GMS Task class: can getResult() return null if isSuccessful()?
There is recently a @Nullable change to GMS tasks library. The first few lines of decompiled .class looks like
public abstract class Task<TResult> {
public Task() {
}
public abstract boolean isComplete();
public abstract boolean isSuccessful();
public abstract boolean isCanceled();
@Nullable
public abstract TResult getResult();
Previously my Kotlin code compiled:
if (task.isSuccessful) {
task.result.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
}
After updating some gms play-services-zzz dependencies the code now has compile error:
LoginActivity.kt: (148, 28): Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type AuthResult?
The question is, does isSuccessful() == true imply that getResult != null? Or would it just be better to change the if test to if (task.result != null)?
android kotlin 
google-play-services asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
add a comment |
There is recently a @Nullable change to GMS tasks library. The first few lines of decompiled .class looks like
public abstract class Task<TResult> {
public Task() {
}
public abstract boolean isComplete();
public abstract boolean isSuccessful();
public abstract boolean isCanceled();
@Nullable
public abstract TResult getResult();
Previously my Kotlin code compiled:
if (task.isSuccessful) {
task.result.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
}
After updating some gms play-services-zzz dependencies the code now has compile error:
LoginActivity.kt: (148, 28): Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type AuthResult?
The question is, does isSuccessful() == true imply that getResult != null? Or would it just be better to change the if test to if (task.result != null)?
android kotlin google-play-services asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
add a comment |
There is recently a @Nullable change to GMS tasks library. The first few lines of decompiled .class looks like
public abstract class Task<TResult> {
public Task() {
}
public abstract boolean isComplete();
public abstract boolean isSuccessful();
public abstract boolean isCanceled();
@Nullable
public abstract TResult getResult();
Previously my Kotlin code compiled:
if (task.isSuccessful) {
task.result.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
}
After updating some gms play-services-zzz dependencies the code now has compile error:
LoginActivity.kt: (148, 28): Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type AuthResult?
The question is, does isSuccessful() == true imply that getResult != null? Or would it just be better to change the if test to if (task.result != null)?
android kotlin google-play-services asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
There is recently a @Nullable change to GMS tasks library. The first few lines of decompiled .class looks like
public abstract class Task<TResult> {
public Task() {
}
public abstract boolean isComplete();
public abstract boolean isSuccessful();
public abstract boolean isCanceled();
@Nullable
public abstract TResult getResult();
Previously my Kotlin code compiled:
if (task.isSuccessful) {
task.result.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
}
After updating some gms play-services-zzz dependencies the code now has compile error:
LoginActivity.kt: (148, 28): Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type AuthResult?
The question is, does isSuccessful() == true imply that getResult != null? Or would it just be better to change the if test to if (task.result != null)?
android kotlin google-play-services android kotlin google-play-services asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
asked Nov 13 '18 at 22:08
androidguyandroidguy
8291613
8291613
add a comment |
add a comment |
1 Answer
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What you are seeing is the Kotlin compiler failing to smart-cast the result to a NonNull type based on the result of isSuccessful, this can happen when interacting with both Java and Kotlin code.
In Kotlin 1.3 an implementation of "Contracts" was added to the language to allow developers to add meta data about a method in a format that the IDE can use to statically analyze and infer type (smart-cast).
See Section 1.2 "Returns and Implies" https://proandroiddev.com/kotlin-contracts-make-great-deals-with-the-compiler-f524e57f11c
So with contracts it would correctly smart-cast if the implementation looked like this:
open class Task<T> {
var result: T? = null
private set
fun isSuccessful(): Boolean {
contract {
returns(true) implies (result != null)
}
return result != null
}
}
In your case however you probably want to throw on another safe call operator ? and call your !task.isSuccessful code with the Elvis operator ?: like this:
if (task.isSuccessful) {
task.result?.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
} ?: handleFailure() // Defensively call just in case
} else {
handleFailure()
}
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
What you are seeing is the Kotlin compiler failing to smart-cast the result to a NonNull type based on the result of isSuccessful, this can happen when interacting with both Java and Kotlin code.
