GNU bug report logs - #77901
tsx-ts-mode: ternary chains are indented as a tree

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

From: Konstantin Kharlamov <Hi-Angel <at> yandex.ru>
To: bug-gnu-emacs <at> gnu.org
Subject: tsx-ts-mode: ternary chains are indented as a tree
Date: Fri, 18 Apr 2025 17:06:34 +0300

Given this correctly indented code:

    const a = cond1 ? 1
      : cond2 ? 2
      : cond3 ? 3
      : 4;

if you reindent it, it turns into:

    const a = cond1 ? 1
      : cond2 ? 2
        : cond3 ? 3
          : 4;

Basically, for every colon it increases indentation. This is different
from other c-like languages (it's is indented as the first form
instead), and it's also different from Python. The "tree-indentation"
is not readable, so there's a reason other modes indent it as the
first example. Would it be possible to change in typescript mode as
well?

Message #8 received at 77901 <at> debbugs.gnu.org (full text, mbox):

From: Konstantin Kharlamov <Hi-Angel <at> yandex.ru>
To: 77901 <at> debbugs.gnu.org
Subject: bug#77901: tsx-ts-mode: ternary chains are indented as a tree
Date: Thu, 01 May 2025 20:39:02 +0700

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

After poking around I wrote a patch (attached). Worth noting though, for
some reason it doesn't work for ternary without starting colon, e.g.:

    const a = cond1 ? 1 :
      cond2 ? 2 :
      cond3 ? 3 : 4;

I'm unclear why, per my understanding the "standalone-parent" of the
whole ternary chain (disregarding where the point is) is the `const a
=` declaration.

Such bug also persists in c++-ts-mode (as opposed to non-ts plain c++-
mode). I'm not sure if it's me misunderstanding something or not…

[1.patch (text/x-patch, attachment)]

Message #11 received at 77901 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Konstantin Kharlamov <Hi-Angel <at> yandex.ru>,
 Yuan Fu <casouri <at> gmail.com>
Cc: 77901 <at> debbugs.gnu.org
Subject: Re: bug#77901: tsx-ts-mode: ternary chains are indented as a tree
Date: Sat, 10 May 2025 13:16:30 +0300

> From: Konstantin Kharlamov <Hi-Angel <at> yandex.ru>
> Date: Thu, 01 May 2025 20:39:02 +0700
> 
> After poking around I wrote a patch (attached). Worth noting though, for
> some reason it doesn't work for ternary without starting colon, e.g.:
> 
>     const a = cond1 ? 1 :
>       cond2 ? 2 :
>       cond3 ? 3 : 4;
> 
> I'm unclear why, per my understanding the "standalone-parent" of the
> whole ternary chain (disregarding where the point is) is the `const a
> =` declaration.
> 
> Such bug also persists in c++-ts-mode (as opposed to non-ts plain c++-
> mode). I'm not sure if it's me misunderstanding something or not…

Yuan, any comments?

Message #14 received at 77901 <at> debbugs.gnu.org (full text, mbox):

From: Yuan Fu <casouri <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 77901 <at> debbugs.gnu.org, Konstantin Kharlamov <Hi-Angel <at> yandex.ru>
Subject: Re: bug#77901: tsx-ts-mode: ternary chains are indented as a tree
Date: Tue, 13 May 2025 12:45:17 -0700

Hey, sorry for the delay.

> On May 10, 2025, at 3:16 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
> 
>> From: Konstantin Kharlamov <Hi-Angel <at> yandex.ru>
>> Date: Thu, 01 May 2025 20:39:02 +0700
>> 
>> After poking around I wrote a patch (attached).

Thanks! LGTM. For some reason I can’t apply the patch on either emacs-30 or master. [1]

>> Worth noting though, for
>> some reason it doesn't work for ternary without starting colon, e.g.:
>> 
>>    const a = cond1 ? 1 :
>>      cond2 ? 2 :
>>      cond3 ? 3 : 4;
>> 
>> I'm unclear why, per my understanding the "standalone-parent" of the
>> whole ternary chain (disregarding where the point is) is the `const a
>> =` declaration.

The standalone rule just keeps going up the parse tree until it finds a node that starts on a new line. In this case, if you start form cond3, it’ll go up until reaching the teneray_expression node containing cond2. This node starts on a new line so standalone-parent stops here. So the cond3 line uses the cond2 line as the anchor, instead of the “const a” line. If you add a cond4 line, it’ll use the cond3 line as anchor.

