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

From: Drew Adams <[email-masked]>
Date: Wed, 16 Aug 2017 13:11:56 -0700 (PDT)

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''