path: root/lib/output.js

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

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

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

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

  Distributed under the BSD license:

    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>

    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.

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

"use strict";

function is_some_comments(comment) {
    // multiline comment
    return comment.type == "comment2" && /@preserve|@license|@cc_on/i.test(comment.value);
}

function OutputStream(options) {

    var readonly = !options;
    options = defaults(options, {
        ascii_only       : false,
        beautify         : false,
        braces           : false,
        comments         : false,
        galio            : false,
        ie8              : false,
        indent_level     : 4,
        indent_start     : 0,
        inline_script    : true,
        keep_quoted_props: false,
        max_line_len     : false,
        preamble         : null,
        preserve_line    : false,
        quote_keys       : false,
        quote_style      : 0,
        semicolons       : true,
        shebang          : true,
        source_map       : null,
        v8               : false,
        webkit           : false,
        width            : 80,
        wrap_iife        : false,
    }, true);

    // Convert comment option to RegExp if neccessary and set up comments filter
    var comment_filter = return_false; // Default case, throw all comments away
    if (options.comments) {
        var comments = options.comments;
        if (typeof options.comments === "string" && /^\/.*\/[a-zA-Z]*$/.test(options.comments)) {
            var regex_pos = options.comments.lastIndexOf("/");
            comments = new RegExp(
                options.comments.substr(1, regex_pos - 1),
                options.comments.substr(regex_pos + 1)
            );
        }
        if (comments instanceof RegExp) {
            comment_filter = function(comment) {
                return comment.type != "comment5" && comments.test(comment.value);
            };
        } else if (typeof comments === "function") {
            comment_filter = function(comment) {
                return comment.type != "comment5" && comments(this, comment);
            };
        } else if (comments === "some") {
            comment_filter = is_some_comments;
        } else { // NOTE includes "all" option
            comment_filter = return_true;
        }
    }

    var indentation = options.indent_start;
    var current_col = 0;
    var current_line = 1;
    var current_pos = 0;
    var OUTPUT = "";

    var to_utf8 = options.ascii_only ? function(str, identifier) {
        if (identifier) str = str.replace(/[\ud800-\udbff][\udc00-\udfff]/g, function(ch) {
            return "\\u{" + (ch.charCodeAt(0) - 0xd7c0 << 10 | ch.charCodeAt(1) - 0xdc00).toString(16) + "}";
        });
        return str.replace(/[\u0000-\u001f\u007f-\uffff]/g, function(ch) {
            var code = ch.charCodeAt(0).toString(16);
            if (code.length <= 2 && !identifier) {
                while (code.length < 2) code = "0" + code;
                return "\\x" + code;
            } else {
                while (code.length < 4) code = "0" + code;
                return "\\u" + code;
            }
        });
    } : function(str) {
        var s = "";
        for (var i = 0, j = 0; i < str.length; i++) {
            var code = str.charCodeAt(i);
            if (is_surrogate_pair_head(code)) {
                if (is_surrogate_pair_tail(str.charCodeAt(i + 1))) {
                    i++;
                    continue;
                }
            } else if (!is_surrogate_pair_tail(code)) {
                continue;
            }
            s += str.slice(j, i) + "\\u" + code.toString(16);
            j = i + 1;
        }
        return j == 0 ? str : s + str.slice(j);
    };

    function make_string(str, quote) {
        var dq = 0, sq = 0;
        str = str.replace(/[\\\b\f\n\r\v\t\x22\x27\u2028\u2029\0\ufeff]/g, function(s, i) {
            switch (s) {
              case '"': ++dq; return '"';
              case "'": ++sq; return "'";
              case "\\": return "\\\\";
              case "\n": return "\\n";
              case "\r": return "\\r";
              case "\t": return "\\t";
              case "\b": return "\\b";
              case "\f": return "\\f";
              case "\x0B": return options.ie8 ? "\\x0B" : "\\v";
              case "\u2028": return "\\u2028";
              case "\u2029": return "\\u2029";
              case "\ufeff": return "\\ufeff";
              case "\0":
                  return /[0-9]/.test(str.charAt(i+1)) ? "\\x00" : "\\0";
            }
            return s;
        });
        function quote_single() {
            return "'" + str.replace(/\x27/g, "\\'") + "'";
        }
        function quote_double() {
            return '"' + str.replace(/\x22/g, '\\"') + '"';
        }
        str = to_utf8(str);
        switch (options.quote_style) {
          case 1:
            return quote_single();
          case 2:
            return quote_double();
          case 3:
            return quote == "'" ? quote_single() : quote_double();
          default:
            return dq > sq ? quote_single() : quote_double();
        }
    }

    function encode_string(str, quote) {
        var ret = make_string(str, quote);
        if (options.inline_script) {
            ret = ret.replace(/<\x2f(script)([>\/\t\n\f\r ])/gi, "<\\/$1$2");
            ret = ret.replace(/\x3c!--/g, "\\x3c!--");
            ret = ret.replace(/--\x3e/g, "--\\x3e");
        }
        return ret;
    }

    function make_name(name) {
        name = name.toString();
        name = to_utf8(name, true);
        return name;
    }

