MappedCode Class — svelte Architecture

Source Code

packages/svelte/src/compiler/utils/mapped_code.js lines 75–249

export class MappedCode {
	/**
	 * @type {string}
	 */
	string = /** @type {any} */ (undefined);

	/**
	 * @type {DecodedSourceMap}
	 */
	map = /** @type {any} */ (undefined);

	/**
	 * @param {string} string
	 * @param {DecodedSourceMap | null} map
	 */
	constructor(string = '', map = null) {
		this.string = string;
		if (map) {
			this.map = map;
		} else {
			this.map = {
				version: 3,
				mappings: [],
				sources: [],
				names: []
			};
		}
	}
	/**
	 * concat in-place (mutable), return this (chainable)
	 * will also mutate the `other` object
	 * @param {MappedCode} other
	 * @returns {MappedCode}
	 */
	concat(other) {
		// noop: if one is empty, return the other
		if (other.string == '') return this;
		if (this.string == '') {
			this.string = other.string;
			this.map = other.map;
			return this;
		}
		// compute last line length before mutating
		const column_offset = last_line_length(this.string);
		this.string += other.string;
		const m1 = this.map;
		const m2 = other.map;
		if (m2.mappings.length == 0) return this;
		// combine sources and names
		const [sources, new_source_idx, sources_changed, sources_idx_changed] = merge_tables(
			m1.sources,
			m2.sources
		);
		const [names, new_name_idx, names_changed, names_idx_changed] = merge_tables(
			m1.names,
			m2.names
		);
		if (sources_changed) m1.sources = sources;
		if (names_changed) m1.names = names;
		// unswitched loops are faster
		if (sources_idx_changed && names_idx_changed) {
			for (let line = 0; line < m2.mappings.length; line++) {
				const segment_list = m2.mappings[line];
				for (let segment = 0; segment < segment_list.length; segment++) {
					const seg = segment_list[segment];
					// @ts-ignore
					if (seg[1] >= 0) seg[1] = new_source_idx[seg[1]];
					// @ts-ignore
					if (seg[4] >= 0) seg[4] = new_name_idx[seg[4]];
				}
			}
		} else if (sources_idx_changed) {
			for (let line = 0; line < m2.mappings.length; line++) {
				const segment_list = m2.mappings[line];
				for (let segment = 0; segment < segment_list.length; segment++) {
					const seg = segment_list[segment];
					// @ts-ignore
					if (seg[1] >= 0) seg[1] = new_source_idx[seg[1]];
				}
			}
		} else if (names_idx_changed) {