babel-plugin-transform-es2015-parameters/lib/rest.js

"use strict";

exports.__esModule = true;
exports.visitor = undefined;

var _getIterator2 = require("babel-runtime/core-js/get-iterator");

var _getIterator3 = _interopRequireDefault(_getIterator2);

var _babelTemplate = require("babel-template");

var _babelTemplate2 = _interopRequireDefault(_babelTemplate);

var _babelTypes = require("babel-types");

var t = _interopRequireWildcard(_babelTypes);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

var buildRest = (0, _babelTemplate2.default)("\n  for (var LEN = ARGUMENTS.length,\n           ARRAY = Array(ARRAY_LEN),\n           KEY = START;\n       KEY < LEN;\n       KEY++) {\n    ARRAY[ARRAY_KEY] = ARGUMENTS[KEY];\n  }\n");

var restIndex = (0, _babelTemplate2.default)("\n  ARGUMENTS.length <= INDEX ? undefined : ARGUMENTS[INDEX]\n");

var restIndexImpure = (0, _babelTemplate2.default)("\n  REF = INDEX, ARGUMENTS.length <= REF ? undefined : ARGUMENTS[REF]\n");

var restLength = (0, _babelTemplate2.default)("\n  ARGUMENTS.length <= OFFSET ? 0 : ARGUMENTS.length - OFFSET\n");

var memberExpressionOptimisationVisitor = {
  Scope: function Scope(path, state) {
    if (!path.scope.bindingIdentifierEquals(state.name, state.outerBinding)) {
      path.skip();
    }
  },
  Flow: function Flow(path) {
    if (path.isTypeCastExpression()) return;

    path.skip();
  },


  "Function|ClassProperty": function FunctionClassProperty(path, state) {
    var oldNoOptimise = state.noOptimise;
    state.noOptimise = true;
    path.traverse(memberExpressionOptimisationVisitor, state);
    state.noOptimise = oldNoOptimise;

    path.skip();
  },

  ReferencedIdentifier: function ReferencedIdentifier(path, state) {
    var node = path.node;

    if (node.name === "arguments") {
      state.deopted = true;
    }

    if (node.name !== state.name) return;

    if (state.noOptimise) {
      state.deopted = true;
    } else {
      var parentPath = path.parentPath;

      if (parentPath.listKey === "params" && parentPath.key < state.offset) {
        return;
      }

      if (parentPath.isMemberExpression({ object: node })) {
        var grandparentPath = parentPath.parentPath;

        var argsOptEligible = !state.deopted && !(grandparentPath.isAssignmentExpression() && parentPath.node === grandparentPath.node.left || grandparentPath.isLVal() || grandparentPath.isForXStatement() || grandparentPath.isUpdateExpression() || grandparentPath.isUnaryExpression({ operator: "delete" }) || (grandparentPath.isCallExpression() || grandparentPath.isNewExpression()) && parentPath.node === grandparentPath.node.callee);

        if (argsOptEligible) {
          if (parentPath.node.computed) {
            if (parentPath.get("property").isBaseType("number")) {
              state.candidates.push({ cause: "indexGetter", path: path });
              return;
            }
          } else if (parentPath.node.property.name === "length") {
              state.candidates.push({ cause: "lengthGetter", path: path });
              return;
            }
        }
      }

      if (state.offset === 0 && parentPath.isSpreadElement()) {
        var call = parentPath.parentPath;
        if (call.isCallExpression() && call.node.arguments.length === 1) {
          state.candidates.push({ cause: "argSpread", path: path });
          return;
        }
      }

      state.references.push(path);
    }
  },
  BindingIdentifier: function BindingIdentifier(_ref, state) {
    var node = _ref.node;

    if (node.name === state.name) {
      state.deopted = true;
    }
  }
};
function hasRest(node) {
  return t.isRestElement(node.params[node.params.length - 1]);
}

