feat(statusx): expose error metadata via x-status-metadata response header#593
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…eader vproto.ValidationError has no metadata field, so metadata set via statusx.WithMetadata would be lost on the vproto HTTP error path (unlike the connect path, which carries it natively in error details). Expose it out-of-band on the x-status-metadata response header: a JSON-encoded, URL-escaped map[string]string, set only when the error carries metadata. Add var ExposedHeaders (symmetric to AllowHeaders) so downstreams using the vproto path can wire the header into their CORS ExposedHeaders. The header ownership stays in statusx; httpx is left unchanged. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
molon
approved these changes
Jun 16, 2026
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What
On the vproto HTTP error path, error metadata set via
statusx.WithMetadatawas being dropped, becausevproto.ValidationErrorhas no metadata field. This exposes it out-of-band on a response header.x-status-metadata(JSON-encoded, URL-escapedmap[string]string) on the response, only when the error actually carries metadata.var ExposedHeaders(symmetric to the existingvar AllowHeaders) so downstreams using the vproto path can concat it into their CORSExposedHeaders.Why this lives in statusx, not httpx
The connect protocol path already carries metadata natively in the error details (see
ConvertToConnectError), so it needs no header. Only the vproto path needs this workaround, because its message schema lacks the field.That means it would be wrong to wire the header into
httpx.Security(the generic CORS middleware) — a service that doesn't use vproto would get anx-status-metadataheader exposed that it never sets. The header is part of statusx's error protocol, so its ownership and itsExposedHeadersdeclaration stay in statusx.httpxis left untouched. Downstreams that use the vproto path opt in by addingstatusx.ExposedHeadersto their CORS config.Test
TestWriteVProtoHTTPError_MetadataHeader: header is set with the correct encoding when metadata is present, and omitted when absent.🤖 Generated with Claude Code