487 lines
20 KiB
JavaScript
487 lines
20 KiB
JavaScript
/***********************************************************************
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A JavaScript tokenizer / parser / beautifier / compressor.
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https://github.com/mishoo/UglifyJS2
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-------------------------------- (C) ---------------------------------
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Author: Mihai Bazon
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<mihai.bazon@gmail.com>
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http://mihai.bazon.net/blog
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Distributed under the BSD license:
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Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above
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copyright notice, this list of conditions and the following
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disclaimer.
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* Redistributions in binary form must reproduce the above
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copyright notice, this list of conditions and the following
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disclaimer in the documentation and/or other materials
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provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
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TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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SUCH DAMAGE.
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***********************************************************************/
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import {
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AST_Accessor,
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AST_Assign,
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AST_BlockStatement,
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AST_Class,
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AST_ClassExpression,
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AST_ClassStaticBlock,
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AST_DefaultAssign,
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AST_DefClass,
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AST_Definitions,
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AST_Defun,
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AST_Destructuring,
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AST_EmptyStatement,
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AST_Expansion,
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AST_Export,
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AST_For,
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AST_ForIn,
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AST_Function,
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AST_LabeledStatement,
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AST_Lambda,
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AST_Number,
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AST_Scope,
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AST_SimpleStatement,
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AST_SymbolBlockDeclaration,
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AST_SymbolCatch,
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AST_SymbolDeclaration,
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AST_SymbolFunarg,
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AST_SymbolRef,
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AST_SymbolVar,
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AST_Toplevel,
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AST_Unary,
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AST_Var,
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TreeTransformer,
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TreeWalker,
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walk,
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} from "../ast.js";
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import {
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keep_name,
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make_node,
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map_add,
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MAP,
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remove,
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return_false,
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} from "../utils/index.js";
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import { SymbolDef } from "../scope.js";
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import {
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WRITE_ONLY,
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UNUSED,
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has_flag,
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set_flag,
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} from "./compressor-flags.js";
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import {
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make_sequence,
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maintain_this_binding,
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is_empty,
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is_ref_of,
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can_be_evicted_from_block,
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} from "./common.js";
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const r_keep_assign = /keep_assign/;
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/** Drop unused variables from this scope */
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AST_Scope.DEFMETHOD("drop_unused", function(compressor) {
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if (!compressor.option("unused")) return;
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if (compressor.has_directive("use asm")) return;
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if (!this.variables) return; // not really a scope (eg: AST_Class)
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var self = this;
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if (self.pinned()) return;
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var drop_funcs = !(self instanceof AST_Toplevel) || compressor.toplevel.funcs;
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var drop_vars = !(self instanceof AST_Toplevel) || compressor.toplevel.vars;
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const assign_as_unused = r_keep_assign.test(compressor.option("unused")) ? return_false : function(node) {
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if (node instanceof AST_Assign
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&& !node.logical
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&& (has_flag(node, WRITE_ONLY) || node.operator == "=")
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) {
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return node.left;
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}
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if (node instanceof AST_Unary && has_flag(node, WRITE_ONLY)) {
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return node.expression;
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}
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};
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var in_use_ids = new Map();
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var fixed_ids = new Map();
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if (self instanceof AST_Toplevel && compressor.top_retain) {
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self.variables.forEach(function(def) {
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if (compressor.top_retain(def)) {
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in_use_ids.set(def.id, def);
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}
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});
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}
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var var_defs_by_id = new Map();
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var initializations = new Map();
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var self_referential_classes = new Set();
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// pass 1: find out which symbols are directly used in
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// this scope (not in nested scopes).
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var scope = this;
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var tw = new TreeWalker(function(node, descend) {
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if (node instanceof AST_Lambda && node.uses_arguments && !tw.has_directive("use strict")) {
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node.argnames.forEach(function(argname) {
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if (!(argname instanceof AST_SymbolDeclaration)) return;
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var def = argname.definition();
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in_use_ids.set(def.id, def);
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});
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}
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if (node === self) return;
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if (node instanceof AST_Class && node.has_side_effects(compressor)) {
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if (node.is_self_referential()) self_referential_classes.add(node);
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node.visit_nondeferred_class_parts(tw);
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}
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if (node instanceof AST_Defun || node instanceof AST_DefClass) {
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var node_def = node.name.definition();
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const in_export = tw.parent() instanceof AST_Export;
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if (in_export || !drop_funcs && scope === self) {
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if (node_def.global) {
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in_use_ids.set(node_def.id, node_def);
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}
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}
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map_add(initializations, node_def.id, node);
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return true; // don't go in nested scopes
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}
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// In the root scope, we drop things. In inner scopes, we just check for uses.
