Open enum union proposal #2787
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Open enum union proposal #2787
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msosnicki
commented
Sep 30, 2025
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| ## Abstract | ||
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| In the Smithy 2.0 specification enums and unions are treated as strictly **open**: adding a member is always treated as a backward‑compatible change and clients are expected to handle unknown members at runtime. This RFC proposes to update the spec and loosen the strict requirements around open enums and unions, acknowledging the fact that for some use cases and protocols it may not be desireable. It will also align the spec closer to reality, as smithy4s do not follow the current spec. |
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Currently the smithy-trait-codegen also do not follow the spec, see here
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Background
Proposal to loosen the enum and union openness requirement in the smithy spec
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