    /* -----[ beautification/minification ]----- */

    var has_parens = false;
    var line_end = 0;
    var line_fixed = true;
    var might_need_space = false;
    var might_need_semicolon = false;
    var need_newline_indented = false;
    var need_space = false;
    var newline_insert = -1;
    var last = "";
    var mapping_token, mapping_name, mappings = options.source_map && [];

    var adjust_mappings = mappings ? function(line, col) {
        mappings.forEach(function(mapping) {
            mapping.line += line;
            mapping.col += col;
        });
    } : noop;

    var flush_mappings = mappings ? function() {
        mappings.forEach(function(mapping) {
            options.source_map.add(
                mapping.token.file,
                mapping.line, mapping.col,
                mapping.token.line, mapping.token.col,
                !mapping.name && mapping.token.type == "name" ? mapping.token.value : mapping.name
            );
        });
        mappings = [];
    } : noop;

    function insert_newlines(count) {
        var index = OUTPUT.lastIndexOf("\n");
        if (line_end < index) line_end = index;
        var left = OUTPUT.slice(0, line_end);
        var right = OUTPUT.slice(line_end);
        adjust_mappings(count, right.length - current_col);
        current_line += count;
        current_pos += count;
        current_col = right.length;
        OUTPUT = left;
        while (count--) OUTPUT += "\n";
        OUTPUT += right;
    }

    var fix_line = options.max_line_len ? function() {
        if (line_fixed) {
            if (current_col > options.max_line_len) {
                AST_Node.warn("Output exceeds {max_line_len} characters", options);
            }
            return;
        }
        if (current_col > options.max_line_len) insert_newlines(1);
        line_fixed = true;
        flush_mappings();
    } : noop;

    var requireSemicolonChars = makePredicate("( [ + * / - , .");

    function print(str) {
        str = String(str);
        var ch = str.charAt(0);
        if (need_newline_indented && ch) {
            need_newline_indented = false;
            if (ch != "\n") {
                print("\n");
                indent();
            }
        }
        if (need_space && ch) {
            need_space = false;
            if (!/[\s;})]/.test(ch)) {
                space();
            }
        }
        newline_insert = -1;
        var prev = last.slice(-1);
        if (might_need_semicolon) {
            might_need_semicolon = false;

            if (prev == ":" && ch == "}" || (!ch || ";}".indexOf(ch) < 0) && prev != ";") {
                if (options.semicolons || requireSemicolonChars[ch]) {
                    OUTPUT += ";";
                    current_col++;
                    current_pos++;
                } else {
                    fix_line();
                    OUTPUT += "\n";
                    current_pos++;
                    current_line++;
                    current_col = 0;

                    if (/^\s+$/.test(str)) {
                        // reset the semicolon flag, since we didn't print one
                        // now and might still have to later
                        might_need_semicolon = true;
                    }
                }

                if (!options.beautify)
                    might_need_space = false;
            }
        }

        if (might_need_space) {
            if (is_identifier_char(prev) && (is_identifier_char(ch) || ch == "\\")
                || (ch == "/" && ch == prev)
                || ((ch == "+" || ch == "-") && ch == last)
                || str == "--" && last == "!"
                || str == "in" && prev == "/"
                || last == "--" && ch == ">") {
                OUTPUT += " ";
                current_col++;
                current_pos++;
            }
            if (prev != "<" || str != "!") might_need_space = false;
        }

        if (mapping_token) {
            mappings.push({
                token: mapping_token,
                name: mapping_name,
                line: current_line,
                col: current_col
            });
            mapping_token = false;
            if (line_fixed) flush_mappings();
        }

        OUTPUT += str;
        has_parens = str.slice(-1) == "(";
        current_pos += str.length;
        var a = str.split(/\r?\n/), n = a.length - 1;
        current_line += n;
        current_col += a[0].length;
        if (n > 0) {
            fix_line();
            current_col = a[n].length;
        }
        last = str;
    }

    var space = options.beautify ? function() {
        print(" ");
    } : function() {
        might_need_space = true;
    };

    var indent = options.beautify ? function(half) {
        print(repeat_string(" ", half ? indentation - (options.indent_level >> 1) : indentation));
    } : noop;

    var with_indent = options.beautify ? function(col, cont) {
        if (col === true) col = next_indent();
        var save_indentation = indentation;
        indentation = col;
        var ret = cont();
        indentation = save_indentation;
        return ret;
    } : function(col, cont) { return cont() };

    var may_add_newline = options.max_line_len || options.preserve_line ? function() {
        fix_line();
        line_end = OUTPUT.length;
        line_fixed = false;
    } : noop;

    var newline = options.beautify ? function() {
        if (newline_insert < 0) return print("\n");
        if (OUTPUT[newline_insert] != "\n") {
            OUTPUT = OUTPUT.slice(0, newline_insert) + "\n" + OUTPUT.slice(newline_insert);
            current_pos++;
            current_line++;
        }
        newline_insert++;
    } : may_add_newline;

    var semicolon = options.beautify ? function() {
        print(";");
    } : function() {
        might_need_semicolon = true;
    };

    function force_semicolon() {
        if (might_need_semicolon) print(";");
        print(";");
    }

    function next_indent() {
        return indentation + options.indent_level;
    }

    function with_block(cont) {
        var ret;
        print("{");
        newline();
        with_indent(next_indent(), function() {
            ret = cont();
        });
        indent();
        print("}");
        return ret;
    }

    function with_parens(cont) {
        print("(");
        may_add_newline();
        //XXX: still nice to have that for argument lists
        //var ret = with_indent(current_col, cont);
        var ret = cont();
        may_add_newline();
        print(")");
        return ret;
    }

    function with_square(cont) {
        print("[");
        may_add_newline();
        //var ret = with_indent(current_col, cont);
        var ret = cont();
        may_add_newline();
        print("]");
        return ret;
    }

