[ion-elgreco]

Which issue does this PR close?

• Closes Allow coerce_primitives in JsonSource #26560.

Rationale for this change

When a JSON file has a number or a boolean in a column that the schema declares as a string, the scan fails with an error such as expected string got false. arrow-json can keep these values as text with ReaderBuilder::with_coerce_primitive, but JsonSource does not expose that option. We now have to write a custom JSON source.

What changes are included in this PR?

• Add JsonSource::with_coerce_primitive and the getter JsonSource::coerce_primitive. The default is false, so current behavior does not change.
• Add JsonOpener::with_coerce_primitive. The opener passes the value to ReaderBuilder::with_coerce_primitive on every read path: byte range, local file, and stream, for newline-delimited JSON and JSON arrays.
• Add optional bool coerce_primitive = 3 to the JsonScanExecNode protobuf message

What is the testing strategy for this PR?

• test_coerce_primitive in datafusion/datasource-json/src/source.rs covers each read path
• json_exec_coerce_primitive in datafusion/core/src/datasource/physical_plan/json.rs e2e test through DataSourceExec.
• roundtrip_json_scan_preserves_format_options in datafusion/proto/tests/cases/plans/sources.rs now checks that the option survives a protobuf round trip

Are there any user-facing changes?

Yes. New public API:

• JsonSource::with_coerce_primitive
• JsonSource::coerce_primitive
• JsonOpener::with_coerce_primitive
• JsonScanExecNode::coerce_primitive (new optional protobuf field)

The default behavior does not change. Code that builds or destructures JsonScanExecNode with all fields named must add the new field.

[kosiew]

🚀
@ion-elgreco
Thank you for your contribution.

Can you amend the PR description as per .github/pull_request_template.md?

[ion-elgreco]

@kosiew done!