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fix await inside catch/finally in async try (#1659) #1709

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Merged
Perryvw merged 3 commits into from
Apr 18, 2026
Merged

fix await inside catch/finally in async try (#1659) #1709

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589be9e
fix await inside catch/finally in async try
RealColdFry Apr 15, 2026
638b819
Merge upstream/master into fix/async-try-await-in-catch-finally
RealColdFry Apr 17, 2026
c9e7b33
add test for awaited return value from catch in async try
RealColdFry Apr 17, 2026
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45 changes: 27 additions & 18 deletions src/transformation/visitors/errors.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -40,35 +40,44 @@ const transformAsyncTry: FunctionVisitor<ts.TryStatement> = (statement, context)
let catchScope: Scope | undefined;
const chainCalls: lua.Statement[] = [];

if (statement.finallyBlock) {
const awaiterFinally = lua.createTableIndexExpression(awaiterIdentifier, lua.createStringLiteral("finally"));
const finallyFunction = lua.createFunctionExpression(
lua.createBlock(context.transformStatements(statement.finallyBlock.statements))
);
const finallyCall = lua.createCallExpression(
awaiterFinally,
[awaiterIdentifier, finallyFunction],
statement.finallyBlock
);
chainCalls.push(lua.createExpressionStatement(finallyCall));
}

if (statement.catchClause) {
// ____try = ____try.catch(<catch function>)
const [catchFunction, cScope] = transformCatchClause(context, statement.catchClause);
catchScope = cScope;
if (catchFunction.params) {
catchFunction.params.unshift(lua.createAnonymousIdentifier());
}

const catchBodyStatements = catchFunction.body ? catchFunction.body.statements : [];
const asyncWrappedCatch = wrapInAsyncAwaiter(context, [...catchBodyStatements], false);
catchFunction.body = lua.createBlock([lua.createReturnStatement([asyncWrappedCatch])]);

const awaiterCatch = lua.createTableIndexExpression(awaiterIdentifier, lua.createStringLiteral("catch"));
const catchCall = lua.createCallExpression(awaiterCatch, [awaiterIdentifier, catchFunction]);
const promiseAwait = transformLuaLibFunction(context, LuaLibFeature.Await, statement, catchCall);
chainCalls.push(lua.createExpressionStatement(promiseAwait, statement));
} else {
const promiseAwait = transformLuaLibFunction(context, LuaLibFeature.Await, statement, awaiterIdentifier);
chainCalls.push(lua.createExpressionStatement(promiseAwait, statement));
chainCalls.push(lua.createAssignmentStatement(lua.cloneIdentifier(awaiterIdentifier), catchCall));
}

if (statement.finallyBlock) {
// ____try = ____try.finally(<finally function>)
const finallyStatements = context.transformStatements(statement.finallyBlock.statements);
const asyncWrappedFinally = wrapInAsyncAwaiter(context, finallyStatements, false);
const finallyFunction = lua.createFunctionExpression(
lua.createBlock([lua.createReturnStatement([asyncWrappedFinally])])
);

const awaiterFinally = lua.createTableIndexExpression(awaiterIdentifier, lua.createStringLiteral("finally"));
const finallyCall = lua.createCallExpression(
awaiterFinally,
[awaiterIdentifier, finallyFunction],
statement.finallyBlock
);
chainCalls.push(lua.createAssignmentStatement(lua.cloneIdentifier(awaiterIdentifier), finallyCall));
}

// __TS__Await(____try)
const promiseAwait = transformLuaLibFunction(context, LuaLibFeature.Await, statement, awaiterIdentifier);
chainCalls.push(lua.createExpressionStatement(promiseAwait, statement));

const hasReturn = tryScope.asyncTryHasReturn ?? catchScope?.asyncTryHasReturn;
const hasBreak = tryScope.asyncTryHasBreak ?? catchScope?.asyncTryHasBreak;
const hasContinue = tryScope.asyncTryHasContinue ?? catchScope?.asyncTryHasContinue;
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114 changes: 114 additions & 0 deletions test/unit/builtins/async-await.spec.ts
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Expand Up @@ -816,6 +816,120 @@ describe("try/catch in async function", () => {
});
});

// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1659
test("await inside catch handler resolves correctly (#1659)", () => {
util.testFunction`
let reject: (reason: string) => void = () => {};

async function failing() {
return new Promise((_, rej) => { reject = rej; });
}

async function run() {
try {
await failing();
} catch (e) {
log("catch");
const a = await Promise.resolve(true);
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@Perryvw Perryvw Apr 16, 2026

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Could you add a test where this promise is not instantly resolved, and its return value is returned to run? Something like:

try {
    await failing();
    return "succeeded";
} catch (e) {
    return await somePromiseResolvedLater();
}

and then resolving the promise after rejecting the first one

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@RealColdFry RealColdFry Apr 17, 2026

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Done: https://github.com/TypeScriptToLua/TypeScriptToLua/pull/1709/changes#diff-392634086752122c2ace4b89fd9640371efcc3700127844e6f941e672826f720R908

log("a", a);
}
}

run();
reject("error");

return allLogs;
`
.setTsHeader(promiseTestLib)
.expectToEqual(["catch", "a", true]);
});

// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1659
test("await inside finally handler resolves correctly (#1659)", () => {
util.testFunction`
let reject: (reason: string) => void = () => {};

async function failing() {
return new Promise((_, rej) => { reject = rej; });
}

async function run() {
try {
await failing();
} finally {
log("finally");
const a = await Promise.resolve(true);
log("a", a);
}
}

run().catch(() => {});
reject("error");

return allLogs;
`
.setTsHeader(promiseTestLib)
.expectToEqual(["finally", "a", true]);
});

// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1659
test("await inside both catch and finally handlers (#1659)", () => {
util.testFunction`
let reject: (reason: string) => void = () => {};

async function failing() {
return new Promise((_, rej) => { reject = rej; });
}

async function run() {
try {
await failing();
} catch (e) {
log("catch");
const a = await Promise.resolve("caught");
log("a", a);
} finally {
log("finally");
const b = await Promise.resolve("done");
log("b", b);
}
}

run();
reject("error");

return allLogs;
`
.setTsHeader(promiseTestLib)
.expectToEqual(["catch", "a", "caught", "finally", "b", "done"]);
});

// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1659
test("awaited value in catch is returned from async function (#1659)", () => {
util.testFunction`
const failing = defer<string>();
const recovery = defer<string>();

async function run() {
try {
await failing.promise;
return "succeeded";
} catch (e) {
return await recovery.promise;
}
}

run().then(value => log("result", value));

failing.reject("error");
recovery.resolve("recovered");

return allLogs;
`
.setTsHeader(promiseTestLib)
.expectToEqual(["result", "recovered"]);
});

// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1706
test("return inside try with deferred promise (#1706)", () => {
util.testFunction`
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