Fix a race condition when evaluating Eshell commands

* lisp/eshell/esh-cmd.el (eshell-do-eval): Don't defer when all the
processes are done.

* test/lisp/eshell/esh-cmd-tests.el
(esh-cmd-test/pipeline-wait/nested-pipes): New test.

2 files changed, 16 insertions, 2 deletions

diff --git a/lisp/eshell/esh-cmd.el b/lisp/eshell/esh-cmd.el
index dae1a77552f..57aeff59266 100644
--- a/lisp/eshell/esh-cmd.el
+++ b/lisp/eshell/esh-cmd.el
@@ -1287,13 +1287,15 @@ have been replaced by constants."
                     (setcdr form (cdr new-form)))
                   (eshell-do-eval form synchronous-p))
               (if-let (((memq (car form) eshell-deferrable-commands))
-                       (procs (eshell-make-process-list result)))
+                       (procs (eshell-make-process-list result))
+                       (active (seq-some #'eshell-process-active-p procs)))
                   (if synchronous-p
                       (apply #'eshell/wait procs)
                     (eshell-manipulate form "inserting ignore form"
                       (setcar form 'ignore)
                       (setcdr form nil))
-                    (throw 'eshell-defer procs))
+                    (when active
+                      (throw 'eshell-defer procs)))
                 (list 'quote result))))))))))))
 
 ;; command invocation
diff --git a/test/lisp/eshell/esh-cmd-tests.el b/test/lisp/eshell/esh-cmd-tests.el
index ef965a896c1..d84f8802bdc 100644
--- a/test/lisp/eshell/esh-cmd-tests.el
+++ b/test/lisp/eshell/esh-cmd-tests.el
@@ -213,6 +213,18 @@ This should also wait for the subcommand."
    (eshell-match-command-output "echo ${*echo hi | *cat} | *cat"
                                 "hi")))
 
+(ert-deftest esh-cmd-test/pipeline-wait/nested-pipes ()
+  "Check that piping a subcommand with its own pipe works.
+This should also wait for the subcommand."
+  (skip-unless (and (executable-find "echo")
+                    (executable-find "cat")
+                    (executable-find "sh")
+                    (executable-find "sleep")))
+  (with-temp-eshell
+    (eshell-match-command-output
+     "{ sh -c 'sleep 1; echo goodbye 1>&2' | *echo hello } | *cat"
+     "hello\ngoodbye\n")))
+
 (ert-deftest esh-cmd-test/reset-in-pipeline/subcommand ()
   "Check that subcommands reset `eshell-in-pipeline-p'."
   (skip-unless (executable-find "cat"))