    function comma() {
        may_add_newline();
        print(",");
        may_add_newline();
        space();
    }

    function colon() {
        print(":");
        space();
    }

    var add_mapping = mappings ? function(token, name) {
        mapping_token = token;
        mapping_name = name;
    } : noop;

    function get() {
        if (!line_fixed) fix_line();
        return OUTPUT;
    }

    function has_nlb() {
        var index = OUTPUT.lastIndexOf("\n");
        return /^ *$/.test(OUTPUT.slice(index + 1));
    }

    function prepend_comments(node) {
        var self = this;
        var scan = node instanceof AST_Exit && node.value;
        var comments = dump(node);
        if (!comments) comments = [];

        if (scan) {
            var tw = new TreeWalker(function(node) {
                var parent = tw.parent();
                if (parent instanceof AST_Exit
                    || parent instanceof AST_Binary && parent.left === node
                    || parent.TYPE == "Call" && parent.expression === node
                    || parent instanceof AST_Conditional && parent.condition === node
                    || parent instanceof AST_Dot && parent.expression === node
                    || parent instanceof AST_Sequence && parent.expressions[0] === node
                    || parent instanceof AST_Sub && parent.expression === node
                    || parent instanceof AST_UnaryPostfix) {
                    var before = dump(node);
                    if (before) comments = comments.concat(before);
                } else {
                    return true;
                }
            });
            tw.push(node);
            node.value.walk(tw);
        }

        if (current_pos == 0) {
            if (comments.length > 0 && options.shebang && comments[0].type == "comment5") {
                print("#!" + comments.shift().value + "\n");
                indent();
            }
            var preamble = options.preamble;
            if (preamble) {
                print(preamble.replace(/\r\n?|[\n\u2028\u2029]|\s*$/g, "\n"));
            }
        }

        comments = comments.filter(comment_filter, node);
        if (comments.length == 0) return;
        var last_nlb = has_nlb();
        comments.forEach(function(c, i) {
            if (!last_nlb) {
                if (c.nlb) {
                    print("\n");
                    indent();
                    last_nlb = true;
                } else if (i > 0) {
                    space();
                }
            }
            if (/comment[134]/.test(c.type)) {
                print("//" + c.value.replace(/[@#]__PURE__/g, " ") + "\n");
                indent();
                last_nlb = true;
            } else if (c.type == "comment2") {
                print("/*" + c.value.replace(/[@#]__PURE__/g, " ") + "*/");
                last_nlb = false;
            }
        });
        if (!last_nlb) {
            if (node.start.nlb) {
                print("\n");
                indent();
            } else {
                space();
            }
        }

        function dump(node) {
            var token = node.start;
            if (!token) {
                if (!scan) return;
                node.start = token = new AST_Token();
            }
            var comments = token.comments_before;
            if (!comments) {
                if (!scan) return;
                token.comments_before = comments = [];
            }
            if (comments._dumped === self) return;
            comments._dumped = self;
            return comments;
        }
    }

    function append_comments(node, tail) {
        var self = this;
        var token = node.end;
        if (!token) return;
        var comments = token[tail ? "comments_before" : "comments_after"];
        if (!comments || comments._dumped === self) return;
        if (!(node instanceof AST_Statement || all(comments, function(c) {
            return !/comment[134]/.test(c.type);
        }))) return;
        comments._dumped = self;
        var insert = OUTPUT.length;
        comments.filter(comment_filter, node).forEach(function(c, i) {
            need_space = false;
            if (need_newline_indented) {
                print("\n");
                indent();
                need_newline_indented = false;
            } else if (c.nlb && (i > 0 || !has_nlb())) {
                print("\n");
                indent();
            } else if (i > 0 || !tail) {
                space();
            }
            if (/comment[134]/.test(c.type)) {
                print("//" + c.value.replace(/[@#]__PURE__/g, " "));
                need_newline_indented = true;
            } else if (c.type == "comment2") {
                print("/*" + c.value.replace(/[@#]__PURE__/g, " ") + "*/");
                need_space = true;
            }
        });
        if (OUTPUT.length > insert) newline_insert = insert;
    }

    var stack = [];
    return {
        get             : get,
        toString        : get,
        indent          : indent,
        should_break    : readonly ? noop : function() {
            return options.width && current_col - indentation >= options.width;
        },
        has_parens      : function() { return has_parens },
        newline         : newline,
        print           : print,
        space           : space,
        comma           : comma,
        colon           : colon,
        last            : function() { return last },
        semicolon       : semicolon,
        force_semicolon : force_semicolon,
        to_utf8         : to_utf8,
        print_name      : function(name) { print(make_name(name)) },
        print_string    : function(str, quote) { print(encode_string(str, quote)) },
        next_indent     : next_indent,
        with_indent     : with_indent,
        with_block      : with_block,
        with_parens     : with_parens,
        with_square     : with_square,
        add_mapping     : add_mapping,
        option          : function(opt) { return options[opt] },
        prepend_comments: readonly ? noop : prepend_comments,
        append_comments : readonly || comment_filter === return_false ? noop : append_comments,
        line            : function() { return current_line },
        col             : function() { return current_col },
        pos             : function() { return current_pos },
        push_node       : function(node) { stack.push(node) },
        pop_node        : options.preserve_line ? function() {
            var node = stack.pop();
            if (node.start && node.start.line > current_line) {
                insert_newlines(node.start.line - current_line);
            }
        } : function() {
            stack.pop();
        },
        parent          : function(n) {
            return stack[stack.length - 2 - (n || 0)];
        },
    };
}

