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Name	Size	Last Modified
[F]common.js Edit	10.83 KB	2022-10-08 17:28:28
[F]compressor-flags.js Edit	2.75 KB	2022-10-08 17:28:28
[F]drop-side-effect-free.js Edit	12.62 KB	2022-10-08 17:28:28
[F]evaluate.js Edit	14.80 KB	2022-10-08 17:28:28
[F]index.js Edit	153.45 KB	2022-10-08 17:28:29
[F]inference.js Edit	36.04 KB	2022-10-08 17:28:29
[F]inline.js Edit	22.34 KB	2022-10-08 17:28:29
[F]native-objects.js Edit	4.70 KB	2022-10-08 17:28:30
[F]reduce-vars.js Edit	18.93 KB	2022-10-08 17:28:30
[F]tighten-body.js Edit	56.74 KB	2022-10-08 17:28:31

Editing: tighten-body.js

/***********************************************************************

A JavaScript tokenizer / parser / beautifier / compressor.
  https://github.com/mishoo/UglifyJS2

-------------------------------- (C) ---------------------------------

Author: Mihai Bazon
                         <mihai.bazon@gmail.com>
                       http://mihai.bazon.net/blog

Distributed under the BSD license:

Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

* Redistributions of source code must retain the above
          copyright notice, this list of conditions and the following
          disclaimer.

* Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials
          provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.

***********************************************************************/

import {
    AST_Array,
    AST_Arrow,
    AST_Assign,
    AST_Await,
    AST_Binary,
    AST_Block,
    AST_BlockStatement,
    AST_Break,
    AST_Call,
    AST_Case,
    AST_Catch,
    AST_Chain,
    AST_Class,
    AST_Conditional,
    AST_Const,
    AST_Constant,
    AST_Continue,
    AST_Debugger,
    AST_Default,
    AST_Definitions,
    AST_Defun,
    AST_Destructuring,
    AST_Directive,
    AST_Dot,
    AST_DWLoop,
    AST_EmptyStatement,
    AST_Exit,
    AST_Expansion,
    AST_Export,
    AST_Finally,
    AST_For,
    AST_ForIn,
    AST_If,
    AST_Import,
    AST_IterationStatement,
    AST_Lambda,
    AST_Let,
    AST_LoopControl,
    AST_Node,
    AST_Number,
    AST_Object,
    AST_ObjectKeyVal,
    AST_PropAccess,
    AST_RegExp,
    AST_Return,
    AST_Scope,
    AST_Sequence,
    AST_SimpleStatement,
    AST_Sub,
    AST_Switch,
    AST_Symbol,
    AST_SymbolConst,
    AST_SymbolDeclaration,
    AST_SymbolDefun,
    AST_SymbolFunarg,
    AST_SymbolLambda,
    AST_SymbolLet,
    AST_SymbolRef,
    AST_SymbolVar,
    AST_This,
    AST_Try,
    AST_Unary,
    AST_UnaryPostfix,
    AST_UnaryPrefix,
    AST_Undefined,
    AST_Var,
    AST_VarDef,
    AST_With,
    AST_Yield,

TreeTransformer,
    TreeWalker,
    walk,
    walk_abort,

_NOINLINE
} from "../ast.js";
import {
    make_node,
    MAP,
    member,
    remove,
    has_annotation
} from "../utils/index.js";

import { pure_prop_access_globals } from "./native-objects.js";
import {
    lazy_op,
    unary_side_effects,
    is_modified,
    is_lhs,
    aborts
} from "./inference.js";
import { WRITE_ONLY, clear_flag } from "./compressor-flags.js";
import {
    make_sequence,
    merge_sequence,
    maintain_this_binding,
    is_func_expr,
    is_identifier_atom,
    is_ref_of,
    can_be_evicted_from_block,
    as_statement_array,
} from "./common.js";

function loop_body(x) {
    if (x instanceof AST_IterationStatement) {
        return x.body instanceof AST_BlockStatement ? x.body : x;
    }
    return x;
}

