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Re: eldoc recursion error


From: Kyle Meyer
Subject: Re: eldoc recursion error
Date: Sun, 20 Sep 2020 00:54:31 -0400

James N. V. Cash writes:

> Kyle Meyer <kyle@kyleam.com> writes:

>> Okay, so when eldoc-documentation-functions is defined (Emacs >=28), we
>> take the first function and go with it.  That might not be exactly what
>> you'd see in the native buffer, depending on whether there are other
>> members of eldoc-documentation-functions and how they interact.  (I'm
>> being vague, because I don't really know anything about eldoc, but it
>> seems like that must be the case.)  Anyway, I'd guess it will be good
>> enough in most cases, and it's certainly better than the recursion
>> error.
>
> Ah yes, very true. I've attached another patch, which tries to better
> preserve how the new eldoc strategy works, by passing through the
> callback to the mode-local eldoc function if available, which will be a
> closure over the configured documentation strategy with
> eldoc-documentation-functions bound to the appropriate mode-local value.

Thanks, sounds good.

> Subject: [PATCH] Address org-eldoc-recursion issue
[...]
> @@ -116,8 +116,13 @@
>          (when (fboundp mode-func)
>            (with-temp-buffer
>              (funcall mode-func)
> -            (setq doc-func (and eldoc-documentation-function
> -                                (symbol-value 
> 'eldoc-documentation-function)))
> +         (setq doc-func (if (boundp 'eldoc-documentation-functions)
> +                            (lexical-let ((doc-funs (symbol-value 
> 'eldoc-documentation-functions)))

Using lexical-let here is problematic because it's obsolete since Emacs
24.  Taking a quick glance, I don't see any issues with switching this
file over to lexical binding by adding " -*- lexical-binding: t; -*-" to
the first line.

Also, why use

    (doc-funs (symbol-value 'eldoc-documentation-functions))

rather than

    (doc-funs eldoc-documentation-functions)

?

> +                              (lambda ()
> +                                (let ((eldoc-documentation-functions 
> doc-funs))
> +                                  (funcall eldoc-documentation-strategy))))
> +                            (and eldoc-documentation-function
> +                                 (symbol-value 
> 'eldoc-documentation-function))))

nit: Please switch this to the Elisp style of indenting the `else' arm
less than the `then' arm.

>              (puthash lang doc-func org-eldoc-local-functions-cache))
>            doc-func)
>        cached-func)))
> @@ -127,7 +132,7 @@
>  (declare-function php-eldoc-function "php-eldoc" ())
>  (declare-function go-eldoc--documentation-function "go-eldoc" ())
>  
> -(defun org-eldoc-documentation-function (&rest _ignored)
> +(defun org-eldoc-documentation-function (&optional callback)

Perhaps even with the callback parameter the &rest should stay around.
The docstring of eldoc-documentation-functions makes me nervous because
it says "each hook function is called with _at least_ one argument" (my
emphasis).

>    "Return breadcrumbs when on a headline, args for src block header-line,
>    calls other documentation functions depending on lang when inside src 
> body."
>    (or
> @@ -161,7 +166,12 @@
>               (string= lang "golang")) (when (require 'go-eldoc nil t)
>                                          (go-eldoc--documentation-function)))
>             (t (let ((doc-fun 
> (org-eldoc-get-mode-local-documentation-function lang)))
> -                (when (functionp doc-fun) (funcall doc-fun))))))))
> +                (when (functionp doc-fun)
> +               (if (functionp callback)
> +                   (condition-case nil
> +                       (funcall doc-fun callback)
> +                     (wrong-number-of-arguments (funcall doc-fun)))
> +                 (funcall doc-fun)))))))))

Hmm, I think the more complete approach you put together for
org-eldoc-get-mode-local-documentation-function, along with your change
to consider the callback parameter here, means we don't need to bother
with the condition-case/wrong-number-of-arguments dance.  The callback
alone should be a reliable indication we're on Emacs 28, in which case
we can expect the function to accept a callback argument (even if they
ignore it like python-eldoc-function does).

Thanks again for working on this.



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