bug#18343: 24.4.50; REGRESSION: `help-echo' property is not added, so no tooltip or echo

[Drew Adams]

> > Why should `help-echo' be on `font-lock-extra-managed-props'?
> 
> I guess the reason is to allow font-lock to propertize parts of the
> buffer with this property.  This issue is a (presumably not trivially
> avoidable) side effect.

By "allow font-lock to propertize parts of the buffer with this
property" do you mean allow it to propertize, with faces, parts
of the buffer that happen to have property `help-echo'?  Or do
you mean allow it to add property `help-echo' parts of the buffer?

If the latter, what is the use case for font-lock doing that?

I'll assume you meant the former -

In that case, why not trivially avoidable?  Why not tell font-lock
hands-off this property, which has nothing to do with highlighting?
Until the recent change that caused this regression, property
`help-echo' was not on the list `font-lock-extra-managed-props'.

Is it clear to you why it needs to be on that list?  It's not
clear to me.