GNU bug report logs - #62092
30.0.50; "case" does not work as dedenter in Python

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Cc: Lele Gaifax <lele <at> metapensiero.it>
Subject: 30.0.50; "case" does not work as dedenter in Python
Date: Fri, 10 Mar 2023 14:33:14 +0900

[Message part 1 (text/plain, inline)]

Hi,

New keywords "match" and "case" were added to block-start in
`python-rx', which enables basic indentation support for these
keywords.  However, "case" does not work as a dedenter.  For example,
try the following code.

#+begin_src python
match a:
    case 1:
        print(1)
        case 2:
#+end_src

At the "case 2:" line, inputting ":" does not dedent the line.
Several TAB keys are needed for correct indentation.

Attached is a patch to make "case" a dedenter with an ERT.

--
In GNU Emacs 30.0.50 (build 3, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0, Xaw scroll bars) of 2023-03-10 built on ubuntu
Repository revision: 8ee205d232574e12921b052c7e93b7e16d6f1187
Repository branch: master
System Description: Ubuntu 22.04.2 LTS

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[0001-Make-case-keyword-a-dedenter-in-Python.patch (application/octet-stream, attachment)]

Message #8 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: kobarity <kobarity <at> gmail.com>
Cc: lele <at> metapensiero.it, 62092 <at> debbugs.gnu.org
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Fri, 10 Mar 2023 09:36:25 +0200

> Cc: Lele Gaifax <lele <at> metapensiero.it>
> Date: Fri, 10 Mar 2023 14:33:14 +0900
> From: kobarity <kobarity <at> gmail.com>
> 
> New keywords "match" and "case" were added to block-start in
> `python-rx', which enables basic indentation support for these
> keywords.  However, "case" does not work as a dedenter.  For example,
> try the following code.

Could you please tell in which version of Emacs did we add those new
keywords?  It's important for deciding on which branch to fix the
problem.

Thanks.

Message #11 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: lele <at> metapensiero.it, 62092 <at> debbugs.gnu.org
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Fri, 10 Mar 2023 17:27:02 +0900

Eli Zaretskii wrote:
> Could you please tell in which version of Emacs did we add those new
> keywords?  It's important for deciding on which branch to fix the
> problem.

Sorry for the lack of information.  Those keywords were added in
Bug#55572.  The commit ID is 35d0190b0b91c085c73bbe6c2b8e93ea8288b589.
So I think it's only for Emacs 29.

Message #14 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: kobarity <kobarity <at> gmail.com>, 62092 <at> debbugs.gnu.org
Cc: Lele Gaifax <lele <at> metapensiero.it>
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Sat, 11 Mar 2023 02:27:57 +0200

On 10/03/2023 07:33, kobarity wrote:
> Attached is a patch to make "case" a dedenter with an ERT.

Here's a minor issue with it, probably not critical:

I type the colon after 'case 2', see it indented correctly, but also a 
message in the echo area:

  Closes case 1:

I type the next case with colon and see:

  Closes case 2:

and so on. They don't do much harm, but they still seem semantically 
incorrect.

Message #17 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: Lele Gaifax <lele <at> metapensiero.it>, 62092 <at> debbugs.gnu.org
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Sat, 11 Mar 2023 11:08:32 +0900

Dmitry Gutov wrote:
> I type the colon after 'case 2', see it indented correctly, but also a
> message in the echo area:
> 
>   Closes case 1:
> 
> I type the next case with colon and see:
> 
>   Closes case 2:
> 
> and so on. They don't do much harm, but they still seem semantically
> incorrect.

Thank you for testing my patch.  I don't think this is a incorrect
message.  Let's discuss with the following code:

#+begin_src python
match a:
    case 1:
        print("a = 1")
        match b:
            case 2:
                print("b = 2")
                case 3
#+end_src

When I type ":" at the last line after "case 3", it will be indented
as follows:

#+begin_src python
match a:
    case 1:
        print("a = 1")
        match b:
            case 2:
                print("b = 2")
            case 3:
#+end_src

The message "Closes case 2:" is shown.  It means that the "case 3:"
corresponds to the "case 2:" in the inner "match" statement, not the
"case 1:" in the outer "match" statement.

When I type TAB twice, the line will be indented as follows:

#+begin_src python
match a:
    case 1:
        print("a = 1")
        match b:
            case 2:
                print("b = 2")
    case 3:
#+end_src

The message "Closes case 1:" is shown.  It is shown to help
distinguishing nested blocks, although it will not be useful if the
case statements are same.

This is the same behavior as "if" blocks, etc.  The term "Closes" may
not be the most appropriate for "case," but I don't think it is wrong.

Message #22 received at 62092-done <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: kobarity <kobarity <at> gmail.com>
Cc: Lele Gaifax <lele <at> metapensiero.it>, 62092-done <at> debbugs.gnu.org
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Sat, 11 Mar 2023 15:18:12 +0200

On 11/03/2023 04:08, kobarity wrote:

> The message "Closes case 1:" is shown.  It is shown to help
> distinguishing nested blocks, although it will not be useful if the
> case statements are same.
> 
> This is the same behavior as "if" blocks, etc.  The term "Closes" may
> not be the most appropriate for "case," but I don't think it is wrong.

Fair enough. I do think it's not ideal ("case" is not a "closer"), but 
neither is "else", for that matter. So the issue is not new.

And it can be useful, like you say, to distinguish nested blocks.

Pushed your change to emacs-29, and closing. Thanks!

Message #25 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: Lele Gaifax <lele <at> metapensiero.it>, 62092 <at> debbugs.gnu.org
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Sat, 25 Mar 2023 23:13:06 +0900

[Message part 1 (text/plain, inline)]

Dmitry Gutov wrote:
> Pushed your change to emacs-29, and closing. Thanks!

