funcall of load-read-function (default nil) in elisp--eval-defun

funcall of load-read-function (default nil) in elisp--eval-defun

[Robert Weiner]

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I see this line in elisp--eval-defun at least Emacs 28 - 30 (pre-release):

          (setq form (funcall load-read-function (current-buffer)))

The default for load-read-function is nil, so it can't be called as a
function by default.  The value for me is indeed nil and is triggering an
error for me when trying to evaluate an ert-deftest expression.

How does this work?  I don't see the value of load-read-function set
anywhere else in elisp-mode.el.  I see it set in debug.el and edebug.el but
not when doing a normal defun eval.

Thanks,

rsw

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Re: funcall of load-read-function (default nil) in elisp--eval-defun

[Michael Heerdegen via Emacs development discussions.]

Robert Weiner <rsw@gnu.org> writes:

> I see this line in elisp--eval-defun at least Emacs 28 - 30 (pre-release):
>
>           (setq form (funcall load-read-function (current-buffer)))
>
> The default for load-read-function is nil, so it can't be called as a
> function by default.

The default has been `read' since Emacs 25.1.

> The value for me is indeed nil and is triggering an error for me when
> trying to evaluate an ert-deftest expression.

I don't see a place in Emacs where this variable is set to nil.  Why
could it be bound to nil for you?


Michael.

RE: [External] : Re: funcall of load-read-function (default nil) in elisp--eval-defun

[Drew Adams]

> > I see this line in elisp--eval-defun at least Emacs 28 - 30 (pre-
> release):
> >
> >           (setq form (funcall load-read-function (current-buffer)))
> >
> > The default for load-read-function is nil, so it can't be called as a
> > function by default.
> 
> The default has been `read' since Emacs 25.1.

Prior to Emacs 28 I don't find that variable at all,
so in those versions it's not the variable value
whose default is `read'; it's the (only) behavior
that's `read'.  But yes, in those prior versions,
function `read' is used literally where Emacs 28+
uses the variable.

It seems that (e.g. in 28.2) the variable is dynamic
and is let-bound in function `debug', in debug.el.
But it is used also in function `elisp--eval-defun'
in elisp-mode.el.  I see no place where it might get
bound to nil, but maybe that happens in some
non-vanilla code.  HTH.