mirror of
https://github.com/S2-/minifyfromhtml.git
synced 2025-08-03 04:10:04 +02:00
536 lines
16 KiB
JavaScript
536 lines
16 KiB
JavaScript
"use strict";
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const Charset = require("./charset");
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const ScopeTracker = require("./scope-tracker");
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const isLabelIdentifier = require("./is-label-identifier");
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const bfsTraverseCreator = require("./bfs-traverse");
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const fixupVarScoping = require("./fixup-var-scoping");
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const _require = require("babel-helper-mark-eval-scopes"),
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markEvalScopes = _require.markEvalScopes,
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isEvalScopesMarked = _require.isMarked,
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hasEval = _require.hasEval;
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const newIssueUrl = "https://github.com/babel/minify/issues/new";
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module.exports = babel => {
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const t = babel.types,
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traverse = babel.traverse;
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const bfsTraverse = bfsTraverseCreator(babel);
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const hop = Object.prototype.hasOwnProperty;
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class Mangler {
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constructor(charset, program, {
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exclude = {},
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keepFnName = false,
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keepClassName = false,
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eval: _eval = false,
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topLevel = false
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} = {}) {
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this.charset = charset;
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this.program = program; // user passed options
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this.exclude = toObject(exclude);
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this.keepFnName = keepFnName;
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this.keepClassName = keepClassName;
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this.topLevel = topLevel;
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this.eval = _eval; // tracking
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this.visitedScopes = new Set();
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this.scopeTracker = new ScopeTracker();
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this.renamedNodes = new Set();
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}
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/**
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* Run the mangler
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*/
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run() {
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this.crawlScope();
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this.collect();
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this.fixup();
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this.charset.sort();
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this.mangle();
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}
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/**
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* Tells if a variable name is excluded
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* @param {String} name
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*/
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isExcluded(name) {
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return hop.call(this.exclude, name) && this.exclude[name];
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}
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/**
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* Clears traverse cache and recrawls the AST
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*
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* to recompute the bindings, references, other scope information
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* and paths because the other transformations in the same pipeline
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* (other plugins and presets) changes the AST and does NOT update
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* the scope objects
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*/
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crawlScope() {
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(traverse.clearCache || traverse.cache.clear)();
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this.program.scope.crawl();
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}
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/**
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* Re-crawling comes with a side-effect that let->var conversion
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* reverts the update of the binding information (block to fn scope).
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* This function takes care of it by updating it again.
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*
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* TODO: This is unnecessary work and needs to be fixed in babel.
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* https://github.com/babel/babel/issues/4818
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*
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* When this is removed, remember to remove fixup's dependency in
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* ScopeTracker
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*/
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fixup() {
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fixupVarScoping(this);
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}
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/**
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* A single pass through the AST to collect info for
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*
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* 1. Scope Tracker
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* 2. Unsafe Scopes (direct eval scopes)
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* 3. Charset considerations for better gzip compression
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*
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* Traversed in the same fashion(BFS) the mangling is done
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*/
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collect() {
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const mangler = this;
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const scopeTracker = mangler.scopeTracker;
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scopeTracker.addScope(this.program.scope);
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/**
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* Same usage as in DCE, whichever runs first
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*/
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if (!isEvalScopesMarked(mangler.program)) {
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markEvalScopes(mangler.program);
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}
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/**
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* The visitors to be used in traversal.
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*
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* Note: BFS traversal supports only the `enter` handlers, `exit`
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* handlers are simply dropped without Errors
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*
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* Collects items defined in the ScopeTracker
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*/
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const collectVisitor = {
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Scopable({
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scope
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}) {
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scopeTracker.addScope(scope); // Collect bindings defined in the scope
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Object.keys(scope.bindings).forEach(name => {
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scopeTracker.addBinding(scope.bindings[name]); // add all constant violations as references
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scope.bindings[name].constantViolations.forEach(() => {
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scopeTracker.addReference(scope, scope.bindings[name], name);
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});
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});
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},
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/**
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* This is necessary because, in Babel, the scope.references
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* does NOT contain the references in that scope. Only the program
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* scope (top most level) contains all the references.
