Decorators

Decorators add metadata, validation, and constraints to declarations. Kite has 17 built-in decorators.

Syntax

@decoratorName
@decoratorName(argument)
@decoratorName(namedArg: value)

Multiple decorators can be stacked:

@description("Server port")
@minValue(1)
@maxValue(65535)
input number port = 8080

Validation Decorators

@minValue(n)

Minimum value constraint for numbers.

@minValue(1)
input number port  = 8080
@minValue(0)
input number count = 10

@maxValue(n)

Maximum value constraint for numbers.

@maxValue(65535)
input number port       = 8080
@maxValue(100)
input number percentage = 50

@minLength(n)

Minimum length for strings and arrays.

@minLength(3)
input string name
@minLength(1)
input string[] tags

@maxLength(n)

Maximum length for strings and arrays.

@maxLength(255)
input string name
@maxLength(10)
input string[] tags

@nonEmpty

Ensures strings or arrays are not empty.

@nonEmpty
input string name
@nonEmpty
input string[] requiredTags

@validate(regex: "pattern")

Custom validation with regex pattern or preset.

// Regex validation
@validate(regex: "^[a-z]+$")
input string name
@validate(regex: "^[a-z0-9-]+$")
input string slug
// Preset validation
@validate(preset: "email")
input string email

@allowed([values])

Whitelist of allowed values.

@allowed(["dev", "staging", "prod"])
input string environment = "dev"
@allowed([80, 443, 8080])
input number port        = 80

@unique

Ensures array elements are unique.

@unique
input string[] tags  = ["web", "api"]
@unique
input number[] ports = [80, 443, 8080]

Schema Decorators

@cloud

Marks properties as cloud-generated (set by provider after creation).

schema AwsInstance {
    string name                      // User-set
    @cloud string arn                // Cloud-generated
    @cloud(importable) string id     // Cloud-generated, importable
}

Syntax forms:

@cloud - Cloud-generated, not importable
@cloud(importable) - Shorthand for importable=true
@cloud(importable=true) - Explicit true
@cloud(importable=false) - Same as plain @cloud

Resource Decorators

@existing("reference")

Reference existing cloud resources.

@existing("arn:aws:s3:::my-bucket")
resource S3.Bucket existingBucket {}
@existing("i-0123456789abcdef0")
resource EC2.Instance existingServer {}

Supported formats:

ARN: arn:aws:s3:::bucket-name
URL: https://example.com or s3://bucket/key
EC2 Instance ID: i-0123456789abcdef0
KMS Alias: alias/my-key
Log Group: /aws/lambda/my-function
Tags: Environment=prod,Team=platform

@sensitive

Mark sensitive data (passwords, secrets, API keys).

@sensitive
input string apiKey
@sensitive
output string connectionString
@sensitive
resource RDS.Instance database { ... }

@dependsOn(resources)

Explicit dependency declaration.

resource VPC.Subnet subnet { ... }
@dependsOn(subnet)
resource EC2.Instance server { ... }
@dependsOn([vpc, subnet, securityGroup])
resource RDS.Instance database { ... }

@tags(tags)

Add cloud provider tags.

// Object format
@tags({ Environment: "prod", Team: "platform" })
resource S3.Bucket photos { ... }
// Array format
@tags(["Environment =prod", "Team=platform"])
resource EC2.Instance server { ... }
// String format
@tags("Environment  =prod")
resource RDS.Instance db { ... }

@provider(providers)

Target specific cloud providers.

@provider("aws")
resource S3.Bucket photos { ... }
@provider(["aws", "azure"])
resource Storage.Bucket multiCloud { ... }

@count(n)

Create multiple instances. Injects count variable (0-indexed).

@count(3)
resource EC2.Instance server {
    name               = "server-${count}"  // server-0, server-1, server-2
}
@count(replicas)
component WebServer api {
    input number index = count
}

Metadata Decorators

@description("text")

Documentation for any declaration.

@description("The port number for the web server")
input number port = 8080
@description("Main application database")
resource RDS.Instance database { ... }
@description("User configuration schema")
schema Config { ... }
@description("Calculate the area of a rectangle")
fun area(number w, number h) number { ... }

Quick Reference

Decorator	Arguments	Targets
`@minValue(n)`	number	input, output
`@maxValue(n)`	number	input, output
`@minLength(n)`	number	input, output
`@maxLength(n)`	number	input, output
`@nonEmpty`	none	input
`@validate(regex:, preset:)`	named strings	input, output
`@allowed([...])`	array	input, schema property
`@unique`	none	input
`@cloud`	optional: importable	schema property
`@existing("ref")`	string	resource
`@sensitive`	none	input, output
`@dependsOn(res)`	reference(s)	resource, component
`@tags({...})`	object/array/string	resource, component
`@provider("...")`	string/array	resource, component
`@description("...")`	string	all declarations
`@count(n)`	number	resource, component

Syntax Rules

// Valid - single positional argument
@provider("aws")
@provider(["aws", "azure"])  // Array is ONE argument
// Valid - named arguments
@validate(regex: "^[a-z]+$")
// Invalid - multiple positional arguments
@provider("aws", "azure")  // ERROR: use array instead

Object Key Validation

Decorator object keys must be alphanumeric:

// Valid
@tags({ envStage: "prod" })      // underscore OK
@tags({ cloudProvider: "aws" })  // hyphen OK
@tags({ Environment: "production" })
// Invalid
@tags({ "env stage": "prod" })    // space not allowed
@tags({ "123start": "value" })    // can't start with number

Pattern: ^[a-zA-Z][a-zA-Z0-9_-]*$

Next: Learn about the Standard Library - built-in functions.