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* bug#57129: 29.0.50; Improve behavior of conditionals in Eshell
@ 2022-08-11  2:43 Jim Porter
  2022-08-11  2:46 ` Jim Porter
  0 siblings, 1 reply; 57+ messages in thread
From: Jim Porter @ 2022-08-11  2:43 UTC (permalink / raw)
  To: 57129

In Eshell, you can use conditionals pretty much like you'd expect from 
other shells. Starting from 'emacs -Q -f eshell':

   ~ $ [ foo = foo ] && echo hi
   hi
   ~ $ [ foo = bar ] && echo hi
   ~ $ [ foo = foo ] || echo hi
   ~ $ [ foo = bar ] || echo hi
   hi
   ~ $ if {[ foo = foo ]} {echo yes} {echo no}
   yes
   ~ $ if {[ foo = bar ]} {echo yes} {echo no}
   no

However, that only works for external commands. If the command is 
implemented in Lisp, it doesn't work:

   ~ $ (zerop 0) && echo hi
   t
   hi
   ~ $ (zerop 1) && echo hi
   hi  ;; Shouldn't say hi.

That's because the exit status is always 0 for Lisp commands. This works 
correctly for external commands:

   ~ $ [ foo = foo ]; echo status $? result $$
   ("status" 0 "result" nil)
   ~ $ [ foo = bar ]; echo status $? result $$
   ("status" 1 "result" nil)

But not for Lisp commands:

   ~ $ (zerop 0); echo status $? result $$
   t
   ("status" 0 "result" t)
   ~ $ (zerop 1); echo status $? result $$
   ("status" 0 "result" nil)
   ~ $ (zerop "foo"); echo status $? result $$
   Wrong type argument: number-or-marker-p, "foo"
   ("status" 0 "result" nil)

The manual says that the status should be 1 when a Lisp command fails, 
but it's 0 no matter what, even if it signaled an error. (Likewise, the 
manual says that the "result" variable should be t for successful 
external commands, but it's always nil.)

Similarly to the above, you can't use variable expansions for conditionals:

   ~ $ (setq foo t)
   t
   ~ $ if $foo {echo yes} {echo no}
   yes
   ~ $ (setq foo nil)
   ~ $ if $foo {echo yes} {echo no}
   yes  ;; Should say no.

Patch forthcoming. Just splitting it into two messages since it seemed 
more readable that way...





^ permalink raw reply	[flat|nested] 57+ messages in thread

end of thread, other threads:[~2023-03-16  5:35 UTC | newest]

Thread overview: 57+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-08-11  2:43 bug#57129: 29.0.50; Improve behavior of conditionals in Eshell Jim Porter
2022-08-11  2:46 ` Jim Porter
2022-08-12 15:22   ` Lars Ingebrigtsen
2022-08-13  5:14     ` Jim Porter
2022-08-13  7:01       ` Eli Zaretskii
2022-08-13 18:56         ` Jim Porter
2022-08-14  5:07           ` Eli Zaretskii
2022-08-14  5:37             ` Jim Porter
2022-08-14  7:30               ` Eli Zaretskii
2022-08-14 21:40                 ` Jim Porter
2022-08-15 12:13                   ` Eli Zaretskii
2022-08-15 16:14                     ` Jim Porter
2022-08-15 16:49                       ` Eli Zaretskii
2022-08-15 18:08                         ` Jim Porter
2022-08-15 18:21                           ` Eli Zaretskii
2022-08-15 18:30                             ` Jim Porter
2022-08-15 18:58                               ` Eli Zaretskii
2022-08-15 20:55                                 ` Paul Eggert
     [not found]                                 ` <af0af29b-2362-77db-081e-046158937808@cs.ucla.edu>
2022-08-15 21:22                                   ` Bruno Haible
2022-08-16 11:04                                   ` Eli Zaretskii
     [not found]                                   ` <835yish2l1.fsf@gnu.org>
2022-08-16 13:35                                     ` Bruno Haible
     [not found]                                     ` <1871347.6tgchFWduM@nimes>
2022-08-16 13:51                                       ` Eli Zaretskii
     [not found]                                       ` <838rnofgad.fsf@gnu.org>
2022-08-16 14:40                                         ` Bruno Haible
2022-08-16 16:25                                           ` Eli Zaretskii
     [not found]                                           ` <83wnb8dukz.fsf@gnu.org>
2022-08-16 16:54                                             ` Paul Eggert
     [not found]                                             ` <206e38df-2db4-a46a-e0ff-952bc8ab939c@cs.ucla.edu>
2022-08-16 17:04                                               ` Eli Zaretskii
     [not found]                                               ` <83sflwdsr2.fsf@gnu.org>
2022-08-16 17:30                                                 ` Paul Eggert
2022-08-16 17:41                                                 ` Eli Zaretskii
     [not found]                                                 ` <ceeeaa86-6199-93b1-ff65-bbd3e531e235@cs.ucla.edu>
2022-08-16 17:56                                                   ` Eli Zaretskii
2022-08-16 17:25                                             ` Paul Eggert
2022-08-16 17:29                                             ` Bruno Haible
     [not found]                                             ` <f329244a-cba7-65cd-2e5d-2630eba3e9e9@cs.ucla.edu>
2022-08-16 17:47                                               ` Eli Zaretskii
2022-08-16 19:11                                                 ` Paul Eggert
     [not found]                                                 ` <d95734ab-6bbc-7403-c1f8-fbf742badda4@cs.ucla.edu>
2022-08-16 20:12                                                   ` Bruno Haible
2022-08-17 11:08                                                   ` Eli Zaretskii
     [not found]                                                   ` <83h72bdt4z.fsf@gnu.org>
2022-08-18  6:05                                                     ` Paul Eggert
     [not found]                                                     ` <57b8f10f-8e9b-5951-e5ad-8cba2a8cb569@cs.ucla.edu>
2022-08-18  6:44                                                       ` Eli Zaretskii
     [not found]                                             ` <2594092.Isy0gbHreE@nimes>
2022-08-16 17:52                                               ` Eli Zaretskii
2022-08-16 20:06                                                 ` Bruno Haible
     [not found]                                                 ` <2606289.q0ZmV6gNhb@nimes>
2022-08-17 11:29                                                   ` Eli Zaretskii
2022-08-16 19:59                                         ` Bruno Haible
     [not found]                                         ` <2135151.C4sosBPzcN@nimes>
2022-08-16 20:53                                           ` Paul Eggert
2022-08-21 16:20                                             ` Bruno Haible
2022-08-21 16:32                                               ` Eli Zaretskii
2022-08-21 17:17                                               ` Bruno Haible
2022-08-22 20:47                                                 ` Paul Eggert
     [not found]                                                 ` <2dc7ede0-eca7-baf5-f89a-f5d292b80808@cs.ucla.edu>
2022-08-23  0:13                                                   ` Bruno Haible
     [not found]                                                   ` <3893771.2iPT33SAM4@nimes>
2022-08-23 11:18                                                     ` Eli Zaretskii
     [not found]                                                     ` <831qt79pjj.fsf@gnu.org>
2022-08-23 14:49                                                       ` Bruno Haible
2022-08-23 16:07                                                         ` Eli Zaretskii
2022-08-20 18:03                                 ` Jim Porter
2022-08-20 18:14                                   ` Eli Zaretskii
2022-08-20 18:49                                     ` Jim Porter
2022-08-24 21:41                                   ` Jim Porter
2022-08-26  5:10                                     ` Jim Porter
2023-03-16  5:35                                       ` Jim Porter
2022-08-14  5:03       ` Sean Whitton

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