There’re several ways to fix it. The best way is to add a new anchor to the presets that does what standalone-parent does, but additionally excludes some nodes. Something like (standalone-parent-excluding “regexp”). Then this can be used for both typescript and c/c++ (and java, etc).

>> 
>> Such bug also persists in c++-ts-mode (as opposed to non-ts plain c++-
>> mode). I'm not sure if it's me misunderstanding something or not…
> 
> Yuan, any comments?

Yeah we should fix this in c/c++-ts-mode too. In c/c++, the baseline-indent-rule can handle

  int a = cond1 ? 1
	: cond2 ? 2
	: cond3 ? 3
	: 4;

Which is nice, but the other case needs special case override:

  int a = cond1 ? 1 :
    cond2 ? 2 :
      cond3 ? 3 :
        cond 4: 5;

Yuan

[1] I got this error:

128 git … am --3way -- /Users/yuan/downloads/1-3.patch
Applying: typescript-ts: align ternary-chain branches (bug#78187)
error: sha1 information is lacking or useless (test/lisp/progmodes/typescript-ts-mode-resources/indent.erts).
error: could not build fake ancestor
Patch failed at 0001 typescript-ts: align ternary-chain branches (bug#78187)
hint: Use 'git am --show-current-patch=diff' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

Message #17 received at 77901 <at> debbugs.gnu.org (full text, mbox):

From: Konstantin Kharlamov <Hi-Angel <at> yandex.ru>
To: Yuan Fu <casouri <at> gmail.com>, Eli Zaretskii <eliz <at> gnu.org>
Cc: 77901 <at> debbugs.gnu.org
Subject: Re: bug#77901: tsx-ts-mode: ternary chains are indented as a tree
Date: Wed, 14 May 2025 21:50:56 +0700

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

On Tue, 2025-05-13 at 12:45 -0700, Yuan Fu wrote:
> Hey, sorry for the delay.
>
> > On May 10, 2025, at 3:16 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
> >
> > > From: Konstantin Kharlamov <Hi-Angel <at> yandex.ru>
> > > Date: Thu, 01 May 2025 20:39:02 +0700
> > >
> > > After poking around I wrote a patch (attached).
>
> Thanks! LGTM. For some reason I can’t apply the patch on either
> emacs-30 or master. [1]

Oh, interesting.  I kind of know where the error is coming from, but
only partially.  The reason for the error is that the patch I sent was
applied over the patch for #78121 (which is pending btw 😊) as I'm
using them both for coding.   At the same time, I don't really
understand the source of the error as the same parameters work for me:

    ╰─λ git am --3way -- /tmp/1.patch
    Applying: typescript-ts: align ternary-chain branches (bug#78187)
    Using index info to reconstruct a base tree...
    M       lisp/progmodes/typescript-ts-mode.el
    M       test/lisp/progmodes/typescript-ts-mode-resources/indent.erts
    Falling back to patching base and 3-way merge...
    Auto-merging test/lisp/progmodes/typescript-ts-mode-resources/indent.erts
    Auto-merging lisp/progmodes/typescript-ts-mode.el

Either way, I redone the patch on top of the tree, please try this one

> > > Worth noting though, for
> > > some reason it doesn't work for ternary without starting colon,
> > > e.g.:
> > >
> > >    const a = cond1 ? 1 :
> > >      cond2 ? 2 :
> > >      cond3 ? 3 : 4;
> > >
> > > I'm unclear why, per my understanding the "standalone-parent" of
> > > the
> > > whole ternary chain (disregarding where the point is) is the
> > > `const a
> > > =` declaration.
>
> The standalone rule just keeps going up the parse tree until it finds
> a node that starts on a new line. In this case, if you start form
> cond3, it’ll go up until reaching the teneray_expression node
> containing cond2. This node starts on a new line so standalone-parent
> stops here. So the cond3 line uses the cond2 line as the anchor,
> instead of the “const a” line. If you add a cond4 line, it’ll use the
> cond3 line as anchor.
>
> There’re several ways to fix it. The best way is to add a new anchor
> to the presets that does what standalone-parent does, but
> additionally excludes some nodes. Something like (standalone-parent-
> excluding “regexp”). Then this can be used for both typescript and
> c/c++ (and java, etc).

Oh, I see, thank you!

[3.patch (text/x-patch, attachment)]

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