Empty package sometimes evaluates as an empty object, sometimes as undefined

[mikol]

Expected Behavior

Empty packages should evaluate consistently, ideally as an empty object {}

Actual Behavior

Empty packages evaluate differently depending on how the Rego is written

Steps to Reproduce the Problem

1. Given an empty package:

package x.y.z

2. Reference the package elsewhere:

package undefined
z = data.x.y.z

3. Access data.undefined.z in the REPL:

opa run .
> data.undefined.z
undefined

4. Reference the package elsewhere using a variable instead of a static reference:

package defined
k = "y"
z = data.x[k].z

5. Access data.defined.z in the REPL:

opa run .
> data.defined.z
{}

Additional Info

Version: 0.14.2
Build Commit: db9855d
Build Timestamp: 2019-10-04T15:28:33Z
Build Hostname: 65ca4a7c4e81