/* -----[ code generators ]----- */

(function() {

    /* -----[ utils ]----- */

    function DEFPRINT(nodetype, generator) {
        nodetype.DEFMETHOD("_codegen", generator);
    }

    var use_asm = false;

    AST_Node.DEFMETHOD("print", function(stream, force_parens) {
        var self = this;
        stream.push_node(self);
        if (force_parens || self.needs_parens(stream)) {
            stream.with_parens(doit);
        } else {
            doit();
        }
        stream.pop_node();

        function doit() {
            stream.prepend_comments(self);
            self.add_source_map(stream);
            self._codegen(stream);
            stream.append_comments(self);
        }
    });
    AST_Node.DEFMETHOD("print_to_string", function(options) {
        var s = OutputStream(options);
        this.print(s);
        return s.get();
    });

    /* -----[ PARENTHESES ]----- */

    function PARENS(nodetype, func) {
        nodetype.DEFMETHOD("needs_parens", func);
    }

    PARENS(AST_Node, return_false);

    // a function expression needs parens around it when it's provably
    // the first token to appear in a statement.
    PARENS(AST_Function, function(output) {
        if (!output.has_parens() && first_in_statement(output)) return true;
        if (output.option("webkit")) {
            var p = output.parent();
            if (p instanceof AST_PropAccess && p.expression === this) return true;
        }
        if (output.option("wrap_iife")) {
            var p = output.parent();
            if (p instanceof AST_Call && p.expression === this) return true;
        }
    });

    // same goes for an object literal, because otherwise it would be
    // interpreted as a block of code.
    function needs_parens_obj(output) {
        return !output.has_parens() && first_in_statement(output);
    }
    PARENS(AST_Object, needs_parens_obj);

    PARENS(AST_Unary, function(output) {
        var p = output.parent();
        return (p instanceof AST_Call || p instanceof AST_PropAccess) && p.expression === this;
    });

    PARENS(AST_Sequence, function(output) {
        var p = output.parent();
            // [ 1, (2, 3), 4 ] ==> [ 1, 3, 4 ]
        return p instanceof AST_Array
            // 1 + (2, 3) + 4 ==> 8
            || p instanceof AST_Binary
            // new (foo, bar) or foo(1, (2, 3), 4)
            || p instanceof AST_Call
            // (false, true) ? (a = 10, b = 20) : (c = 30)
            // ==> 20 (side effect, set a := 10 and b := 20)
            || p instanceof AST_Conditional
            // { [(1, 2)]: 3 }[2] ==> 3
            // { foo: (1, 2) }.foo ==> 2
            || p instanceof AST_DestructuredKeyVal
            || p instanceof AST_ObjectProperty
            // (1, {foo:2}).foo or (1, {foo:2})["foo"] ==> 2
            || p instanceof AST_PropAccess && p.expression === this
            // ...(foo, bar, baz)
            || p instanceof AST_Spread
            // !(foo, bar, baz)
            || p instanceof AST_Unary
            // var a = (1, 2), b = a + a; ==> b == 4
            || p instanceof AST_VarDef;
    });

    PARENS(AST_Binary, function(output) {
        var p = output.parent();
        // this deals with precedence: 3 * (2 + 1)
        if (p instanceof AST_Binary) {
            var po = p.operator, pp = PRECEDENCE[po];
            var so = this.operator, sp = PRECEDENCE[so];
            return pp > sp || (pp == sp && this === p.right);
        }
        // (foo && bar)()
        if (p instanceof AST_Call) return p.expression === this;
        // (foo && bar)["prop"], (foo && bar).prop
        if (p instanceof AST_PropAccess) return p.expression === this;
        // typeof (foo && bar)
        if (p instanceof AST_Unary) return true;
    });

    PARENS(AST_PropAccess, function(output) {
        var node = this;
        var p = output.parent();
        if (p instanceof AST_New && p.expression === node) {
            // i.e. new (foo().bar)
            //
            // if there's one call into this subtree, then we need
            // parens around it too, otherwise the call will be
            // interpreted as passing the arguments to the upper New
            // expression.
            do {
                node = node.expression;
            } while (node instanceof AST_PropAccess);
            return node.TYPE == "Call";
        }
    });

    PARENS(AST_Call, function(output) {
        var p = output.parent();
        if (p instanceof AST_New) return p.expression === this;
        // https://bugs.webkit.org/show_bug.cgi?id=123506
        if (output.option("webkit")) {
            var g = output.parent(1);
            return this.expression instanceof AST_Function
                && p instanceof AST_PropAccess
                && p.expression === this
                && g instanceof AST_Assign
                && g.left === p;
        }
    });

    PARENS(AST_New, function(output) {
        if (need_constructor_parens(this, output)) return false;
        var p = output.parent();
        // (new foo)(bar)
        if (p instanceof AST_Call) return p.expression === this;
        // (new Date).getTime(), (new Date)["getTime"]()
        return p instanceof AST_PropAccess;
    });

