feat(codegen): experimental SSE (text/event-stream) event stream protocol#2177
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goelakash wants to merge 2 commits into
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feat(codegen): experimental SSE (text/event-stream) event stream protocol#2177goelakash wants to merge 2 commits into
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Server SDK generation stubbed the event stream serde context type as `& any` and never supplied an event stream marshaller, so generated SSDK code for operations with event streams did not type-check. Type the response serializer / request deserializer context with __EventStreamSerdeContext, and wire the Node eventStreamSerdeProvider into the handler's serde context base (it only needs utf8 encode/decode, which the base already provides). Adds server event stream codegen tests, which were previously absent.
Adds an experimental sseJson protocol whose event streams are framed as Server-Sent Events instead of the binary vnd.amazon.eventstream encoding, so a Smithy model can generate a server that streams over text/event-stream. - SseEventStreamMarshaller in @smithy/core/event-streams: an EventStreamMarshaller that frames messages as SSE, with the same options and callback contract as the binary marshaller. - ProtocolGenerator.getEventStreamSerdeProviderName lets a protocol choose which provider the generated handler wires into its serde context; defaults to the binary provider. - SseJsonProtocolGenerator + sseJson trait: an HTTP protocol that overrides the provider to emit the SSE marshaller. Document body serde for non-streaming members is not yet implemented. Gated behind the experimentalSseProtocol smithy-build setting; when unset, the protocol is not registered and codegen output is unchanged.
This was referenced Jul 22, 2026
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Implements the proposal in #2176: lets a Smithy model generate a server whose event streams are framed as Server-Sent Events (
text/event-stream) instead of the binaryvnd.amazon.eventstreamencoding.Opt-in, twice over: everything is gated behind the
experimentalSseProtocolsmithy-build setting (registered in the CONTRIBUTING experimental-features table), and even then only activates on services carrying the newsseJsontrait. With the flag unset — the default — the protocol isn't registered and codegen output is byte-for-byte unchanged; a test asserts this.What's inside:
SseEventStreamMarshallerin@smithy/core/event-streams: same options and callback contract as the binary marshaller, so the two are interchangeable. Maps:event-typeto the SSEevent:field, body todata:line(s), modeled exceptions toevent: exception:<code>. WHATWG-spec line-terminator handling (CR/LF/CRLF), incremental cross-chunk parsing.ProtocolGenerator.getEventStreamSerdeProviderName(): a protocol can now choose which provider the generated handler wires into its serde context (default: binary). This is the seam from fix(codegen): support event streams in server SDK serde context #2175.sseJsontrait +SseJsonProtocolGenerator: an HTTP-binding protocol that selects the SSE provider. Scope note: document body serde for non-streaming members is stubbed — this PR is about the event stream framing; full JSON body serde is follow-up work.Testing: marshaller round-trip/chunk-boundary/CR-CRLF/exception specs; codegen tests generating an SSDK from an
@sseJsonmodel asserting the SSE provider wiring; a gate test proving inertness without the flag. Full gradle build passes (checkstyle, spotbugs).Note: this branch is stacked on #2175 (its first commit) — the serde-context seam it builds on.