fix(netty): preserve all redirect body types - #2316

Summary

• Build keep-body redirects from the original request, preserving every supported body representation and per-request setting.
• Clear target-specific routing and credential state when a redirect crosses an origin, including separately stored Cookie objects.
• Preserve an explicit Content-Length when replaying a raw InputStream or an unknown-length InputStreamBodyGenerator.
• Replay resettable streams and fail promptly for consumed raw streams, streamed multipart parts, and vanished files that cannot be replayed safely.
• Pin body bytes, headers, body-selection precedence, caller-owned ByteBuf references, and the new failure modes with focused tests.

Problem

Redirect30xInterceptor rebuilds a request when it follows a strict 302, 307, or 308 redirect. Its keep-body copy chain handled form parameters, strings, byte arrays, ByteBuffer, body generators, and multipart bodies, but omitted four real request send paths:

• List<byte[]> / composite byte arrays
• Netty ByteBuf
• InputStream
• File

The redirected request therefore kept its method and Content-Type but sent zero bytes. The File case is especially risky for uploads because the target can accept an apparently valid empty PUT or POST. Reconstructing the request field by field also omitted unrelated per-request state such as the read timeout and range offset, and maintaining a second body-selection chain alongside NettyRequestFactory made future drift likely.

This is a pre-existing omission. AHC issue #1643 previously fixed the same class of bug for multipart bodies. The copy chain was carried through pull request #1843 without a policy discussion. Focused searches found no existing issue or pull request covering these four representations.

Change

Build a keep-body redirect with request.toBuilder() and then replace only redirect-specific state. This preserves all current and future body representations and per-request options without duplicating NettyRequestFactory.body. Headers are copied before redirect-only values are removed, so the original request is not mutated.

On a cross-origin redirect, the copied request drops the previous resolved address, virtual host, realm, authorization headers, and Cookie objects before the cookie store adds cookies that legitimately match the new URI. The body is not covered by that boundary. It follows the existing keep-body policy, which means a File or InputStream body that a cross-origin redirect leg previously received as empty is now sent in full, and a target that keeps redirecting can receive it once per hop up to maxRedirects. That is the same exposure byte arrays, strings, form parameters, and multipart bodies already have today.

Composite byte arrays, caller-owned ByteBufs, and files are repeatable. A resettable InputStream, such as ByteArrayInputStream, also replays. A caller-supplied Content-Length is retained for a raw InputStream or an InputStreamBodyGenerator without a declared length, because neither has an intrinsic size from which to recompute it. A consumed stream that cannot be reset reaches the existing fail-fast guard added in #2312 and completes the future with IOException; that is preferable to silently succeeding with an empty body.

An InputStreamPart is closed by the first multipart send and has no equivalent replay guard, so a keep-body redirect now fails promptly instead of risking a hang or incomplete multipart request. A selected File or FileBodyGenerator is also checked before dispatching the redirect; if it disappeared after the first send, the future fails with IOException before a target pooled channel can be removed and an unchecked constructor exception can escape. The validation follows NettyRequestFactory precedence so a sticky File field is ignored when a higher-priority body representation was actually sent.

The change does not alter which methods or status codes keep a body, nor does it introduce a new cross-origin policy. It makes the existing strict-302, 307, and 308 behavior complete for every supported request-body representation.

Compatibility

There is no public API change. Requests that previously sent an empty body on a keep-body redirect now resend their configured body.

Behavior changes:

• A non-resettable InputStream on a keep-body redirect previously completed successfully after sending an empty redirected request. It now completes the request future exceptionally with IOException. This includes FileInputStream, which is closed after the first send and cannot be reset for replay.
• A multipart InputStreamPart now fails promptly with IOException when a keep-body redirect requires replay. Reusing its already-consumed and closed stream could previously hang or send incomplete multipart content.
• A selected file that disappears between the first request and redirect now fails with IOException before redirect dispatch rather than allowing an unchecked IllegalArgumentException to escape while constructing the next request.
• A File or InputStream body is now sent on a keep-body redirect to a different origin, where the redirected request previously carried no body. Credentials are still stripped at that boundary, but the payload is not.

Callers that accidentally relied on an empty or incomplete redirected request will observe an exception, but the failure is explicit instead of silently losing configured content. There is no public API change.

AI disclosure

OpenAI Codex on behalf of Matthias Kurz. The commit includes Co-Authored-By: OpenAI Codex <codex@openai.com> per AGENTS.md.

Test plan

• On untouched upstream/main, the focused suite reproduced five failures: four body types arrived as zero bytes and a non-resettable stream incorrectly completed successfully.
• Before the generator fix, a one-argument InputStreamBodyGenerator sent Content-Length: 13 on the first leg and no Content-Length on the redirected leg.
• ./mvnw -pl client -Dtest=RedirectBodyTest,RedirectCredentialSecurityTest test on JDK 11: 40 tests passed, including Netty leak detection.
• ./mvnw clean verify on JDK 11: 1,496 tests passed and Revapi completed without failures (BUILD SUCCESS).

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