streams: drop dead ended = false in NetworkSink and FetchRequestBodySink start

[robobun]

What

NetworkSink::start and FetchRequestBodySink::start both return early when self.ended is set and then assigned self.ended = false a few lines later, so the assignment could only ever write false over false. Removed in both places. No behaviour change.

Related: #36770 reworks NetworkSink's lifecycle flags more broadly; this is just the two dead lines.

Verification

bun bd test test/js/bun/s3/s3.test.ts test/js/web/fetch/fetch.stream.test.ts test/js/web/fetch/body.test.ts test/js/web/fetch/fetch-abort-stream-body.test.ts passes (the S3 cases that run against a local server included).

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Review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 9fcdea8 and c85871d.

📒 Files selected for processing (2)

• src/runtime/webcore/fetch/FetchRequestBodySink.rs
• src/runtime/webcore/streams.rs

---

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[claude]

LGTM — both removed assignments are provably dead.

What was reviewed:

• Confirmed both start() methods early-return when self.ended is true, so the removed self.ended = false could only ever write false over false.
• Checked that ended defaults to false in both structs, so no first-call initialization is lost.
• No other callers or side effects touched.

Extended reasoning...

Overview

This PR removes one dead line from each of NetworkSink::start (src/runtime/webcore/streams.rs) and FetchRequestBodySink::start (src/runtime/webcore/fetch/FetchRequestBodySink.rs). Both functions begin with if self.ended { return Ok(()); }, so control flow can only reach the removed self.ended = false; when self.ended is already false. The assignment is a tautological no-op.

Security risks

None. This is pure dead-code removal in stream sink initialization; no input handling, allocation, or lifecycle logic is changed.

Level of scrutiny

Very low. The change is two deleted lines whose deadness is locally provable from the guard three lines above each. ended is initialized to false in Default::default() for both structs, so there is no scenario where this assignment did useful first-time initialization. The PR description accurately characterizes the change and references #36770 as the broader lifecycle rework this trims ahead of.

Other factors

The author ran the relevant fetch/S3 stream test suites. No new tests are needed since there is no observable behavior to assert — this is exactly the "delete dead code in the same PR that makes it dead" pattern the review guidelines call for. No prior reviewer comments to address.

[github-actions]

This PR may be a duplicate of:

1. streams: collapse NetworkSink and HTTPServerWritable lifecycle bools into ordered state enums #36770 - Replaces NetworkSink's lifecycle bools with a state enum and deletes the identical self.ended = false; line from NetworkSink::start in src/runtime/webcore/streams.rs.
2. streams: remove NetworkSink's write-only cancel flag and unreachable EOF branch #37407 - Removes dead NetworkSink lifecycle-flag code (cancel field, unreachable if !self.ended EOF branch) in the same struct and file, from the same cleanup sweep.

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