bug#30134: ehsell and process-environment variable

bug#30134: ehsell and process-environment variable

[SK Kim]

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I found weird situation and looked into it by myself but I couldn't
solve it. so I'm writing down this mail now.

I wanted to make a new term with modifed process-environment but it
did not work properly when I make a new term from eshell buffer.  The
situation can be reproduced as below.

1) start emacs with 'emacs -Q'

2) evaluate below code in any buffer.
    (let ((process-environment (cons "TEST=1234" process-environment)))
        (make-term "test-term" "/bin/bash"))

3) moved to buffer 'test-term' and type 'echo $TEST' and you can see
   the result '1234'

Above is what I expected modified process-environment variable would
work and it actually works as I expected. However there is a condition
it doesn't work as I expected.

1) start emacs with 'emacs -Q'

2) 'M-x eshell' to open eshell buffer.

3) evaluate below code in eshell buffer.
    (let ((process-environment (cons "TEST=1234" process-environment)))
        (make-term "test-term" "/bin/bash"))

4) moved to buffer 'test-term' and type 'echo $TEST' and you can see
   nothing.

The modified process-environment variable is not properly affected if
the code is evaluated in eshell buffer. The eshell buffer is the only
buffer that I found the above code is not working properly.

This is tested on GNU Emacs 25.3.1 (x86_64-pc-linux-gnu, X toolkit,
Xaw scroll bars) of 2017-12-13

Possibly this might not be a bug and there is specific reason it works
that way but I couldn't have found any information about this and
couldn't have solved this by myself neither. So now I am sending this
bug report.

Thanks for everyone contributing to emacs. I appreciate it.

Thanks.

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bug#30134: ehsell and process-environment variable

[Eli Zaretskii]

> From: SK Kim <tttuuu888@gmail.com>
> Date: Tue, 16 Jan 2018 11:31:27 +0900
> 
> 1) start emacs with 'emacs -Q'
> 
> 2) 'M-x eshell' to open eshell buffer.
> 
> 3) evaluate below code in eshell buffer.
>     (let ((process-environment (cons "TEST=1234" process-environment)))
>         (make-term "test-term" "/bin/bash"))
> 
> 4) moved to buffer 'test-term' and type 'echo $TEST' and you can see
>    nothing.
> 
> The modified process-environment variable is not properly affected if
> the code is evaluated in eshell buffer. The eshell buffer is the only
> buffer that I found the above code is not working properly.

process-environment is for invoking other programs from Emacs.  By
contrast, Eshell does not invoke any other program, it is implemented
in Emacs itself.  And process-environment doesn't affect Emacs itself.
That is why you see the difference with other programs, in particular
shells invoked from Emacs.

bug#30134: ehsell and process-environment variable

[Eli Zaretskii]

[Please keep the bug address on the CC list.]

> From: SK Kim <tttuuu888@gmail.com>
> Date: Tue, 16 Jan 2018 16:09:17 +0900
> 
> So that means, this result is natural in Emacs and package authors
> should also avoid such a code. Is this right?

Yes, I think so.

> Maybe if I want to guarantee the code is working properly in any
> buffers of Emacs, I should wrap the code with 'with-temp-buffer' as below.
> 
> (with-temp-buffer
>   (let ((process-environment (cons "TEST=1234" process-environment)))
>     (make-term "test-term" "/bin/bash")))

Maybe.  I will take another look in a couple of days.

bug#30134: ehsell and process-environment variable

[Glenn Morris]

Eli Zaretskii wrote:

>> 2) 'M-x eshell' to open eshell buffer.
>> 
>> 3) evaluate below code in eshell buffer.
>>     (let ((process-environment (cons "TEST=1234" process-environment)))
>>         (make-term "test-term" "/bin/bash"))
>> 
>> 4) moved to buffer 'test-term' and type 'echo $TEST' and you can see
>>    nothing.
[...]
> process-environment is for invoking other programs from Emacs.  By
> contrast, Eshell does not invoke any other program, it is implemented
> in Emacs itself.  And process-environment doesn't affect Emacs itself.
> That is why you see the difference with other programs, in particular
> shells invoked from Emacs.