// Remove code which we know is unreachable.
export function trim_unreachable_code(compressor, stat, target) {
    walk(stat, node => {
        if (node instanceof AST_Var) {
            node.remove_initializers();
            target.push(node);
            return true;
        }
        if (
            node instanceof AST_Defun
            && (node === stat || !compressor.has_directive("use strict"))
        ) {
            target.push(node === stat ? node : make_node(AST_Var, node, {
                definitions: [
                    make_node(AST_VarDef, node, {
                        name: make_node(AST_SymbolVar, node.name, node.name),
                        value: null
                    })
                ]
            }));
            return true;
        }
        if (node instanceof AST_Export || node instanceof AST_Import) {
            target.push(node);
            return true;
        }
        if (node instanceof AST_Scope) {
            return true;
        }
    });
}

/** Tighten a bunch of statements together, and perform statement-level optimization. */
export function tighten_body(statements, compressor) {
    var in_loop, in_try;
    var scope = compressor.find_parent(AST_Scope).get_defun_scope();
    find_loop_scope_try();
    var CHANGED, max_iter = 10;
    do {
        CHANGED = false;
        eliminate_spurious_blocks(statements);
        if (compressor.option("dead_code")) {
            eliminate_dead_code(statements, compressor);
        }
        if (compressor.option("if_return")) {
            handle_if_return(statements, compressor);
        }
        if (compressor.sequences_limit > 0) {
            sequencesize(statements, compressor);
            sequencesize_2(statements, compressor);
        }
        if (compressor.option("join_vars")) {
            join_consecutive_vars(statements);
        }
        if (compressor.option("collapse_vars")) {
            collapse(statements, compressor);
        }
    } while (CHANGED && max_iter-- > 0);

