webpack/lib/runtime/baseUri.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
	Author Alexander Akait @alexander-akait
*/

"use strict";

const RuntimeGlobals = require("../RuntimeGlobals");

const SCHEME_REGEXP = /^[a-z][a-z\d+\-.]*:/i;

/**
 * Whether `new URL(path, baseUri)` can resolve against it. Parsing is not the question:
 * an opaque scheme like `data:` or `mailto:` is a valid url and still no base for
 * anything, so the resolution itself is what gets asked.
 * @param {string} baseUri an entry's base uri
 * @returns {boolean} true when a relative path resolves against it
 */
const isAbsoluteBaseUri = (baseUri) => {
	try {
		// eslint-disable-next-line no-new
		new URL("./", baseUri);
		return true;
	} catch (_error) {
		return false;
	}
};

/**
 * Whether a base names a place relative to the chunk, so a literal can spell it. A
 * scheme makes it a base of its own, and a protocol-relative one takes its scheme from
 * wherever the chunk was loaded — neither is something a literal can state.
 * @param {string} baseUri an entry's base uri
 * @returns {boolean} true when it can be baked beside the chunk
 */
const isChunkRelativeBaseUri = (baseUri) =>
	!SCHEME_REGEXP.test(baseUri) && !baseUri.startsWith("//");

/**
 * Assignment of `__webpack_require__.b` for a chunk. An entry `baseUri` replaces the
 * base an asset url resolves against, but only an absolute one is a base by itself —
 * a relative one is read against the base this target would use without it, so it
 * lands beside the chunk rather than throwing wherever the runtime reads it.
 * @param {string | undefined} baseUri the entry's base uri, if it set one
 * @param {string} fallback expression for the base this target uses without one
 * @returns {string} the assignment, ending with `;`
 */
const renderBaseUri = (baseUri, fallback) => {
	// An empty one names no base of its own, so it leaves the target's alone.
	if (!baseUri) return `${RuntimeGlobals.baseURI} = ${fallback};`;
	// A scheme already makes it a base of its own. Whether anything resolves against an
	// opaque one is the user's to answer, as it was before.
	if (SCHEME_REGEXP.test(baseUri)) {
		return `${RuntimeGlobals.baseURI} = ${JSON.stringify(baseUri)};`;
	}
	return `${RuntimeGlobals.baseURI} = new URL(${JSON.stringify(
		baseUri
	)}, ${fallback}).href;`;
};

module.exports.isAbsoluteBaseUri = isAbsoluteBaseUri;
module.exports.isChunkRelativeBaseUri = isChunkRelativeBaseUri;
module.exports.renderBaseUri = renderBaseUri;