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*
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* We collect the references in a fashion where all the scopes between
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* and including the referenced scope and scope where it is declared
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* is considered as scope referencing that identifier
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*/
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ReferencedIdentifier(path) {
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if (isLabelIdentifier(path)) {
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return;
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}
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const scope = path.scope,
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name = path.node.name;
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const binding = scope.getBinding(name);
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if (!binding) {
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// Do not collect globals as they are already available via
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// babel's API
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if (scope.hasGlobal(name)) {
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return;
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} // This should NOT happen ultimately. Panic if this code block is
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// reached
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throw new Error(`Binding not found for ReferencedIdentifier "${name}" ` + `present in "${path.parentPath.type}". ` + `Please report this at ${newIssueUrl}`);
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} else {
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// Add it to our scope tracker if everything is fine
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scopeTracker.addReference(scope, binding, name);
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}
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}
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};
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/**
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* These visitors are for collecting the Characters used in the program
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* to measure the frequency and generate variable names for mangling so
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* as to improve the gzip compression - as gzip likes repetition
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*/
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if (this.charset.shouldConsider) {
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collectVisitor.Identifier = function Identifer(path) {
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const node = path.node; // We don't mangle properties, so we collect them as they contribute
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// to the frequency of characters
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if (path.parentPath.isMemberExpression({
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property: node
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}) || path.parentPath.isObjectProperty({
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key: node
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})) {
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mangler.charset.consider(node.name);
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}
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};
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collectVisitor.Literal = function Literal({
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node
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}) {
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mangler.charset.consider(String(node.value));
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};
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} // Traverse the AST
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bfsTraverse(mangler.program, collectVisitor);
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}
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/**
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* Tells if a binding is exported as a NamedExport - so as to NOT mangle
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*
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* Babel treats NamedExports as a binding referenced by this NamedExport decl
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* @param {Binding} binding
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*/
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isExportedWithName(binding) {
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// short circuit
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if (!this.topLevel) {
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return false;
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}
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const refs = binding.referencePaths;
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var _iteratorNormalCompletion = true;
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var _didIteratorError = false;
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var _iteratorError = undefined;
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try {
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for (var _iterator = refs[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
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const ref = _step.value;
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if (ref.isExportNamedDeclaration()) {
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return true;
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}
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} // default
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} catch (err) {
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_didIteratorError = true;
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_iteratorError = err;
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} finally {
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try {
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if (!_iteratorNormalCompletion && _iterator.return != null) {
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_iterator.return();
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}
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} finally {
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if (_didIteratorError) {
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throw _iteratorError;
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}
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}
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}
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return false;
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}
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/**
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* Mangle the scope
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* @param {Scope} scope
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*/
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mangleScope(scope) {
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const mangler = this;
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const scopeTracker = mangler.scopeTracker; // Unsafe Scope
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if (!mangler.eval && hasEval(scope)) {
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return;
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} // Already visited
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// This is because for a function, in Babel, the function and
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// the function body's BlockStatement has the same scope, and will
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// be visited twice by the Scopable handler, and we want to mangle
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// it only once
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if (mangler.visitedScopes.has(scope)) {
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return;
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}
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mangler.visitedScopes.add(scope); // Helpers to generate names
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let i = 0;
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function getNext() {
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return mangler.charset.getIdentifier(i++);
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}
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function resetNext() {
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i = 0;
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}
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const bindings = scopeTracker.bindings.get(scope);
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const names = [...bindings.keys()];
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/**
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* 1. Iterate through the list of BindingIdentifiers
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* 2. Rename each of them in-place
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* 3. Update the scope tree.
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*/
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for (let i = 0; i < names.length; i++) {
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const oldName = names[i];
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const binding = bindings.get(oldName); // Names which should NOT be mangled
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if ( // arguments - for non-strict mode
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oldName === "arguments" || // labels
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binding.path.isLabeledStatement() || // ClassDeclaration has binding in two scopes
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// 1. The scope in which it is declared
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// 2. The class's own scope
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binding.path.isClassDeclaration() && binding.path === scope.path || // excluded
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mangler.isExcluded(oldName) || ( // function names
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mangler.keepFnName ? isFunction(binding.path) : false) || ( // class names
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mangler.keepClassName ? isClass(binding.path) : false) || // named export
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mangler.isExportedWithName(binding)) {
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continue;
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}
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let next;
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do {
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next = getNext();
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} while (!t.isValidIdentifier(next) || scopeTracker.hasBinding(scope, next) || scope.hasGlobal(next) || scopeTracker.hasReference(scope, next) || !scopeTracker.canUseInReferencedScopes(binding, next)); // Reset so variables which are removed can be reused
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resetNext(); // Once we detected a valid `next` Identifier which could be used,
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// call the renamer
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mangler.rename(scope, binding, oldName, next);
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}
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}
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/**
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* The mangle function that traverses through all the Scopes in a BFS
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* fashion - calls mangleScope
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*/
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mangle() {
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const mangler = this;
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bfsTraverse(this.program, {
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Scopable(path) {
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if (!path.isProgram() || mangler.topLevel) mangler.mangleScope(path.scope);
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}
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});
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}
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/**
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* Given a NodePath, collects all the Identifiers which are BindingIdentifiers
