webpack/lib/dependencies/PureExpressionDependency.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 { UsageState } = require("../ExportsInfo");
const makeSerializable = require("../util/makeSerializable");
const NullDependency = require("./NullDependency");

/** @typedef {import("webpack-sources").ReplaceSource} ReplaceSource */
/** @typedef {import("../ChunkGraph")} ChunkGraph */
/** @typedef {import("../Dependency")} Dependency */
/** @typedef {import("../Dependency").UpdateHashContext} UpdateHashContext */
/** @typedef {import("../DependencyTemplate").DependencyTemplateContext} DependencyTemplateContext */
/** @typedef {import("../ModuleGraph")} ModuleGraph */
/** @typedef {import("../ModuleGraphConnection").ConnectionState} ConnectionState */
/** @typedef {import("../util/Hash")} Hash */

class PureExpressionDependency extends NullDependency {
	/**
	 * @param {[number, number]} range the source range
	 */
	constructor(range) {
		super();
		this.range = range;
		/** @type {Set<string> | false} */
		this.usedByExports = false;
	}

	/**
	 * Update the hash
	 * @param {Hash} hash hash to be updated
	 * @param {UpdateHashContext} context context
	 * @returns {void}
	 */
	updateHash(hash, context) {
		hash.update(this.range + "");
	}

	/**
	 * @param {ModuleGraph} moduleGraph the module graph
	 * @returns {ConnectionState} how this dependency connects the module to referencing modules
	 */
	getModuleEvaluationSideEffectsState(moduleGraph) {
		return false;
	}

	serialize(context) {
		const { write } = context;
		write(this.range);
		write(this.usedByExports);
		super.serialize(context);
	}

	deserialize(context) {
		const { read } = context;
		this.range = read();
		this.usedByExports = read();
		super.deserialize(context);
	}
}

makeSerializable(
	PureExpressionDependency,
	"webpack/lib/dependencies/PureExpressionDependency"
);

PureExpressionDependency.Template = class PureExpressionDependencyTemplate extends NullDependency.Template {
	/**
	 * @param {Dependency} dependency the dependency for which the template should be applied
	 * @param {ReplaceSource} source the current replace source which can be modified
	 * @param {DependencyTemplateContext} templateContext the context object
	 * @returns {void}
	 */
	apply(dependency, source, { moduleGraph, runtime }) {
		const dep = /** @type {PureExpressionDependency} */ (dependency);

		if (dep.usedByExports !== false) {
			const selfModule = moduleGraph.getParentModule(dep);
			const exportsInfo = moduleGraph.getExportsInfo(selfModule);
			for (const exportName of dep.usedByExports) {
				if (exportsInfo.getUsed(exportName, runtime) !== UsageState.Unused) {
					return;
				}
			}
		}

		source.insert(
			dep.range[0],
			"(/* unused pure expression or super */ null && ("
		);
		source.insert(dep.range[1], "))");
	}
};

module.exports = PureExpressionDependency;