cuelang.org: cue eval -p documentation is incorrect

[PierreR]

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

$ cue version
cue version 0.4.0 linux/amd64

Does this issue reproduce with the latest release?

yes

What did you do?

Given 2 files foo.cue and bar.cue

src/foo.cue

package foo

foo: "hello"

src/bar.cue

package bar

bar: "world"

cue eval -p foo ./src 
found packages "foo" (foo.cue) and "bar" (bar.cue) in ".../src"

What did you expect to see?

I expect the error message to be printed when using cue eval ./src and to disappear when adding the -p option as in the documentation at https://cuelang.org/docs/concepts/packages/#files-belonging-to-a-package

What did you see instead?

Same behavior with or without -p

[myitcv]

Hmm, this appears to be a bug in the docs. Because, to my knowledge, -p has never been used for this purpose. -p is used for specifying a package where one cannot be inferred from context, e.g. where OpenAPI is consumed as input, and the user wants to specify a package as part of the output.

In the case you link to from the docs, the package selection happens as part of the package pattern specified on the command line:

# One package in the current directory
exec cue eval

# Two packages in the x directory
! exec cue eval ./x

# Choose package x
exec cue eval ./x:x

# Choose package y
exec cue eval ./x:y

-- a.cue --
package a

import "mod.com/x"

x
-- cue.mod/module.cue --
module: "mod.com"
-- x/x.cue --
package x

x: 5
-- x/y.cue --
package y

y: 5

Gives:

# One package in the current directory (0.048s)
> exec cue eval
[stdout]
x: 5
# Two packages in the x directory (0.033s)
> ! exec cue eval ./x
[stderr]
found packages "x" (x.cue) and y (y.cue) in "$WORK/x"
[exit status 1]
# Choose package x (0.041s)
> exec cue eval ./x:x
[stdout]
x: 5
# Choose package y (0.039s)
> exec cue eval ./x:y
[stdout]
y: 5
PASS

So I will repurpose this issue for fixing up those docs.

But I've also raised #1138, because I think the behaviour of imports and cmd/cue package resolution should be consistent with respect to ambiguous package selection.

[vikstrous2]

I ran into this today too. This is very confusing since even the docs got it wrong.

[adrienbrault]

Was able to figure out how to export a specific package thanks to this issue.

$ cue export
found packages "config" (config.cue) and hello (hello.cue) in "..."

$ cue export :config
{
    "foo": "bar"
}

$ cue export :hello
{
    "hello": "world"
}