Use (eval-when-compile 'treesit) to save us from writing declare-function forms

Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Yuan Fu]

Some of my recent changes to c-ts-mode.el uses some more C treesit functions, and I (again) forgot to add their declare-function forms to c-ts-mode.el, and Andrea has to fix it for me. The main problem for me is that (I think) you don’t get warning for them unless you build a non-tree-sitter build of Emacs. So I’m prone to forgot about them. Also it’s a burden for anyone wanting to use tree-sitter functions.

treesit.el already has all the declare-function forms, how about we use (eval-when-compile 'treesit) in other files? I believe that should alleviate us from adding those declare-function forms in other files?

I want to ask because IIRC I proposed this a while back but there were objections, the details of which I forgot.

Yuan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Andrea Corallo]

Yuan Fu <casouri@gmail.com> writes:

> Some of my recent changes to c-ts-mode.el uses some more C treesit
> functions, and I (again) forgot to add their declare-function forms to
> c-ts-mode.el, and Andrea has to fix it for me. The main problem for me
> is that (I think) you don’t get warning for them unless you build a
> non-tree-sitter build of Emacs. So I’m prone to forgot about
> them. Also it’s a burden for anyone wanting to use tree-sitter
> functions.
>
> treesit.el already has all the declare-function forms, how about we
> use (eval-when-compile 'treesit) in other files? I believe that should
> alleviate us from adding those declare-function forms in other files?
>
> I want to ask because IIRC I proposed this a while back but there were objections, the details of which I forgot.
>
> Yuan

Hi Yuan,

I was not part of the discussion and I don't know what's the downside of
(eval-when-compile 'treesit), maybe another alternative would be to have
like a dedicated treesit-delcs.el to require where necessary?

  Andrea

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Mon, 2 Dec 2024 22:31:48 -0800
> 
> Some of my recent changes to c-ts-mode.el uses some more C treesit functions, and I (again) forgot to add their declare-function forms to c-ts-mode.el, and Andrea has to fix it for me. The main problem for me is that (I think) you don’t get warning for them unless you build a non-tree-sitter build of Emacs. So I’m prone to forgot about them. Also it’s a burden for anyone wanting to use tree-sitter functions.
> 
> treesit.el already has all the declare-function forms, how about we use (eval-when-compile 'treesit) in other files? I believe that should alleviate us from adding those declare-function forms in other files?

I don't understand" c-ts-mode.el already does

  (require 'treesit)

So what would eval-when-compile add to that?

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Yuan Fu]

> On Dec 3, 2024, at 5:12 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Mon, 2 Dec 2024 22:31:48 -0800
>> 
>> Some of my recent changes to c-ts-mode.el uses some more C treesit functions, and I (again) forgot to add their declare-function forms to c-ts-mode.el, and Andrea has to fix it for me. The main problem for me is that (I think) you don’t get warning for them unless you build a non-tree-sitter build of Emacs. So I’m prone to forgot about them. Also it’s a burden for anyone wanting to use tree-sitter functions.
>> 
>> treesit.el already has all the declare-function forms, how about we use (eval-when-compile 'treesit) in other files? I believe that should alleviate us from adding those declare-function forms in other files?
> 
> I don't understand" c-ts-mode.el already does
> 
>  (require 'treesit)
> 
> So what would eval-when-compile add to that?

When Emacs is built without tree-sitter, none of the treesit.c functions are available (except for treesit-ready-p). Now if this Emacs compiles c-ts-mode.el, it’ll signal undefined function error for all those functions. So we add declare-function forms for all the treesit.c functions used in c-ts-mode.el, and have to update the declare-function forms whenever we use some new treesit.c functions.

If we use eval-when-compile, we don’t need to write declare-function forms in c-ts-mode.el anymore, because treesit.el has declare-function forms for all treesit.c functions.

