webpack/lib/optimize/ModuleConcatenationPlugin.js

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

const HarmonyImportDependency = require("../dependencies/HarmonyImportDependency");
const ConcatenatedModule = require("./ConcatenatedModule");
const HarmonyExportImportedSpecifierDependency = require("../dependencies/HarmonyExportImportedSpecifierDependency");

class ModuleConcatenationPlugin {
	constructor(options) {
		if(typeof options !== "object") options = {};
		this.options = options;
	}

	apply(compiler) {
		compiler.plugin("compilation", (compilation, params) => {
			params.normalModuleFactory.plugin("parser", (parser, parserOptions) => {
				parser.plugin("call eval", () => {
					parser.state.module.meta.hasEval = true;
				});
			});
			const bailoutReasonMap = new Map();
			function setBailoutReason(module, reason) {
				bailoutReasonMap.set(module, reason);
				module.optimizationBailout.push(reason);
			}
			function getBailoutReason(module, requestShortener) {
				const reason = bailoutReasonMap.get(module);
				if(typeof reason === "function") return reason(requestShortener);
				return reason;
			}
			compilation.plugin("optimize-chunk-modules", (chunks, modules) => {
				chunks.forEach(chunk => {
					const relevantModules = [];
					const possibleInners = new Set();
					for(const module of chunk.modulesIterable) {
						// Only harmony modules are valid for optimization
						if(!module.meta || !module.meta.harmonyModule) {
							continue;
						}

						// Module must not be in other chunks
						// TODO add an option to allow module to be in other entry points
						if(module.getNumberOfChunks() !== 1) {
							setBailoutReason(module, "ModuleConcatenation: module is in multiple chunks");
							continue;
						}

						// Because of variable renaming we can't use modules with eval
						if(module.meta && module.meta.hasEval) {
							setBailoutReason(module, "ModuleConcatenation: eval is used in the module");
							continue;
						}

						relevantModules.push(module);

						// Module must not be the entry points
						if(chunk.entryModule === module) {
							setBailoutReason(module, "ModuleConcatenation (inner): module is an entrypoint");
							continue;
						}

						// Exports must be known (and not dynamic)
						if(!Array.isArray(module.providedExports)) {
							setBailoutReason(module, "ModuleConcatenation (inner): exports are not known");
							continue;
						}

						// Using dependency variables is not possible as this wraps the code in a function
						if(module.variables.length > 0) {
							setBailoutReason(module, "ModuleConcatenation (inner): dependency variables are used (i. e. ProvidePlugin)");
							continue;
						}

						// Module must only be used by Harmony Imports
						const nonHarmonyReasons = module.reasons.filter(reason => !(reason.dependency instanceof HarmonyImportDependency));
						if(nonHarmonyReasons.length > 0) {
							const importingModules = new Set(nonHarmonyReasons.map(r => r.module));
							setBailoutReason(module, (requestShortener) => {
								const names = Array.from(importingModules).map(m => m.readableIdentifier(requestShortener));
								return `ModuleConcatenation (inner): module is used with non-harmony imports from ${names.join(", ")}`;
							});
							continue;
						}

						possibleInners.add(module);
					}
					// sort by depth
					// modules with lower depth are more likly suited as roots
					// this improves performance, because modules already selected as inner are skipped
					relevantModules.sort((a, b) => {
						return a.depth - b.depth;
					});
					const concatConfigurations = [];
					const usedAsInner = new Set();
					for(const currentRoot of relevantModules) {
						// when used by another configuration as inner:
						// the other configuration is better and we can skip this one
						if(usedAsInner.has(currentRoot))
							continue;

						// create a configuration with the root
						const currentConfiguration = new ConcatConfiguration(currentRoot);

						// cache failures to add modules
						const failureCache = new Map();

