Function extractSourceMap

lib/util/extractSourceMap.js:222–316

* Extract source map from code content * @param {StringOrBuffer} stringOrBuffer The input code content as string or buffer * @param {string} resourcePath The path to the resource file * @param {ReadResource} readResource The read resource function * @returns {Promise<{ source: StringOrBuffer, so

(stringOrBuffer, resourcePath, readResource)

 * @returns {Promise<{ source: StringOrBuffer, sourceMap: string | RawSourceMap | undefined }>} Promise resolving to extracted source map information
 */
async function extractSourceMap(stringOrBuffer, resourcePath, readResource) {
	const input =
		typeof stringOrBuffer === "string"
			? stringOrBuffer
			: stringOrBuffer.toString("utf8");
	const inputSourceMap = undefined;
	const output = {
		source: stringOrBuffer,
		sourceMap: inputSourceMap
	};
	const { sourceMappingURL, replacementString } = getSourceMappingURL(input);

	if (!sourceMappingURL) {
		return output;
	}

	const baseContext = path.dirname(resourcePath);

	const { sourceURL, sourceContent } = await fetchFromURL(
		readResource,
		baseContext,
		sourceMappingURL
	);

	if (!sourceContent) {
		return output;
	}

	/** @type {RawSourceMap} */
	const map = JSON.parse(
		sourceContent.toString("utf8").replace(/^\)\]\}'/, "")
	);

	const context = sourceURL ? path.dirname(sourceURL) : baseContext;

	const resolvedSources = await Promise.all(
		map.sources.map(
			async (/** @type {string} */ source, /** @type {number} */ i) => {
				const originalSourceContent =
					map.sourcesContent &&
					typeof map.sourcesContent[i] !== "undefined" &&
					map.sourcesContent[i] !== null
						? map.sourcesContent[i]
						: undefined;
				const skipReading = typeof originalSourceContent !== "undefined";
				// We do not skipReading here, because we need absolute paths in sources.
				// This is necessary so that for sourceMaps with the same file structure in sources, name collisions do not occur.
				// https://github.com/webpack-contrib/source-map-loader/issues/51
				let { sourceURL, sourceContent } = await fetchFromURL(
					readResource,
					context,
					source,
					map.sourceRoot,
					skipReading
				);

				if (skipReading) {
					sourceContent = originalSourceContent;