Converting a list of objects to YAML document ('---') with cue export

[cueckoo]

Originally opened by @PierreR in cuelang/cue#996

Is there a way to convert a list of objects to a '---'-separated stream of YAML values with cue export --out yaml ?

Or do I always need to use MarshalStream together with cue cmd

[cueckoo]

Original reply by @seh in cuelang/cue#996 (comment)

I was getting ready to ask the same question, as, to my surprise, this desire has come up several times over the last week.

I don't think using yaml.MarshalStream necessitates using cue cmd, though; you can emit a top-level string value and request the output format be "text." What I can't remember, though, is whether this works without use of the --expression flag. I found that trying to emit a top-level string value didn't work, but emitting a struct with a field whose value is of type string works in concert with --expression to select that field's value.

[cueckoo]

Original reply by @seh in cuelang/cue#996 (comment)

This problem with trying to use --out text without the --expression flag bit me again today.

If my top-level value is yaml.MarshalStream(v) and I run cue eval file --out text, it fails with "incomplete value." If instead I revise that to be x: yaml.MarshalStream(v) and run cue eval file --out text --expression x, it works as expected.

[cueckoo]

Original reply by @myitcv in cuelang/cue#996 (comment)

@seh please can you provide a repro?

[cueckoo]

Original reply by @myitcv in cuelang/cue#996 (comment)

(grrr that sent too early).

Because I seemingly can't reproduce the issue you are referring to.

[cueckoo]

Original reply by @seh in cuelang/cue#996 (comment)

I'm not sure if the previous time this happened it was due to the same cause, but later yesterday I realized that I made a mistake: I was trying to export two different top-level string values from the same package. The error message didn't make clear that that was the problem. By nesting that string value inside of a field, that then revealed an error about trying to unify a struct and a string, which tipped me off further.

[cueckoo]

Original reply by @myitcv in cuelang/cue#996 (comment)

Got it, that makes sense. If you are able to provide a repro for the poor error message, they're always good to fix.