TSLint - Promises must be handled appropriately with `finally`
I'm getting this error from TSLint and I'm trying to understand why it is complaining about.
I have a function which invokes another method which returns a promise but the first function does not return the promise because it just waits for it to finish and update an internal state.
I've simplified it to this function and just use Q() to simulate an invocation that returns a promise.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
}).finally(() => {
log.info("at finally")
});
}
When I run tslint on my project now I'm getting the following error:
ERROR: C:/dev/local_cache_service.ts[31, 5]: Promises must be handled appropriately
If I remove the finally call tslint passes without errors.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
});
}
When I create the same function on a seed typescript project this behavior does not reproduce...
typescript q tslint
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
add a comment |
I'm getting this error from TSLint and I'm trying to understand why it is complaining about.
I have a function which invokes another method which returns a promise but the first function does not return the promise because it just waits for it to finish and update an internal state.
I've simplified it to this function and just use Q() to simulate an invocation that returns a promise.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
}).finally(() => {
log.info("at finally")
});
}
When I run tslint on my project now I'm getting the following error:
ERROR: C:/dev/local_cache_service.ts[31, 5]: Promises must be handled appropriately
If I remove the finally call tslint passes without errors.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
});
}
When I create the same function on a seed typescript project this behavior does not reproduce...
typescript q tslint
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
add a comment |
I'm getting this error from TSLint and I'm trying to understand why it is complaining about.
I have a function which invokes another method which returns a promise but the first function does not return the promise because it just waits for it to finish and update an internal state.
I've simplified it to this function and just use Q() to simulate an invocation that returns a promise.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
}).finally(() => {
log.info("at finally")
});
}
When I run tslint on my project now I'm getting the following error:
ERROR: C:/dev/local_cache_service.ts[31, 5]: Promises must be handled appropriately
If I remove the finally call tslint passes without errors.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
});
}
When I create the same function on a seed typescript project this behavior does not reproduce...
typescript q tslint
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
I'm getting this error from TSLint and I'm trying to understand why it is complaining about.
I have a function which invokes another method which returns a promise but the first function does not return the promise because it just waits for it to finish and update an internal state.
I've simplified it to this function and just use Q() to simulate an invocation that returns a promise.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
}).finally(() => {
log.info("at finally")
});
}
When I run tslint on my project now I'm getting the following error:
ERROR: C:/dev/local_cache_service.ts[31, 5]: Promises must be handled appropriately
If I remove the finally call tslint passes without errors.
export function DoSomethingAsync(): void {
Q().then(r => {
console.log('test');
}).catch(err => {
log.error("wow");
});
}
When I create the same function on a seed typescript project this behavior does not reproduce...
typescript q tslint
typescript q tslint
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
edited Nov 26 '18 at 8:01
Ido Ran
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
asked Nov 26 '18 at 6:48
Ido RanIdo Ran
4,346851103
4,346851103
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
This is a complaint from the no-floating-promises rule. As per its description:
Creating a Promise and not storing or returning it may let other code run independently of its result. This can cause unexpected and/or non-deterministic behavior depending on external timing factors.
It’s typically better to return Promises from functions that start them, then handle them in calling code.
Use
no-unused-expressionin addition to this rule to reveal even more floating promises.
Specifically in your case, it's because you're running code in a .finally block after the .catch block. That's considered dangerous by the rule because if the code within the .finally throws an error, it'll be unhandled by the calling code.
The best thing for you to do would be to return the promise, so the function's return type is a Promise/Q instead of void.
Tip: you can run tslint -t stylish or tslint -t verbose to see rule names along with their complaints!
answered Nov 27 '18 at 4:23
JoshJosh
821512
Thank you. Return the promise will not solve the problem, it will just move it to the called of this function, which in this case is a private function and by design I don't want to return this promise as it's an internal operation that the caller should not wait on.
