webpack/lib/prefetch/parseResourceHintOptions.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

const UnsupportedFeatureWarning = require("../errors/UnsupportedFeatureWarning");

/** @typedef {import("../Dependency").DependencyLocation} DependencyLocation */
/** @typedef {import("../NormalModule")} NormalModule */

/**
 * @typedef {object} ResourceHintOptions
 * @property {true=} prefetch
 * @property {true=} preload
 * @property {("high" | "low" | "auto")=} fetchPriority
 * @property {string=} as
 * @property {string=} type
 * @property {string=} media
 */

/**
 * Reads `webpackPrefetch` / `webpackPreload` / `webpackFetchPriority` /
 * `webpackAs` / `webpackType` / `webpackMedia` from a parsed magic-comment
 * options object. Invalid values emit warnings to the given module.
 * @param {Record<string, EXPECTED_ANY> | null | undefined} importOptions parsed comment options
 * @param {NormalModule} module the module to attach warnings to
 * @param {DependencyLocation} loc location for warnings
 * @returns {ResourceHintOptions} parsed hints (empty when no comments matched)
 */
const parseResourceHintOptions = (importOptions, module, loc) => {
	/** @type {ResourceHintOptions} */
	const hints = {};
	if (!importOptions) return hints;

	/**
	 * @param {string} message warning text
	 * @returns {void}
	 */
	const warn = (message) => {
		module.addWarning(new UnsupportedFeatureWarning(message, loc));
	};

	if (importOptions.webpackPrefetch !== undefined) {
		if (importOptions.webpackPrefetch === true) {
			hints.prefetch = true;
		} else {
			warn(
				`\`webpackPrefetch\` expected true, but received: ${importOptions.webpackPrefetch}.`
			);
		}
	}
	if (importOptions.webpackPreload !== undefined) {
		if (importOptions.webpackPreload === true) {
			hints.preload = true;
		} else {
			warn(
				`\`webpackPreload\` expected true, but received: ${importOptions.webpackPreload}.`
			);
		}
	}
	if (importOptions.webpackFetchPriority !== undefined) {
		const fp = importOptions.webpackFetchPriority;
		if (fp === "high" || fp === "low" || fp === "auto") {
			hints.fetchPriority = fp;
		} else {
			warn(
				`\`webpackFetchPriority\` expected "low", "high" or "auto", but received: ${fp}.`
			);
		}
	}
	if (importOptions.webpackAs !== undefined) {
		if (typeof importOptions.webpackAs === "string") {
			hints.as = importOptions.webpackAs;
		} else {
			warn(
				`\`webpackAs\` expected a string, but received: ${importOptions.webpackAs}.`
			);
		}
	}
	if (importOptions.webpackType !== undefined) {
		if (typeof importOptions.webpackType === "string") {
			hints.type = importOptions.webpackType;
		} else {
			warn(
				`\`webpackType\` expected a string, but received: ${importOptions.webpackType}.`
			);
		}
	}
	if (importOptions.webpackMedia !== undefined) {
		if (typeof importOptions.webpackMedia === "string") {
			hints.media = importOptions.webpackMedia;
		} else {
			warn(
				`\`webpackMedia\` expected a string, but received: ${importOptions.webpackMedia}.`
			);
		}
	}

	return hints;
};

module.exports = parseResourceHintOptions;