feat(propagation): adopt envcar carrier for TRACEPARENT#36
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Why: #33 / #390 - align env-based trace context propagation with the OTel env-carriers spec by reusing the shared go.opentelemetry.io/contrib carrier instead of hand-formatting TRACEPARENT= strings. Approach: Postel's law, per Amy's guidance. Accept leniently, emit strictly. - Read: envcar.Carrier.Get("traceparent") (spec key normalization) parsed by otel-cli's lenient w3c parser, so upper-case hex is still accepted and downcased rather than rejected. - Emit: route injection through propagation.TraceContext.Inject + an envcar.Carrier{SetEnvFunc}, which guarantees only spec-valid lower-case W3C is ever written, and refuses to emit an invalid/all-zero context. - New otelcli/propagation.go holds the bridge (envCarrierTraceparent, injectTraceparent, spanContextFromTraceparent). config_span.go reads via it; exec.go injects child env via it. Learned: the standard W3C propagator is strict (rejects upper-case + all-zero), so we deliberately keep our lenient parser on the read side and only delegate the *emit* side to the propagator. The pre-existing upper-case fixture stays green because we still accept it and already emit lower-case. Tests: - otelcli/propagation_test.go: graceful upper-case read, empty carrier, strict lower-case emit, and skip-invalid emit. All proven to fail when broken. - functional: exec normalizes an upper-case TRACEPARENT into the child env. Next: #34 - TRACESTATE + BAGGAGE via a composite propagator. Refs #31, #33 🤖 Claude <claude@anthropic.com>
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Closes #33. Part of #31 (mirrors equinix-labs/otel-cli#390).
Routes otel-cli's environment-variable trace context propagation through the shared
go.opentelemetry.io/contrib/propagators/envcarcarrier instead of hand-formattingTRACEPARENT=strings.Design: Postel's law (per maintainer guidance)
Accept leniently, emit strictly.
envcar.Carrier.Get("traceparent")(spec key-normalization) parsed by otel-cli's existing lenient W3C parser. Upper-case hex and other lenient input is still accepted and downcased, not rejected. The standardpropagation.TraceContextpropagator is deliberately not used on the read side because it's spec-strict (rejects upper-case + all-zero).propagation.TraceContext.Inject+ anenvcar.Carrier{SetEnvFunc}, which guarantees only spec-valid lower-case W3C is ever written into a child process env, and refuses to emit an invalid/all-zero context.New
otelcli/propagation.goholds the bridge:envCarrierTraceparent,injectTraceparent,spanContextFromTraceparent.config_span.goreads through it;exec.goinjects the child env through it.Compatibility
--tp-*flags,OTEL_CLI_*env vars,--tp-required/--tp-ignore-env, the{{traceparent}}arg substitution, and the shell-sourceabletp-carrierfile format are unchanged (w3c/traceparentstays the file parser/encoder — envcar is env-only).TRACEPARENTfixture stays green: we still accept it and already emit lower-case.Tests
otelcli/propagation_test.go— graceful upper-case read, empty carrier, strict lower-case emit, skip-invalid emit. Each verified to fail when the implementation is broken.otel-cli execnormalizes an upper-caseTRACEPARENTinto a strict lower-case value in the child's environment (proven to bite).Verification
go build✅ ·go vet ./...✅ ·gofmt -l .clean ✅ ·go test ./...(full functional + unit) ✅Follow-ups (noted, out of scope)
{{traceparent}}shadowing in exec non-recording mode;w3c/traceparent.LoadFromEnvnow has no production callers. (tracked in docs/issues.md)Refs #31, #33
🤖 Generated with Claude Code