60 lines
2.1 KiB
JavaScript
60 lines
2.1 KiB
JavaScript
/**
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* Polyfill for the optional chain operator, `?.`, given previous conversion of the expression into an array of values,
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* descriptors, and functions, for situations in which at least one part of the expression is async.
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*
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* Adapted from Sucrase (https://github.com/alangpierce/sucrase) See
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* https://github.com/alangpierce/sucrase/blob/265887868966917f3b924ce38dfad01fbab1329f/src/transformers/OptionalChainingNullishTransformer.ts#L15
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*
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* @param ops Array result of expression conversion
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* @returns The value of the expression
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*/
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async function _asyncOptionalChain(ops) {
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let lastAccessLHS = undefined;
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let value = ops[0];
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let i = 1;
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while (i < ops.length) {
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const op = ops[i] ;
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const fn = ops[i + 1] ;
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i += 2;
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// by checking for loose equality to `null`, we catch both `null` and `undefined`
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if ((op === 'optionalAccess' || op === 'optionalCall') && value == null) {
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// really we're meaning to return `undefined` as an actual value here, but it saves bytes not to write it
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return;
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}
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if (op === 'access' || op === 'optionalAccess') {
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lastAccessLHS = value;
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value = await fn(value);
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} else if (op === 'call' || op === 'optionalCall') {
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value = await fn((...args) => (value ).call(lastAccessLHS, ...args));
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lastAccessLHS = undefined;
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}
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}
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return value;
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}
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// Sucrase version:
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// async function _asyncOptionalChain(ops) {
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// let lastAccessLHS = undefined;
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// let value = ops[0];
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// let i = 1;
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// while (i < ops.length) {
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// const op = ops[i];
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// const fn = ops[i + 1];
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// i += 2;
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// if ((op === 'optionalAccess' || op === 'optionalCall') && value == null) {
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// return undefined;
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// }
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// if (op === 'access' || op === 'optionalAccess') {
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// lastAccessLHS = value;
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// value = await fn(value);
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// } else if (op === 'call' || op === 'optionalCall') {
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// value = await fn((...args) => value.call(lastAccessLHS, ...args));
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// lastAccessLHS = undefined;
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// }
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// }
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// return value;
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// }
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export { _asyncOptionalChain };
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//# sourceMappingURL=_asyncOptionalChain.js.map
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