react-native-web-headroom/docs/node_modules/babel-plugin-transform-simplify-comparison-operators/lib/index.js

React Native Web Headroom

"use strict";

module.exports = function (_ref) {
  var t = _ref.types;

  // custom implementation of getTypeAnnotation that fixes
  // the type information that is lost during sequence expression transformation
  // https://github.com/babel/minify/issues/323
  function customTypeAnnotation(path) {
    if (path.typeAnnotation) {
      return path.typeAnnotation;
    } // We are not handling the case of literals and other base types
    // since they are already handled via getTypeAnnotation


    var node = path.node;
    var binding = path.parentPath.scope.getBinding(node.name);
    var types = [];

    if (binding && binding.constantViolations) {
      if (binding.identifier.typeAnnotation) {
        return binding.identifier.typeAnnotation;
      }

      if (binding.constantViolations) {
        var violations = binding.constantViolations;
        var _iteratorNormalCompletion = true;
        var _didIteratorError = false;
        var _iteratorError = undefined;

        try {
          for (var _iterator = violations[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
            var _violation = _step.value;
            types.push(_violation.getTypeAnnotation());
          }
        } catch (err) {
          _didIteratorError = true;
          _iteratorError = err;
        } finally {
          try {
            if (!_iteratorNormalCompletion && _iterator.return != null) {
              _iterator.return();
            }
          } finally {
            if (_didIteratorError) {
              throw _iteratorError;
            }
          }
        }
      }
    }

    if (types.length > 0) {
      return t.createUnionTypeAnnotation(types);
    }

    return types;
  } // Based on the type inference in Babel


  function baseTypeStrictlyMatches(left, right) {
    var leftTypes, rightTypes;

    if (t.isIdentifier(left)) {
      leftTypes = customTypeAnnotation(left);
    } else if (t.isIdentifier(right)) {
      rightTypes = customTypeAnnotation(right);
    } // Early exit


    if (t.isAnyTypeAnnotation(leftTypes) || t.isAnyTypeAnnotation(rightTypes)) {
      return false;
    }

    leftTypes = [].concat(leftTypes, left.getTypeAnnotation());
    rightTypes = [].concat(rightTypes, right.getTypeAnnotation());
    leftTypes = t.createUnionTypeAnnotation(leftTypes);
    rightTypes = t.createUnionTypeAnnotation(rightTypes);

    if (!t.isAnyTypeAnnotation(leftTypes) && t.isFlowBaseAnnotation(leftTypes)) {
      return leftTypes.type === rightTypes.type;
    }
  }

  return {
    name: "transform-simplify-comparison-operators",
    visitor: {
      // simplify comparison operations if we're 100% certain
      // that each value will always be of the same type
      BinaryExpression(path) {
        var node = path.node;
        var op = node.operator;

        if (op !== "===" && op !== "!==") {
          return;
        }

        var left = path.get("left");
        var right = path.get("right");
        var strictMatch = baseTypeStrictlyMatches(left, right);

        if (strictMatch) {
          node.operator = node.operator.slice(0, -1);
        }
      }

    }
  };
};