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SideEffectsFlagPlugin.js
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Sat, Feb 15, 19:56

SideEffectsFlagPlugin.js
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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
const glob2regexp = require("glob-to-regexp");
const { STAGE_DEFAULT } = require("../OptimizationStages");
const HarmonyExportImportedSpecifierDependency = require("../dependencies/HarmonyExportImportedSpecifierDependency");
const HarmonyImportSpecifierDependency = require("../dependencies/HarmonyImportSpecifierDependency");
const formatLocation = require("../formatLocation");
/** @typedef {import("../Compiler")} Compiler */
/** @typedef {import("../Dependency")} Dependency */
/** @typedef {import("../Module")} Module */
/** @typedef {import("../javascript/JavascriptParser")} JavascriptParser */
/**
* @typedef {Object} ExportInModule
* @property {Module} module the module
* @property {string} exportName the name of the export
* @property {boolean} checked if the export is conditional
*/
/**
* @typedef {Object} ReexportInfo
* @property {Map<string, ExportInModule[]>} static
* @property {Map<Module, Set<string>>} dynamic
*/
/** @type {WeakMap<any, Map<string, RegExp>>} */
const globToRegexpCache = new WeakMap();
/**
* @param {string} glob the pattern
* @param {Map<string, RegExp>} cache the glob to RegExp cache
* @returns {RegExp} a regular expression
*/
const globToRegexp = (glob, cache) => {
const cacheEntry = cache.get(glob);
if (cacheEntry !== undefined) return cacheEntry;
if (!glob.includes("/")) {
glob = `**/${glob}`;
}
const baseRegexp = glob2regexp(glob, { globstar: true, extended: true });
const regexpSource = baseRegexp.source;
const regexp = new RegExp("^(\\./)?" + regexpSource.slice(1));
cache.set(glob, regexp);
return regexp;
};
class SideEffectsFlagPlugin {
/**
* @param {boolean} analyseSource analyse source code for side effects
*/
constructor(analyseSource = true) {
this._analyseSource = analyseSource;
}
/**
* Apply the plugin
* @param {Compiler} compiler the compiler instance
* @returns {void}
*/
apply(compiler) {
let cache = globToRegexpCache.get(compiler.root);
if (cache === undefined) {
cache = new Map();
globToRegexpCache.set(compiler.root, cache);
}
compiler.hooks.compilation.tap(
"SideEffectsFlagPlugin",
(compilation, { normalModuleFactory }) => {
const moduleGraph = compilation.moduleGraph;
normalModuleFactory.hooks.module.tap(
"SideEffectsFlagPlugin",
(module, data) => {
const resolveData = data.resourceResolveData;
if (
resolveData &&
resolveData.descriptionFileData &&
resolveData.relativePath
) {
const sideEffects = resolveData.descriptionFileData.sideEffects;
if (sideEffects !== undefined) {
if (module.factoryMeta === undefined) {
module.factoryMeta = {};
}
const hasSideEffects = SideEffectsFlagPlugin.moduleHasSideEffects(
resolveData.relativePath,
sideEffects,
cache
);
module.factoryMeta.sideEffectFree = !hasSideEffects;
}
}
return module;
}
);
normalModuleFactory.hooks.module.tap(
"SideEffectsFlagPlugin",
(module, data) => {
if (typeof data.settings.sideEffects === "boolean") {
if (module.factoryMeta === undefined) {
module.factoryMeta = {};
}
module.factoryMeta.sideEffectFree = !data.settings.sideEffects;
}
return module;
}
);
if (this._analyseSource) {
/**
* @param {JavascriptParser} parser the parser
* @returns {void}
*/
const parserHandler = parser => {
let sideEffectsStatement;
parser.hooks.program.tap("SideEffectsFlagPlugin", () => {
sideEffectsStatement = undefined;
});
parser.hooks.statement.tap(
{ name: "SideEffectsFlagPlugin", stage: -100 },
statement => {
if (sideEffectsStatement) return;
if (parser.scope.topLevelScope !== true) return;
switch (statement.type) {
case "ExpressionStatement":
if (
!parser.isPure(statement.expression, statement.range[0])
) {
sideEffectsStatement = statement;
}
break;
case "IfStatement":
case "WhileStatement":
