script: Add json and yaml commands

[joamaki]

This provides simple "jq" style facility for transforming a JSON/YAML document to make it easier to write assertions against more complex data.

While a Go implementation of jq does exist it is very large, so opting instead for this much simpler one.

This uses the sigs.k8s.io/yaml to load a YAML document as this way we handle them the same way as Kubernetes and can work on e.g. CRDs in the way one expects.

[joamaki]

Another option here could be to use k8s.io/client-go/util/jsonpath instead as that's already vendored into cilium/cilium. It would be less expressive than JMESPath, but might be enough for most use-cases.

Both still have the problem that they don't fully support comparisons. JMESPath can do some filtering to do some of it but would be nice to find a lightweight option that allows doing jq-style comparisons, e.g.

echo '{"foo": 1}' | jq '.foo >= 1'
true

We could consider embedding gojq and only exposing it via scripttest to avoid it ending up in production binaries, but I'm not sure if it's worth pulling such a big dependency in. Linking the test binaries in cilium/cilium is already incredibly slow due the massive generated typed k8s client code...

[christarazi]

Did you consider whether we can use this in combination with db/show --format ...? The issue currently is that both the json and yaml commands only support loading one object, instead of multiple which is how db/show prints a table formatted in JSON or YAML. I'm not sure if this is a limitation on the JMESPath side or not.

[joamaki]

Did you consider whether we can use this in combination with db/show --format ...? The issue currently is that both the json and yaml commands only support loading one object, instead of multiple which is how db/show prints a table formatted in JSON or YAML. I'm not sure if this is a limitation on the JMESPath side or not.

Ah good point. I'll think about this.

[joamaki]

I'm now starting to lean towards just using gojq even though it's massive. If it's only a dependency of scripttest it shouldn't be too bad, or can even just have an extras package that has these sort of commands.