Yuan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Yuan Fu]

> On Dec 3, 2024, at 12:30 AM, Andrea Corallo <acorallo@gnu.org> wrote:
> 
> Yuan Fu <casouri@gmail.com> writes:
> 
>> Some of my recent changes to c-ts-mode.el uses some more C treesit
>> functions, and I (again) forgot to add their declare-function forms to
>> c-ts-mode.el, and Andrea has to fix it for me. The main problem for me
>> is that (I think) you don’t get warning for them unless you build a
>> non-tree-sitter build of Emacs. So I’m prone to forgot about
>> them. Also it’s a burden for anyone wanting to use tree-sitter
>> functions.
>> 
>> treesit.el already has all the declare-function forms, how about we
>> use (eval-when-compile 'treesit) in other files? I believe that should
>> alleviate us from adding those declare-function forms in other files?
>> 
>> I want to ask because IIRC I proposed this a while back but there were objections, the details of which I forgot.
>> 
>> Yuan
> 
> Hi Yuan,
> 
> I was not part of the discussion and I don't know what's the downside of
> (eval-when-compile 'treesit), maybe another alternative would be to have
> like a dedicated treesit-delcs.el to require where necessary?
> 

That’ll be ok too. Though 99.99% the case, if some package uses tree-sitter, they’d need something in treesit.el too.

Yuan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Wed, 4 Dec 2024 10:19:42 -0800
> Cc: emacs-devel@gnu.org
> 
> 
> 
> > On Dec 3, 2024, at 5:12 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> > I don't understand" c-ts-mode.el already does
> > 
> >  (require 'treesit)
> > 
> > So what would eval-when-compile add to that?
> 
> When Emacs is built without tree-sitter, none of the treesit.c functions are available (except for treesit-ready-p). Now if this Emacs compiles c-ts-mode.el, it’ll signal undefined function error for all those functions. So we add declare-function forms for all the treesit.c functions used in c-ts-mode.el, and have to update the declare-function forms whenever we use some new treesit.c functions.
> 
> If we use eval-when-compile, we don’t need to write declare-function forms in c-ts-mode.el anymore, because treesit.el has declare-function forms for all treesit.c functions.

That's what I don't understand: how will eval-when-compile which loads
treesit.el be different from (require 'treesit) we already have in
c-ts-mode?  Don't they both load treesit.el?

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Yuan Fu]

> On Dec 4, 2024, at 10:57 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Wed, 4 Dec 2024 10:19:42 -0800
>> Cc: emacs-devel@gnu.org
>> 
>> 
>> 
>>> On Dec 3, 2024, at 5:12 AM, Eli Zaretskii <eliz@gnu.org> wrote:
>>> 
>>> I don't understand" c-ts-mode.el already does
>>> 
>>> (require 'treesit)
>>> 
>>> So what would eval-when-compile add to that?
>> 
>> When Emacs is built without tree-sitter, none of the treesit.c functions are available (except for treesit-ready-p). Now if this Emacs compiles c-ts-mode.el, it’ll signal undefined function error for all those functions. So we add declare-function forms for all the treesit.c functions used in c-ts-mode.el, and have to update the declare-function forms whenever we use some new treesit.c functions.
>> 
>> If we use eval-when-compile, we don’t need to write declare-function forms in c-ts-mode.el anymore, because treesit.el has declare-function forms for all treesit.c functions.
> 
> That's what I don't understand: how will eval-when-compile which loads
> treesit.el be different from (require 'treesit) we already have in
> c-ts-mode?  Don't they both load treesit.el?

I maybe wrong here, but I thought if you don’t use eval-when-compile, simply byte-compiling c-ts-mode.el wouldn’t load treesit.el?

Yuan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Wed, 4 Dec 2024 22:25:33 -0800
> Cc: emacs-devel@gnu.org
> 
> >> If we use eval-when-compile, we don’t need to write declare-function forms in c-ts-mode.el anymore, because treesit.el has declare-function forms for all treesit.c functions.
> > 
> > That's what I don't understand: how will eval-when-compile which loads
> > treesit.el be different from (require 'treesit) we already have in
> > c-ts-mode?  Don't they both load treesit.el?
> 
> I maybe wrong here, but I thought if you don’t use eval-when-compile, simply byte-compiling c-ts-mode.el wouldn’t load treesit.el?

Yes, it would.  You can clearly see this in a debugger if you put a
breakpoint in Fload and then byte-compile c-ts-mode.el.

