fix(span): skip zero parent span id from empty traceparent (#23)

[tobert]

Summary

• When --tp-ignore-env is set, LoadTraceparent() returns a traceparent with Initialized=true but zeroed SpanId
• The code unconditionally set ParentSpanId = tp.SpanId, producing a span with an all-zeros parent
• Now checks bytes.Equal against GetEmptySpanId() before setting parent span id
• Added functional test that verifies --tp-ignore-env produces empty parent span id

Test plan

• New functional test in data_for_test.go: --tp-ignore-env with TRACEPARENT set, verify parent_span_id is empty
• All existing tests pass (go test && go test ./...)

Fixes #23

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes span parent linkage when a traceparent is “initialized” but has an all-zero SpanID (notably with --tp-ignore-env), preventing emission of a zero-valued parent_span_id.

Changes:

• Prevent setting ParentSpanId when the loaded traceparent SpanID is empty/all-zeros.
• Add a functional fixture verifying --tp-ignore-env results in an empty parent_span_id.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
otelcli/config_span.go	Adds a guard to avoid assigning an all-zero parent span id from traceparent.
data_for_test.go	Adds a functional test/fixture to validate empty parent_span_id behavior with --tp-ignore-env.

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[Copilot]

Minor readability improvement: consider storing otlpclient.GetEmptySpanId() in a local variable (e.g., emptySpanID := ...) before the if, so the comparison reads more clearly and avoids repeating a function call in the condition.

Suggested change

	if tp.Initialized {
	span.TraceId = tp.TraceId
	span.ParentSpanId = tp.SpanId
	// only set parent span id when the traceparent has a real (non-zero) span id (#23)
	if !bytes.Equal(tp.SpanId, otlpclient.GetEmptySpanId()) {
	emptySpanID := otlpclient.GetEmptySpanId()
	if tp.Initialized {
	span.TraceId = tp.TraceId
	// only set parent span id when the traceparent has a real (non-zero) span id (#23)
	if !bytes.Equal(tp.SpanId, emptySpanID) {

[Copilot]

The comment says “zero-valued parent span id”, but the assertion checks for an empty string (i.e., omitted/empty parent_span_id), not the all-zeros hex representation. Consider rewording the comment and/or test name to explicitly say the parent span id should be empty/omitted (and not 0000000000000000).

Suggested change

	// #23: --tp-ignore-env should not produce a zero-valued parent span id
	{
	{
	Name: "#23 --tp-ignore-env should not send zero parent span id",
	// #23: --tp-ignore-env should result in an empty/omitted parent span id (not 0000000000000000)
	{
	{
	Name: "#23 --tp-ignore-env should omit parent span id (empty/omitted, not 0000000000000000)",

[Copilot]

The comment says “zero-valued parent span id”, but the assertion checks for an empty string (i.e., omitted/empty parent_span_id), not the all-zeros hex representation. Consider rewording the comment and/or test name to explicitly say the parent span id should be empty/omitted (and not 0000000000000000).