Ignore null in generic lambdas parameters #419
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jvican
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dwijnand
previously approved these changes
Sep 29, 2017
| @@ -496,12 +498,18 @@ object ClassToAPI { | |||
| api.Projection.of(api.Singleton.of(pathFromString(p)), cls) | |||
| } | |||
| } | |||
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| // sbt/zinc#389: Ignore nulls coming from generic parameter types of lambdas | |||
| private[this] def ignoreNulls[T: scala.reflect.ClassTag](genericTypes: Array[T]): Array[T] = | |||
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Things that I need to do before merge:
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dwijnand
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Sep 29, 2017
| private[this] def parameterTypes(m: Method): Array[Type] = | ||
| ignoreNulls(m.getGenericParameterTypes) | ||
| private[this] def parameterTypes(c: Constructor[_]): Array[Type] = | ||
| ignoreNulls(c.getGenericParameterTypes) |
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Did the previous iteration of this patch that only applied the filter on getActualTypeArguments fail the test in CI?
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Yes, the issue is that I forgot to push the latest local changes last night, which included this.
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This slipped through the rocks. Handling tomorrow. |
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It looks like I cannot sign in into JDK's issue tracker, so I won't be filing a ticket. I'm updating the commit message with the reason behind this problem. |
`Method.getGenericParameterType` may sometimes return `null` for the return types when the method's return type is indeed generic. It's not clear yet where this "sometimes" happens, but it looks like the JDK is not able to tell the return type of a lambda returning the generic class. This can be seen in the `java-lambda-typeparams` scripted test. In this context, lambda metafactory synthesizes a lambda class that returns a class that is parameterized in its return type. In that context, when `ClassToAPI` inspects the synthesized lambda and tries to figure out the full return type of it, the `null` is returned. It looks like the Java reflection API sparingly returns `null`s. We can see that in `ClassToAPI` where we guard against `null`s in lots of other places. So the guard added by this commit is not a novelty, but rather the norm. Fixes sbt#389.
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This PR has been updated with a better commit message. |
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So this should target 1.0.x branch, right? |
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Closing this in favor of #446. |
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Thanks for the rebase. I missed this notification. |
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This is a WIP and needs to be double-checked before merge.
Related but not exact reasons why this happens can be found in JDK's
issue tracker: https://bugs.openjdk.java.net/browse/JDK-8178523?jql=text%20%7E%20%22lambda%20generic%20type%22
We ignore nulls that are returned by
getActualTypeArguments.It would be good to file a ticket in JIRA before merge.
Fixes #389.