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Yuan Fu]

> On Dec 4, 2024, at 11:07 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Wed, 4 Dec 2024 22:25:33 -0800
>> Cc: emacs-devel@gnu.org
>> 
>>>> If we use eval-when-compile, we don’t need to write declare-function forms in c-ts-mode.el anymore, because treesit.el has declare-function forms for all treesit.c functions.
>>> 
>>> That's what I don't understand: how will eval-when-compile which loads
>>> treesit.el be different from (require 'treesit) we already have in
>>> c-ts-mode?  Don't they both load treesit.el?
>> 
>> I maybe wrong here, but I thought if you don’t use eval-when-compile, simply byte-compiling c-ts-mode.el wouldn’t load treesit.el?
> 
> Yes, it would.  You can clearly see this in a debugger if you put a
> breakpoint in Fload and then byte-compile c-ts-mode.el.

Does that mean declare-function forms only affect the file it’s in? Because if treesit.el has declare-function forms for all the treesit.c functions, and c-ts-mode.el requires treesit.el, why do we need to have declare-function forms in c-ts-mode.el?

Yuan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Fri, 6 Dec 2024 17:12:38 -0800
> Cc: emacs-devel@gnu.org
> 
> 
> 
> > On Dec 4, 2024, at 11:07 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> From: Yuan Fu <casouri@gmail.com>
> >> Date: Wed, 4 Dec 2024 22:25:33 -0800
> >> Cc: emacs-devel@gnu.org
> >> 
> >>>> If we use eval-when-compile, we don’t need to write declare-function forms in c-ts-mode.el anymore, because treesit.el has declare-function forms for all treesit.c functions.
> >>> 
> >>> That's what I don't understand: how will eval-when-compile which loads
> >>> treesit.el be different from (require 'treesit) we already have in
> >>> c-ts-mode?  Don't they both load treesit.el?
> >> 
> >> I maybe wrong here, but I thought if you don’t use eval-when-compile, simply byte-compiling c-ts-mode.el wouldn’t load treesit.el?
> > 
> > Yes, it would.  You can clearly see this in a debugger if you put a
> > breakpoint in Fload and then byte-compile c-ts-mode.el.
> 
> Does that mean declare-function forms only affect the file it’s in? Because if treesit.el has declare-function forms for all the treesit.c functions, and c-ts-mode.el requires treesit.el, why do we need to have declare-function forms in c-ts-mode.el?

Seems like that.  Stefan, am I missing something here?

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Stefan Monnier]

>> Does that mean declare-function forms only affect the file it’s in?
>> Because if treesit.el has declare-function forms for all the treesit.c
>> functions, and c-ts-mode.el requires treesit.el, why do we need to have
>> declare-function forms in c-ts-mode.el?
> Seems like that.  Stefan, am I missing something here?

Yes, `declare-function` *should* follow the same principles as `(defvar
FOO)`, meaning that they are compiler directives not functions to
execute.  They affect warnings only in the current lexical scope, and
requiring a file full of `(defvar FOO)` and `declare-function` will have
no effect at all.

[ Side note regarding this *should*: it currently doesn't work quite as
  well as `defvar` because its effect is always file-wide, whereas it
  should be limited to the current scope.  ]


        Stefan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Yuan Fu]

[-- Attachment #1: Type: text/plain, Size: 1151 bytes --]



> On Dec 7, 2024, at 5:47 AM, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> 
>>> Does that mean declare-function forms only affect the file it’s in?
>>> Because if treesit.el has declare-function forms for all the treesit.c
>>> functions, and c-ts-mode.el requires treesit.el, why do we need to have
>>> declare-function forms in c-ts-mode.el?
>> Seems like that.  Stefan, am I missing something here?
> 
> Yes, `declare-function` *should* follow the same principles as `(defvar
> FOO)`, meaning that they are compiler directives not functions to
> execute.  They affect warnings only in the current lexical scope, and
> requiring a file full of `(defvar FOO)` and `declare-function` will have
> no effect at all.
> 
> [ Side note regarding this *should*: it currently doesn't work quite as
>  well as `defvar` because its effect is always file-wide, whereas it
>  should be limited to the current scope.  ]

Defining a macro that contains the declare-function forms, and calling it in eval-when-compile forms seem to work (see patch), WDYT? The name (treesit-declare-c-functions) could be better, any ideas?

