kibana/docs/development/plugins/expressions/server/kibana-plugin-plugins-expressions-server.expressionfunctiondefinition.md

Home > kibana-plugin-plugins-expressions-server > ExpressionFunctionDefinition

ExpressionFunctionDefinition interface

ExpressionFunctionDefinition is the interface plugins have to implement to register a function in expressions plugin.

Signature:

export interface ExpressionFunctionDefinition<Name extends string, Input, Arguments extends Record<string, any>, Output, Context extends ExecutionContext = ExecutionContext> extends PersistableStateDefinition<ExpressionAstFunction['arguments']> 

Properties

Property	Type	Description
aliases	string[]	What is this?
args	{ [key in keyof Arguments]: ArgumentType<Arguments[key]>; }	Specification of arguments that function supports. This list will also be used for autocomplete functionality when your function is being edited.
context	{ types: AnyExpressionFunctionDefinition['inputTypes']; }
disabled	boolean	if set to true function will be disabled (but its migrate function will still be available)
help	string	Help text displayed in the Expression editor. This text should be internationalized.
inputTypes	Array<TypeToString<Input>>	List of allowed type names for input value of this function. If this property is set the input of function will be cast to the first possible type in this list. If this property is missing the input will be provided to the function as-is.
name	Name	The name of the function, as will be used in expression.
type	TypeToString<UnwrapPromiseOrReturn<Output>>	Name of type of value this function outputs.

Methods

Method	Description
fn(input, args, context)	The actual implementation of the function.