Handle 'eshell-pipe-broken' when evaluating Lisp forms in Eshell

* lisp/eshell/esh-cmd.el (eshell-exec-lisp): Handle
'eshell-pipe-broken'.

* lisp/eshell/esh-io.el (eshell-output-object-to-target): Only signal
'eshell-pipe-broken' if the process being written to has finished.

* test/lisp/eshell/esh-proc-tests.el
(esh-proc-test/pipeline-connection-type/middle)
(esh-proc-test/pipeline-connection-type/last): Remove ':unstable'.

Ref: https://lists.gnu.org/archive/html/emacs-devel/2022-08/msg00524.html

lisp/eshell/esh-cmd.el

@@ -1347,6 +1347,15 @@ case."
                  (apply func-or-form args)))))
         (and result (funcall printer result))
         result)
+    (eshell-pipe-broken
+     ;; If FUNC-OR-FORM tried and failed to write some output to a
+     ;; process, it will raise an `eshell-pipe-broken' signal (this is
+     ;; analogous to SIGPIPE on POSIX systems).  In this case, set the
+     ;; command status to some non-zero value to indicate an error; to
+     ;; match GNU/Linux, we use 141, which the numeric value of
+     ;; SIGPIPE on GNU/Linux (13) with the high bit (2^7) set.
+     (setq eshell-last-command-status 141)
+     nil)
     (error
      (setq eshell-last-command-status 1)
      (let ((msg (error-message-string err)))

lisp/eshell/esh-io.el

@@ -498,10 +498,16 @@ Returns what was actually sent, or nil if nothing was sent."
    ((eshell-processp target)
     (unless (stringp object)
       (setq object (eshell-stringify object)))
-    (condition-case nil
+    (condition-case err
         (process-send-string target object)
-      ;; If `process-send-string' raises an error, treat it as a broken pipe.
-      (error (signal 'eshell-pipe-broken (list target)))))
+      (error
+       ;; If `process-send-string' raises an error and the process has
+       ;; finished, treat it as a broken pipe.  Otherwise, just
+       ;; re-throw the signal.
+       (if (memq (process-status target)
+		 '(run stop open closed))
+           (signal (car err) (cdr err))
+         (signal 'eshell-pipe-broken (list target))))))
 
    ((consp target)
     (apply (car target) object (cdr target))))

test/lisp/eshell/esh-proc-tests.el

@@ -74,8 +74,6 @@
 (ert-deftest esh-proc-test/pipeline-connection-type/middle ()
   "Test that all streams are pipes when a command is in the middle of a
 pipeline."
-  ;; Repeated unreproducible errors.
-  :tags '(:unstable)
   (skip-unless (and (executable-find "sh")
                     (executable-find "cat")))
   (eshell-command-result-equal
@@ -84,8 +82,6 @@ pipeline."
 
 (ert-deftest esh-proc-test/pipeline-connection-type/last ()
   "Test that only output streams are PTYs when a command ends a pipeline."
-  ;; Repeated unreproducible errors.
-  :tags '(:unstable)
   (skip-unless (executable-find "sh"))
   (eshell-command-result-equal
    (concat "echo | " esh-proc-test--detect-pty-cmd)