In Kotlin 1.3 an implementation of "Contracts" was added to the language to allow developers to add meta data about a method in a format that the IDE can use to statically analyze and infer type (smart-cast).
See Section 1.2 "Returns and Implies" https://proandroiddev.com/kotlin-contracts-make-great-deals-with-the-compiler-f524e57f11c
So with contracts it would correctly smart-cast if the implementation looked like this:
open class Task<T> {
var result: T? = null
private set
fun isSuccessful(): Boolean {
contract {
returns(true) implies (result != null)
}
return result != null
}
}
In your case however you probably want to throw on another safe call operator ? and call your !task.isSuccessful code with the Elvis operator ?: like this:
if (task.isSuccessful) {
task.result?.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
} ?: handleFailure() // Defensively call just in case
} else {
handleFailure()
}
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
add a comment |
What you are seeing is the Kotlin compiler failing to smart-cast the result to a NonNull type based on the result of isSuccessful, this can happen when interacting with both Java and Kotlin code.
In Kotlin 1.3 an implementation of "Contracts" was added to the language to allow developers to add meta data about a method in a format that the IDE can use to statically analyze and infer type (smart-cast).
See Section 1.2 "Returns and Implies" https://proandroiddev.com/kotlin-contracts-make-great-deals-with-the-compiler-f524e57f11c
So with contracts it would correctly smart-cast if the implementation looked like this:
open class Task<T> {
var result: T? = null
private set
fun isSuccessful(): Boolean {
contract {
returns(true) implies (result != null)
}
return result != null
}
}
In your case however you probably want to throw on another safe call operator ? and call your !task.isSuccessful code with the Elvis operator ?: like this:
if (task.isSuccessful) {
task.result?.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
} ?: handleFailure() // Defensively call just in case
} else {
handleFailure()
}
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
add a comment |
What you are seeing is the Kotlin compiler failing to smart-cast the result to a NonNull type based on the result of isSuccessful, this can happen when interacting with both Java and Kotlin code.
In Kotlin 1.3 an implementation of "Contracts" was added to the language to allow developers to add meta data about a method in a format that the IDE can use to statically analyze and infer type (smart-cast).
See Section 1.2 "Returns and Implies" https://proandroiddev.com/kotlin-contracts-make-great-deals-with-the-compiler-f524e57f11c
So with contracts it would correctly smart-cast if the implementation looked like this:
open class Task<T> {
var result: T? = null
private set
fun isSuccessful(): Boolean {
contract {
returns(true) implies (result != null)
}
return result != null
}
}
In your case however you probably want to throw on another safe call operator ? and call your !task.isSuccessful code with the Elvis operator ?: like this:
if (task.isSuccessful) {
task.result?.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
} ?: handleFailure() // Defensively call just in case
} else {
handleFailure()
}
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
What you are seeing is the Kotlin compiler failing to smart-cast the result to a NonNull type based on the result of isSuccessful, this can happen when interacting with both Java and Kotlin code.
In Kotlin 1.3 an implementation of "Contracts" was added to the language to allow developers to add meta data about a method in a format that the IDE can use to statically analyze and infer type (smart-cast).
See Section 1.2 "Returns and Implies" https://proandroiddev.com/kotlin-contracts-make-great-deals-with-the-compiler-f524e57f11c
So with contracts it would correctly smart-cast if the implementation looked like this:
open class Task<T> {
var result: T? = null
private set
fun isSuccessful(): Boolean {
contract {
returns(true) implies (result != null)
}
return result != null
}
}
In your case however you probably want to throw on another safe call operator ? and call your !task.isSuccessful code with the Elvis operator ?: like this:
if (task.isSuccessful) {
task.result?.user?.getIdToken(false)?.addOnCompleteListener { taskk ->
this.emailIdTokenCompleteListener()(taskk)
} ?: handleFailure() // Defensively call just in case
} else {
handleFailure()
}
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
answered Nov 13 '18 at 22:36
waterPoweredMonkeywaterPoweredMonkey
594
594
add a comment |
add a comment |
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