I don't think that's relevant to this report, where a bash shell is
being invoked, it just happens to be launched from an eshell buffer.

eshell seems to have some special handling for process-environment,
which is (presumably) the cause of this difference from other buffers.

bug#30134: ehsell and process-environment variable

[SK Kim]

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I have looked into eshell and make-term source and narrowed down the
range of the issue somewhat.

If I evaluate the test code from eshell buffer, process-environment
lose "TEST=1234" inside make-term function as below.

(defun make-term (name program &optional startfile &rest switches)
  (let ((buffer (get-buffer-create (concat "*" name "*"))))
    (cond ((not (term-check-proc buffer))
    ;; Here, process-environemnt still have "TEST=1234"
   (with-current-buffer buffer
       ;; Here, process-environemnt lost "TEST=1234"
     (term-mode))
   (term-exec buffer name program startfile switches)))
    buffer))

I still don't know why but process-environment lost some values when
creating new buffer with 'get-buffer-create' function.

You can test this as below:

1-1) emacs -Q
1-2) evaluate below code.
     (let ((process-environment (cons "TEST=1234" process-environment)))
       (get-buffer-create "test-buffer")
       (switch-to-buffer "test-buffer")
       (member "TEST=1234" process-environment))
1-3) you can see "TEST=1234" is a member of process-environment in new
buffer.

2-1) emacs -Q
2-2) M-x eshell
2-3) evaluate below code in eshell buffer.
     (let ((process-environment (cons "TEST=1234" process-environment)))
       (get-buffer-create "test-buffer")
       (switch-to-buffer "test-buffer")
       (member "TEST=1234" process-environment))
2-4) you can see "TEST=1234" is lost from process-environment.


You can also test this simply as below.

3-1) emacs -Q
3-2) M-x eshell
3-3) evaluate below code in eshell buffer.
     (let ((process-environment (cons "TEST=1234" process-environment)))
       (with-temp-buffer
         (member "TEST=1234" process-environment)))
3-4) you can see "TEST=1234" is lost from process-environment.

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bug#30134: ehsell and process-environment variable

[Glenn Morris]

[Please reply-to-all]

SK Kim wrote:

> I still don't know why but process-environment lost some values when
> creating new buffer with 'get-buffer-create' function.

Eshell makes process-environment buffer-local.

bug#30134: ehsell and process-environment variable

[Noam Postavsky]

On Thu, Jan 18, 2018 at 1:11 AM, SK Kim <tttuuu888@gmail.com> wrote:

> I still don't know why but process-environment lost some values when
> creating new buffer with 'get-buffer-create' function.

Probably because it's made into a buffer-local variable in eshell buffers:

(defun eshell-var-initialize ()
  "Initialize the variable handle code."
  ;; Break the association with our parent's environment.  Otherwise,
  ;; changing a variable will affect all of Emacs.
  (unless eshell-modify-global-environment
    (set (make-local-variable 'process-environment)
     (eshell-copy-environment)))
  [...]

bug#30134: ehsell and process-environment variable

[Glenn Morris]

Glenn Morris wrote:

> Eshell makes process-environment buffer-local.

If you repeat your experiment with

emacs -Q --eval '(setq eshell-modify-global-environment t)' -f eshell

it works as you wanted.

bug#30134: ehsell and process-environment variable

[SK Kim]

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Thank you for kind reply. I appreciate it.

2018. 1. 19. 오전 2:54에 "Glenn Morris" <rgm@gnu.org>님이 작성:

> Glenn Morris wrote:
>
> > Eshell makes process-environment buffer-local.
>
> If you repeat your experiment with
>
> emacs -Q --eval '(setq eshell-modify-global-environment t)' -f eshell
>
> it works as you wanted.
>

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