Merge not working with :extend()

[d13]

When I use this LESS:

.error {
  background-color: #f00;
  color: #fff;
  box-shadow+: inset 0 0 0 1px #300;
}
.error-glowing {
  &:extend(.error all);
  box-shadow+: 0 0 10px 0 #d00;
}

I expect this:

.error {
  background-color: #f00;
  color: #fff;
  box-shadow: inset 0 0 0 1px #300;
}
.error-glowing {
  box-shadow: inset 0 0 0 1px #300, 0 0 10px 0 #d00;
}

The actual result is:

.error,
.error-glowing {
  background-color: #f00;
  color: #fff;
  box-shadow: inset 0 0 0 1px #300;
}
.error-glowing {
  box-shadow: 0 0 10px 0 #d00;
}

When I use .error like a mixin:

.error {
  background-color: #f00;
  color: #fff;
  box-shadow+: inset 0 0 0 1px #300;
}
.error-glowing {
  .error;
  box-shadow+: 0 0 10px 0 #d00;
}

It does the merge, but it has duplicate styles, of course:

.error {
  background-color: #f00;
  color: #fff;
  box-shadow: inset 0 0 0 1px #300;
}
.error-glowing {
  background-color: #f00;
  color: #fff;
  box-shadow: inset 0 0 0 1px #300, 0 0 10px 0 #d00;
}

Thanks.

[seven-phases-max]

Well, this is kind of expected. Simply by definition, extend is supposed to affect only selectors without taking into account what actually is going on inside of the affected rulesets. So in short, if you use merge don't use extend and vice-versa.

Technically (if we consider this as a feature request), in theory it is possible to have some "more smart" extend-like feature that will analyse both extended and extending rulesets and cast mixin-like behaviour where necessary but I doubt we'll have anything like this any time soon. (I guess this idea has been already mentioned somewhere among those tens of extend dedicated threads, for example in #2095 -> route:2)

[d13]

Thought I'd throw it out there. Fortunately, there's a gazillion ways to skin a cat with LESS.

[lukeapage]

If we implemented this I can see someone wanting a way to extend and not merge ..
It's a nice idea, but I think it's not worth it.

[seven-phases-max]

OK, I guess we can close this for now as something that's barely to be considered to be implemented in the foreseeable future.