Aias00 opened a new pull request, #3433:
URL: https://github.com/apache/dubbo-go/pull/3433
## Problem
`metadataSupplier` in `filter/otel/trace/attachment.go` has a type mismatch
between `Get` and `Set`:
- **`Set`** stores values as `string`: `s.metadata[key] = value`
- **`Get`** reads values as `[]string`: `s.metadata[key].([]string)`
When the OTel propagator calls `Inject` (which uses `Set`) followed by
`Extract` (which uses `Get`), the type assertion in `Get` fails and returns an
empty string. This breaks trace context propagation — `traceparent` and other
W3C trace headers are silently lost.
This is also a partial root cause of #3240 (traceparent being broken by
triple_invoker).
## Fix
### `Set` — store `[]string{value}` instead of `string`
This aligns with how triple's `generateAttachments` stores `http.Header`
values (as `[]string`), which is the data source on the Extract (server) side.
### `Get` — add defensive `string` type handling
In addition to `[]string`, `Get` now also handles plain `string` values.
This matches the pattern used by `RPCInvocation.GetAttachment` and provides
robustness against externally-set string values.
## Test Coverage
- Added `string value (defensive read)` test case — verifies Get reads
string type
- Added `non-string non-slice value` test case — verifies safe fallback
- Added `Test_metadataSupplier_SetGetRoundTrip` — the core bug scenario: Set
then Get must succeed, and stored type must be `[]string`
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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