cue/cmd: export encoding is hiding errors

[verdverm]

What version of CUE are you using (cue version)?

0.4.0

What did you do?

Given foo.cue

package foo

#SomeBaseType: {
 "a" | "b"
 #AUTO: "z"
}

V1: ("x" | "y") | *"z"
V2: ("x" | "y") | *#SomeBaseType.#AUTO

No error is printed, but exit code is 1

$ cue export foo.cue

$ echo $?
1

Specifying the output format does help a little

$ cue export foo.cue --out yaml
yaml: unsupported node "x"|"y" (*ast.BinaryExpr)

$ cue export foo.cue --out json

$ cue export foo.cue --out cue
V1: "z"
V2: "x" | "y"

What did you expect to see?

errors about V2 not being concrete

[verdverm]

Related to #1152

[myitcv]

Thanks for raising this, @verdverm.

I think the following captures the essence of the bug:

# Default export mode
! exec cue export x.cue
stderr 'incomplete'

# Yaml
! exec cue export --out yaml x.cue
stderr 'incomplete'

# JSON
! exec cue export --out json x.cue
stderr 'incomplete'

-- x.cue --
package foo

#SomeBaseType: {
	"a" | "b"
	#AUTO: "z"
}

V1: ("x" | "y") | *"z"
V2: ("x" | "y") | *#SomeBaseType.#AUTO

Namely that regardless of export format, we should be seeing an error related to the incomplete-ness of V2.

(grr, hit Cmd+Enter instead of enter!)

The current output is:

# Default export mode (0.021s)
> ! exec cue export x.cue
[stderr]

[exit status 1]
> stderr 'incomplete'
FAIL: /tmp/testscript967438656/repro.txt/script.txt:3: no match for `incomplete` found in stderr

Confirmed with 370fac9.

[mpvl]

This is an intriguing case. One could argue that this is not an incomplete error. According to the current CUE spec, it should be an error though. I guess in the future we could relax this, if we can define a good way to hold this.

[myitcv]

One could argue that this is not an incomplete error.

What type of error do you think it should be?