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const in_root_scope = scope === self;
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if (node instanceof AST_SymbolFunarg && in_root_scope) {
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map_add(var_defs_by_id, node.definition().id, node);
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}
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if (node instanceof AST_Definitions && in_root_scope) {
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const in_export = tw.parent() instanceof AST_Export;
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node.definitions.forEach(function(def) {
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if (def.name instanceof AST_SymbolVar) {
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map_add(var_defs_by_id, def.name.definition().id, def);
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}
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if (in_export || !drop_vars) {
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walk(def.name, node => {
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if (node instanceof AST_SymbolDeclaration) {
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const def = node.definition();
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if (def.global) {
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in_use_ids.set(def.id, def);
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}
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}
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});
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}
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if (def.name instanceof AST_Destructuring) {
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def.walk(tw);
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}
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if (def.name instanceof AST_SymbolDeclaration && def.value) {
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var node_def = def.name.definition();
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map_add(initializations, node_def.id, def.value);
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if (!node_def.chained && def.name.fixed_value() === def.value) {
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fixed_ids.set(node_def.id, def);
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}
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if (def.value.has_side_effects(compressor)) {
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def.value.walk(tw);
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}
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}
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});
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return true;
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}
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return scan_ref_scoped(node, descend);
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});
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self.walk(tw);
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// pass 2: for every used symbol we need to walk its
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// initialization code to figure out if it uses other
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// symbols (that may not be in_use).
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tw = new TreeWalker(scan_ref_scoped);
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in_use_ids.forEach(function (def) {
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var init = initializations.get(def.id);
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if (init) init.forEach(function(init) {
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init.walk(tw);
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});
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});
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self_referential_classes.forEach(function (cls) {
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cls.walk(tw);
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});
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// pass 3: we should drop declarations not in_use
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var tt = new TreeTransformer(
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function before(node, descend, in_list) {
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var parent = tt.parent();
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if (drop_vars) {
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const sym = assign_as_unused(node);
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if (sym instanceof AST_SymbolRef) {
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var def = sym.definition();
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var in_use = in_use_ids.has(def.id);
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if (node instanceof AST_Assign) {
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if (!in_use || fixed_ids.has(def.id) && fixed_ids.get(def.id) !== node) {
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return maintain_this_binding(parent, node, node.right.transform(tt));
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}
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} else if (!in_use) {
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return in_list ? MAP.skip : make_node(AST_Number, node, { value: 0 });
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}
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}
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}
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if (scope !== self) return;
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var def;
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if (node.name
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&& (node instanceof AST_ClassExpression
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&& !keep_name(compressor.option("keep_classnames"), (def = node.name.definition()).name)
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|| node instanceof AST_Function
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&& !keep_name(compressor.option("keep_fnames"), (def = node.name.definition()).name))) {
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// any declarations with same name will overshadow
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// name of this anonymous function and can therefore
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// never be used anywhere
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if (!in_use_ids.has(def.id) || def.orig.length > 1) node.name = null;
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}
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if (node instanceof AST_Lambda && !(node instanceof AST_Accessor)) {
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var trim = !compressor.option("keep_fargs");
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for (var a = node.argnames, i = a.length; --i >= 0;) {
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var sym = a[i];
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if (sym instanceof AST_Expansion) {
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sym = sym.expression;
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}
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if (sym instanceof AST_DefaultAssign) {
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sym = sym.left;
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}
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// Do not drop destructuring arguments.
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// They constitute a type assertion of sorts
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if (
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!(sym instanceof AST_Destructuring)
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&& !in_use_ids.has(sym.definition().id)
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) {
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set_flag(sym, UNUSED);
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if (trim) {
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a.pop();
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}
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} else {
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trim = false;
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}
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}
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}
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if (node instanceof AST_DefClass && node !== self) {
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const def = node.name.definition();
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descend(node, this);
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const keep_class = def.global && !drop_funcs || in_use_ids.has(def.id);
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if (!keep_class) {
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const kept = node.drop_side_effect_free(compressor);
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if (kept == null) {
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def.eliminated++;
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return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
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}
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return kept;
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}
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return node;
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}
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if (node instanceof AST_Defun && node !== self) {
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const def = node.name.definition();
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const keep = def.global && !drop_funcs || in_use_ids.has(def.id);
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if (!keep) {
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def.eliminated++;
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return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
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}
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}
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if (node instanceof AST_Definitions && !(parent instanceof AST_ForIn && parent.init === node)) {
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var drop_block = !(parent instanceof AST_Toplevel) && !(node instanceof AST_Var);
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// place uninitialized names at the start
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var body = [], head = [], tail = [];
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// for unused names whose initialization has
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// side effects, we can cascade the init. code
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// into the next one, or next statement.
