improve generics of promise

[sclassen]

resolves #154

Note: This is a breaking API change
Never the less I think this will improve the experience of using jdeferred as the typing becomes more strict and therefore reduces possible runtime exceptions (such as ClassCastException)

On the same time by using "? super" and "? extends" the typing becomes relaxed as we now can do the following

Promise<Integer, Throwable, Void> integerPromise = createIntegerPromise();
Promise<Float, Throwable, Void> floatPromise = createFloatPromise();
integerPromise.then(Helper::numberLogger)
floatPromise.then(Helper::numberLogger)

where

public class Helper {
    public void numberLogger(Number n) {
        /* log number */
    }
}

The Java Stream API also uses "? super" and "? extends" to allow maximal flexibility

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This change is 

[coveralls]

Coverage remained the same at 55.912% when pulling b7ef67d on sclassen:154_improveGenericsOfPromise into ccd35d4 on jdeferred:2.x.

[aalmiray]

Reviewed 8 of 8 files at r1.
Review status: all files reviewed at latest revision, 1 unresolved discussion.

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subprojects/jdeferred-core/src/test/java/org/jdeferred/impl/PipedPromiseTest.java, line 40 at r1 (raw file):

		};
		
		deferredManager.when(task).then(new DonePipe<Integer, Integer, Throwable, Void>() {

just curious, why the change from String to Throwable?

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[sclassen]

Review status: all files reviewed at latest revision, 1 unresolved discussion.

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subprojects/jdeferred-core/src/test/java/org/jdeferred/impl/PipedPromiseTest.java, line 40 at r1 (raw file):

Previously, aalmiray (Andres Almiray) wrote…

just curious, why the change from String to Throwable?

You mean from Void to Throwable.
This is do to the stricter typing enforced by the changes. The deferredManager.when(task) returns a Promise<Integer, Throwable, Void> therefore the DonePipe also needs to return a Promise<D_OUT, Throwable, Void>. D_OUT is Integer in this the concrete implementation.
This is one of the cases where the API is breaking but it is more stringent because if the DonePipe would return Promise<D_OUT, F_OUT, Void> where F_OUT != F then there are two possible rejected types.

1. Throwable if the original promise is rejected
2. F_OUT if the promise returned from the DonePipe.pipeDone() is rejected

This may be OK for untyped languages such as Javascript but for Java we should prevent this cases

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[aalmiray]

Review status: all files reviewed at latest revision, 1 unresolved discussion, all commit checks successful.

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subprojects/jdeferred-core/src/test/java/org/jdeferred/impl/PipedPromiseTest.java, line 40 at r1 (raw file):

Previously, sclassen wrote…

You mean from Void to Throwable.
This is do to the stricter typing enforced by the changes. The deferredManager.when(task) returns a Promise<Integer, Throwable, Void> therefore the DonePipe also needs to return a Promise<D_OUT, Throwable, Void>. D_OUT is Integer in this the concrete implementation.
This is one of the cases where the API is breaking but it is more stringent because if the DonePipe would return Promise<D_OUT, F_OUT, Void> where F_OUT != F then there are two possible rejected types.

1. Throwable if the original promise is rejected
2. F_OUT if the promise returned from the DonePipe.pipeDone() is rejected

This may be OK for untyped languages such as Javascript but for Java we should prevent this cases

Not really, no. I meant the change made to testDoneRewireToFail where the failure used to be of type String but now is of type Throwable. The test still works anyway.

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[sclassen]

Review status: all files reviewed at latest revision, 1 unresolved discussion.

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subprojects/jdeferred-core/src/test/java/org/jdeferred/impl/PipedPromiseTest.java, line 40 at r1 (raw file):

Previously, aalmiray (Andres Almiray) wrote…

Not really, no. I meant the change made to testDoneRewireToFail where the failure used to be of type String but now is of type Throwable. The test still works anyway.

Same reasoning. The deferredManager.when(new Callable<Integer>() {...}) returns a Promise<Integer, Throwable, Void> and if we only specify a DonePipe and no FailPipe then F_OUT must be the same as F.

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[aalmiray]

Review status: all files reviewed at latest revision, 1 unresolved discussion.

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subprojects/jdeferred-core/src/test/java/org/jdeferred/impl/PipedPromiseTest.java, line 40 at r1 (raw file):

Previously, sclassen wrote…

Same reasoning. The deferredManager.when(new Callable<Integer>() {...}) returns a Promise<Integer, Throwable, Void> and if we only specify a DonePipe and no FailPipe then F_OUT must be the same as F.

ah got it :-)

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[aalmiray]

@saturnism we'll have to merge with caution due to #156. In other words the fix for #156 should go last

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Review status: all files reviewed at latest revision, 1 unresolved discussion.

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[saturnism]

@aalmiray agreed; let's close out the last of the PRs before #156.

[saturnism]

Reviewed 7 of 8 files at r1.
Review status: all files reviewed at latest revision, 1 unresolved discussion.

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[saturnism]

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Review status: all files reviewed at latest revision, 1 unresolved discussion.

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