// Search from right to left for assignment-like expressions:
    // - `var a = x;`
    // - `a = x;`
    // - `++a`
    // For each candidate, scan from left to right for first usage, then try
    // to fold assignment into the site for compression.
    // Will not attempt to collapse assignments into or past code blocks
    // which are not sequentially executed, e.g. loops and conditionals.
    function collapse(statements, compressor) {
        if (scope.pinned())
            return statements;
        var args;
        var candidates = [];
        var stat_index = statements.length;
        var scanner = new TreeTransformer(function (node) {
            if (abort)
                return node;
            // Skip nodes before `candidate` as quickly as possible
            if (!hit) {
                if (node !== hit_stack[hit_index])
                    return node;
                hit_index++;
                if (hit_index < hit_stack.length)
                    return handle_custom_scan_order(node);
                hit = true;
                stop_after = find_stop(node, 0);
                if (stop_after === node)
                    abort = true;
                return node;
            }
            // Stop immediately if these node types are encountered
            var parent = scanner.parent();
            if (node instanceof AST_Assign
                    && (node.logical || node.operator != "=" && lhs.equivalent_to(node.left))
                || node instanceof AST_Await
                || node instanceof AST_Call && lhs instanceof AST_PropAccess && lhs.equivalent_to(node.expression)
                || node instanceof AST_Debugger
                || node instanceof AST_Destructuring
                || node instanceof AST_Expansion
                    && node.expression instanceof AST_Symbol
                    && (
                        node.expression instanceof AST_This
                        || node.expression.definition().references.length > 1
                    )
                || node instanceof AST_IterationStatement && !(node instanceof AST_For)
                || node instanceof AST_LoopControl
                || node instanceof AST_Try
                || node instanceof AST_With
                || node instanceof AST_Yield
                || node instanceof AST_Export
                || node instanceof AST_Class
                || parent instanceof AST_For && node !== parent.init
                || !replace_all
                    && (
                        node instanceof AST_SymbolRef
                        && !node.is_declared(compressor)
                        && !pure_prop_access_globals.has(node)
                    )
                || node instanceof AST_SymbolRef
                    && parent instanceof AST_Call
                    && has_annotation(parent, _NOINLINE)
            ) {
                abort = true;
                return node;
            }
            // Stop only if candidate is found within conditional branches
            if (!stop_if_hit && (!lhs_local || !replace_all)
                && (parent instanceof AST_Binary && lazy_op.has(parent.operator) && parent.left !== node
                    || parent instanceof AST_Conditional && parent.condition !== node
                    || parent instanceof AST_If && parent.condition !== node)) {
                stop_if_hit = parent;
            }
            // Replace variable with assignment when found
            if (can_replace
                && !(node instanceof AST_SymbolDeclaration)
                && lhs.equivalent_to(node)
                && !shadows(node.scope, lvalues)
            ) {
                if (stop_if_hit) {
                    abort = true;
                    return node;
                }
                if (is_lhs(node, parent)) {
                    if (value_def)
                        replaced++;
                    return node;
                } else {
                    replaced++;
                    if (value_def && candidate instanceof AST_VarDef)
                        return node;
                }
                CHANGED = abort = true;
                if (candidate instanceof AST_UnaryPostfix) {
                    return make_node(AST_UnaryPrefix, candidate, candidate);
                }
                if (candidate instanceof AST_VarDef) {
                    var def = candidate.name.definition();
                    var value = candidate.value;
                    if (def.references.length - def.replaced == 1 && !compressor.exposed(def)) {
                        def.replaced++;
                        if (funarg && is_identifier_atom(value)) {
                            return value.transform(compressor);
                        } else {
                            return maintain_this_binding(parent, node, value);
                        }
                    }
                    return make_node(AST_Assign, candidate, {
                        operator: "=",
                        logical: false,
                        left: make_node(AST_SymbolRef, candidate.name, candidate.name),
                        right: value
                    });
                }
                clear_flag(candidate, WRITE_ONLY);
                return candidate;
            }
            // These node types have child nodes that execute sequentially,
            // but are otherwise not safe to scan into or beyond them.
            var sym;
            if (node instanceof AST_Call
                || node instanceof AST_Exit
                && (side_effects || lhs instanceof AST_PropAccess || may_modify(lhs))
                || node instanceof AST_PropAccess
                && (side_effects || node.expression.may_throw_on_access(compressor))
                || node instanceof AST_SymbolRef
                && ((lvalues.has(node.name) && lvalues.get(node.name).modified) || side_effects && may_modify(node))
                || node instanceof AST_VarDef && node.value
                && (lvalues.has(node.name.name) || side_effects && may_modify(node.name))
                || (sym = is_lhs(node.left, node))
                && (sym instanceof AST_PropAccess || lvalues.has(sym.name))
                || may_throw
                && (in_try ? node.has_side_effects(compressor) : side_effects_external(node))) {
                stop_after = node;
                if (node instanceof AST_Scope)
                    abort = true;
            }
            return handle_custom_scan_order(node);
        }, function (node) {
            if (abort)
                return;
            if (stop_after === node)
                abort = true;
            if (stop_if_hit === node)
                stop_if_hit = null;
        });

while (--stat_index >= 0) {
            // Treat parameters as collapsible in IIFE, i.e.
            //   function(a, b){ ... }(x());
            // would be translated into equivalent assignments:
            //   var a = x(), b = undefined;
            if (stat_index == 0 && compressor.option("unused"))
                extract_args();
            // Find collapsible assignments
            var hit_stack = [];
            extract_candidates(statements[stat_index]);
            while (candidates.length > 0) {
                hit_stack = candidates.pop();
                var hit_index = 0;
                var candidate = hit_stack[hit_stack.length - 1];
                var value_def = null;
                var stop_after = null;
                var stop_if_hit = null;
                var lhs = get_lhs(candidate);
                if (!lhs || is_lhs_read_only(lhs) || lhs.has_side_effects(compressor))
                    continue;
                // Locate symbols which may execute code outside of scanning range
                var lvalues = get_lvalues(candidate);
                var lhs_local = is_lhs_local(lhs);
                if (lhs instanceof AST_SymbolRef) {
                    lvalues.set(lhs.name, { def: lhs.definition(), modified: false });
                }
                var side_effects = value_has_side_effects(candidate);
                var replace_all = replace_all_symbols();
                var may_throw = candidate.may_throw(compressor);
                var funarg = candidate.name instanceof AST_SymbolFunarg;
                var hit = funarg;
                var abort = false, replaced = 0, can_replace = !args || !hit;
                if (!can_replace) {
                    for (var j = compressor.self().argnames.lastIndexOf(candidate.name) + 1; !abort && j < args.length; j++) {
                        args[j].transform(scanner);
                    }
                    can_replace = true;
                }
                for (var i = stat_index; !abort && i < statements.length; i++) {
                    statements[i].transform(scanner);
                }
                if (value_def) {
                    var def = candidate.name.definition();
                    if (abort && def.references.length - def.replaced > replaced)
                        replaced = false;
                    else {
                        abort = false;
                        hit_index = 0;
                        hit = funarg;
                        for (var i = stat_index; !abort && i < statements.length; i++) {
                            statements[i].transform(multi_replacer);
                        }
                        value_def.single_use = false;
                    }
                }
                if (replaced && !remove_candidate(candidate))
                    statements.splice(stat_index, 1);
            }
        }

