fix: methods returning Promise<RpcStub<T>> no longer produce stub-of-stub result types - #253
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…ult types The string-keyed `__RPC_TARGET_BRAND` (and the workers brands in capnweb-validate) leaked into the keyof-based Provider/ValidatedStub key mapping, so a stub of a branded target still matched `Stubable` structurally. A method declared as `Promise<RpcStub<T>>` therefore had its already-stubbed result stubified again, producing a broken stub-of-stub type: awaits yielded `RpcStub<RpcStub<T>>` (TS2322) and passing the result as a pipelined argument failed (TS2345). Excluding the brand keys from stub surfaces fixes the root cause; on top of that, `Result` now elides declared stub returns via `ElideStub`, so `Promise<RpcStub<T>>` returns produce exactly the same `RpcPromise<T>` as `Promise<T>` returns. Elision is the chosen policy for stubable payloads only: such stubs await back to a stub either way, so the two declarations are genuinely interchangeable. Plain-interface stubs (`RpcStub<PlainApi>`) and `RpcStub<any>` are deliberately NOT elided — their awaited type would change if they were. The workerd interop tests gain `<any>` casts where a userspace stub is handed to workers-types' native `RpcStub`: without the leaked brand, a userspace stub no longer statically matches workers-types' `Stubable` (runtime interop is unchanged).
Restoring `__RPC_TARGET_BRAND` in the Provider key mapping keeps userspace stubs structurally assignable to workers-types' `Stubable`, so `new RpcStub(userspaceStub)` from `cloudflare:workers` typechecks again without casts (as it did before the brand exclusion). The brand exclusion turns out to be unnecessary for the stub-of-stub fix: `Stubify`/`Result`/`ElideStub` all check `StubBase` before `Stubable`, so a stub matching `Stubable` is caught as a stub first and never re-stubified. That ordering is the same mechanism that already protects callable stubs, which genuinely match `Stubable` and cannot have that excluded. Known residual: an explicit `RpcPromise<RpcStub<T>>` annotation still produces the old double-stub shape (matching main); the changeset already directs users to write `RpcPromise<T>` instead.
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type level tests, woop woop
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Presently declaring an RPC method to return
Promise<RpcStub<T>>gave you a broken type: an internal brand property made the type machinery treat the already-stubbed result as something that still needed wrapping, so awaiting yieldedRpcStub<RpcStub<T>>(TS2322) and passing the result into another RPC call failed to compile (TS2345), even though the runtime behaved correctly.Now the type machinery recognizes existing stubs before re-wrapping, so a
Promise<RpcStub<T>>return types identically to aPromise<T>return and awaits, pipelined calls, and .map() over stub arrays all compile.Nothing changes at runtime; the one migration is rewriting any explicit
RpcPromise<RpcStub<T>>annotation asRpcPromise<T>.