cmd/cue: cmd definition adds significant time to export of yaml

[cueckoo]

Originally opened by @myitcv in https://github.com/cuelang/cue/issues/757

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

$ cue version
cue version +760aa115 linux/amd64

Does this issue reproduce with the latest release?

Yes

What did you do?

Like #756, this is a non-minimal repro in order to demonstrate a perceivable timing difference.

Given this issue is based on the same example as #756, it's possible the slowdown here is a function of the underlying cause of #756. Nonetheless, reporting this for completeness.

That said, a number of people have anecdotally said "cue cmd makes things slower". This issue seeks to demonstrate the difference between a cue eval --out yaml and a cue cmd command that does exactly the same thing (in fact marginally less).

https://gist.github.com/myitcv/849b8aeaecf2469706ce0a15251c0040

The cue cmd command is defined as follows:

package ci

import (

	"encoding/yaml"

	"tool/file"
)

command: genworkflows: {
	"test.yml": file.Create & {
		filename: "tmp/test.yml"
		contents: yaml.Marshal(test)
	}
}

where test is one of our GitHub workflow declarations.

The cue export command run is:

cue eval --out yaml -o tmp/out

What did you expect to see?

Similar timings between the two

What did you see instead?

The cue cmd command taking almost twice as long:

> exec time -p cue eval --out yaml -o tmp/out
[stderr]
real 0.95
> exec time -p cue cmd genworkflows
[stderr]
real 1.74

Tentatively marking this as v0.3.0... but on the basis we're looking to rewrite cue cmd as cuerun we may choose to simply ignore this for now.

[myitcv]

Dropping the now-defunct v0.4.x milestone from this issue, but leaving the zGarden label such that we come round to considering what milestone this should sit in.