node/lib/internal/modules/esm/assert.js
Antoine du Hamel 2cc7a91a5d esm: add support for JSON import assertion
Remove V8 flag for import assertions, enabling support for the syntax;
require the import assertion syntax for imports of JSON.

Support import assertions in user loaders.

Use both resolved module URL and import assertion type as the key for
caching modules.

Co-authored-by: Geoffrey Booth <webadmin@geoffreybooth.com>

PR-URL: https://github.com/nodejs/node/pull/40250
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
2021-11-03 20:06:55 -07:00

103 lines
3.2 KiB
JavaScript

'use strict';
const {
ArrayPrototypeIncludes,
ObjectCreate,
ObjectValues,
ObjectPrototypeHasOwnProperty,
Symbol,
} = primordials;
const { validateString } = require('internal/validators');
const {
ERR_IMPORT_ASSERTION_TYPE_FAILED,
ERR_IMPORT_ASSERTION_TYPE_MISSING,
ERR_IMPORT_ASSERTION_TYPE_UNSUPPORTED,
} = require('internal/errors').codes;
const kImplicitAssertType = Symbol('implicit assert type');
/**
* Define a map of module formats to import assertion types (the value of `type`
* in `assert { type: 'json' }`).
* @type {Map<string, string | typeof kImplicitAssertType}
*/
const formatTypeMap = {
'__proto__': null,
'builtin': kImplicitAssertType,
'commonjs': kImplicitAssertType,
'json': 'json',
'module': kImplicitAssertType,
'wasm': kImplicitAssertType, // Should probably be 'webassembly' per https://github.com/tc39/proposal-import-assertions
};
/** @type {Array<string, string | typeof kImplicitAssertType} */
const supportedAssertionTypes = ObjectValues(formatTypeMap);
/**
* Test a module's import assertions.
* @param {string} url The URL of the imported module, for error reporting.
* @param {string} format One of Node's supported translators
* @param {Record<string, string>} importAssertions Validations for the
* module import.
* @returns {true}
* @throws {TypeError} If the format and assertion type are incompatible.
*/
function validateAssertions(url, format,
importAssertions = ObjectCreate(null)) {
const validType = formatTypeMap[format];
switch (validType) {
case undefined:
// Ignore assertions for module types we don't recognize, to allow new
// formats in the future.
return true;
case importAssertions.type:
// The asserted type is the valid type for this format.
return true;
case kImplicitAssertType:
// This format doesn't allow an import assertion type, so the property
// must not be set on the import assertions object.
if (!ObjectPrototypeHasOwnProperty(importAssertions, 'type')) {
return true;
}
return handleInvalidType(url, importAssertions.type);
default:
// There is an expected type for this format, but the value of
// `importAssertions.type` was not it.
if (!ObjectPrototypeHasOwnProperty(importAssertions, 'type')) {
// `type` wasn't specified at all.
throw new ERR_IMPORT_ASSERTION_TYPE_MISSING(url, validType);
}
handleInvalidType(url, importAssertions.type);
}
}
/**
* Throw the correct error depending on what's wrong with the type assertion.
* @param {string} url The resolved URL for the module to be imported
* @param {string} type The value of the import assertion `type` property
*/
function handleInvalidType(url, type) {
// `type` might have not been a string.
validateString(type, 'type');
// `type` was not one of the types we understand.
if (!ArrayPrototypeIncludes(supportedAssertionTypes, type)) {
throw new ERR_IMPORT_ASSERTION_TYPE_UNSUPPORTED(type);
}
// `type` was the wrong value for this format.
throw new ERR_IMPORT_ASSERTION_TYPE_FAILED(url, type);
}
module.exports = {
kImplicitAssertType,
validateAssertions,
};