webpack/lib/javascript/JavascriptGenerator.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support 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 Tobias Koppers @sokra
*/

"use strict";

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

/** @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("../Module")} Module */
/** @typedef {import("../Module").ConcatenationBailoutReasonContext} ConcatenationBailoutReasonContext */
/** @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)",
	"DEP_WEBPACK_JAVASCRIPT_GENERATOR_GET_INIT_FRAGMENTS"
);

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

class JavascriptGenerator extends Generator {
	/**
	 * @param {NormalModule} module fresh module
	 * @returns {Set<string>} available types (do not mutate)
	 */
	getTypes(module) {
		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 bailout reason should be determined
	 * @param {ConcatenationBailoutReasonContext} context context
	 * @returns {string | undefined} reason why this module can't be concatenated, undefined when it can be concatenated
	 */
	getConcatenationBailoutReason(module, context) {
		// Only harmony modules are valid for optimization
		if (
			!module.buildMeta ||
			module.buildMeta.exportsType !== "namespace" ||
			module.presentationalDependencies === undefined ||
			!module.presentationalDependencies.some(
				d => d instanceof HarmonyCompatibilityDependency
			)
		) {
			return "Module is not an ECMAScript module";
		}

		// Some expressions are not compatible with module concatenation
		// because they may produce unexpected results. The plugin bails out
		// if some were detected upfront.
		if (module.buildInfo && module.buildInfo.moduleConcatenationBailout) {
			return `Module uses ${module.buildInfo.moduleConcatenationBailout}`;
		}
	}

	/**
	 * @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);

		return InitFragment.addToSource(source, initFragments, generateContext);
	}

	/**
	 * @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
			);
		}

		if (module.presentationalDependencies !== undefined) {
			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,
			runtime: generateContext.runtime,
			runtimeRequirements: generateContext.runtimeRequirements,
			concatenationScope: generateContext.concatenationScope,
			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;