graphql-typed-client/src/cliHelpers/schemaTask.ts

A tool that generates a strongly typed client library for any GraphQL endpoint. The client allows writing GraphQL queries as plain JS objects (with type safety, awesome code completion experience, custom scalar type mapping, type guards and more)

import { buildASTSchema, assertValidSchema, GraphQLSchema } from 'graphql'
import { ListrTask } from 'listr'
import { Config } from '../config'
import { requireModuleFromPath } from '../helpers/files'
import { customFetchSchema, fetchSchema, SchemaFetcher } from '../schema/fetchSchema'
import { loadSchema } from 'graphql-toolkit'

export const schemaTask = (config: Config): ListrTask => {
  if (config.endpoint) {
    const endpoint = config.endpoint

    return {
      title: `fetching schema using ${config.post ? 'POST' : 'GET'} ${endpoint}`,
      task: async ctx => {
        ctx.schema = await fetchSchema(endpoint, config.post)
      },
    }
  } else if (config.fetcher) {
    const fetcher = config.fetcher

    return {
      title: 'fetching schema using custom fetcher',
      task: async ctx => {
        const resolvedFetcher = typeof fetcher === 'string' ? <SchemaFetcher>requireModuleFromPath([fetcher]) : fetcher
        ctx.schema = await customFetchSchema(resolvedFetcher, config.options && config.options.schemaValidation)
      },
    }
  } else if (config.schema) {
    const schema = config.schema

    return {
      title: 'loading schema',
      task: async ctx => {
        const options = config.options && config.options.schemaBuild
        const document = await loadSchema(schema)
        ctx.schema = document instanceof GraphQLSchema ? document : buildASTSchema(document, options)

        try {
          assertValidSchema(ctx.schema)
        } catch (e) {
          if (e.message === 'Query root type must be provided.') return
          throw e
        }
      },
    }
  } else {
    throw new Error('either `endpoint`, `fetcher` or `schema` must be defined in the config')
  }
}