    PARENS(AST_Number, function(output) {
        var p = output.parent();
        if (p instanceof AST_PropAccess && p.expression === this) {
            var value = this.value;
                // https://github.com/mishoo/UglifyJS/issues/115
            return value < 0
                // https://github.com/mishoo/UglifyJS/pull/1009
                || output.option("galio") && /^0/.test(make_num(value));
        }
    });

    function needs_parens_assign_cond(self, output) {
        var p = output.parent();
        // 1 + (a = 2) + 3 → 6, side effect setting a = 2
        if (p instanceof AST_Binary) return !(p instanceof AST_Assign);
        // (a = func)() —or— new (a = Object)()
        if (p instanceof AST_Call) return p.expression === self;
        // (a = foo) ? bar : baz
        if (p instanceof AST_Conditional) return p.condition === self;
        // (a = foo)["prop"] —or— (a = foo).prop
        if (p instanceof AST_PropAccess) return p.expression === self;
        // !(a = false) → true
        if (p instanceof AST_Unary) return true;
    }
    PARENS(AST_Assign, function(output) {
        if (needs_parens_assign_cond(this, output)) return true;
        //  v8 parser bug   =>     workaround
        // f([1], [a] = []) => f([1], ([a] = []))
        if (output.option("v8")) return this.left instanceof AST_Destructured;
        // ({ p: a } = o);
        if (this.left instanceof AST_DestructuredObject) return needs_parens_obj(output);
    });
    PARENS(AST_Conditional, function(output) {
        return needs_parens_assign_cond(this, output);
    });

    /* -----[ PRINTERS ]----- */

    DEFPRINT(AST_Directive, function(output) {
        var quote = this.quote;
        var value = this.value;
        switch (output.option("quote_style")) {
          case 0:
          case 2:
            if (value.indexOf('"') == -1) quote = '"';
            break;
          case 1:
            if (value.indexOf("'") == -1) quote = "'";
            break;
        }
        output.print(quote + value + quote);
        output.semicolon();
    });
    DEFPRINT(AST_Debugger, function(output) {
        output.print("debugger");
        output.semicolon();
    });

    /* -----[ statements ]----- */

    function display_body(body, is_toplevel, output, allow_directives) {
        var last = body.length - 1;
        var in_directive = allow_directives;
        var was_asm = use_asm;
        body.forEach(function(stmt, i) {
            if (in_directive) {
                if (stmt instanceof AST_Directive) {
                    if (stmt.value == "use asm") use_asm = true;
                } else if (!(stmt instanceof AST_EmptyStatement)) {
                    if (stmt instanceof AST_SimpleStatement && stmt.body instanceof AST_String) {
                        output.force_semicolon();
                    }
                    in_directive = false;
                }
            }
            if (stmt instanceof AST_EmptyStatement) return;
            output.indent();
            stmt.print(output);
            if (i == last && is_toplevel) return;
            output.newline();
            if (is_toplevel) output.newline();
        });
        use_asm = was_asm;
    }

    DEFPRINT(AST_Statement, function(output) {
        this.body.print(output);
        output.semicolon();
    });
    DEFPRINT(AST_Toplevel, function(output) {
        display_body(this.body, true, output, true);
        output.print("");
    });
    DEFPRINT(AST_LabeledStatement, function(output) {
        this.label.print(output);
        output.colon();
        this.body.print(output);
    });
    DEFPRINT(AST_SimpleStatement, function(output) {
        this.body.print(output);
        output.semicolon();
    });
    function print_braced_empty(self, output) {
        output.print("{");
        output.with_indent(output.next_indent(), function() {
            output.append_comments(self, true);
        });
        output.print("}");
    }
    function print_braced(self, output, allow_directives) {
        if (self.body.length > 0) {
            output.with_block(function() {
                display_body(self.body, false, output, allow_directives);
            });
        } else print_braced_empty(self, output);
    }
    DEFPRINT(AST_BlockStatement, function(output) {
        print_braced(this, output);
    });
    DEFPRINT(AST_EmptyStatement, function(output) {
        output.semicolon();
    });
    DEFPRINT(AST_Do, function(output) {
        var self = this;
        output.print("do");
        output.space();
        make_block(self.body, output);
        output.space();
        output.print("while");
        output.space();
        output.with_parens(function() {
            self.condition.print(output);
        });
        output.semicolon();
    });
    DEFPRINT(AST_While, function(output) {
        var self = this;
        output.print("while");
        output.space();
        output.with_parens(function() {
            self.condition.print(output);
        });
        output.space();
        force_statement(self.body, output);
    });
    DEFPRINT(AST_For, function(output) {
        var self = this;
        output.print("for");
        output.space();
        output.with_parens(function() {
            if (self.init) {
                if (self.init instanceof AST_Definitions) {
                    self.init.print(output);
                } else {
                    parenthesize_for_noin(self.init, output, true);
                }
                output.print(";");
                output.space();
            } else {
                output.print(";");
            }
            if (self.condition) {
                self.condition.print(output);
                output.print(";");
                output.space();
            } else {
                output.print(";");
            }
            if (self.step) {
                self.step.print(output);
            }
        });
        output.space();
        force_statement(self.body, output);
    });
    DEFPRINT(AST_ForIn, function(output) {
        var self = this;
        output.print("for");
        output.space();
        output.with_parens(function() {
            self.init.print(output);
            output.space();
            output.print("in");
            output.space();
            self.object.print(output);
        });
        output.space();
        force_statement(self.body, output);
    });
    DEFPRINT(AST_With, function(output) {
        var self = this;
        output.print("with");
        output.space();
        output.with_parens(function() {
            self.expression.print(output);
        });
        output.space();
        force_statement(self.body, output);
    });

    /* -----[ functions ]----- */
    DEFPRINT(AST_Lambda, function(output, nokeyword) {
        var self = this;
        if (!nokeyword) {
            output.print("function");
        }
        if (self.name) {
            output.space();
            self.name.print(output);
        }
        output.with_parens(function() {
            self.argnames.forEach(function(arg, i) {
                if (i) output.comma();
                arg.print(output);
            });
        });
        output.space();
        print_braced(self, output, true);
    });