Yuan


[-- Attachment #2: declare-function.patch --]
[-- Type: application/octet-stream, Size: 7491 bytes --]

From ba77886d5e250770251d8c1abec93d4fcf0e0268 Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Sat, 7 Dec 2024 22:13:07 -0800
Subject: [PATCH] declare-function POC

---
 lisp/progmodes/c-ts-mode.el |  17 +-----
 lisp/treesit.el             | 103 ++++++++++++++++++++----------------
 2 files changed, 60 insertions(+), 60 deletions(-)

diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index dec9411b87c..4a1f616b048 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -73,21 +73,8 @@
 (require 'c-ts-common)
 (eval-when-compile (require 'rx))
 
-(declare-function treesit-parser-create "treesit.c")
-(declare-function treesit-parser-root-node "treesit.c")
-(declare-function treesit-parser-set-included-ranges "treesit.c")
-(declare-function treesit-node-parent "treesit.c")
-(declare-function treesit-node-start "treesit.c")
-(declare-function treesit-node-end "treesit.c")
-(declare-function treesit-node-child "treesit.c")
-(declare-function treesit-node-child-by-field-name "treesit.c")
-(declare-function treesit-node-type "treesit.c")
-(declare-function treesit-node-prev-sibling "treesit.c")
-(declare-function treesit-node-first-child-for-pos "treesit.c")
-(declare-function treesit-node-next-sibling "treesit.c")
-(declare-function treesit-node-eq "treesit.c")
-(declare-function treesit-node-match-p "treesit.c")
-(declare-function treesit-query-compile "treesit.c")
+(eval-when-compile
+  (treesit-declare-c-functions))
 
 ;;; Custom variables
 
diff --git a/lisp/treesit.el b/lisp/treesit.el
index db3a706f016..2e189394983 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -39,61 +39,74 @@
 
 ;;; Function declarations
 
-(declare-function treesit-language-available-p "treesit.c")
-(declare-function treesit-language-version "treesit.c")
+(defmacro treesit-declare-c-functions ()
+  "Declare C functions and variables defined in treesit.c.
 
-(declare-function treesit-parser-p "treesit.c")
-(declare-function treesit-node-p "treesit.c")
-(declare-function treesit-compiled-query-p "treesit.c")
-(declare-function treesit-query-p "treesit.c")
-(declare-function treesit-query-language "treesit.c")
+This macro is only needed for byte-compiling in Emacs not built with
+tree-sitter library.  It should be used with `eval-when-compile' like
+this:
 
-(declare-function treesit-node-parser "treesit.c")
+    (eval-when-compile
+      (treesit-declare-c-functions))"
+  '(progn
+     (declare-function treesit-language-available-p "treesit.c")
+     (declare-function treesit-language-version "treesit.c")
 
-(declare-function treesit-parser-create "treesit.c")
-(declare-function treesit-parser-delete "treesit.c")
-(declare-function treesit-parser-list "treesit.c")
-(declare-function treesit-parser-buffer "treesit.c")
-(declare-function treesit-parser-language "treesit.c")
-(declare-function treesit-parser-tag "treesit.c")
+     (declare-function treesit-parser-p "treesit.c")
+     (declare-function treesit-node-p "treesit.c")
+     (declare-function treesit-compiled-query-p "treesit.c")
+     (declare-function treesit-query-p "treesit.c")
+     (declare-function treesit-query-language "treesit.c")
 
-(declare-function treesit-parser-root-node "treesit.c")
+     (declare-function treesit-node-parser "treesit.c")
 
-(declare-function treesit-parser-set-included-ranges "treesit.c")
-(declare-function treesit-parser-included-ranges "treesit.c")
-(declare-function treesit-parser-changed-ranges "treesit.c")
-(declare-function treesit-parser-add-notifier "treesit.c")
+     (declare-function treesit-parser-create "treesit.c")
+     (declare-function treesit-parser-delete "treesit.c")
+     (declare-function treesit-parser-list "treesit.c")
+     (declare-function treesit-parser-buffer "treesit.c")
+     (declare-function treesit-parser-language "treesit.c")
+     (declare-function treesit-parser-tag "treesit.c")
 
