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JavaScript

// Manually “tree shaken” from:
// <https://github.com/nodejs/node/blob/45f5c9b/lib/internal/modules/esm/get_format.js>
// Last checked on: Nov 2, 2023.
import {fileURLToPath} from 'node:url'
import {getPackageType} from './resolve-get-package-type.js'
import {codes} from './errors.js'
const {ERR_UNKNOWN_FILE_EXTENSION} = codes
const hasOwnProperty = {}.hasOwnProperty
/** @type {Record<string, string>} */
const extensionFormatMap = {
// @ts-expect-error: hush.
__proto__: null,
'.cjs': 'commonjs',
'.js': 'module',
'.json': 'json',
'.mjs': 'module'
}
/**
* @param {string | null} mime
* @returns {string | null}
*/
function mimeToFormat(mime) {
if (
mime &&
/\s*(text|application)\/javascript\s*(;\s*charset=utf-?8\s*)?/i.test(mime)
)
return 'module'
if (mime === 'application/json') return 'json'
return null
}
/**
* @callback ProtocolHandler
* @param {URL} parsed
* @param {{parentURL: string, source?: Buffer}} context
* @param {boolean} ignoreErrors
* @returns {string | null | void}
*/
/**
* @type {Record<string, ProtocolHandler>}
*/
const protocolHandlers = {
// @ts-expect-error: hush.
__proto__: null,
'data:': getDataProtocolModuleFormat,
'file:': getFileProtocolModuleFormat,
'http:': getHttpProtocolModuleFormat,
'https:': getHttpProtocolModuleFormat,
'node:'() {
return 'builtin'
}
}
/**
* @param {URL} parsed
*/
function getDataProtocolModuleFormat(parsed) {
const {1: mime} = /^([^/]+\/[^;,]+)[^,]*?(;base64)?,/.exec(
parsed.pathname
) || [null, null, null]
return mimeToFormat(mime)
}
/**
* Returns the file extension from a URL.
*
* Should give similar result to
* `require('node:path').extname(require('node:url').fileURLToPath(url))`
* when used with a `file:` URL.
*
* @param {URL} url
* @returns {string}
*/
function extname(url) {
const pathname = url.pathname
let index = pathname.length
while (index--) {
const code = pathname.codePointAt(index)
if (code === 47 /* `/` */) {
return ''
}
if (code === 46 /* `.` */) {
return pathname.codePointAt(index - 1) === 47 /* `/` */
? ''
: pathname.slice(index)
}
}
return ''
}
/**
* @type {ProtocolHandler}
*/
function getFileProtocolModuleFormat(url, _context, ignoreErrors) {
const ext = extname(url)
if (ext === '.js') {
const packageType = getPackageType(url)
if (packageType !== 'none') {
return packageType
}
return 'commonjs'
}
if (ext === '') {
const packageType = getPackageType(url)
// Legacy behavior
if (packageType === 'none' || packageType === 'commonjs') {
return 'commonjs'
}
// Note: we dont implement WASM, so we dont need
// `getFormatOfExtensionlessFile` from `formats`.
return 'module'
}
const format = extensionFormatMap[ext]
if (format) return format
// Explicit undefined return indicates load hook should rerun format check
if (ignoreErrors) {
return undefined
}
const filepath = fileURLToPath(url)
throw new ERR_UNKNOWN_FILE_EXTENSION(ext, filepath)
}
function getHttpProtocolModuleFormat() {
// To do: HTTPS imports.
}
/**
* @param {URL} url
* @param {{parentURL: string}} context
* @returns {string | null}
*/
export function defaultGetFormatWithoutErrors(url, context) {
const protocol = url.protocol
if (!hasOwnProperty.call(protocolHandlers, protocol)) {
return null
}
return protocolHandlers[protocol](url, context, true) || null
}