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* and replaces them with the new name
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*
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* For example,
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* var a = 1, { b } = c; // a and b are BindingIdentifiers
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*
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* @param {NodePath} path
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* @param {String} oldName
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* @param {String} newName
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* @param {Function} predicate
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*/
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renameBindingIds(path, oldName, newName, predicate = () => true) {
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const bindingIds = path.getBindingIdentifierPaths(true, false);
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for (const name in bindingIds) {
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if (name !== oldName) continue;
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var _iteratorNormalCompletion2 = true;
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var _didIteratorError2 = false;
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var _iteratorError2 = undefined;
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try {
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for (var _iterator2 = bindingIds[name][Symbol.iterator](), _step2; !(_iteratorNormalCompletion2 = (_step2 = _iterator2.next()).done); _iteratorNormalCompletion2 = true) {
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const idPath = _step2.value;
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if (predicate(idPath)) {
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idPath.node.name = newName; // babel-7 don't requeue
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// idPath.replaceWith(t.identifier(newName));
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this.renamedNodes.add(idPath.node);
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}
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}
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} catch (err) {
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_didIteratorError2 = true;
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_iteratorError2 = err;
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} finally {
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try {
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if (!_iteratorNormalCompletion2 && _iterator2.return != null) {
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_iterator2.return();
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}
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} finally {
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if (_didIteratorError2) {
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throw _iteratorError2;
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}
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}
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}
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}
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}
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/**
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* The Renamer:
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* Renames the following for one Binding in a Scope
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*
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* 1. Binding in that Scope
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* 2. All the Binding's constant violations
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* 3. All its References
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* 4. Updates mangler.scopeTracker
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* 5. Updates Babel's Scope tracking
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*
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* @param {Scope} scope
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* @param {Binding} binding
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* @param {String} oldName
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* @param {String} newName
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*/
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rename(scope, binding, oldName, newName) {
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const mangler = this;
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const scopeTracker = mangler.scopeTracker; // rename at the declaration level
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this.renameBindingIds(binding.path, oldName, newName, idPath => idPath.node === binding.identifier); // update mangler's ScopeTracker
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scopeTracker.renameBinding(scope, oldName, newName); // update all constant violations
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const violations = binding.constantViolations;
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for (let i = 0; i < violations.length; i++) {
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if (violations[i].isLabeledStatement()) continue;
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this.renameBindingIds(violations[i], oldName, newName);
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scopeTracker.updateReference(violations[i].scope, binding, oldName, newName);
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} // update all referenced places
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const refs = binding.referencePaths;
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for (let i = 0; i < refs.length; i++) {
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const path = refs[i];
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const node = path.node;
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if (!path.isIdentifier()) {
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// Ideally, this should not happen
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// it happens in these places now -
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// case 1: Export Statements
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// This is a bug in babel
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// https://github.com/babel/babel/pull/3629
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// case 2: Replacements in other plugins
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// eg: https://github.com/babel/minify/issues/122
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// replacement in dce from `x` to `!x` gives referencePath as `!x`
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path.traverse({
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ReferencedIdentifier(refPath) {
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if (refPath.node.name !== oldName) {
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return;
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}
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const actualBinding = refPath.scope.getBinding(oldName);
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if (actualBinding !== binding) {
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return;
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}
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refPath.node.name = newName; // babel-7 don't requeue
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// refPath.replaceWith(t.identifier(newName));
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mangler.renamedNodes.add(refPath.node);
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scopeTracker.updateReference(refPath.scope, binding, oldName, newName);
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}
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});
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} else if (!isLabelIdentifier(path)) {
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if (path.node.name === oldName) {
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path.node.name = newName; // babel-7 don't requeue
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// path.replaceWith(t.identifier(newName));
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mangler.renamedNodes.add(path.node);
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scopeTracker.updateReference(path.scope, binding, oldName, newName);
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} else if (mangler.renamedNodes.has(path.node)) {
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// already renamed,
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// just update the references
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scopeTracker.updateReference(path.scope, binding, oldName, newName);
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} else {
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throw new Error(`Unexpected Rename Error: ` + `Trying to replace "${node.name}": from "${oldName}" to "${newName}". ` + `Please report it at ${newIssueUrl}`);
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}
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} // else label identifier - silently ignore
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} // update babel's internal tracking
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binding.identifier.name = newName; // update babel's internal scope tracking
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const bindings = scope.bindings;
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bindings[newName] = binding;
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delete bindings[oldName];
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}
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}
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return {
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name: "minify-mangle-names",
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visitor: {
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/**
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* Mangler is run as a single pass. It's the same pattern as used in DCE
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*/
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Program: {
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exit(path) {
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// If the source code is small then we're going to assume that the user
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// is running on this on single files before bundling. Therefore we
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// need to achieve as much determinisim and we will not do any frequency
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// sorting on the character set. Currently the number is pretty arbitrary.
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const shouldConsiderSource = path.getSource().length > 70000;
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const charset = new Charset(shouldConsiderSource);
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const mangler = new Mangler(charset, path, this.opts);
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mangler.run();
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}
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}
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}
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};
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}; // convert value to object
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function toObject(value) {
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if (!Array.isArray(value)) {
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return value;
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}
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const map = {};
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for (let i = 0; i < value.length; i++) {
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map[value[i]] = true;
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}
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return map;
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} // for keepFnName
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function isFunction(path) {
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return path.isFunctionExpression() || path.isFunctionDeclaration();
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} // for keepClassName
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function isClass(path) {
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return path.isClassExpression() || path.isClassDeclaration();
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} |