case "DoWhileStatement":
if (!parser.isPure(statement.test, statement.range[0])) {
sideEffectsStatement = statement;
}
// statement hook will be called for child statements too
break;
case "ForStatement":
if (
!parser.isPure(statement.init, statement.range[0]) ||
!parser.isPure(
statement.test,
statement.init
? statement.init.range[1]
: statement.range[0]
) ||
!parser.isPure(
statement.update,
statement.test
? statement.test.range[1]
: statement.init
? statement.init.range[1]
: statement.range[0]
)
) {
sideEffectsStatement = statement;
}
// statement hook will be called for child statements too
break;
case "SwitchStatement":
if (
!parser.isPure(statement.discriminant, statement.range[0])
) {
sideEffectsStatement = statement;
}
// statement hook will be called for child statements too
break;
case "VariableDeclaration":
case "ClassDeclaration":
case "FunctionDeclaration":
if (!parser.isPure(statement, statement.range[0])) {
sideEffectsStatement = statement;
}
break;
case "ExportNamedDeclaration":
case "ExportDefaultDeclaration":
if (
!parser.isPure(statement.declaration, statement.range[0])
) {
sideEffectsStatement = statement;
}
break;
case "LabeledStatement":
case "BlockStatement":
// statement hook will be called for child statements too
break;
case "EmptyStatement":
break;
case "ExportAllDeclaration":
case "ImportDeclaration":
// imports will be handled by the dependencies
break;
default:
sideEffectsStatement = statement;
break;
}
}
);
parser.hooks.finish.tap("SideEffectsFlagPlugin", () => {
if (sideEffectsStatement === undefined) {
parser.state.module.buildMeta.sideEffectFree = true;
} else {
const { loc, type } = sideEffectsStatement;
moduleGraph
.getOptimizationBailout(parser.state.module)
.push(
() =>
`Statement (${type}) with side effects in source code at ${formatLocation(
loc
)}`
);
}
});
};
for (const key of [
"javascript/auto",
"javascript/esm",
"javascript/dynamic"
]) {
normalModuleFactory.hooks.parser
.for(key)
.tap("SideEffectsFlagPlugin", parserHandler);
}
}
compilation.hooks.optimizeDependencies.tap(
{
name: "SideEffectsFlagPlugin",
stage: STAGE_DEFAULT
},
modules => {
const logger = compilation.getLogger(
"webpack.SideEffectsFlagPlugin"
);
logger.time("update dependencies");
for (const module of modules) {
if (module.getSideEffectsConnectionState(moduleGraph) === false) {
const exportsInfo = moduleGraph.getExportsInfo(module);
for (const connection of moduleGraph.getIncomingConnections(
module
)) {
const dep = connection.dependency;
let isReexport;
if (
(isReexport =
dep instanceof
HarmonyExportImportedSpecifierDependency) ||
(dep instanceof HarmonyImportSpecifierDependency &&
!dep.namespaceObjectAsContext)
) {
// TODO improve for export *
if (isReexport && dep.name) {
const exportInfo = moduleGraph.getExportInfo(
connection.originModule,
dep.name
);
exportInfo.moveTarget(
moduleGraph,
({ module }) =>
module.getSideEffectsConnectionState(moduleGraph) ===
false
);
}
// TODO improve for nested imports
const ids = dep.getIds(moduleGraph);
if (ids.length > 0) {
const exportInfo = exportsInfo.getExportInfo(ids[0]);
const target = exportInfo.getTarget(
moduleGraph,
({ module }) =>
module.getSideEffectsConnectionState(moduleGraph) ===
false
);
if (!target) continue;
moduleGraph.updateModule(dep, target.module);
moduleGraph.addExplanation(
dep,
"(skipped side-effect-free modules)"
);
dep.setIds(
moduleGraph,
target.export
? [...target.export, ...ids.slice(1)]
: ids.slice(1)
);
}
}
}
}
}
logger.timeEnd("update dependencies");
}
);
}
);
}
static moduleHasSideEffects(moduleName, flagValue, cache) {
switch (typeof flagValue) {
case "undefined":
return true;
case "boolean":
return flagValue;
case "string":
return globToRegexp(flagValue, cache).test(moduleName);
case "object":
return flagValue.some(glob =>
SideEffectsFlagPlugin.moduleHasSideEffects(moduleName, glob, cache)
);
}
}
}
module.exports = SideEffectsFlagPlugin;

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