-(declare-function treesit-node-type "treesit.c")
-(declare-function treesit-node-start "treesit.c")
-(declare-function treesit-node-end "treesit.c")
-(declare-function treesit-node-string "treesit.c")
-(declare-function treesit-node-parent "treesit.c")
-(declare-function treesit-node-child "treesit.c")
-(declare-function treesit-node-check "treesit.c")
-(declare-function treesit-node-field-name-for-child "treesit.c")
-(declare-function treesit-node-child-count "treesit.c")
-(declare-function treesit-node-child-by-field-name "treesit.c")
-(declare-function treesit-node-next-sibling "treesit.c")
-(declare-function treesit-node-prev-sibling "treesit.c")
-(declare-function treesit-node-first-child-for-pos "treesit.c")
-(declare-function treesit-node-descendant-for-range "treesit.c")
-(declare-function treesit-node-eq "treesit.c")
+     (declare-function treesit-parser-root-node "treesit.c")
 
-(declare-function treesit-pattern-expand "treesit.c")
-(declare-function treesit-query-expand "treesit.c")
-(declare-function treesit-query-compile "treesit.c")
-(declare-function treesit-query-capture "treesit.c")
+     (declare-function treesit-parser-set-included-ranges "treesit.c")
+     (declare-function treesit-parser-included-ranges "treesit.c")
+     (declare-function treesit-parser-changed-ranges "treesit.c")
+     (declare-function treesit-parser-add-notifier "treesit.c")
 
-(declare-function treesit-search-subtree "treesit.c")
-(declare-function treesit-search-forward "treesit.c")
-(declare-function treesit-induce-sparse-tree "treesit.c")
-(declare-function treesit-subtree-stat "treesit.c")
-(declare-function treesit-node-match-p "treesit.c")
+     (declare-function treesit-node-type "treesit.c")
+     (declare-function treesit-node-start "treesit.c")
+     (declare-function treesit-node-end "treesit.c")
+     (declare-function treesit-node-string "treesit.c")
+     (declare-function treesit-node-parent "treesit.c")
+     (declare-function treesit-node-child "treesit.c")
+     (declare-function treesit-node-check "treesit.c")
+     (declare-function treesit-node-field-name-for-child "treesit.c")
+     (declare-function treesit-node-child-count "treesit.c")
+     (declare-function treesit-node-child-by-field-name "treesit.c")
+     (declare-function treesit-node-next-sibling "treesit.c")
+     (declare-function treesit-node-prev-sibling "treesit.c")
+     (declare-function treesit-node-first-child-for-pos "treesit.c")
+     (declare-function treesit-node-descendant-for-range "treesit.c")
+     (declare-function treesit-node-eq "treesit.c")
 
-(declare-function treesit-available-p "treesit.c")
+     (declare-function treesit-pattern-expand "treesit.c")
+     (declare-function treesit-query-expand "treesit.c")
+     (declare-function treesit-query-compile "treesit.c")
+     (declare-function treesit-query-capture "treesit.c")
 
-(defvar treesit-thing-settings)
+     (declare-function treesit-search-subtree "treesit.c")
+     (declare-function treesit-search-forward "treesit.c")
+     (declare-function treesit-induce-sparse-tree "treesit.c")
+     (declare-function treesit-subtree-stat "treesit.c")
+     (declare-function treesit-node-match-p "treesit.c")
+
+     (declare-function treesit-available-p "treesit.c")
+
+     (defvar treesit-thing-settings)))
+
+(eval-when-compile
+  (treesit-declare-c-functions))
 
 ;;; Custom options
 
-- 
2.39.5 (Apple Git-151)


[-- Attachment #3: Type: text/plain, Size: 2 bytes --]

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Sat, 7 Dec 2024 22:39:21 -0800
> Cc: Eli Zaretskii <eliz@gnu.org>,
>  emacs-devel@gnu.org
> 
> > On Dec 7, 2024, at 5:47 AM, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> > 
> >>> Does that mean declare-function forms only affect the file it’s in?
> >>> Because if treesit.el has declare-function forms for all the treesit.c
> >>> functions, and c-ts-mode.el requires treesit.el, why do we need to have
> >>> declare-function forms in c-ts-mode.el?
> >> Seems like that.  Stefan, am I missing something here?
> > 
> > Yes, `declare-function` *should* follow the same principles as `(defvar
> > FOO)`, meaning that they are compiler directives not functions to
> > execute.  They affect warnings only in the current lexical scope, and
> > requiring a file full of `(defvar FOO)` and `declare-function` will have
> > no effect at all.
> > 
> > [ Side note regarding this *should*: it currently doesn't work quite as
> >  well as `defvar` because its effect is always file-wide, whereas it
> >  should be limited to the current scope.  ]
> 
> Defining a macro that contains the declare-function forms, and calling it in eval-when-compile forms seem to work (see patch), WDYT? The name (treesit-declare-c-functions) could be better, any ideas?