						// try to add all imports
						for(const imp of this.getImports(currentRoot)) {
							const problem = this.tryToAdd(currentConfiguration, imp, possibleInners, failureCache);
							if(problem) {
								failureCache.set(imp, problem);
								currentConfiguration.addWarning(imp, problem);
							}
						}
						if(!currentConfiguration.isEmpty()) {
							concatConfigurations.push(currentConfiguration);
							for(const module of currentConfiguration.modules) {
								if(module !== currentConfiguration.rootModule)
									usedAsInner.add(module);
							}
						}
					}
					// HACK: Sort configurations by length and start with the longest one
					// to get the biggers groups possible. Used modules are marked with usedModules
					// TODO: Allow to reuse existing configuration while trying to add dependencies.
					// This would improve performance. O(n^2) -> O(n)
					concatConfigurations.sort((a, b) => {
						return b.modules.size - a.modules.size;
					});
					const usedModules = new Set();
					for(const concatConfiguration of concatConfigurations) {
						if(usedModules.has(concatConfiguration.rootModule))
							continue;
						const orderedModules = new Set();
						this.addInOrder(concatConfiguration.rootModule, concatConfiguration.modules, orderedModules);
						const newModule = new ConcatenatedModule(concatConfiguration.rootModule, Array.from(orderedModules));
						for(const warning of concatConfiguration.warnings) {
							newModule.optimizationBailout.push((requestShortener) => {
								const reason = getBailoutReason(warning[0], requestShortener);
								const reasonPrefix = reason ? `: ${reason}` : "";
								if(warning[0] === warning[1])
									return `ModuleConcatenation: Cannot concat with ${warning[0].readableIdentifier(requestShortener)}${reasonPrefix}`;
								else
									return `ModuleConcatenation: Cannot concat with ${warning[0].readableIdentifier(requestShortener)} because of ${warning[1].readableIdentifier(requestShortener)}${reasonPrefix}`;
							});
						}
						for(const m of orderedModules) {
							usedModules.add(m);
							chunk.removeModule(m);
						}
						chunk.addModule(newModule);
						compilation.modules.push(newModule);
						if(chunk.entryModule === concatConfiguration.rootModule)
							chunk.entryModule = newModule;
						newModule.reasons.forEach(reason => reason.dependency.module = newModule);
						newModule.dependencies.forEach(dep => {
							if(dep.module) {
								dep.module.reasons.forEach(reason => {
									if(reason.dependency === dep)
										reason.module = newModule;
								});
							}
						});
					}
					compilation.modules = compilation.modules.filter(m => !usedModules.has(m));
				});
			});
		});
	}

	getImports(module) {
		return Array.from(new Set(module.dependencies

			// Only harmony Dependencies
			.filter(dep => dep instanceof HarmonyImportDependency && dep.module)

			// Dependencies are simple enough to concat them
			.filter(dep => {
				return !module.dependencies.some(d =>
					d instanceof HarmonyExportImportedSpecifierDependency &&
					d.importDependency === dep &&
					!d.id &&
					!Array.isArray(dep.module.providedExports)
				);
			})

			// Take the imported module
			.map(dep => dep.module)
		));
	}

	tryToAdd(config, module, possibleModules, failureCache) {
		const cacheEntry = failureCache.get(module);
		if(cacheEntry) {
			return cacheEntry;
		}

		// Already added?
		if(config.has(module)) {
			return null;
		}

		// Not possible to add?
		if(!possibleModules.has(module)) {
			return module;
		}

		// Clone config to make experimental changes
		const testConfig = config.clone();

		// Add the module
		testConfig.add(module);

		// Every module which depends on the added module must be in the configuration too.
		for(const reason of module.reasons) {
			const problem = this.tryToAdd(testConfig, reason.module, possibleModules, failureCache);
			if(problem) {
				failureCache.set(module, problem); // cache failures for performance
				return problem;
			}
		}

		// Eagerly try to add imports too if possible
		for(const imp of this.getImports(module)) {
			const problem = this.tryToAdd(testConfig, imp, possibleModules, failureCache);
			if(problem) {
				config.addWarning(module, problem);
			}
		}

		// Commit experimental changes
		config.set(testConfig);
		return null;
	}

	addInOrder(module, unorderedSet, orderedSet) {
		if(orderedSet.has(module)) return;
		if(!unorderedSet.has(module)) return;
		orderedSet.add(module);
		for(const imp of this.getImports(module))
			this.addInOrder(imp, unorderedSet, orderedSet);
		orderedSet.delete(module);
		orderedSet.add(module);
	}
}

class ConcatConfiguration {
	constructor(rootModule) {
		this.rootModule = rootModule;
		this.modules = new Set([rootModule]);
		this.warnings = new Map();
	}

	add(module) {
		this.modules.add(module);
	}

	has(module) {
		return this.modules.has(module);
	}

	isEmpty() {
		return this.modules.size === 1;
	}

	addWarning(module, problem) {
		this.warnings.set(module, problem);
	}

	clone() {
		const clone = new ConcatConfiguration(this.rootModule);
		for(const module of this.modules)
			clone.add(module);
		for(const pair of this.warnings)
			clone.addWarning(pair[0], pair[1]);
		return clone;
	}

	set(config) {
		this.rootModule = config.rootModule;
		this.modules = new Set(config.modules);
		this.warnings = new Map(config.warnings);
	}
}

module.exports = ModuleConcatenationPlugin;