react app

react-app/node_modules/jstransform/visitors/es7-rest-property-helpers.js

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+/**
+ * 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*/
+
+/**
+ * Desugars ES7 rest properties into ES5 object iteration.
+ */
+
+var Syntax = require('esprima-fb').Syntax;
+
+// TODO: This is a pretty massive helper, it should only be defined once, in the
+// transform's runtime environment. We don't currently have a runtime though.
+var restFunction =
+  '(function(source, exclusion) {' +
+    'var rest = {};' +
+    'var hasOwn = Object.prototype.hasOwnProperty;' +
+    'if (source == null) {' +
+      'throw new TypeError();' +
+    '}' +
+    'for (var key in source) {' +
+      'if (hasOwn.call(source, key) && !hasOwn.call(exclusion, key)) {' +
+        'rest[key] = source[key];' +
+      '}' +
+    '}' +
+    'return rest;' +
+  '})';
+
+function getPropertyNames(properties) {
+  var names = [];
+  for (var i = 0; i < properties.length; i++) {
+    var property = properties[i];
+    if (property.type === Syntax.SpreadProperty) {
+      continue;
+    }
+    if (property.type === Syntax.Identifier) {
+      names.push(property.name);
+    } else {
+      names.push(property.key.name);
+    }
+  }
+  return names;
+}
+
+function getRestFunctionCall(source, exclusion) {
+  return restFunction + '(' + source + ',' + exclusion + ')';
+}
+
+function getSimpleShallowCopy(accessorExpression) {
+  // This could be faster with 'Object.assign({}, ' + accessorExpression + ')'
+  // but to unify code paths and avoid a ES6 dependency we use the same
+  // helper as for the exclusion case.
+  return getRestFunctionCall(accessorExpression, '{}');
+}
+
+function renderRestExpression(accessorExpression, excludedProperties) {
+  var excludedNames = getPropertyNames(excludedProperties);
+  if (!excludedNames.length) {
+    return getSimpleShallowCopy(accessorExpression);
+  }
+  return getRestFunctionCall(
+    accessorExpression,
+    '{' + excludedNames.join(':1,') + ':1}'
+  );
+}
+
+exports.renderRestExpression = renderRestExpression;