babel/lib/6to5/generation/generator.js

module.exports = function (ast, opts, code) {
  var gen = new CodeGenerator(ast, opts, code);
  return gen.generate();
};

module.exports.CodeGenerator = CodeGenerator;

var Whitespace = require("./whitespace");
var SourceMap  = require("./source-map");
var Position   = require("./position");
var Buffer     = require("./buffer");
var util       = require("../util");
var n          = require("./node");
var t          = require("../types");
var _          = require("lodash");

function CodeGenerator(ast, opts, code) {
  opts = opts || {};

  this.comments = ast.comments || [];
  this.tokens   = ast.tokens || [];
  this.format   = CodeGenerator.normaliseOptions(opts);
  this.ast      = ast;

  this.whitespace = new Whitespace(this.tokens, this.comments);
  this.position   = new Position;
  this.map        = new SourceMap(this.position, opts, code);
  this.buffer     = new Buffer(this.position, this.format);
}

_.each(Buffer.prototype, function (fn, key) {
  CodeGenerator.prototype[key] = function () {
    return fn.apply(this.buffer, arguments);
  };
});

CodeGenerator.normaliseOptions = function (opts) {
  opts = opts.format || {};

  opts = _.merge({
    parentheses: true,
    semicolons: true,
    comments: true,
    compact: false,
    indent: {
      adjustMultilineComment: true,
      style: "  ",
      base: 0
    }
  }, opts);

  return opts;
};

CodeGenerator.generators = {
  arrayComprehensions: require("./generators/array-comprehensions"),
  templateLiterals:    require("./generators/template-literals"),
  expressions:         require("./generators/expressions"),
  statements:          require("./generators/statements"),
  classes:             require("./generators/classes"),
  methods:             require("./generators/methods"),
  modules:             require("./generators/modules"),
  types:               require("./generators/types"),
  base:                require("./generators/base"),
  jsx:                 require("./generators/jsx")
};

_.each(CodeGenerator.generators, function (generator) {
  _.extend(CodeGenerator.prototype, generator);
});

CodeGenerator.prototype.generate = function () {
  var ast = this.ast;

  this.print(ast);

  return {
    map:  this.map.get(),
    ast:  ast,
    code: this.buffer.get()
  };
};

CodeGenerator.prototype.buildPrint = function (parent) {
  var self = this;

  var print = function (node, opts) {
    return self.print(node, parent, opts);
  };

  print.sequence = function (nodes, opts) {
    opts = opts || {};
    opts.statement = true;
    return self.printJoin(print, nodes, opts);
  };

  print.join = function (nodes, opts) {
    return self.printJoin(print, nodes, opts);
  };

  print.block = function (node) {
    return self.printBlock(print, node);
  };

  print.indentOnComments = function (node) {
    return self.printAndIndentOnComments(print, node);
  };

  return print;
};

CodeGenerator.prototype.print = function (node, parent, opts) {
  if (!node) return "";

  var self = this;
  opts = opts || {};

  var newline = function (leading) {
    var ignoreDuplicates = false;

    if (!opts.statement && !n.isUserWhitespacable(node, parent)) {
      return;
    }

    var lines = 0;

    if (node.start != null) {
      // user node
      if (leading) {
        lines = self.whitespace.getNewlinesBefore(node);
      } else {
        lines = self.whitespace.getNewlinesAfter(node);
      }
    } else {
      // generated node
      if (!leading) lines++; // always include at least a single line after

      var needs = n.needsWhitespaceAfter;
      if (leading) needs = n.needsWhitespaceBefore;
      lines += needs(node, parent);
    }

    self.newline(lines, ignoreDuplicates);
  };

  if (this[node.type]) {
    this.printLeadingComments(node, parent);

    newline(true);

    if (opts.before) opts.before();
    this.map.mark(node, "start");

    // only compute if this node needs parens if our parent has been changed
    // since acorn would've wrapped us in a ParanthesizedExpression
    var needsParens = parent !== node._parent && n.needsParens(node, parent);
    if (needsParens) this.push("(");

    this[node.type](node, this.buildPrint(node), parent);

    if (needsParens) this.push(")");

    this.map.mark(node, "end");
    if (opts.after) opts.after();

    newline(false);

    this.printTrailingComments(node, parent);
  } else {
    throw new ReferenceError("unknown node " + node.type + " " + JSON.stringify(node));
  }
};

CodeGenerator.prototype.printJoin = function (print, nodes, opts) {
  opts = opts || {};

  var self = this;
  var len  = nodes.length;

  if (opts.indent) self.indent();

  _.each(nodes, function (node, i) {
    print(node, {
      statement: opts.statement,
      after: function () {
        if (opts.iterator) {
          opts.iterator(node, i);
        }

        if (opts.separator && i < len - 1) {
          self.push(opts.separator);
        }
      }
    });
  });

  if (opts.indent) self.dedent();
};

CodeGenerator.prototype.printAndIndentOnComments = function (print, node) {
  var indent = !!node.leadingComments;
  if (indent) this.indent();
  print(node);
  if (indent) this.dedent();
};

CodeGenerator.prototype.printBlock = function (print, node) {
  if (t.isEmptyStatement(node)) {
    this.semicolon();
  } else {
    this.push(" ");
    print(node);
  }
};

CodeGenerator.prototype.generateComment = function (comment) {
  var val = comment.value;
  if (comment.type === "Line") {
    val = "//" + val;
  } else {
    val = "/*" + val + "*/";
  }
  return val;
};

CodeGenerator.prototype.printTrailingComments = function (node, parent) {
  this._printComments(this.getComments("trailingComments", node, parent));
};

CodeGenerator.prototype.printLeadingComments = function (node, parent) {
  this._printComments(this.getComments("leadingComments", node, parent));
};

CodeGenerator.prototype.getComments = function (key, node, parent) {
  if (t.isExpressionStatement(parent)) {
    return [];
  }

  var comments = [];
  var nodes    = [node];
  var self     = this;

  if (t.isExpressionStatement(node)) {
    nodes.push(node.argument);
  }

  _.each(nodes, function (node) {
    comments = comments.concat(self._getComments(key, node));
  });

  return comments;
};

CodeGenerator.prototype._getComments = function (key, node) {
  return (node && node[key]) || [];
};

CodeGenerator.prototype._printComments = function (comments) {
  if (this.format.compact) return;
  if (!this.format.comments) return;
  if (!comments || !comments.length) return;

  var self = this;

  _.each(comments, function (comment) {
    // whitespace before
    self.newline(self.whitespace.getNewlinesBefore(comment));

    var column = self.position.column;
    var val    = self.generateComment(comment);

    if (column && !self.isLast(["\n", " ", "[", "{"])) {
      self._push(" ");
      column++;
    }

    //

    if (comment.type === "Block" && self.format.indent.adjustMultilineComment) {
      var offset = comment.loc.start.column;
      if (offset) {
        var newlineRegex = new RegExp("\\n\\s{1," + offset + "}", "g");
        val = val.replace(newlineRegex, "\n");
      }

      var indent = Math.max(self.indentSize(), column);
      val = val.replace(/\n/g, "\n" + util.repeat(indent));
    }

    if (column === 0) {
      val = self.getIndent() + val;
    }

    //

    self._push(val);

    // whitespace after
    self.newline(self.whitespace.getNewlinesAfter(comment));
  });
};