function handle_custom_scan_order(node) {
            // Skip (non-executed) functions
            if (node instanceof AST_Scope)
                return node;

// Scan case expressions first in a switch statement
            if (node instanceof AST_Switch) {
                node.expression = node.expression.transform(scanner);
                for (var i = 0, len = node.body.length; !abort && i < len; i++) {
                    var branch = node.body[i];
                    if (branch instanceof AST_Case) {
                        if (!hit) {
                            if (branch !== hit_stack[hit_index])
                                continue;
                            hit_index++;
                        }
                        branch.expression = branch.expression.transform(scanner);
                        if (!replace_all)
                            break;
                    }
                }
                abort = true;
                return node;
            }
        }

function mangleable_var(var_def) {
            var value = var_def.value;
            if (!(value instanceof AST_SymbolRef))
                return;
            if (value.name == "arguments")
                return;
            var def = value.definition();
            if (def.undeclared)
                return;
            return value_def = def;
        }

function get_rvalue(expr) {
            if (expr instanceof AST_Assign) {
                return expr.right;
            } else {
                return expr.value;
            }
        }

function is_lhs_local(lhs) {
            while (lhs instanceof AST_PropAccess)
                lhs = lhs.expression;
            return lhs instanceof AST_SymbolRef
                && lhs.definition().scope === scope
                && !(in_loop
                    && (lvalues.has(lhs.name)
                        || candidate instanceof AST_Unary
                        || (candidate instanceof AST_Assign
                            && !candidate.logical
                            && candidate.operator != "=")));
        }

function value_has_side_effects(expr) {
            if (expr instanceof AST_Unary)
                return unary_side_effects.has(expr.operator);
            return get_rvalue(expr).has_side_effects(compressor);
        }

function may_modify(sym) {
            if (!sym.definition)
                return true; // AST_Destructuring
            var def = sym.definition();
            if (def.orig.length == 1 && def.orig[0] instanceof AST_SymbolDefun)
                return false;
            if (def.scope.get_defun_scope() !== scope)
                return true;
            return !def.references.every((ref) => {
                var s = ref.scope.get_defun_scope();
                // "block" scope within AST_Catch
                if (s.TYPE == "Scope")
                    s = s.parent_scope;
                return s === scope;
            });
        }

function side_effects_external(node, lhs) {
            if (node instanceof AST_Assign)
                return side_effects_external(node.left, true);
            if (node instanceof AST_Unary)
                return side_effects_external(node.expression, true);
            if (node instanceof AST_VarDef)
                return node.value && side_effects_external(node.value);
            if (lhs) {
                if (node instanceof AST_Dot)
                    return side_effects_external(node.expression, true);
                if (node instanceof AST_Sub)
                    return side_effects_external(node.expression, true);
                if (node instanceof AST_SymbolRef)
                    return node.definition().scope !== scope;
            }
            return false;
        }

function handle_if_return(statements, compressor) {
        var self = compressor.self();
        var multiple_if_returns = has_multiple_if_returns(statements);
        var in_lambda = self instanceof AST_Lambda;
        for (var i = statements.length; --i >= 0;) {
            var stat = statements[i];
            var j = next_index(i);
            var next = statements[j];