– Ido Ran
Nov 27 '18 at 8:30
In that case, two quick options: * Put a// tslint:disable-next-line:no-floating-promisesabove the line being complained about * Put a.catchafter the.finally, which will handle the case of the.finallycode throwing an error You could also consider having something that receives these floating promises and.catches them.safePromiseCatcher(Q().then(...));.
– Josh
Nov 27 '18 at 19:51
add a comment |
The solution was to add a call to .done() at the end of the promise call chain.
From what I understood done converts any unhandled exceptions to a regular unhandled exception.
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
add a comment |
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2 Answers
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active
oldest
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2 Answers
2
active
oldest
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active
oldest
votes
active
oldest
votes
This is a complaint from the no-floating-promises rule. As per its description:
Creating a Promise and not storing or returning it may let other code run independently of its result. This can cause unexpected and/or non-deterministic behavior depending on external timing factors.
It’s typically better to return Promises from functions that start them, then handle them in calling code.
Use
no-unused-expressionin addition to this rule to reveal even more floating promises.
Specifically in your case, it's because you're running code in a .finally block after the .catch block. That's considered dangerous by the rule because if the code within the .finally throws an error, it'll be unhandled by the calling code.
The best thing for you to do would be to return the promise, so the function's return type is a Promise/Q instead of void.
Tip: you can run tslint -t stylish or tslint -t verbose to see rule names along with their complaints!
answered Nov 27 '18 at 4:23
JoshJosh
821512
Thank you. Return the promise will not solve the problem, it will just move it to the called of this function, which in this case is a private function and by design I don't want to return this promise as it's an internal operation that the caller should not wait on.
– Ido Ran
Nov 27 '18 at 8:30
In that case, two quick options: * Put a// tslint:disable-next-line:no-floating-promisesabove the line being complained about * Put a.catchafter the.finally, which will handle the case of the.finallycode throwing an error You could also consider having something that receives these floating promises and.catches them.safePromiseCatcher(Q().then(...));.
– Josh
Nov 27 '18 at 19:51
add a comment |
This is a complaint from the no-floating-promises rule. As per its description:
Creating a Promise and not storing or returning it may let other code run independently of its result. This can cause unexpected and/or non-deterministic behavior depending on external timing factors.
It’s typically better to return Promises from functions that start them, then handle them in calling code.
Use
no-unused-expressionin addition to this rule to reveal even more floating promises.
Specifically in your case, it's because you're running code in a .finally block after the .catch block. That's considered dangerous by the rule because if the code within the .finally throws an error, it'll be unhandled by the calling code.
The best thing for you to do would be to return the promise, so the function's return type is a Promise/Q instead of void.
Tip: you can run tslint -t stylish or tslint -t verbose to see rule names along with their complaints!
answered Nov 27 '18 at 4:23
JoshJosh
821512
Thank you. Return the promise will not solve the problem, it will just move it to the called of this function, which in this case is a private function and by design I don't want to return this promise as it's an internal operation that the caller should not wait on.
– Ido Ran
Nov 27 '18 at 8:30
In that case, two quick options: * Put a// tslint:disable-next-line:no-floating-promisesabove the line being complained about * Put a.catchafter the.finally, which will handle the case of the.finallycode throwing an error You could also consider having something that receives these floating promises and.catches them.safePromiseCatcher(Q().then(...));.
– Josh
Nov 27 '18 at 19:51
add a comment |
This is a complaint from the no-floating-promises rule. As per its description:
Creating a Promise and not storing or returning it may let other code run independently of its result. This can cause unexpected and/or non-deterministic behavior depending on external timing factors.
It’s typically better to return Promises from functions that start them, then handle them in calling code.
Use
no-unused-expressionin addition to this rule to reveal even more floating promises.
Specifically in your case, it's because you're running code in a .finally block after the .catch block. That's considered dangerous by the rule because if the code within the .finally throws an error, it'll be unhandled by the calling code.
The best thing for you to do would be to return the promise, so the function's return type is a Promise/Q instead of void.
