webpack/lib/javascript/JavascriptGenerator.js

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const util = require("util");
const { ConcatSource, RawSource, ReplaceSource } = require("webpack-sources");
const Generator = require("../Generator");

/** @typedef {import("webpack-sources").Source} Source */
/** @typedef {import("../DependenciesBlock")} DependenciesBlock */
/** @typedef {import("../Dependency")} Dependency */
/** @typedef {import("../DependencyTemplates")} DependencyTemplates */
/** @typedef {import("../Generator").GenerateContext} GenerateContext */
/** @typedef {import("../InitFragment")} InitFragment */
/** @typedef {import("../Module")} Module */
/** @typedef {import("../NormalModule")} NormalModule */
/** @typedef {import("../RuntimeTemplate")} RuntimeTemplate */

// TODO: clean up this file
// replace with newer constructs

const deprecatedGetInitFragments = util.deprecate(
	(template, dependency, templateContext) =>
		template.getInitFragments(dependency, templateContext),
	"DependencyTemplate.getInitFragment is deprecated (use apply(dep, source, { initFragments }) instead)"
);

/**
 * @param {InitFragment} fragment the init fragment
 * @param {number} index index
 * @returns {[InitFragment, number]} tuple with both
 */
const extractFragmentIndex = (fragment, index) => [fragment, index];

/**
 * @param {[InitFragment, number]} a first pair
 * @param {[InitFragment, number]} b second pair
 * @returns {number} sort value
 */
const sortFragmentWithIndex = ([a, i], [b, j]) => {
	const stageCmp = a.stage - b.stage;
	if (stageCmp !== 0) return stageCmp;
	const positionCmp = a.position - b.position;
	if (positionCmp !== 0) return positionCmp;
	return i - j;
};

const TYPES = new Set(["javascript"]);

class JavascriptGenerator extends Generator {
	/**
	 * @returns {Set<string>} available types (do not mutate)
	 */
	getTypes() {
		return TYPES;
	}

	/**
	 * @param {NormalModule} module the module
	 * @param {string=} type source type
	 * @returns {number} estimate size of the module
	 */
	getSize(module, type) {
		const originalSource = module.originalSource();
		if (!originalSource) {
			return 39;
		}
		return originalSource.size();
	}

	/**
	 * @param {NormalModule} module module for which the code should be generated
	 * @param {GenerateContext} generateContext context for generate
	 * @returns {Source} generated code
	 */
	generate(module, generateContext) {
		const originalSource = module.originalSource();
		if (!originalSource) {
			return new RawSource("throw new Error('No source available');");
		}

		const source = new ReplaceSource(originalSource);
		const initFragments = [];

		this.sourceModule(module, initFragments, source, generateContext);

		if (initFragments.length > 0) {
			// Sort fragments by position. If 2 fragments have the same position,
			// use their index.
			const sortedFragments = initFragments
				.map(extractFragmentIndex)
				.sort(sortFragmentWithIndex);

			// Deduplicate fragments. If a fragment has no key, it is always included.
			const keyedFragments = new Map();
			for (const [fragment] of sortedFragments) {
				if (typeof fragment.merge === "function") {
					const oldValue = keyedFragments.get(fragment.key);
					if (oldValue !== undefined) {
						keyedFragments.set(
							fragment.key || Symbol(),
							fragment.merge(oldValue)
						);
						continue;
					}
				}
				keyedFragments.set(fragment.key || Symbol(), fragment);
			}

			const concatSource = new ConcatSource();
			const endContents = [];
			for (const fragment of keyedFragments.values()) {
				concatSource.add(fragment.getContent(generateContext));
				const endContent = fragment.getEndContent(generateContext);
				if (endContent) {
					endContents.push(endContent);
				}
			}

			concatSource.add(source);
			for (const content of endContents.reverse()) {
				concatSource.add(content);
			}
			return concatSource;
		} else {
			return source;
		}
	}

	/**
	 * @param {Module} module the module to generate
	 * @param {InitFragment[]} initFragments mutable list of init fragments
	 * @param {ReplaceSource} source the current replace source which can be modified
	 * @param {GenerateContext} generateContext the generateContext
	 * @returns {void}
	 */
	sourceModule(module, initFragments, source, generateContext) {
		for (const dependency of module.dependencies) {
			this.sourceDependency(
				module,
				dependency,
				initFragments,
				source,
				generateContext
			);
		}

		for (const dependency of module.presentationalDependencies) {
			this.sourceDependency(
				module,
				dependency,
				initFragments,
				source,
				generateContext
			);
		}

		for (const childBlock of module.blocks) {
			this.sourceBlock(
				module,
				childBlock,
				initFragments,
				source,
				generateContext
			);
		}
	}

	/**
	 * @param {Module} module the module to generate
	 * @param {DependenciesBlock} block the dependencies block which will be processed
	 * @param {InitFragment[]} initFragments mutable list of init fragments
	 * @param {ReplaceSource} source the current replace source which can be modified
	 * @param {GenerateContext} generateContext the generateContext
	 * @returns {void}
	 */
	sourceBlock(module, block, initFragments, source, generateContext) {
		for (const dependency of block.dependencies) {
			this.sourceDependency(
				module,
				dependency,
				initFragments,
				source,
				generateContext
			);
		}

		for (const childBlock of block.blocks) {
			this.sourceBlock(
				module,
				childBlock,
				initFragments,
				source,
				generateContext
			);
		}
	}

	/**
	 * @param {Module} module the current module
	 * @param {Dependency} dependency the dependency to generate
	 * @param {InitFragment[]} initFragments mutable list of init fragments
	 * @param {ReplaceSource} source the current replace source which can be modified
	 * @param {GenerateContext} generateContext the render context
	 * @returns {void}
	 */
	sourceDependency(module, dependency, initFragments, source, generateContext) {
		const constructor =
			/** @type {new (...args: any[]) => Dependency} */ (dependency.constructor);
		const template = generateContext.dependencyTemplates.get(constructor);
		if (!template) {
			throw new Error(
				"No template for dependency: " + dependency.constructor.name
			);
		}

		const templateContext = {
			runtimeTemplate: generateContext.runtimeTemplate,
			dependencyTemplates: generateContext.dependencyTemplates,
			moduleGraph: generateContext.moduleGraph,
			chunkGraph: generateContext.chunkGraph,
			module,
			runtimeRequirements: generateContext.runtimeRequirements,
			initFragments
		};

		template.apply(dependency, source, templateContext);

		// TODO remove in webpack 6
		if ("getInitFragments" in template) {
			const fragments = deprecatedGetInitFragments(
				template,
				dependency,
				templateContext
			);

			if (fragments) {
				for (const fragment of fragments) {
					initFragments.push(fragment);
				}
			}
		}
	}
}

module.exports = JavascriptGenerator;