Looks a bit ugly, but maybe this is the best we can do.

Andrea, WDYT?

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Stefan Monnier]

> +(eval-when-compile
> +  (treesit-declare-c-functions))

`treesit-declare-c-functions` is a macro, that expands to
`declare-function`s, i.e. to "no-ops".
Why wrap it within `eval-when-compile`?

If it works within an `eval-when-compile`, it's only by accident (just
like the fact that (eval-when-compile (defvar foo)) "works" is an
accident): code shouldn't rely on it.

It's not the evaluation of `defvar` or `declare-function` that is needed
(because such an evaluation should have no effect, as you can see if
you look at the definition of `declare-function`), but instead the
"calls" to `defvar` or `declare-function` need to be seen/processed by
the compiler.  By wrapping them within an `eval-when-compile` you risk
*hiding* them from the compiler.


        Stefan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Dmitry Gutov]

On 04/12/2024 20:19, Yuan Fu wrote:
> When Emacs is built without tree-sitter, none of the treesit.c functions are available (except for treesit-ready-p)

Have we considered having all of those functions defined but doing 
nothing in that case? Alias them to 'ignore' or something that raises an 
error.

I think then we won't have to maintain these 'declare-function' lists in 
every package that depends on treesit.c.

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Yuan Fu]

> On Dec 8, 2024, at 7:27 AM, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> 
>> +(eval-when-compile
>> +  (treesit-declare-c-functions))
> 
> `treesit-declare-c-functions` is a macro, that expands to
> `declare-function`s, i.e. to "no-ops".
> Why wrap it within `eval-when-compile`?

I thought that might be TRT since they’re only needed for compiling the file.

> 
> If it works within an `eval-when-compile`, it's only by accident (just
> like the fact that (eval-when-compile (defvar foo)) "works" is an
> accident): code shouldn't rely on it.
> 
> It's not the evaluation of `defvar` or `declare-function` that is needed
> (because such an evaluation should have no effect, as you can see if
> you look at the definition of `declare-function`), but instead the
> "calls" to `defvar` or `declare-function` need to be seen/processed by
> the compiler.  By wrapping them within an `eval-when-compile` you risk
> *hiding* them from the compiler.

I thought eval-when-compile is more of a “include if compiling” macro, should’ve checked :)

We can also go with Dmitry’s idea, and just define all the functions in treesit.el if Emacs is not built with tree-sitter. We can detect that with treesit-available-p.

Yuan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Stefan Monnier]

> I thought eval-when-compile is more of a “include if compiling” macro, should’ve checked :)
>
> We can also go with Dmitry’s idea, and just define all the functions in
> treesit.el if Emacs is not built with tree-sitter. We can detect that with
> treesit-available-p.

I haven't really thought about it, so I don't have a strong opinion.
AFAICT your proposal should work fine even if you remove the
`eval-when-compile` wrappers to which I objected.  🙂


        Stefan

Re: Use (eval-when-compile 'treesit) to save us from writing declare-function forms

[Dmitry Gutov]

On 09/12/2024 04:40, Stefan Monnier wrote:
>> I thought eval-when-compile is more of a “include if compiling” macro, should’ve checked 🙂
>>
>> We can also go with Dmitry’s idea, and just define all the functions in
>> treesit.el if Emacs is not built with tree-sitter. We can detect that with
>> treesit-available-p.
> I haven't really thought about it, so I don't have a strong opinion.
> AFAICT your proposal should work fine even if you remove the
> `eval-when-compile` wrappers to which I objected.  🙂

It seems to me that, having taken than route, we would recommend every

   (require 'treesit)

to be accompanied by

   (treesit-declare-c-functions)

...or the familiar declare-function list, of course.

And the same would also be true for transitive dependencies (so, both 
c-ts-common and c-ts-mode, even though otherwise the latter could drop 
the (require 'treesit) form).