fix: use invalid parent for sampler when options.root

[dyladan]

Fixes #2166 by providing a parent span with an invalid span context to the sampler

From the spec:

ShouldSample
Returns the sampling Decision for a Span to be created.

Required arguments:

• Context with parent Span. The Span's SpanContext may be invalid to indicate a root span.

[codecov]

Codecov Report

Merging #2185 (09f4333) into main (3f82ff4) will increase coverage by 1.07%.
The diff coverage is n/a.

❗ Current head 09f4333 differs from pull request most recent head f65c5c8. Consider uploading reports for the commit f65c5c8 to get more accurate results

@@            Coverage Diff             @@
##             main    #2185      +/-   ##
==========================================
+ Coverage   92.72%   93.79%   +1.07%     
==========================================
  Files         141       53      -88     
  Lines        5087     1709    -3378     
  Branches     1045      356     -689     
==========================================
- Hits         4717     1603    -3114     
+ Misses        370      106     -264     

Impacted Files	Coverage Δ
...s/opentelemetry-core/src/platform/node/sdk-info.ts	0.00% <0.00%> (-100.00%)	⬇️
...pentelemetry-core/src/platform/node/performance.ts	0.00% <0.00%> (-100.00%)	⬇️
...emetry-api-metrics/src/platform/node/globalThis.ts	0.00% <0.00%> (-100.00%)	⬇️
...ckages/opentelemetry-exporter-zipkin/src/zipkin.ts	83.92% <0.00%> (-16.08%)	⬇️
...y-instrumentation-grpc/src/enums/AttributeNames.ts
...ges/opentelemetry-instrumentation-http/src/http.ts
...ontext-async-hooks/src/AsyncHooksContextManager.ts
...ges/opentelemetry-metrics/src/SumObserverMetric.ts
...emetry-instrumentation-grpc/src/instrumentation.ts
packages/opentelemetry-resources/src/Resource.ts
... and 81 more

[Flarna]

I think context.deleteValue(SPAN_KEY) would be the correct approach here. I have seen several places around where checks like if (getSpan(context) != null) are done to detect presence of a parent.

[dyladan]

Spec states that "The Span's SpanContext may be invalid to indicate a root span." and there is no function to remove span from context currently. We don't have the SPAN_KEY outside of the API

[Flarna]

ok.

Maybe we should add deleteSpan(context) (and deleteBaggage(context)) at some time?

[vmarchaud]

Maybe we should add deleteSpan(context) (and deleteBaggage(context)) at some time?

totally make sense