validation

Abstraction with KCL

Prerequisite

• Firstly, download and install KCL according to the instructions, and then prepare a Kubernetes environment.

Quick Start

1. Show Config

We can run the following command to show the config.

cat schema.k

schema User:
    name: str
    age: int
    message?: str
    data: Data
    labels: {str:}
    hc: [int]
        
    check:
        age > 10, "age must > 10"

schema Data:
    id: int
    value: str

In the schema, we can use the check keyword to write the validation rules of every schema attribute. Each line in the check block corresponds to a conditional expression. When the condition is satisfied, the validation is successful. The conditional expression can be followed by , "check error message" to indicate the message to be displayed when the check fails.

To sum up, the validation kinds supported in KCL schema are:

Kind	Method
Range	Using comparison operators such as <, >
Regex	Using methods such as match from the regex system module
Length	Using the len built-in function to get the length of a variable of type list/dict/str
Enum	Using literal union types
Optional/Required	Using optional/required attributes of schema
Condition	Using the check if conditional expression

2. Validate the Data

There is a JSON format file data.json:

{
    "name": "Alice",
    "age": 18,
    "message": "This is Alice",
    "data": {
        "id": 1,
        "value": "value1"
    },
    "labels": {
        "key": "value"
    },
    "hc": [1, 2, 3]
}

Execute the following command:

kcl vet data.json schema.k