es6-template-visitors.js

/**
 * Copyright 2013 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*jslint node:true*/

/**
 * @typechecks
 */
'use strict';

var Syntax = require('esprima-fb').Syntax;
var utils = require('../src/utils');

/**
 * http://people.mozilla.org/~jorendorff/es6-draft.html#sec-12.1.9
 */
function visitTemplateLiteral(traverse, node, path, state) {
  var templateElements = node.quasis;

  utils.append('(', state);
  for (var ii = 0; ii < templateElements.length; ii++) {
    var templateElement = templateElements[ii];
    if (templateElement.value.raw !== '') {
      utils.append(getCookedValue(templateElement), state);
      if (!templateElement.tail) {
        // + between element and substitution
        utils.append(' + ', state);
      }
      // maintain line numbers
      utils.move(templateElement.range[0], state);
      utils.catchupNewlines(templateElement.range[1], state);
    } else {  // templateElement.value.raw === ''
      // Concatenat adjacent substitutions, e.g. `${x}${y}`. Empty templates
      // appear before the first and after the last element - nothing to add in
      // those cases.
      if (ii > 0 && !templateElement.tail) {
        // + between substitution and substitution
        utils.append(' + ', state);
      }
    }

    utils.move(templateElement.range[1], state);
    if (!templateElement.tail) {
      var substitution = node.expressions[ii];
      if (substitution.type === Syntax.Identifier ||
          substitution.type === Syntax.MemberExpression ||
          substitution.type === Syntax.CallExpression) {
        utils.catchup(substitution.range[1], state);
      } else {
        utils.append('(', state);
        traverse(substitution, path, state);
        utils.catchup(substitution.range[1], state);
        utils.append(')', state);
      }
      // if next templateElement isn't empty...
      if (templateElements[ii + 1].value.cooked !== '') {
        utils.append(' + ', state);
      }
    }
  }
  utils.move(node.range[1], state);
  utils.append(')', state);
  return false;
}

visitTemplateLiteral.test = function(node, path, state) {
  return node.type === Syntax.TemplateLiteral;
};

/**
 * http://people.mozilla.org/~jorendorff/es6-draft.html#sec-12.2.6
 */
function visitTaggedTemplateExpression(traverse, node, path, state) {
  var template = node.quasi;
  var numQuasis = template.quasis.length;

  // print the tag
  utils.move(node.tag.range[0], state);
  traverse(node.tag, path, state);
  utils.catchup(node.tag.range[1], state);

  // print array of template elements
  utils.append('(function() { var siteObj = [', state);
  for (var ii = 0; ii < numQuasis; ii++) {
    utils.append(getCookedValue(template.quasis[ii]), state);
    if (ii !== numQuasis - 1) {
      utils.append(', ', state);
    }
  }
  utils.append(']; siteObj.raw = [', state);
  for (ii = 0; ii < numQuasis; ii++) {
    utils.append(getRawValue(template.quasis[ii]), state);
    if (ii !== numQuasis - 1) {
      utils.append(', ', state);
    }
  }
  utils.append(
    ']; Object.freeze(siteObj.raw); Object.freeze(siteObj); return siteObj; }()',
    state
  );

  // print substitutions
  if (numQuasis > 1) {
    for (ii = 0; ii < template.expressions.length; ii++) {
      var expression = template.expressions[ii];
      utils.append(', ', state);

      // maintain line numbers by calling catchupWhiteSpace over the whole
      // previous TemplateElement
      utils.move(template.quasis[ii].range[0], state);
      utils.catchupNewlines(template.quasis[ii].range[1], state);

      utils.move(expression.range[0], state);
      traverse(expression, path, state);
      utils.catchup(expression.range[1], state);
    }
  }

  // print blank lines to push the closing ) down to account for the final
  // TemplateElement.
  utils.catchupNewlines(node.range[1], state);

  utils.append(')', state);

  return false;
}

visitTaggedTemplateExpression.test = function(node, path, state) {
  return node.type === Syntax.TaggedTemplateExpression;
};

function getCookedValue(templateElement) {
  return JSON.stringify(templateElement.value.cooked);
}

function getRawValue(templateElement) {
  return JSON.stringify(templateElement.value.raw);
}

exports.visitorList = [
  visitTemplateLiteral,
  visitTaggedTemplateExpression
];