if (in_lambda && !next && stat instanceof AST_Return) {
                if (!stat.value) {
                    CHANGED = true;
                    statements.splice(i, 1);
                    continue;
                }
                if (stat.value instanceof AST_UnaryPrefix && stat.value.operator == "void") {
                    CHANGED = true;
                    statements[i] = make_node(AST_SimpleStatement, stat, {
                        body: stat.value.expression
                    });
                    continue;
                }
            }

if (stat instanceof AST_If) {
                var ab = aborts(stat.body);
                if (can_merge_flow(ab)) {
                    if (ab.label) {
                        remove(ab.label.thedef.references, ab);
                    }
                    CHANGED = true;
                    stat = stat.clone();
                    stat.condition = stat.condition.negate(compressor);
                    var body = as_statement_array_with_return(stat.body, ab);
                    stat.body = make_node(AST_BlockStatement, stat, {
                        body: as_statement_array(stat.alternative).concat(extract_functions())
                    });
                    stat.alternative = make_node(AST_BlockStatement, stat, {
                        body: body
                    });
                    statements[i] = stat.transform(compressor);
                    continue;
                }

if (stat instanceof AST_If && stat.body instanceof AST_Return) {
                var value = stat.body.value;
                //---
                // pretty silly case, but:
                // if (foo()) return; return; ==> foo(); return;
                if (!value && !stat.alternative
                    && (in_lambda && !next || next instanceof AST_Return && !next.value)) {
                    CHANGED = true;
                    statements[i] = make_node(AST_SimpleStatement, stat.condition, {
                        body: stat.condition
                    });
                    continue;
                }
                //---
                // if (foo()) return x; return y; ==> return foo() ? x : y;
                if (value && !stat.alternative && next instanceof AST_Return && next.value) {
                    CHANGED = true;
                    stat = stat.clone();
                    stat.alternative = next;
                    statements[i] = stat.transform(compressor);
                    statements.splice(j, 1);
                    continue;
                }
                //---
                // if (foo()) return x; [ return ; ] ==> return foo() ? x : undefined;
                if (value && !stat.alternative
                    && (!next && in_lambda && multiple_if_returns
                        || next instanceof AST_Return)) {
                    CHANGED = true;
                    stat = stat.clone();
                    stat.alternative = next || make_node(AST_Return, stat, {
                        value: null
                    });
                    statements[i] = stat.transform(compressor);
                    if (next)
                        statements.splice(j, 1);
                    continue;
                }
                //---
                // if (a) return b; if (c) return d; e; ==> return a ? b : c ? d : void e;
                //
                // if sequences is not enabled, this can lead to an endless loop (issue #866).
                // however, with sequences on this helps producing slightly better output for
                // the example code.
                var prev = statements[prev_index(i)];
                if (compressor.option("sequences") && in_lambda && !stat.alternative
                    && prev instanceof AST_If && prev.body instanceof AST_Return
                    && next_index(j) == statements.length && next instanceof AST_SimpleStatement) {
                    CHANGED = true;
                    stat = stat.clone();
                    stat.alternative = make_node(AST_BlockStatement, next, {
                        body: [
                            next,
                            make_node(AST_Return, next, {
                                value: null
                            })
                        ]
                    });
                    statements[i] = stat.transform(compressor);
                    statements.splice(j, 1);
                    continue;
                }
            }
        }

function is_return_void(value) {
            return !value || value instanceof AST_UnaryPrefix && value.operator == "void";
        }

function can_merge_flow(ab) {
            if (!ab)
                return false;
            for (var j = i + 1, len = statements.length; j < len; j++) {
                var stat = statements[j];
                if (stat instanceof AST_Const || stat instanceof AST_Let)
                    return false;
            }
            var lct = ab instanceof AST_LoopControl ? compressor.loopcontrol_target(ab) : null;
            return ab instanceof AST_Return && in_lambda && is_return_void(ab.value)
                || ab instanceof AST_Continue && self === loop_body(lct)
                || ab instanceof AST_Break && lct instanceof AST_BlockStatement && self === lct;
        }

function declarations_only(node) {
        return node.definitions.every((var_def) => !var_def.value
        );
    }

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