[ParthibanRajasekaran]

Which issue does this PR address?

Relates to #4386

Rationale

ProtoEncoderConfig.field_mappings maps protobuf field names to JSON field names. When multiple protobuf fields mapped to the same JSON name, the encoder's reverse lookup depended on HashMap iteration order and could select either field nondeterministically.

The accepted scope is limited to configuration loading. Broader runtime collision behavior and the other field-mapping configurations remain unchanged.

What changed?

Deserializing ProtoEncoderConfig now rejects field_mappings containing duplicate JSON field names. Missing, null, empty, and uniquely named mappings retain their existing behavior.

Regression tests cover duplicate rejection and each preserved configuration form.

Local Execution

• Passed cargo fmt --all
• Passed cargo sort --no-format --workspace
• Passed cargo clippy -p iggy_connector_sdk --all-targets --all-features -- -D warnings
• Passed cargo test -p iggy_connector_sdk --all-features
  • 231 unit tests
  • 10 FlatBuffer integration tests
  • 21 protobuf integration tests
• Passed cargo build -p iggy_connector_stdout_sink -p iggy_connector_random_source
• Passed prek run --from-ref 4f58678d^ --to-ref 4f58678d
• Confirmed the duplicate-mapping regression test fails without the validation guard

[github-actions]

This PR is closed because its description has no Closes #N, Fixes #N, Resolves #N or Relates to #N line naming an issue.

Every PR needs an issue that was assigned to you before work started. See CONTRIBUTING.md.

[codecov]

Codecov Report

❌ Patch coverage is 68.10345% with 37 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.89%. Comparing base (d47ff5d) to head (ae5a991).

Files with missing lines	Patch %	Lines
core/connectors/sdk/src/encoders/proto.rs	68.10%	32 Missing and 5 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #4581      +/-   ##
============================================
+ Coverage     80.83%   80.89%   +0.06%     
  Complexity     3107     3107              
============================================
  Files          1467     1467              
  Lines        356533   356620      +87     
  Branches     300421   300508      +87     
============================================
+ Hits         288194   288505     +311     
+ Misses        61617    61237     -380     
- Partials       6722     6878     +156     

Components	Coverage Δ
Rust Core	80.20% <68.10%> (+0.08%)	⬆️
Java SDK	78.15% <ø> (ø)
C# SDK	83.60% <ø> (ø)
Python SDK	85.67% <ø> (ø)
PHP SDK	90.67% <ø> (ø)
Node SDK	96.44% <ø> (ø)
Go SDK	69.13% <ø> (ø)
C++ SDK	85.51% <ø> (ø)

Files with missing lines	Coverage Δ
core/connectors/sdk/src/encoders/proto.rs	77.03% <68.10%> (+0.08%)	⬆️

... and 529 files with indirect coverage changes

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[ByteBaker]

LGTM!

[ParthibanRajasekaran]

CI is currently blocked only by an unrelated integration-test failure in Rust tests / test (1/4): server::delete_segments::should_block_deletion_until_all_consumers_pass_segment::test_case_2_restart_on_expects. It failed all four retries at core/integration/tests/server/scenarios/delete_segments_scenario.rs:832 with transient LaneBlocked values (103, 105, and 104), while the other 816 tests in that shard, all three remaining Rust shards, and the Codecov patch check passed.\n\nThis PR's diff only changes core/connectors/sdk/src/encoders/proto.rs; it does not touch the failing integration scenario. The branch is also current with master and has no conflicts. Could a maintainer please rerun the failed job? I attempted gh run rerun 40493937074 --failed, but GitHub requires repository-admin permission.

[hubcio]

i'll check this flaky test @ParthibanRajasekaran

[mmodzelewski]

Nit: encode_should_resolve_ambiguous_reverse_lookup_to_one_of_the_colliding_keys at core/connectors/sdk/src/encoders/proto.rs:1023 still treats duplicate JSON names as valid input. Once update_config runs the check, change it to expect the rejection.

Nit: core/connectors/sdk/README.md:185 lists the encoder fields but omits field_mappings. Add a bullet that says keys are protobuf names, values are JSON names, and values must be unique.

[kparisa]

/author