I really hope that one day Google can open source GCL, which so many languages have been inspired by without ever really being as good as it is. They all claim to address pitfalls in GCL but at the end of the day they're just worse than GCL.
Anecdotally, I've heard a lot of GCL horror stories, and many Xooglers have chosen to create things like Jsonnet or Skycfg (https://github.com/stripe/skycfg) instead.
Despite the minimalism it is not necessarily simple. There are features like inheritance and late binding. They can be quite complicated, but the thing that really stands out about GCL is it's not complicated to use. The simple cases are easy, straightforward, and readable. The complicated cases are made possible.
I've used it extensively to store and transform data that has to be manually edited by humans. It's a really great format because I can define all the translation rules which can get pretty complicated, but the complexity I expose to the humans who are writing the data is minimal. But if they need to do some transformations on the data or even just, like, string substitutions...the language is there and they can use it. That's what makes writing your data in a configuration language nice.
(Honestly though I think jsonnet is at least vastly superior to skycfg and the whole starlark ecosystem. I swear I'm so sick of languages that intentionally look like Python without being actual Python!)
From that link:
> However, the early design of GCL went for something simpler that coincidentally was also incompatible with the notion of graph unification. This simpler approach proved insufficient, but it was already too late to move to the earlier foreseen approach. Instead, an inheritance-based override model was adopted. Its complexity made the earlier foreseen tooling intractable and they never materialized. The same holds for the GCL offsprings that copied its model.
Needless to say I disagree with the Cue author. I think the inheritance-based override model is fantastic and has made for a great and straightforward configuration language.
Damn network effect, ruining everything :-/