@graphql-tools/executor
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Fork of GraphQL.js' execute function
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JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.flattenAsyncIterable = void 0;
/**
* Given an AsyncIterable of AsyncIterables, flatten all yielded results into a
* single AsyncIterable.
*/
function flattenAsyncIterable(iterable) {
// You might think this whole function could be replaced with
//
// async function* flattenAsyncIterable(iterable) {
// for await (const subIterator of iterable) {
// yield* subIterator;
// }
// }
//
// but calling `.return()` on the iterator it returns won't interrupt the `for await`.
const topIterator = iterable[Symbol.asyncIterator]();
let currentNestedIterator;
let waitForCurrentNestedIterator;
let done = false;
async function next() {
if (done) {
return { value: undefined, done: true };
}
try {
if (!currentNestedIterator) {
// Somebody else is getting it already.
if (waitForCurrentNestedIterator) {
await waitForCurrentNestedIterator;
return await next();
}
// Nobody else is getting it. We should!
let resolve;
waitForCurrentNestedIterator = new Promise(r => {
resolve = r;
});
const topIteratorResult = await topIterator.next();
if (topIteratorResult.done) {
// Given that done only ever transitions from false to true,
// require-atomic-updates is being unnecessarily cautious.
done = true;
return await next();
}
// eslint is making a reasonable point here, but we've explicitly protected
// ourself from the race condition by ensuring that only the single call
// that assigns to waitForCurrentNestedIterator is allowed to assign to
// currentNestedIterator or waitForCurrentNestedIterator.
currentNestedIterator = topIteratorResult.value[Symbol.asyncIterator]();
waitForCurrentNestedIterator = undefined;
resolve();
return await next();
}
const rememberCurrentNestedIterator = currentNestedIterator;
const nestedIteratorResult = await currentNestedIterator.next();
if (!nestedIteratorResult.done) {
return nestedIteratorResult;
}
// The nested iterator is done. If it's still the current one, make it not
// current. (If it's not the current one, somebody else has made us move on.)
if (currentNestedIterator === rememberCurrentNestedIterator) {
currentNestedIterator = undefined;
}
return await next();
}
catch (err) {
done = true;
throw err;
}
}
return {
next,
async return() {
var _a, _b;
done = true;
await Promise.all([(_a = currentNestedIterator === null || currentNestedIterator === void 0 ? void 0 : currentNestedIterator.return) === null || _a === void 0 ? void 0 : _a.call(currentNestedIterator), (_b = topIterator.return) === null || _b === void 0 ? void 0 : _b.call(topIterator)]);
return { value: undefined, done: true };
},
async throw(error) {
var _a, _b;
done = true;
await Promise.all([(_a = currentNestedIterator === null || currentNestedIterator === void 0 ? void 0 : currentNestedIterator.throw) === null || _a === void 0 ? void 0 : _a.call(currentNestedIterator, error), (_b = topIterator.throw) === null || _b === void 0 ? void 0 : _b.call(topIterator, error)]);
/* c8 ignore next */
throw error;
},
[Symbol.asyncIterator]() {
return this;
},
};
}
exports.flattenAsyncIterable = flattenAsyncIterable;