flow-runtime-faker/src/index.js

object faker generation based on flow description

import { faker } from '@faker-js/faker'

const mapper = {
  "NumberType": ()=> faker.datatype.number(1000),
  "StringType": ()=> faker.datatype.string(),
  "BooleanType": () => faker.datatype.boolean(),
  "VoidType": () => undefined,
  "NullLiteralType": () => null,
  "MixedType": () => mapper[["NumberType", "StringType","BooleanType","NullLiteralType"][Math.floor(Math.random()*4)]](),
  "AnyType": () => mapper[["NumberType", "StringType","BooleanType","VoidType","NullLiteralType"][Math.floor(Math.random()*5)]](),
  "NumericLiteralType": content => content.value,
  "StringLiteralType": content => content.value,
  "BooleanLiteralType": content => content.value,
  "UnionType": content => content.types.map(internalTypeSelector)[Math.floor(Math.random()*content.types.length)],
  "NullableType": content => [internalTypeSelector(content.type), null, undefined][Math.floor(Math.random()*3)],
  "ArrayType": content => Array(faker.datatype.number(1000)).fill(0).map(_ => internalTypeSelector(content.elementType)),
  "TypeAlias": content => fake(content),
  "FunctionType": content => () => internalTypeSelector(content.returnType.type),
}

const internalTypeSelector = (type) =>
  type.typeName === "TypeAlias"
    ? fake(type)
    : mapper[type.typeName](type)


const valueGenerator = ({optional, content}) => optional
    ? [mapper[content.typeName](content), undefined][Math.floor(Math.random() * 2)]
    : mapper[content.typeName](content)

const fake = (base) => 
  base.properties
    .map(property => ({key: property.key, content: property.value, optional: property.optional}))
    .reduce((acc, {key, ...rest}) => ({
      ...acc,
      [key]: valueGenerator(rest)
    }), {})

export default fake