[Feature] Top level expression statement value plan.

[Peefy]

Feature

In previous versions of KCL, the values of top-level expression statements were not output to JSON/YAML, such as the following example, which we can now support them.

1
[1, 2, 3]
{
    a = 1
    b = 1
}
Pod {
    apiVersion = "v1"
}

Design

In previous versions of KCL, the values of top-level expression statements did not have any semantics. We can set their semantics to correspond to scalar values in JSON/YAML, giving KCL more semantics that is closer to Jsonlike. For example, the following KCL code will be output as JSON/YAML.

1

The output JSON/YAML is

1

We collectively refer to these values as scalars, The output principle of scalars in KCL is

• All scalars undergo idempotent configuration merging, and an error is thrown when a collision error occurs during the merge. KCL does not output any JSON/YAML values.
• Any scalar and nonscalar types cannot be merged because they are different types. For example, the following code will throw an error:

a = 1
1 # Error: conflict values between {a = 1} and 1

Example

Schema

schema Config:
    id: int

Config {
    id = 1
}

The output YAML is

id: 1

Conflict Value Errors

• Case 1

1
2

• Case 2

a = 1
2

• Case 3

{
   a = 1
}
2

Reference

• cue: https://github.com/cue-lang/cue
• jsonnet: https://github.com/google/jsonnet
• Dhall: https://github.com/dhall-lang/dhall-lang

[Peefy]

Closed by #556