Add support for Promises #1049
Add support for Promises #1049
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Woops, putting this back into draft after realising I forgot the case where |
Problem solved. |
# Conflicts: # src/LuaLib.ts # src/lualib/declarations/global.d.ts
tomblind
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tomblind
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One thing I don't see represented in the tests is direct chaining:
promise.then(...).then(...).catch(...)
It might be good to test this to ensure these calls are returning the correct thing.
test/unit/builtins/promise.spec.ts
Outdated
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| util.testFunction` | ||
| // Wrap function getUserData(id: number, callback: (userData: UserData) => void) into a Promise | ||
| async function getUserDataAsync(id: number): Promise<UserData> { |
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dumb question: how does this work if we don't support async yet?
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It works because async keyword has no special function yet and will just be ignored. You are right that this is a a strange async, and in fact I think it is removed again in my async/await branch. I will remove it here too.
| ` | ||
| .setTsHeader(promiseTestLib) | ||
| .expectToEqual(["finally"]); | ||
| }); |
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Maybe another test for finally that checks that this:
myPromise
.then(response => {
doSomething(response);
runFinalCode();
})
.catch(e => {
returnError(e);
runFinalCode();
});is equivalent to this:
myPromise
.then(response => {
doSomething(response);
})
.catch(e => {
returnError(e);
})
.finally(() => {
runFinalCode();
});Can possibly be implemented like this:
const { noThrow, noThrowResolve } = defer<string>();
const { throw_, throwResolve } = defer<string>();
noThrow.then(
data => { log(data); log("finally"); }
)
.catch(
e => { log(e); log("finally"); }
);
throw_.then(
data => { throw data; log("finally"); }
)
.catch(
e => { log(e); log("finally"); }
);
noThrowResolve("test");
throwResolve("test");
const { finallyNoThrow, finallyNoThrowResolve } = defer<string>();
const { finallyThrow, finallyThrowResolve } = defer<string>();
finallyNoThrow.then(
data => { log(data); }
)
.catch(
e => { log(e); }
)
.finally(
() => { log("finally"); }
);
finallyThrow.then(
data => { throw data; }
)
.catch(
e => { log(e); }
)
.finally(
() => { log("finally"); }
);
finallyNoThrow("test");
finallyThrow("test");
return allLogs;
// expectToEqual(["test", "finally", "test", "finally", "test", "finally", "test", "finally"])
* Initial lualib promise class implementation * First promise tests * More promise tests * Promise class implementation * Implemented Promise.all * Promise.any * Promise.race * Promise.allSettled * fix prettier * Add promise example usage test * Added missing lualib dependencies for PromiseConstructor functions * Immediately call then/catch/finally callbacks on promises that are already resolved * Transform all references to Promise to __TS__Promise * PR feedback * Removed incorrect asyncs * Add test for direct chaining * Add test for finally and correct wrong behavior it caught * Added test throwing in parallel and chained then onFulfilleds * Fixed pull request link in ArrayIsArray lualib comment
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Out of scope: async/await, will be done in follow-up PR
Implemented promises based on https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise and a little bit of https://promisesaplus.com/
Note: For now we are deviating from the spec in an important aspect: currently the promise constructor function is executed immediately, instead of waiting until there is no more user code on stack, like the promise spec mandates.