    /* -----[ jumps ]----- */
    function print_jump(kind, prop) {
        return function(output) {
            output.print(kind);
            var target = this[prop];
            if (target) {
                output.space();
                target.print(output);
            }
            output.semicolon();
        };
    }
    DEFPRINT(AST_Return, print_jump("return", "value"));
    DEFPRINT(AST_Throw, print_jump("throw", "value"));
    DEFPRINT(AST_Break, print_jump("break", "label"));
    DEFPRINT(AST_Continue, print_jump("continue", "label"));

    /* -----[ if ]----- */
    function make_then(self, output) {
        var b = self.body;
        if (output.option("braces") && !(b instanceof AST_Const || b instanceof AST_Let)
            || output.option("ie8") && b instanceof AST_Do)
            return make_block(b, output);
        // The squeezer replaces "block"-s that contain only a single
        // statement with the statement itself; technically, the AST
        // is correct, but this can create problems when we output an
        // IF having an ELSE clause where the THEN clause ends in an
        // IF *without* an ELSE block (then the outer ELSE would refer
        // to the inner IF).  This function checks for this case and
        // adds the block braces if needed.
        if (!b) return output.force_semicolon();
        while (true) {
            if (b instanceof AST_If) {
                if (!b.alternative) {
                    make_block(self.body, output);
                    return;
                }
                b = b.alternative;
            } else if (b instanceof AST_StatementWithBody) {
                b = b.body;
            } else break;
        }
        force_statement(self.body, output);
    }
    DEFPRINT(AST_If, function(output) {
        var self = this;
        output.print("if");
        output.space();
        output.with_parens(function() {
            self.condition.print(output);
        });
        output.space();
        if (self.alternative) {
            make_then(self, output);
            output.space();
            output.print("else");
            output.space();
            if (self.alternative instanceof AST_If)
                self.alternative.print(output);
            else
                force_statement(self.alternative, output);
        } else {
            force_statement(self.body, output);
        }
    });

    /* -----[ switch ]----- */
    DEFPRINT(AST_Switch, function(output) {
        var self = this;
        output.print("switch");
        output.space();
        output.with_parens(function() {
            self.expression.print(output);
        });
        output.space();
        var last = self.body.length - 1;
        if (last < 0) print_braced_empty(self, output);
        else output.with_block(function() {
            self.body.forEach(function(branch, i) {
                output.indent(true);
                branch.print(output);
                if (i < last && branch.body.length > 0)
                    output.newline();
            });
        });
    });
    function print_branch_body(self, output) {
        output.newline();
        self.body.forEach(function(stmt) {
            output.indent();
            stmt.print(output);
            output.newline();
        });
    }
    DEFPRINT(AST_Default, function(output) {
        output.print("default:");
        print_branch_body(this, output);
    });
    DEFPRINT(AST_Case, function(output) {
        var self = this;
        output.print("case");
        output.space();
        self.expression.print(output);
        output.print(":");
        print_branch_body(self, output);
    });

    /* -----[ exceptions ]----- */
    DEFPRINT(AST_Try, function(output) {
        var self = this;
        output.print("try");
        output.space();
        print_braced(self, output);
        if (self.bcatch) {
            output.space();
            self.bcatch.print(output);
        }
        if (self.bfinally) {
            output.space();
            self.bfinally.print(output);
        }
    });
    DEFPRINT(AST_Catch, function(output) {
        var self = this;
        output.print("catch");
        if (self.argname) {
            output.space();
            output.with_parens(function() {
                self.argname.print(output);
            });
        }
        output.space();
        print_braced(self, output);
    });
    DEFPRINT(AST_Finally, function(output) {
        output.print("finally");
        output.space();
        print_braced(this, output);
    });

    function print_definitinos(type) {
        return function(output) {
            var self = this;
            output.print(type);
            output.space();
            self.definitions.forEach(function(def, i) {
                if (i) output.comma();
                def.print(output);
            });
            var p = output.parent();
            if (p && p.init !== self || !(p instanceof AST_For || p instanceof AST_ForIn)) output.semicolon();
        };
    }
    DEFPRINT(AST_Const, print_definitinos("const"));
    DEFPRINT(AST_Let, print_definitinos("let"));
    DEFPRINT(AST_Var, print_definitinos("var"));

    function parenthesize_for_noin(node, output, noin) {
        var parens = false;
        // need to take some precautions here:
        //    https://github.com/mishoo/UglifyJS/issues/60
        if (noin) node.walk(new TreeWalker(function(node) {
            if (parens || node instanceof AST_Scope) return true;
            if (node instanceof AST_Binary && node.operator == "in") {
                parens = true;
                return true;
            }
        }));
        node.print(output, parens);
    }

    DEFPRINT(AST_VarDef, function(output) {
        var self = this;
        self.name.print(output);
        if (self.value) {
            output.space();
            output.print("=");
            output.space();
            var p = output.parent(1);
            var noin = p instanceof AST_For || p instanceof AST_ForIn;
            parenthesize_for_noin(self.value, output, noin);
        }
    });

