Rust: move the redirect option onto the builder — 3.7.0 was breaking

[brentrager]

What went wrong in 3.7.0

I added RequestInit.follow_redirects and shipped it as a minor. Adding a public field to a struct consumers construct is a breaking change in Rust semver.

Building the SmooAI monorepo against 3.7.0:

error[E0063]: missing field `follow_redirects` in initializer of `RequestInit`

129 exhaustive constructors across ~40 crates.

I had this evidence an hour before publishing — adding the field broke this repo's own tests, and I patched them and treated it as test churn rather than the semver signal it was.

The fix

The option moves to FetchBuilder::with_follow_redirects, matching what Go and .NET already do, and RequestInit returns to its 3.6.2 fields.

This isn't only damage control. reqwest's redirect policy is per-Client, not per-request, so the builder was the correct home from the start — the struct field was working against the grain of the underlying library.

Kept fully additive

client::fetch keeps its exact signature and delegates to a new client::fetch_with_redirect_policy that takes the extra argument. So 3.6.2 → 3.7.1 requires no consumer changes at all.

The wiring bug worth naming

with_follow_redirects stored a value that reached FetchClient and then went nowhere — both fetch methods still called the old entry point. The setter compiled; the option did nothing.

That is the same failure as .NET's SmooFetchBuilder.Build() dropping FollowRedirects during its field-by-field copy. In both languages, only an end-to-end test that actually watched for the redirect hop caught it. A unit test asserting "the builder stored the flag" would have passed in both.

Verification

• 14 Rust test suites green, cargo fmt --check and clippy -D warnings clean
• RequestInit has no follow_redirects field — only a doc comment pointing at the builder
• The monorepo's 129 constructors compile untouched

3.7.0 will be yanked from crates.io once this publishes. The other four languages are unaffected: Python added a defaulted dataclass field, Go and .NET added builder methods, TypeScript's change was to stop overriding a caller's existing option.

Pearl: th-86dc77

🤖 Generated with Claude Code

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🦋 Changeset detected

Latest commit: 85b0158

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@smooai/fetch	Patch

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