function optimiseIndexGetter(path, argsId, offset) {
  var index = void 0;

  if (t.isNumericLiteral(path.parent.property)) {
    index = t.numericLiteral(path.parent.property.value + offset);
  } else if (offset === 0) {
    index = path.parent.property;
  } else {
    index = t.binaryExpression("+", path.parent.property, t.numericLiteral(offset));
  }

  var scope = path.scope;

  if (!scope.isPure(index)) {
    var temp = scope.generateUidIdentifierBasedOnNode(index);
    scope.push({ id: temp, kind: "var" });
    path.parentPath.replaceWith(restIndexImpure({
      ARGUMENTS: argsId,
      INDEX: index,
      REF: temp
    }));
  } else {
    path.parentPath.replaceWith(restIndex({
      ARGUMENTS: argsId,
      INDEX: index
    }));
  }
}

function optimiseLengthGetter(path, argsId, offset) {
  if (offset) {
    path.parentPath.replaceWith(restLength({
      ARGUMENTS: argsId,
      OFFSET: t.numericLiteral(offset)
    }));
  } else {
    path.replaceWith(argsId);
  }
}

var visitor = exports.visitor = {
  Function: function Function(path) {
    var node = path.node,
        scope = path.scope;

    if (!hasRest(node)) return;

    var rest = node.params.pop().argument;

    var argsId = t.identifier("arguments");

    argsId._shadowedFunctionLiteral = path;

    var state = {
      references: [],
      offset: node.params.length,

      argumentsNode: argsId,
      outerBinding: scope.getBindingIdentifier(rest.name),

      candidates: [],

      name: rest.name,

      deopted: false
    };

    path.traverse(memberExpressionOptimisationVisitor, state);

    if (!state.deopted && !state.references.length) {
      for (var _iterator = state.candidates, _isArray = Array.isArray(_iterator), _i = 0, _iterator = _isArray ? _iterator : (0, _getIterator3.default)(_iterator);;) {
        var _ref3;

        if (_isArray) {
          if (_i >= _iterator.length) break;
          _ref3 = _iterator[_i++];
        } else {
          _i = _iterator.next();
          if (_i.done) break;
          _ref3 = _i.value;
        }

        var _ref4 = _ref3;
        var _path = _ref4.path,
            cause = _ref4.cause;

        switch (cause) {
          case "indexGetter":
            optimiseIndexGetter(_path, argsId, state.offset);
            break;
          case "lengthGetter":
            optimiseLengthGetter(_path, argsId, state.offset);
            break;
          default:
            _path.replaceWith(argsId);
        }
      }
      return;
    }

    state.references = state.references.concat(state.candidates.map(function (_ref5) {
      var path = _ref5.path;
      return path;
    }));

    state.deopted = state.deopted || !!node.shadow;

    var start = t.numericLiteral(node.params.length);
    var key = scope.generateUidIdentifier("key");
    var len = scope.generateUidIdentifier("len");

    var arrKey = key;
    var arrLen = len;
    if (node.params.length) {
      arrKey = t.binaryExpression("-", key, start);

      arrLen = t.conditionalExpression(t.binaryExpression(">", len, start), t.binaryExpression("-", len, start), t.numericLiteral(0));
    }

    var loop = buildRest({
      ARGUMENTS: argsId,
      ARRAY_KEY: arrKey,
      ARRAY_LEN: arrLen,
      START: start,
      ARRAY: rest,
      KEY: key,
      LEN: len
    });

    if (state.deopted) {
      loop._blockHoist = node.params.length + 1;
      node.body.body.unshift(loop);
    } else {
      loop._blockHoist = 1;

      var target = path.getEarliestCommonAncestorFrom(state.references).getStatementParent();

      target.findParent(function (path) {
        if (path.isLoop()) {
          target = path;
        } else {
          return path.isFunction();
        }
      });

      target.insertBefore(loop);
    }
  }
};