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https://issues.apache.org/jira/browse/BEAM-4769?focusedWorklogId=124639&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-124639
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ASF GitHub Bot logged work on BEAM-4769:
----------------------------------------
Author: ASF GitHub Bot
Created on: 18/Jul/18 21:39
Start Date: 18/Jul/18 21:39
Worklog Time Spent: 10m
Work Description: lukecwik commented on issue #5967: [BEAM-4769] Fix
issue when performing coder inference for wildcard types.
URL: https://github.com/apache/beam/pull/5967#issuecomment-406082866
R: @youngoli
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Issue Time Tracking
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Worklog Id: (was: 124639)
Time Spent: 20m (was: 10m)
> Types$WildcardTypeImpl cannot be cast to java.lang.reflect.TypeVariable
> -----------------------------------------------------------------------
>
> Key: BEAM-4769
> URL: https://issues.apache.org/jira/browse/BEAM-4769
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Affects Versions: 2.5.0
> Reporter: Dzmitry Lazerka
> Assignee: Luke Cwik
> Priority: Minor
> Time Spent: 20m
> Remaining Estimate: 0h
>
> Hi,
> I'm getting the following exception, probably when Beam cannot find a coder
> for a wildcard generic type (although I don't think I use any, gotta find).
> {code:java}
> Exception in thread "main" java.lang.ClassCastException:
> org.apache.beam.repackaged.beam_sdks_java_core.com.google.common.reflect.Types$WildcardTypeImpl
> cannot be cast to java.lang.reflect.TypeVariable
> at
> org.apache.beam.sdk.coders.CoderRegistry.getCoderFromTypeDescriptor(CoderRegistry.java:625)
> at
> org.apache.beam.sdk.coders.CoderRegistry.getCoderFromParameterizedType(CoderRegistry.java:658)
> at
> org.apache.beam.sdk.coders.CoderRegistry.getCoderFromTypeDescriptor(CoderRegistry.java:620)
> at
> org.apache.beam.sdk.coders.CoderRegistry.getCoderFromParameterizedType(CoderRegistry.java:658)
> at
> org.apache.beam.sdk.coders.CoderRegistry.getCoderFromTypeDescriptor(CoderRegistry.java:620)
> at org.apache.beam.sdk.coders.CoderRegistry.getCoder(CoderRegistry.java:254)
> at
> org.apache.beam.sdk.values.PCollection.inferCoderOrFail(PCollection.java:149)
> at
> org.apache.beam.sdk.values.PCollection.finishSpecifyingOutput(PCollection.java:89)
> at
> org.apache.beam.sdk.runners.TransformHierarchy.setOutput(TransformHierarchy.java:208)
> at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:538)
> at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:472)
> at org.apache.beam.sdk.values.PCollection.apply(PCollection.java:286)
> at org.apache.beam.sdk.transforms.ParDo$SingleOutput.expand(ParDo.java:649)
> at org.apache.beam.sdk.transforms.ParDo$SingleOutput.expand(ParDo.java:584)
> at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:537)
> at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:491)
> at org.apache.beam.sdk.values.PCollection.apply(PCollection.java:299)
> at org.apache.beam.sdk.transforms.MapElements.expand(MapElements.java:123)
> at org.apache.beam.sdk.transforms.MapElements.expand(MapElements.java:36)
> at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:537)
> at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:491)
> at org.apache.beam.sdk.values.PCollection.apply(PCollection.java:299)
> {code}
> The error seems to be in the following lines of CoderRegistry.java @ 629:
> {code:java|title=CoderRegistry.java|borderStyle=solid}
> } else if (type instanceof TypeVariable) {
> coder = getCoderFromFactories(typeDescriptor, Collections.emptyList());
> } else if (type instanceof WildcardType) {
> // No coder for an unknown generic type.
> throw new CannotProvideCoderException(
> String.format("Cannot provide a coder for type variable %s"
> + " (declared by %s) because the actual type is unknown due to
> erasure.",
> type,
> ((TypeVariable<?>) type).getGenericDeclaration()),
> ReasonCode.TYPE_ERASURE);
> {code}
> It tries to cast a WildcardType to TypeVariable<?>, although that should've
> been caught above on line 621.
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