking forward/backward navigation of old prompts."
   (with-temp-eshell
+   (let ((debug-on-error nil))
+     (eshell-insert-command "(zerop \"foo\")")) ; A failed command.
    (eshell-insert-command "echo one")
    (eshell-insert-command "echo two")
    (eshell-insert-command "echo three")
@@ -99,8 +120,11 @@ em-prompt-test/next-previous-prompt-with
    (end-of-line)
    (eshell-previous-prompt 2)
    (should (equal (eshell-get-old-input) "echo one"))
-   ;; Go forward three prompts.
-   (eshell-next-prompt 3)
+   ;; Go back one prompt.
+   (eshell-previous-prompt 1)
+   (should (equal (eshell-get-old-input) "(zerop \"foo\")"))
+   ;; Go forward four prompts.
+   (eshell-next-prompt 4)
    (should (equal (eshell-get-old-input) "echo fou"))))
 
 (ert-deftest em-prompt-test/next-previous-prompt ()
@@ -115,6 +139,8 @@ em-prompt-test/next-previous-prompt-multiline
 (defun em-prompt-test/forward-backward-matching-input-with ()
   "Helper for checking forward/backward navigation via regexps."
   (with-temp-eshell
+   (let ((debug-on-error nil))
+     (eshell-insert-command "(zerop \"foo\")")) ; A failed command.
    (eshell-insert-command "echo one")
    (eshell-insert-command "printnl something else")
    (eshell-insert-command "echo two")
@@ -127,8 +153,11 @@ em-prompt-test/forward-backward-matching-input-with
    (end-of-line)
    (eshell-backward-matching-input "echo" 2)
    (should (equal (eshell-get-old-input) "echo one"))
-   ;; Go forward three prompts.
-   (eshell-forward-matching-input "echo" 3)
+   ;; Go back one prompt.
+   (eshell-previous-prompt 1)
+   (should (equal (eshell-get-old-input) "(zerop \"foo\")"))
+   ;; Go forward four prompts.
+   (eshell-forward-matching-input "echo" 4)
    (should (equal (eshell-get-old-input) "echo fou"))))
 
 (ert-deftest em-prompt-test/forward-backward-matching-input ()
-- 
2.42.0