68 lines
1.5 KiB
JavaScript
68 lines
1.5 KiB
JavaScript
/**
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* Copyright (c) 2004-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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'use strict';
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/*eslint consistent-return: 0*/
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/**
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* Transforms function properties of the `Symbol` into
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* the presence check, and fallback string "@@<name>".
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*
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* Example:
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*
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* Symbol.iterator;
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*
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* Transformed to:
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*
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* typeof Symbol.iterator === 'function' ? Symbol.iterator : '@@iterator';
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*/
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module.exports = function symbolMember(babel) {
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const t = babel.types;
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return {
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visitor: {
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MemberExpression(path) {
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if (!isAppropriateMember(path)) {
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return;
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}
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let node = path.node;
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path.replaceWith(
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t.conditionalExpression(
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t.binaryExpression(
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'===',
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t.unaryExpression(
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'typeof',
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t.identifier('Symbol'),
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true
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),
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t.stringLiteral('function')
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),
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node,
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t.stringLiteral(`@@${node.property.name}`)
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)
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);
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// We should stop to avoid infinite recursion, since Babel
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// traverses replaced path, and again would hit our transform.
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path.stop();
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},
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},
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};
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};
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function isAppropriateMember(path) {
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let node = path.node;
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return path.parentPath.type !== 'AssignmentExpression' &&
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node.object.type === 'Identifier' &&
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node.object.name === 'Symbol' &&
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node.property.type === 'Identifier';
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}
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