amitvijapur commented on code in PR #11181:
URL: https://github.com/apache/arrow-rs/pull/11181#discussion_r4281805451
##########
arrow-json/src/reader/mod.rs:
##########
@@ -4381,4 +4381,68 @@ mod tests {
let err = read(false);
assert!(err.contains("returned 0 values for 1 rows"), "{err}");
}
+
+ #[test]
+ fn test_scalar_promoted_to_list() {
+ let buf = r#"{"a": 1}
Review Comment:
@alamb @Jefffrey, the source comparison supports treating scalar-to-list
promotion as a policy choice rather than assuming it should be the default:
- At the checked commit, Arrow C++ rejects numeric scalars for list fields
and established scalar/array kind changes. Its [array
parser](https://github.com/apache/arrow/blob/9b34c4a6a8856212b885f6a1e934795af04f3192/cpp/src/arrow/json/parser.cc#L902)
requires an array builder, and [scalar
appends](https://github.com/apache/arrow/blob/9b34c4a6a8856212b885f6a1e934795af04f3192/cpp/src/arrow/json/parser.cc#L998)
reject mismatched builder kinds. This does not rule out promotion from a null
builder during inference.
- Jackson 2.14 offers
[ACCEPT_SINGLE_VALUE_AS_ARRAY](https://fasterxml.github.io/jackson-databind/javadoc/2.14/com/fasterxml/jackson/databind/DeserializationFeature.html#ACCEPT_SINGLE_VALUE_AS_ARRAY),
disabled by default. That wraps single values when deserializing into
array/collection targets, not during schema inference.
My patch makes the reader accept the schema inference already produces, but
that does not establish that promotion is the right default. I can rework the
inference side instead once we agree on the intended behavior and compatibility
requirements.
Codex assisted this source/documentation comparison and drafted this reply.
No local runtime comparisons were performed.
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