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Re: [O] ob-python newline & indentation behavior

From: Kyle Meyer
Subject: Re: [O] ob-python newline & indentation behavior
Date: Mon, 20 Nov 2017 01:25:31 -0500

Jack Kamm <address@hidden> writes:

> Here is the new version of the patch:

I haven't had any luck applying this patch to master.  Perhaps your
email client is altering the inline patch; you can instead attach the
output file of 'git format-patch'.

> From f009da37d3b7e2730abb8cbb10f4d07b3d456dd8 Mon Sep 17 00:00:00 2001
> From: Jack Kamm <address@hidden>
> Date: Sun, 19 Nov 2017 07:13:56 +0000
> Subject: [PATCH] Squashed commit of the following:
> commit d1fe88a9f61a8e7082f08b7c190a29737bb655d5
> Author: Jack Kamm <address@hidden>
> Date:   Sun Nov 19 07:08:31 2017 +0000
>     fix block ending in blank lines; send multiline blocks to tmpfile
> commit fcc5a7795e882716775c9d925b0cd5b657da041b
> Author: Jack Kamm <address@hidden>
> Date:   Sat Nov 18 22:40:31 2017 +0000
>     fix newlines and blanklines when sending codeblock to tmpfile
> commit a5d553ece9f6ee35cd1e273e554a21a19e80ec3c
> Author: Jack Kamm <address@hidden>
> Date:   Sat Nov 18 21:47:09 2017 +0000
>     fix newline/indentation issues in ob-python :session

Please see <http://orgmode.org/worg/org-contribute.html#commit-messages>
for information on Org's convention for commit messages.  In addition to
following this format, ideally the message would contain a brief
description of the problem the patch is fixing.

> ---
>  lisp/ob-python.el | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)

This patch probably passes the TINYCHANGE threshold, so please see
<http://orgmode.org/worg/org-contribute.html#copyright-issues> for
information about assigning copyright.

> diff --git a/lisp/ob-python.el b/lisp/ob-python.el
> index 60ec5fa47..c3dba1565 100644
> --- a/lisp/ob-python.el
> +++ b/lisp/ob-python.el
> @@ -303,6 +303,9 @@ last statement in BODY, as elisp."
>                        (mapc (lambda (line) (insert line) (funcall
> send-wait))
>                              (split-string body "[\r\n]"))
>                        (funcall send-wait)))
> +        (body (if (string-match-p ".\n+." body) ;; Multiline

nitpick: When a comments is on the same line as code, the convention is
to use a single ";".

I see your point that sending all multiline code through a temporary
file is consistent with python.el's behavior.  When you say that it
"gives more consistent behavior for ":results output", I believe you're
talking about problems with ">>>" and "..."  markers leaking into the
output.  I agree that this change should be an improvement since I think
most of the prompt issues are racy problems related to sending multiple
lines.  (I think there still might be a unrelated prompt issue regarding
python.el's startup message leaking into the output of the first
executed block.)

Looking back at my summary of ob-python problems in
this seems like a good way to take the solution to problem #3
(indentation, multiline syntax errors) and apply it to problem #1
(markers leaking into the output).  Nice, hadn't occurred to me.

Assuming we do go this direction, I wonder if there's any ob-python code
that can be cleaned up or simplified since the multiline processing
logic is no longer needed.

> +                  (org-babel-python--replace-body-tmpfile body)
> +                body))
>           (results
>            (pcase result-type
>              (`output
> @@ -340,6 +343,32 @@ last statement in BODY, as elisp."
>        (substring string 1 -1)
>      string))
> +
> +(defun org-babel-python--replace-body-tmpfile (body)
> +  "Place body in tmpfile, and return string to exec the tmpfile.

nitpick: s/body/BODY/ here and below

> +If last line of body is not indented, place it at end of exec string
> +instead of tmpfile, so shell can see the result"

nitpick: missing trailing period

This is the part of the patch that I'm unsure about.  I don't like that

  * can fail if the last line is a non-indented, continued string

  * doesn't allow you to get a return value for commons things like
    conditionals, try-except blocks, context statements.

I can't think of a good solution, though.  Stepping back a bit, I think
it's unfortunate that python blocks handle ":results value" differently
depending on whether the block is hooked up to a session or not.  For
non-sessions, you have to use return.  Using the same approach
(org-babel-python-wrapper-method) for ":session :results value", we
could then get the return value reliably, but the problem with this
approach is that any variables defined in a ":results value" block
wouldn't be defined in the session after executing the block because the
code is wrapped in a function.

So at this point I think the choice is between

  * restricting the return value to unindented last lines and not
    supporting continued strings in the last line

  * wrapping the return value with org-babel-python-wrapper-method and
    not supporting persistent session variables in that block

  * not supporting ":session :results value"

> +  (let* ((body (string-trim-right body))
> +        (tmp-file (org-babel-temp-file "python-"))
> +        (lines (split-string body "[\r\n]"))
> +        (lastline (car (last lines)))
> +        (newbody (concat
> +                  (format "__pyfilename = '%s'; " tmp-file)

Since you're already using concat, I prefer to avoid the format here.
Or you could add a defconst that just defines that format string and
then only have a format call here.

> +                  "__pyfile = open(__pyfilename); "

Right, the leading underscores are good to reduce the risk of clobbering
a variable that the user may have defined in the shell.  Since this is
generated code, I wonder if you should be even more specific and use
ugly names like "__org_babel_python_fname" and "__org_babel_python_fh".

> +                  "exec(compile("
> +                  "__pyfile.read(), __pyfilename, 'exec'"
> +                  ")); "
> +                  "__pyfile.close()")))
> +    (if (string-match-p "^[ \t]" lastline)
> +       (progn
> +         (with-temp-file tmp-file (insert body))
> +         newbody)
> +      (with-temp-file tmp-file
> +       (insert (mapconcat 'identity
> +                          (butlast lines) "\n")))
> +      (concat newbody "\n" lastline)))
> +  )

nitpick: Move this trailing paren to the previous line.

Also, it'd be nice to add a few tests to testing/lisp/test-ob-python.el.

Thanks for working on this.


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