hutiefang76 opened a new issue, #12869:
URL: https://github.com/apache/seatunnel/issues/12869
### Search before asking
- [x] Searched open/closed issues and PRs for `hasDecimalType` and JSON
decimal precision; no same-purpose fix found.
### What happened
JSON parsing loses digits when the schema's DECIMAL values occur only inside
arrays. With `amounts ARRAY<DECIMAL(38,20)>`, input
`{"amounts":[3.14159265358979323846]}` yields `3.141592653589793`. The same
value in a scalar DECIMAL remains exact. `ARRAY<ARRAY<DECIMAL>>` and
`ARRAY<ROW<DECIMAL>>` also lose precision; adding a scalar DECIMAL sibling
makes those array values exact.
Reproduced on dev in the existing `JsonRowDataSerDeSchemaTest`: 32 tests,
three expected precision failures, zero errors/skips. Scalar, scalar-sibling
and ordinary-array controls pass.
`hasDecimalType` checks `CompositeType` children, but `ArrayType` is not a
`CompositeType`, so the decimal-preserving mapper setting is not enabled for
these schemas. I will extend that check to array elements and cover nested
arrays and rows, without changing APIs, schema types or options.
That mapper setting applies to the whole input document, as it already does
with scalar DECIMAL schemas. After the fix, a bare numeric JSON token mapped to
a STRING sibling may retain more digits in an array-only DECIMAL schema too. I
will document this in English/Chinese and the upgrade notes. Quoted strings and
schemas without DECIMAL remain unchanged. This scope is the plain JSON schema
traversal; it does not change Kafka-Connect mapper setup.
### SeaTunnel Version
Dev at `e2957d27afa29d4de4324cf642450757d865b902`.
### SeaTunnel Config
Direct `JsonDeserializationSchema` test with `ArrayType.of(new
DecimalType(38, 20))`; no connector or job was run.
### Running Command
```sh
./mvnw -pl seatunnel-formats/seatunnel-format-json -am \
-Dtest=JsonRowDataSerDeSchemaTest -Dsurefire.failIfNoSpecifiedTests=false
package
```
### Error Exception
```text
Tests run: 32, Failures: 3, Errors: 0, Skipped: 0
DECIMAL element of ARRAY<DECIMAL> must keep the exact input precision
DECIMAL element of ARRAY<ARRAY<DECIMAL>> must keep the exact input precision
DECIMAL field of ROW inside ARRAY<ROW<DECIMAL>> must keep the exact precision
```
### Java or Scala Version
JDK 17.0.18, macOS ARM64.
### Are you willing to submit PR?
- [x] Yes, I am contributing this fix to Apache SeaTunnel.
### Code of Conduct
- [x] I agree to follow this project's Code of Conduct.
<sub>Reproduction and report prepared and posted by an AI assistant for
@hutiefang76.</sub>
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