bug#28113: 25.2; `ignore-errors' around `require'

bug#28113: 25.2; `ignore-errors' around `require'

[Drew Adams]

I'm guessing that there is not a bug here, as this seems to happen for
all Emacs versions I have.  But it seems like it should be a bug.  I
would like to understand it, in any case.

In crosshairs.el I require vline.el and hl-line+.el:

(require 'vline)
(require 'hl-line+)

In start.el I wrap requiring crosshairs.el with `ignore-errors'
(`condition-case', for compatibility with older releases):

(condition-case nil
   (require 'crosshairs nil t)
  (error nil))

If I remove vline.el from my load-path and then try to load
crosshairs.el then I get this error:

Debugger entered--Lisp error: (file-error "Cannot open load file" "No such file or directory" "vline")
  require(vline)
  byte-code("..." [require vline custom-declare-group column-highlight nil "..."] 20)
  require(col-highlight)
  byte-code("..." [require hl-line+ col-highlight custom-declare-group crosshairs nil "..." ...] 20)
  require(crosshairs nil t)

Why is that?  Shouldn't the `condition-case' cause the load error for
vline.el to be ignored, since it occurs as part of the loading of
crosshairs.el?

In GNU Emacs 25.2.1 (x86_64-w64-mingw32)
 of 2017-04-24 built on LAPHROAIG
Windowing system distributor 'Microsoft Corp.', version 6.1.7601
Configured using:
 'configure --without-dbus --without-compress-install 'CFLAGS=-O2
 -static -g3''

bug#28113: 25.2; `ignore-errors' around `require'

[Noam Postavsky]

tags 28113 + unreproducible
quit

On Wed, Aug 16, 2017 at 4:11 PM, Drew Adams <drew.adams@oracle.com> wrote:
> I'm guessing that there is not a bug here, as this seems to happen for
> all Emacs versions I have.

Works for me. I tried

    emacs -Q -f toggle-debug-on-error -l start.el

where start.el has

    (condition-case err
        (let ((load-path (cons default-directory load-path)))
          (require 'load-some-nonexistent-files))
      (error (message "caught error: %S" err)))

And load-some-nonexistent-files.el has

    (require 'there-is-no-such-file)

    (provide 'load-some-nonexistent-files)

I get

    Debug on Error enabled globally
    caught error: (file-error "Cannot open load file"
                  "no such file or directory"
                  "there-is-no-such-file")

in *Messages*.


Tested in 24.3 and 25.1.

bug#28113: 25.2; `ignore-errors' around `require'

[Drew Adams]

> tags 28113 + unreproducible
> quit
> 
> Works for me. I tried
>     emacs -Q -f toggle-debug-on-error -l start.el
> where start.el has
>     (condition-case err
>         (let ((load-path (cons default-directory load-path)))
>           (require 'load-some-nonexistent-files))
>       (error (message "caught error: %S" err)))
> And load-some-nonexistent-files.el has
>     (require 'there-is-no-such-file)
>     (provide 'load-some-nonexistent-files)
> 
> I get
>     Debug on Error enabled globally
>     caught error: (file-error "Cannot open load file"
>                   "no such file or directory"
>                   "there-is-no-such-file")
> 
> in *Messages*.
> Tested in 24.3 and 25.1.

OK, I won't worry about it.  It's actually more complicated, and I
don't have the time or worry to track it down more.

FYI - The files all exist and are in my load path, when I byte-compile
them.  If I then start with emacs -Q and set the load-path so that it
can see all except vline.el (which is in a different dir) then the error
is raised.

I'm guessing that it is because of the files being compiled (no error
was raised when compiling because the load-path then was fuller, picking
up vline.el).

Also (perhaps relevant), the condition-case is itself not at top level
but is wrapped in a (when...) test for an emacs-major-version minimum.

Anyway, thanks for taking a look.