[Hardik K (hardikkaurani)]

Fixes #12325

Description

TCGC supplies wireType for encoded bytes. In @typespec/http-client-python, supportedPythonEncodings previously only listed �ase64 and �ase64url for �ytes. Consequently, when raw bytes were annotated with Encode (@encode)("bytes") and TCGC supplied a string wireType, the Python emitter fell back to treating it as an unsupported custom encoding, replacing the client-facing type with string.

This regression caused binary streams (such as XML byte streams) to change from Iterator[bytes] to str, triggering lossy XML scalar deserialization instead of binary streaming.

This PR adds �ytes to supportedPythonEncodings for the �ytes kind, ensuring that raw bytes encoding preserves the �ytes type, maintains binary streaming responses, and prevents fallback to string.

Validation

• Added focused unit test in packages/http-client-python/emitter/test/types.test.ts
• Verified unit test passes with 100% success (8/8 passed)
• Added Chronus change description

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[azure-pipelines]

Azure Pipelines:
Successfully started running 1 pipeline(s).
1 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[Hardik K (hardikkaurani)]

Hi Yuchao Yan (@msyyc) Timothee Guerin (@timotheeguerin) Vincent Biret (@baywet),

I've opened this PR to resolve issue #12325.

Summary

• Added �ytes to supportedPythonEncodings for the �ytes type in packages/http-client-python/emitter/src/types.ts.
• Prevents raw bytes with a wire type from falling back to string, preserving the �ytes type and binary streaming response contracts.
• Added unit test in packages/http-client-python/emitter/test/types.test.ts verifying that bytes encoded as �ytes preserves { type: "bytes", encode: "bytes" }.
• Added Chronus change file.

Whenever you have a moment, please take a look. Thank you!

[Vincent Biret (baywet)]

Hardik K (@hardikkaurani) please do not mention me on this repository, I don't have review permissions and it's disruptive.

[Hardik K (hardikkaurani)]

Sorry, Vincent Biret (@baywet) I apologize for mentioning you on the microsoft/typespec repository without realizing it would be disruptive. I understand, and I’ll make sure not to mention you on this repository again. Thanks for letting me know.

[Libba Lawrence (l0lawrence)]

Hardik K (@hardikkaurani) there is already a pr out to address this, thank you for the contribution. Closing this as a duplicate