Fix Variant encoding and decoding edge cases - #1830
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getBuiltinTypeId read an Integer out of a BiMap and returned it as an int, so a class that backs no builtin type produced a NullPointerException on unboxing rather than a value. Two callers already branch on a -1 sentinel that could therefore never be reached: Variant.getDataTypeId and OpcUaBinaryEncoder.encodeVariant. Return -1 as those callers expect, and document it. That makes encodeVariant's dead branch live. It logged a warning and then carried on to write `typeId | 0x80` as the encoding mask, which for -1 is 0xFF: a corrupt message the peer rejects as a framing error, far from where the mistake was made. Throw Bad_EncodingError instead, matching how the rest of the encoder reports an unencodable value. OpcUaJsonEncoder gets the same guard. It used the sentinel as a "UaType" value without checking it, so the contract change would have turned an exception into silently malformed JSON. Reproduced by: new Variant(new Object()) — the Variant constructor performs no verification, so a non-builtin can reach either encoder. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
encodeVariant picked an OptionSet's builtin type by casting value to OptionSetUInteger and inspecting the instance. That only holds for a scalar. When a Variant carries an array or a Matrix of option sets, valueClass comes from the element type but value is still the container, so the cast fails: ClassCastException, or an AssertionError from the preceding assert when assertions are enabled. Derive the type from the element class instead, walking the OptionSetUI8/16/32/64 hierarchy. That is what OpcUaJsonEncoder and OpcUaXmlEncoder already do; the binary encoder was the outlier. It also resolves empty arrays, which have no element to inspect. Reachable from any Variant holding an option set array, e.g. a Read of an AccessLevelType-typed array Variable. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
decodeVariant returned early for a -1 array length without reading the ArrayDimensions field when the dimensions bit was set, leaving those bytes in the buffer and desynchronizing every subsequent read in the enclosing message. Reproduced by: encoding mask with array and dimensions bits set, length -1, followed by a dimensions field — any field decoded after the Variant reads misaligned bytes. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
kevinherron
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binary-serialization-performance
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July 29, 2026 11:02
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Summary
Stacked on #1829. One commit per fix, consolidating the fixes that were floating on individual
fix/*branches:-1guards inVariant.getDataTypeIdandencodeVariantdead code.encodeVariantnow throwsBad_EncodingErrorinstead of writing a corrupt encoding mask, andOpcUaJsonEncodergets the same guard.encodeVariantpicked an OptionSet's builtin type by casting the value toOptionSetUInteger, which only holds for scalars; a Variant carrying an array or Matrix of option sets failed with ClassCastException (or AssertionError with assertions enabled). The type is now derived from the element class, as the JSON and XML encoders already do.decodeVariantreturned early on a -1 array length without reading the ArrayDimensions field when the dimensions bit was set, desynchronizing every subsequent read in the message.Testing
spotless:checkand thestack-core+encoding-jsontest suites pass, including new regression tests for each fix.🤖 Generated with Claude Code