fix(translation): accept SSE data without a space

[ting-hong-shieh]

What

• accept both data:{...} and data: {...} SSE fields
• remove at most one optional ASCII space after the field-name colon
• cover a no-space JSON payload and data:[DONE] in the shared stream decoder

Why

The SSE parser matched only the literal data: prefix, so valid upstream events without the optional space were silently ignored.

Closes #399

Validation

• cargo test -p switchyard-translation decode_stream_accepts_sse_data_without_optional_space -- --nocapture — passed
• cargo test -p switchyard-translation — passed
• cargo fmt --all --check — passed
• cargo clippy --workspace --all-targets -- -D warnings — passed
• cargo test --workspace — passed with loopback access enabled for the repository's local mock servers
• git diff --check — passed

No live provider calls or secrets were used.

Summary by CodeRabbit

• Bug Fixes
  • Improved streaming response parsing to accept data fields with or without a space after the colon.
  • Preserved support for termination markers such as [DONE].
• Tests
  • Added regression coverage for both supported data field formats.

[ting-hong-shieh]

Before / after output snapshot

I ran the same in-process SSE decode at the PR base (b256d936) and current head (a1f747bd). No HTTP or provider call was involved.

Input:

data:{"choices":[{"delta":{"content":"Hello"}}]}

data:[DONE]

Before (b256d936):

{"decoded_text":"","event_count":0}

Both no-space data: fields were ignored, so the text and terminal marker disappeared.

After (a1f747bd):

{"decoded_text":"Hello","event_count":1}

The JSON field is decoded and the no-space data:[DONE] marker terminates the stream without producing an extra event.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between b256d93 and a1f747b.

📒 Files selected for processing (2)

• crates/switchyard-translation/src/helpers.rs
• crates/switchyard-translation/src/sse.rs

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Walkthrough

The SSE parser now accepts data: fields with or without one space after the colon. A regression test covers space-less payload and [DONE] frames.

Changes

SSE parser fix

Layer / File(s)	Summary
SSE data parsing and regression coverage crates/switchyard-translation/src/sse.rs, crates/switchyard-translation/src/helpers.rs	The parser accepts both data: and data: prefixes and removes at most one optional space. The regression test validates payload decoding and [DONE] termination without the space.

Estimated code review effort: 2 (Simple) | ~10 minutes

Mergeability Score: ⚪ Minimal · up to a1f74

The decoder now accepts valid SSE data fields with or without one optional space, with no actionable merge-blocking risk remaining after normal checks and review.

Poem

I’m a rabbit with ears held high,
Parsing data as it hops by.
With one space or none in sight,
[DONE] ends the stream just right.
Carrots cheer the passing test!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: accepting SSE data fields without a space.
Linked Issues check	✅ Passed	The parser change and regression test satisfy issue #399 by accepting both SSE data formats and handling data:[DONE].
Out of Scope Changes check	✅ Passed	The changes are limited to the SSE parser fix and focused regression coverage required by issue #399.

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