    /* -----[ other expressions ]----- */
    function print_call_args(self, output) {
        if (self.expression instanceof AST_Call || self.expression instanceof AST_Lambda) {
            output.add_mapping(self.start);
        }
        output.with_parens(function() {
            self.args.forEach(function(expr, i) {
                if (i) output.comma();
                expr.print(output);
            });
        });
    }
    DEFPRINT(AST_Call, function(output) {
        this.expression.print(output);
        print_call_args(this, output);
    });
    DEFPRINT(AST_New, function(output) {
        var self = this;
        output.print("new");
        output.space();
        self.expression.print(output);
        if (need_constructor_parens(self, output)) print_call_args(self, output);
    });
    DEFPRINT(AST_Sequence, function(output) {
        this.expressions.forEach(function(node, index) {
            if (index > 0) {
                output.comma();
                if (output.should_break()) {
                    output.newline();
                    output.indent();
                }
            }
            node.print(output);
        });
    });
    DEFPRINT(AST_Dot, function(output) {
        var self = this;
        var expr = self.expression;
        expr.print(output);
        var prop = self.property;
        if (output.option("ie8") && RESERVED_WORDS[prop]) {
            output.print("[");
            output.add_mapping(self.end);
            output.print_string(prop);
            output.print("]");
        } else {
            if (expr instanceof AST_Number && expr.value >= 0) {
                if (!/[xa-f.)]/i.test(output.last())) {
                    output.print(".");
                }
            }
            output.print(".");
            // the name after dot would be mapped about here.
            output.add_mapping(self.end);
            output.print_name(prop);
        }
    });
    DEFPRINT(AST_Sub, function(output) {
        this.expression.print(output);
        output.print("[");
        this.property.print(output);
        output.print("]");
    });
    DEFPRINT(AST_Spread, function(output) {
        output.print("...");
        this.expression.print(output);
    });
    DEFPRINT(AST_UnaryPrefix, function(output) {
        var op = this.operator;
        var exp = this.expression;
        output.print(op);
        if (/^[a-z]/i.test(op)
            || (/[+-]$/.test(op)
                && exp instanceof AST_UnaryPrefix
                && /^[+-]/.test(exp.operator))) {
            output.space();
        }
        exp.print(output);
    });
    DEFPRINT(AST_UnaryPostfix, function(output) {
        this.expression.print(output);
        output.print(this.operator);
    });
    DEFPRINT(AST_Binary, function(output) {
        var self = this;
        self.left.print(output);
        output.space();
        output.print(self.operator);
        output.space();
        self.right.print(output);
    });
    DEFPRINT(AST_Conditional, function(output) {
        var self = this;
        self.condition.print(output);
        output.space();
        output.print("?");
        output.space();
        self.consequent.print(output);
        output.space();
        output.colon();
        self.alternative.print(output);
    });

    /* -----[ literals ]----- */
    DEFPRINT(AST_Array, function(output) {
        var a = this.elements, len = a.length;
        output.with_square(len > 0 ? function() {
            output.space();
            a.forEach(function(exp, i) {
                if (i) output.comma();
                exp.print(output);
                // If the final element is a hole, we need to make sure it
                // doesn't look like a trailing comma, by inserting an actual
                // trailing comma.
                if (i === len - 1 && exp instanceof AST_Hole)
                  output.comma();
            });
            output.space();
        } : noop);
    });
    DEFPRINT(AST_DestructuredArray, function(output) {
        var a = this.elements, len = a.length;
        output.with_square(len > 0 ? function() {
            output.space();
            a.forEach(function(exp, i) {
                if (i) output.comma();
                exp.print(output);
                // If the final element is a hole, we need to make sure it
                // doesn't look like a trailing comma, by inserting an actual
                // trailing comma.
                if (i === len - 1 && exp instanceof AST_Hole)
                  output.comma();
            });
            output.space();
        } : noop);
    });
    DEFPRINT(AST_DestructuredKeyVal, print_key_value);
    DEFPRINT(AST_DestructuredObject, function(output) {
        var props = this.properties;
        if (props.length > 0) output.with_block(function() {
            props.forEach(function(prop, i) {
                if (i) {
                    output.print(",");
                    output.newline();
                }
                output.indent();
                prop.print(output);
            });
            output.newline();
        });
        else print_braced_empty(this, output);
    });
    DEFPRINT(AST_Object, function(output) {
        var props = this.properties;
        if (props.length > 0) output.with_block(function() {
            props.forEach(function(prop, i) {
                if (i) {
                    output.print(",");
                    output.newline();
                }
                output.indent();
                prop.print(output);
            });
            output.newline();
        });
        else print_braced_empty(this, output);
    });

    function print_property_key(self, output) {
        var key = self.key;
        if (key instanceof AST_Node) {
            output.with_square(function() {
                key.print(output);
            });
        } else if (output.option("quote_keys")) {
            output.print_string(key);
        } else if ("" + +key == key && key >= 0) {
            output.print(make_num(key));
        } else {
            var quote = self.start && self.start.quote;
            if (RESERVED_WORDS[key] ? !output.option("ie8") : is_identifier_string(key)) {
                if (quote && output.option("keep_quoted_props")) {
                    output.print_string(key, quote);
                } else {
                    output.print_name(key);
                }
            } else {
                output.print_string(key, quote);
            }
        }
    }

    function print_key_value(output) {
        var self = this;
        print_property_key(self, output);
        output.colon();
        self.value.print(output);
    }
    DEFPRINT(AST_ObjectKeyVal, print_key_value);
    function print_accessor(type) {
        return function(output) {
            var self = this;
            output.print(type);
            output.space();
            print_property_key(self, output);
            self.value._codegen(output, true);
        };
    }
    DEFPRINT(AST_ObjectGetter, print_accessor("get"));
    DEFPRINT(AST_ObjectSetter, print_accessor("set"));
    DEFPRINT(AST_Symbol, function(output) {
        var def = this.definition();
        output.print_name(def && def.mangled_name || this.name);
    });
    DEFPRINT(AST_Hole, noop);
    DEFPRINT(AST_This, function(output) {
        output.print("this");
    });
    DEFPRINT(AST_Constant, function(output) {
        output.print(this.value);
    });
    DEFPRINT(AST_String, function(output) {
        output.print_string(this.value, this.quote);
    });
    DEFPRINT(AST_Number, function(output) {
        var start = this.start;
        if (use_asm && start && start.raw != null) {
            output.print(start.raw);
        } else {
            output.print(make_num(this.value));
        }
    });