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var side_effects = [];
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node.definitions.forEach(function(def) {
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if (def.value) def.value = def.value.transform(tt);
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var is_destructure = def.name instanceof AST_Destructuring;
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var sym = is_destructure
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? new SymbolDef(null, { name: "<destructure>" }) /* fake SymbolDef */
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: def.name.definition();
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if (drop_block && sym.global) return tail.push(def);
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if (!(drop_vars || drop_block)
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|| is_destructure
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&& (def.name.names.length
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|| def.name.is_array
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|| compressor.option("pure_getters") != true)
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|| in_use_ids.has(sym.id)
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) {
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if (def.value && fixed_ids.has(sym.id) && fixed_ids.get(sym.id) !== def) {
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def.value = def.value.drop_side_effect_free(compressor);
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}
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if (def.name instanceof AST_SymbolVar) {
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var var_defs = var_defs_by_id.get(sym.id);
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if (var_defs.length > 1 && (!def.value || sym.orig.indexOf(def.name) > sym.eliminated)) {
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if (def.value) {
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var ref = make_node(AST_SymbolRef, def.name, def.name);
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sym.references.push(ref);
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var assign = make_node(AST_Assign, def, {
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operator: "=",
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logical: false,
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left: ref,
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right: def.value
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});
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if (fixed_ids.get(sym.id) === def) {
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fixed_ids.set(sym.id, assign);
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}
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side_effects.push(assign.transform(tt));
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}
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remove(var_defs, def);
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sym.eliminated++;
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return;
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}
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}
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if (def.value) {
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if (side_effects.length > 0) {
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if (tail.length > 0) {
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side_effects.push(def.value);
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def.value = make_sequence(def.value, side_effects);
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} else {
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body.push(make_node(AST_SimpleStatement, node, {
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body: make_sequence(node, side_effects)
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}));
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}
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side_effects = [];
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}
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tail.push(def);
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} else {
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head.push(def);
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}
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} else if (sym.orig[0] instanceof AST_SymbolCatch) {
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var value = def.value && def.value.drop_side_effect_free(compressor);
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if (value) side_effects.push(value);
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def.value = null;
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head.push(def);
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} else {
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var value = def.value && def.value.drop_side_effect_free(compressor);
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if (value) {
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side_effects.push(value);
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}
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sym.eliminated++;
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}
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});
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if (head.length > 0 || tail.length > 0) {
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node.definitions = head.concat(tail);
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body.push(node);
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}
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if (side_effects.length > 0) {
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body.push(make_node(AST_SimpleStatement, node, {
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body: make_sequence(node, side_effects)
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}));
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}
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switch (body.length) {
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case 0:
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return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
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case 1:
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return body[0];
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default:
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return in_list ? MAP.splice(body) : make_node(AST_BlockStatement, node, { body });
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}
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}
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// certain combination of unused name + side effect leads to:
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// https://github.com/mishoo/UglifyJS2/issues/44
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// https://github.com/mishoo/UglifyJS2/issues/1830
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// https://github.com/mishoo/UglifyJS2/issues/1838
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// that's an invalid AST.
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// We fix it at this stage by moving the `var` outside the `for`.
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if (node instanceof AST_For) {
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descend(node, this);
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var block;
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if (node.init instanceof AST_BlockStatement) {
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block = node.init;
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node.init = block.body.pop();
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block.body.push(node);
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}
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if (node.init instanceof AST_SimpleStatement) {
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node.init = node.init.body;
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} else if (is_empty(node.init)) {
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node.init = null;
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}
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return !block ? node : in_list ? MAP.splice(block.body) : block;
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}
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if (node instanceof AST_LabeledStatement
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&& node.body instanceof AST_For
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) {
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descend(node, this);
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if (node.body instanceof AST_BlockStatement) {
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var block = node.body;
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node.body = block.body.pop();
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block.body.push(node);
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return in_list ? MAP.splice(block.body) : block;
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}
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return node;
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}
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if (node instanceof AST_BlockStatement) {
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descend(node, this);
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if (in_list && node.body.every(can_be_evicted_from_block)) {
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return MAP.splice(node.body);
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}
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return node;
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}
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if (node instanceof AST_Scope && !(node instanceof AST_ClassStaticBlock)) {
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const save_scope = scope;
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scope = node;
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descend(node, this);
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scope = save_scope;
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return node;
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}
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}
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);
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self.transform(tt);
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function scan_ref_scoped(node, descend) {
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var node_def;
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const sym = assign_as_unused(node);
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if (sym instanceof AST_SymbolRef
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&& !is_ref_of(node.left, AST_SymbolBlockDeclaration)
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&& self.variables.get(sym.name) === (node_def = sym.definition())
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) {
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if (node instanceof AST_Assign) {
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node.right.walk(tw);
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if (!node_def.chained && node.left.fixed_value() === node.right) {
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fixed_ids.set(node_def.id, node);
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}
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}
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return true;
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}
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if (node instanceof AST_SymbolRef) {
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node_def = node.definition();
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if (!in_use_ids.has(node_def.id)) {
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in_use_ids.set(node_def.id, node_def);
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if (node_def.orig[0] instanceof AST_SymbolCatch) {
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const redef = node_def.scope.is_block_scope()
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&& node_def.scope.get_defun_scope().variables.get(node_def.name);
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if (redef) in_use_ids.set(redef.id, redef);
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}
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}
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return true;
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}
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if (node instanceof AST_Class) {
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descend();
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return true;
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}
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if (node instanceof AST_Scope && !(node instanceof AST_ClassStaticBlock)) {
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var save_scope = scope;
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scope = node;
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descend();
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scope = save_scope;
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return true;
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}
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}
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});
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