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#3704 Fix NPE when forging a mapping to an Optional target with a wildcard type argument - #4139
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sharanggupta wants to merge 1 commit into
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… with a wildcard type argument A target setter such as `setDate(Optional<? extends Nested>)` made `MappingBuilderContext#canGenerateAutoSubMappingFor` dereference the `TypeElement` of the wildcard `Optional` base type, which is `null`, and the processor crashed with an internal `NullPointerException`. Resolve the wildcard bound before forging (as is already done for `Map` targets) so that an `Optional<Nested>` sub-mapping method is generated and assigned to the wildcard setter, and make the exclusion check null-safe.
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Fixes #3704
Problem — With a target setter like
setDate(Optional<? extends Nested>)(common for Immutables-generated builders) and a sourceOptional<SourceNested>, the processor crashes onmainwithInternal error in the mapping processor: java.lang.NullPointerExceptioninDefaultMappingExclusionProvider.isExcluded, called fromMappingBuilderContext#canGenerateAutoSubMappingFor: theOptionalbase type is a wildcard whoseTypeElementisnull. On 1.6.x the same code reported "Can't map property … Optional<? extends …>" instead of generating a mapping.Regression — The NPE site was introduced with the
Optionalsupport from #3971 (#674, 2026-01-30) and ships in 1.7.0.Beta1 and Beta2; on 1.4.2 and 1.6.0 the same mapper produced the "Can't map property" diagnostic instead of crashing. It would be good to have this in 1.7.0.RC1.Fix —
PropertyMapping#forgeMapping(SourceRHS)now forges the sub-mapping againsttargetType.withoutBounds()forOptionaltargets (the same approachforgeMapMappingalready uses forMap<? extends K, ? extends V>), so a methodOptional<Nested> nestedOptionalToNestedOptional(Optional<SourceNested>)is generated and assigned to the wildcard setter.canGenerateAutoSubMappingForis also made null-safe for theOptionalbranch, mirroring the existing non-Optionalbranch.Tests —
Issue3704Test(bugs/_3704): present/emptyOptionalmapped through a wildcard setter with fixture comparison, plus the exact scenario from the issue thread (overloadedsetDate+ generic<T> Optional<T> wrapOptional(T))../mvnw -pl processor verifyis green (3649 tests, checkstyle, license, forbidden-apis). Reverting the two production changes makesIssue3704Testfail 6/6 (javac and Eclipse JDT) with the reported NPE, so the test is load-bearing.Design note — The wildcard bound is resolved in
forgeMapping, consistent with howforgeMapMappinghandlesMap<? extends K, ? extends V>. If you would rather have the check closer to theOptionalhandling (Type#getOptionalBaseType()/canGenerateAutoSubMappingFor), I am happy to move it.