Eli Zaretskii <eliz@gnu.org> writes:

>> > If we can make it so that existing customizations of
>> > browse-url-secondary-browser-function will keep working as they did,
>> > then the backward incompatibility issue will disappear, and such a
>> > change becomes possible.  But in any case, the doc string of
>> > browse-url-secondary-browser-function should be amended if we are
>> > going to support its setting to eww.
>> 
>> Okay, I can do that.
>> 
>> > Also, are we sure all the relevant functions always have the
>> > 'browse-url-browser-kind property? what about user-defined functions,
>> > for example?
>> 
>> User-defined functions may not have the property. But we can be
>> conservative and preserve the existing behavior in the case where the
>> property is unavailable, treating the missing property like the value
>> `external'. Only if the property is found and `internal', the
>> `browse-url-with-browser-kind' will be used to make sure that an
>> external browser is used. As I mentioned, alternatively one can be even
>> more conservative and only use `browse-url-with-browser-kind' if
>> `browse-url-secondary-browser-function' is set to `eww-browse-url'. That
>> might be a little bit too restrictive, but it would be completely
>> backward compatible.
>
> Looking forward to seeing an updated patch which preserves the current
> behavior wrt browse-url-secondary-browser-function's customization.
>
> Thanks.

Updated patch attached.