Tip: you can run tslint -t stylish or tslint -t verbose to see rule names along with their complaints!
answered Nov 27 '18 at 4:23
JoshJosh
821512
This is a complaint from the no-floating-promises rule. As per its description:
Creating a Promise and not storing or returning it may let other code run independently of its result. This can cause unexpected and/or non-deterministic behavior depending on external timing factors.
It’s typically better to return Promises from functions that start them, then handle them in calling code.
Use
no-unused-expressionin addition to this rule to reveal even more floating promises.
Specifically in your case, it's because you're running code in a .finally block after the .catch block. That's considered dangerous by the rule because if the code within the .finally throws an error, it'll be unhandled by the calling code.
The best thing for you to do would be to return the promise, so the function's return type is a Promise/Q instead of void.
Tip: you can run tslint -t stylish or tslint -t verbose to see rule names along with their complaints!
answered Nov 27 '18 at 4:23
JoshJosh
821512
answered Nov 27 '18 at 4:23
JoshJosh
821512
answered Nov 27 '18 at 4:23
JoshJosh
821512
answered Nov 27 '18 at 4:23
JoshJosh
821512
821512
Thank you. Return the promise will not solve the problem, it will just move it to the called of this function, which in this case is a private function and by design I don't want to return this promise as it's an internal operation that the caller should not wait on.
– Ido Ran
Nov 27 '18 at 8:30
In that case, two quick options: * Put a// tslint:disable-next-line:no-floating-promisesabove the line being complained about * Put a.catchafter the.finally, which will handle the case of the.finallycode throwing an error You could also consider having something that receives these floating promises and.catches them.safePromiseCatcher(Q().then(...));.
– Josh
Nov 27 '18 at 19:51
add a comment |
Thank you. Return the promise will not solve the problem, it will just move it to the called of this function, which in this case is a private function and by design I don't want to return this promise as it's an internal operation that the caller should not wait on.
– Ido Ran
Nov 27 '18 at 8:30
In that case, two quick options: * Put a// tslint:disable-next-line:no-floating-promisesabove the line being complained about * Put a.catchafter the.finally, which will handle the case of the.finallycode throwing an error You could also consider having something that receives these floating promises and.catches them.safePromiseCatcher(Q().then(...));.
– Josh
Nov 27 '18 at 19:51
Thank you. Return the promise will not solve the problem, it will just move it to the called of this function, which in this case is a private function and by design I don't want to return this promise as it's an internal operation that the caller should not wait on.
– Ido Ran
Nov 27 '18 at 8:30
Thank you. Return the promise will not solve the problem, it will just move it to the called of this function, which in this case is a private function and by design I don't want to return this promise as it's an internal operation that the caller should not wait on.
– Ido Ran
Nov 27 '18 at 8:30
In that case, two quick options: * Put a
// tslint:disable-next-line:no-floating-promises above the line being complained about * Put a .catch after the .finally, which will handle the case of the .finally code throwing an error You could also consider having something that receives these floating promises and .catches them. safePromiseCatcher(Q().then(...));.– Josh
Nov 27 '18 at 19:51
In that case, two quick options: * Put a
// tslint:disable-next-line:no-floating-promises above the line being complained about * Put a .catch after the .finally, which will handle the case of the .finally code throwing an error You could also consider having something that receives these floating promises and .catches them. safePromiseCatcher(Q().then(...));.– Josh
Nov 27 '18 at 19:51
add a comment |
The solution was to add a call to .done() at the end of the promise call chain.
From what I understood done converts any unhandled exceptions to a regular unhandled exception.
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
add a comment |
The solution was to add a call to .done() at the end of the promise call chain.
From what I understood done converts any unhandled exceptions to a regular unhandled exception.
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
add a comment |
The solution was to add a call to .done() at the end of the promise call chain.
From what I understood done converts any unhandled exceptions to a regular unhandled exception.
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
The solution was to add a call to .done() at the end of the promise call chain.
From what I understood done converts any unhandled exceptions to a regular unhandled exception.
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
answered Nov 27 '18 at 14:35
Ido RanIdo Ran
4,346851103
4,346851103
add a comment |
add a comment |
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