bug#20466: 25.0.50; REGRESSION in `isearch-mode-map': <backspace> is not translated to DEL

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: drew.adams@oracle.com,  20466@debbugs.gnu.org
> Date: Fri, 01 May 2015 14:03:26 -0400
> 
> >> What you're basically saying is that we should give up on the
> >> function-key-map binding which remaps `backspace' to DEL.
> > No, I'm saying it's unreliable, in the sense that a user who wants to
> > customize DEL cannot rely on Backspace continue doing what DEL does.
> 
> Exactly: you're saying "it's unreliable, so just forget about ti and
> always bind both keys".

Or don't bind either, in which case you don't need to "just forget
about it".

> And if both keys are bound in foo-map, then both keys also need to
> be bound in any other bar-map if the two ever happen to be active at
> the same time

You lost me.  What do you mean by "active at the same time"?

> so whoever follows your advice will force other people to follow it
> as well.

Good advice is like that, yes.

> The end result is that <backspace> will always be bound and the
> function-key-map binding will be useless.

Not if these keys are left at their default bindings, no.

> The purpose of the function-key-map binding is to make sure that if
> you want the same behavior for both, then you only need one binding
> (the one on DEL).

Which doesn't work if the mode binds Backspace.

> > Whatever you do, my rule will always yield more reliable results.
> 
> And will break more other cases where people have followed the path
> usually recommended (i.e. "only bind the DEL or TAB event unless you
> want to distinguish the two").

But this is exactly what the OP did, and look where it got him.