Go API: Get value attributes as a slice

[cueckoo]

Originally opened by @verdverm in cuelang/cue#670

Is your feature request related to a problem? Please describe.

I'd like to retrieve all the attributes for a value as a slice for further processing within my application. The current API does not allow this and requires knowing the key (https://pkg.go.dev/cuelang.org/go@v0.3.0-alpha6/cue#Value.Attribute). The same applies for retrieving the key/value pairs from an attribute, which is of more interest to extract actually. The POC returns the key/value pairs for an attribute as a Go map.

My users can specify a regex so I cannot know the keys beforehand and thus the need for extra processing.

Describe the solution you'd like

cuelang/cue#529 is a POC

Describe alternatives you've considered

The API does not support this. I currently maintain a small patch to expose the above.

[cueckoo]

Original reply by @verdverm in cuelang/cue#670 (comment)

@mpvl would the query proposal (#165) support searching attributes?

[cueckoo]

Original reply by @mpvl in cuelang/cue#670 (comment)

@verdverm Very likely not. By doing so attributes would matter for evaluation. The whole purpose of attributes is that they are not part of the language.

The only thing imagine is that one could analyze CUE in the tooling layer, including getting attributes. But they should not influence regular evaluation.