Guarantee of no broken dependencies?

[Peter Polidoro <peter@polidoro.io>]

For every commit to the Guix master branch, is there a guarantee that there are no packages with broken dependencies?

I have not experienced packages with broken dependencies, so I am curious how that is checked. In theory, someone could make a commit that accidentally breaks other packages correct? Aren’t most inputs just found by name, not name and version or hash?

Do packages not get broken, though, because right before every commit the updated package is built, along with every package that depends on the updated package? Is that enough to make sure all dependencies are fine? There are no race conditions with other people making updates at the same time?

How can we do such a consistency check or have such a guarantee when we use multiple channels? Does we just rebuild every package in every non-Guix channel every time we update Guix to find out what breaks?