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fix(csharp): serialize NaN and infinity in struct JSON - #4921
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Utf8JsonWriter rejects non-finite numbers, so reading a struct with a NaN or infinite float or double field threw ArgumentException under StructBehavior.JsonString. Write these values as the strings "NaN", "Infinity" and "-Infinity". Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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What changed in this PR
Fixes struct JSON serialization for NaN and infinite floating-point values by emitting named JSON strings instead of throwing exceptions.
Changes:
- Serialize non-finite float and double values safely.
- Add regression tests for JSON output and preserved values.
| File | Description |
|---|---|
csharp/src/Apache.Arrow.Adbc/Extensions/IArrowArrayExtensions.cs |
Handles non-finite float and double JSON values. |
csharp/test/Apache.Arrow.Adbc.Tests/SerializeStructToJsonTests.cs |
Tests serialization of non-finite values. |
Review effort: Lite
CurtHagenlocher
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Oct 18, 2026
## What's changed Adds the variant test promised in #4919. Variants converted to JSON use the same writer as structs, so they already get the behavior from #4921: NaN and ±Infinity are written as the strings `"NaN"`, `"Infinity"` and `"-Infinity"`. This test pins that down. `VariantNonFiniteValues` reads a variant column with a non-finite double and float inside an object and an array, and a top-level NaN: - With `StructBehavior.JsonString`, it checks the exact JSON. - With `StructBehavior.Strict`, it checks that the .NET values keep the actual NaN and infinity values. With the #4921 change reverted, the JSON case fails with the original `ArgumentException`. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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What's changed
When a struct is serialized to JSON (the default
StructBehavior.JsonString), float and double fields are written withUtf8JsonWriter.WriteNumberValue. That throwsArgumentExceptionfor NaN and ±Infinity, so a single non-finite value made its whole row unreadable.These values are now written as the strings
"NaN","Infinity"and"-Infinity". That's how System.Text.Json writes them whenJsonNumberHandling.AllowNamedFloatingPointLiteralsis set.StructBehavior.Strictis unchanged and still returns the actualfloat/doublevalues.This came up in review of #4919, where variants serialized to JSON use the same writer.
Tests
NonFiniteFloatandNonFiniteDoublecheck the JSON for NaN, Infinity and -Infinity.NonFiniteDoublealso checks that the struct result keeps the actual NaN value. Without the fix, both throw theArgumentException.🤖 Generated with Claude Code