fastify/lib/schema-compilers.js

'use strict'

const Ajv = require('ajv')
const fastJsonStringify = require('fast-json-stringify')

function ValidatorSelector () {
  const validatorPool = new Map()
  const cache = new Map()
  cache.put = cache.set

  return function buildCompilerFromPool (externalSchemas, options) {
    const externals = JSON.stringify(externalSchemas)
    const ajvConfig = JSON.stringify(options.customOptions)

    const uniqueAjvKey = `${externals}${ajvConfig}`
    if (validatorPool.has(uniqueAjvKey)) {
      return validatorPool.get(uniqueAjvKey)
    }

    const compiler = ValidatorCompiler(externalSchemas, options, cache)
    validatorPool.set(uniqueAjvKey, compiler)

    return compiler
  }
}

function ValidatorCompiler (externalSchemas, options, cache) {
  // This instance of Ajv is private
  // it should not be customized or used
  const ajv = new Ajv(Object.assign({
    coerceTypes: true,
    useDefaults: true,
    removeAdditional: true,
    // Explicitly set allErrors to `false`.
    // When set to `true`, a DoS attack is possible.
    allErrors: false,
    nullable: true
  }, options.customOptions, { cache }))

  if (options.plugins && options.plugins.length > 0) {
    for (const plugin of options.plugins) {
      plugin[0](ajv, plugin[1])
    }
  }

  Object.values(externalSchemas).forEach(s => ajv.addSchema(s))

  return ({ schema, method, url, httpPart }) => {
    return ajv.compile(schema)
  }
}

function SerializerCompiler (externalSchemas) {
  return function ({ schema, method, url, httpStatus }) {
    return fastJsonStringify(schema, { schema: externalSchemas })
  }
}

module.exports.ValidatorCompiler = ValidatorCompiler
module.exports.ValidatorSelector = ValidatorSelector
module.exports.SerializerCompiler = SerializerCompiler