Thank you for applying the patch.  However, I overlooked one problem.

#+begin_src python
match a:
    case 1:
        match b:
            case 2
#+end_src

When I type ":" at the last line after "case 2", the message "Closes
case 1:" is shown.  This is wrong because it cannot be the "case"
block of the outer "match" block (match a:).  I'm sorry if you were
mentioning this case.

Similar message can be shown with "elif":

#+begin_src python
for c in (1, 2):
    if a == 1:
        for d in (3, 4):
            elif b == 1:
#+end_src

However, this is not a correct Python code because "elif" cannot be
the first sentence in a block.

Dedenters other than "case" can never be the first sentence of a
block, whereas "case" can be the first sentence of a block.

So I think it is appropriate that the first "case" in the block should
not be considered a dedenter.  Attached is a patch to add a condition
in `python-info-dedenter-statement-p'.

[0001-Improve-indenting-case-in-Python.patch (application/octet-stream, attachment)]

Message #28 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: kobarity <kobarity <at> gmail.com>
Cc: Lele Gaifax <lele <at> metapensiero.it>, 62092 <at> debbugs.gnu.org
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Sun, 26 Mar 2023 05:04:12 +0300

On 25/03/2023 16:13, kobarity wrote:
> 
> Dmitry Gutov wrote:
>> Pushed your change to emacs-29, and closing. Thanks!
> 
> Thank you for applying the patch.  However, I overlooked one problem.
> 
> #+begin_src python
> match a:
>      case 1:
>          match b:
>              case 2
> #+end_src
> 
> When I type ":" at the last line after "case 2", the message "Closes
> case 1:" is shown.  This is wrong because it cannot be the "case"
> block of the outer "match" block (match a:).  I'm sorry if you were
> mentioning this case.

Not really, I wasn't thinking about this one in particular.

> Similar message can be shown with "elif":
> 
> #+begin_src python
> for c in (1, 2):
>      if a == 1:
>          for d in (3, 4):
>              elif b == 1:
> #+end_src
> 
> However, this is not a correct Python code because "elif" cannot be
> the first sentence in a block.
> 
> Dedenters other than "case" can never be the first sentence of a
> block, whereas "case" can be the first sentence of a block.
> 
> So I think it is appropriate that the first "case" in the block should
> not be considered a dedenter.  Attached is a patch to add a condition
> in `python-info-dedenter-statement-p'.

Thanks! I've pushed it to emacs-29 as well.

Message #35 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: Mattias Engdegård <mattias.engdegard <at> gmail.com>
To: kobarity <kobarity <at> gmail.com>
Cc: Lele Gaifax <lele <at> metapensiero.it>, 62092 <at> debbugs.gnu.org,
 Dmitry Gutov <dgutov <at> yandex.ru>
Subject: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Mon, 14 Aug 2023 17:12:15 +0200

The test python-info-dedenter-opening-block-positions-7 added as part of this bug in 8f42db010d ends with

+   (equal (list (python-tests-look-at "case 2:" -1)
+                (python-tests-look-at "case 1:" -1 t))
+            (python-info-dedenter-opening-block-positions))))

which, as you can see, isn't actually a check; the `equal` result is thrown away.
(Emacs master was just changed to detect this, so there is a byte-compiler warning.)

Unfortunately, wrapping the call in `should` fails, so there is more to it.
Would you please take a look?

Message #38 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: Mattias Engdegård <mattias.engdegard <at> gmail.com>
Cc: Lele Gaifax <lele <at> metapensiero.it>, 62092 <at> debbugs.gnu.org,
 Dmitry Gutov <dgutov <at> yandex.ru>
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Tue, 15 Aug 2023 22:43:19 +0900

[Message part 1 (text/plain, inline)]

Mattias Engdegård wrote:
> 
> The test python-info-dedenter-opening-block-positions-7 added as part of this bug in 8f42db010d ends with
> 
> +   (equal (list (python-tests-look-at "case 2:" -1)
> +                (python-tests-look-at "case 1:" -1 t))
> +            (python-info-dedenter-opening-block-positions))))
> 
> which, as you can see, isn't actually a check; the `equal` result is thrown away.
> (Emacs master was just changed to detect this, so there is a byte-compiler warning.)
> 
> Unfortunately, wrapping the call in `should` fails, so there is more to it.
> Would you please take a look?

Sorry, I meant to use `should'.  Another mistake was forgetting to use
RESTORE-POINT argument when calling `python-tests-look-at'.  Attached
is the patch to fix this.  It also includes the indentation fix for 
`python-info-dedenter-opening-block-positions-6'.

[0001-Fix-test-in-python-tests.el-added-by-bug-62092.patch (application/octet-stream, attachment)]

Message #41 received at 62092 <at> debbugs.gnu.org (full text, mbox):

From: Mattias Engdegård <mattias.engdegard <at> gmail.com>
To: kobarity <kobarity <at> gmail.com>
Cc: Lele Gaifax <lele <at> metapensiero.it>, 62092 <at> debbugs.gnu.org,
 Dmitry Gutov <dgutov <at> yandex.ru>
Subject: Re: bug#62092: 30.0.50; "case" does not work as dedenter in Python
Date: Tue, 15 Aug 2023 17:09:18 +0200

15 aug. 2023 kl. 15.43 skrev kobarity <kobarity <at> gmail.com>:

> Sorry, I meant to use `should'.  Another mistake was forgetting to use
> RESTORE-POINT argument when calling `python-tests-look-at'.  Attached
> is the patch to fix this.  It also includes the indentation fix for 
> `python-info-dedenter-opening-block-positions-6'.

Excellent, thank you! Applied to master.

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