    DEFPRINT(AST_RegExp, function(output) {
        var regexp = this.value;
        var str = regexp.toString();
        var end = str.lastIndexOf("/");
        if (regexp.raw_source) {
            str = "/" + regexp.raw_source + str.slice(end);
        } else if (end == 1) {
            str = "/(?:)" + str.slice(end);
        } else if (str.indexOf("/", 1) < end) {
            str = "/" + str.slice(1, end).replace(/\\\\|[^/]?\//g, function(match) {
                return match[0] == "\\" ? match : match.slice(0, -1) + "\\/";
            }) + str.slice(end);
        }
        output.print(output.to_utf8(str).replace(/\\(?:\0(?![0-9])|[^\0])/g, function(match) {
            switch (match[1]) {
              case "\n": return "\\n";
              case "\r": return "\\r";
              case "\t": return "\t";
              case "\b": return "\b";
              case "\f": return "\f";
              case "\0": return "\0";
              case "\x0B": return "\v";
              case "\u2028": return "\\u2028";
              case "\u2029": return "\\u2029";
              default: return match;
            }
        }).replace(/[\n\r\u2028\u2029]/g, function(c) {
            switch (c) {
              case "\n": return "\\n";
              case "\r": return "\\r";
              case "\u2028": return "\\u2028";
              case "\u2029": return "\\u2029";
            }
        }));
        var p = output.parent();
        if (p instanceof AST_Binary && /^in/.test(p.operator) && p.left === this)
            output.print(" ");
    });

    function force_statement(stat, output) {
        if (output.option("braces") && !(stat instanceof AST_Const || stat instanceof AST_Let)) {
            make_block(stat, output);
        } else if (!stat || stat instanceof AST_EmptyStatement) {
            output.force_semicolon();
        } else {
            stat.print(output);
        }
    }

    // self should be AST_New.  decide if we want to show parens or not.
    function need_constructor_parens(self, output) {
        // Always print parentheses with arguments
        if (self.args.length > 0) return true;

        return output.option("beautify");
    }

    function best_of(a) {
        var best = a[0], len = best.length;
        for (var i = 1; i < a.length; ++i) {
            if (a[i].length < len) {
                best = a[i];
                len = best.length;
            }
        }
        return best;
    }

    function make_num(num) {
        var str = num.toString(10).replace(/^0\./, ".").replace("e+", "e");
        var candidates = [ str ];
        if (Math.floor(num) === num) {
            if (num < 0) {
                candidates.push("-0x" + (-num).toString(16).toLowerCase());
            } else {
                candidates.push("0x" + num.toString(16).toLowerCase());
            }
        }
        var match, len, digits;
        if (match = /^\.0+/.exec(str)) {
            len = match[0].length;
            digits = str.slice(len);
            candidates.push(digits + "e-" + (digits.length + len - 1));
        } else if (match = /0+$/.exec(str)) {
            len = match[0].length;
            candidates.push(str.slice(0, -len) + "e" + len);
        } else if (match = /^(\d)\.(\d+)e(-?\d+)$/.exec(str)) {
            candidates.push(match[1] + match[2] + "e" + (match[3] - match[2].length));
        }
        return best_of(candidates);
    }

    function make_block(stmt, output) {
        if (!stmt || stmt instanceof AST_EmptyStatement)
            output.print("{}");
        else if (stmt instanceof AST_BlockStatement)
            stmt.print(output);
        else output.with_block(function() {
            output.indent();
            stmt.print(output);
            output.newline();
        });
    }

    /* -----[ source map generators ]----- */

    function DEFMAP(nodetype, generator) {
        nodetype.forEach(function(nodetype) {
            nodetype.DEFMETHOD("add_source_map", generator);
        });
    }

    DEFMAP([
        // We could easily add info for ALL nodes, but it seems to me that
        // would be quite wasteful, hence this noop in the base class.
        AST_Node,
        // since the label symbol will mark it
        AST_LabeledStatement,
    ], noop);

    // XXX: I'm not exactly sure if we need it for all of these nodes,
    // or if we should add even more.
    DEFMAP([
        AST_Array,
        AST_BlockStatement,
        AST_Catch,
        AST_Constant,
        AST_Debugger,
        AST_Definitions,
        AST_Destructured,
        AST_Finally,
        AST_Jump,
        AST_Lambda,
        AST_New,
        AST_Object,
        AST_StatementWithBody,
        AST_Symbol,
        AST_Switch,
        AST_SwitchBranch,
        AST_Try,
    ], function(output) {
        output.add_mapping(this.start);
    });

    DEFMAP([ AST_DestructuredKeyVal, AST_ObjectProperty ], function(output) {
        if (typeof this.key == "string") output.add_mapping(this.start, this.key);
    });
})();