[processor/tailsampling] fix InvertNotSampled decision precedence when inside and sub policy

.chloggen/fix-tailsampling-and-policy-precedence.yaml

@@ -0,0 +1,9 @@
+change_type: bug_fix
+component: tailsamplingprocessor
+note: Fix precedence of inverted match in and policy
+issues: [33671]
+subtext: |
+  Previously if the decision from a policy evaluation was `NotSampled` or `InvertNotSampled` it would return a `NotSampled` decision regardless, effectively downgrading the result.
+
+  This was breaking the documented behaviour that inverted decisions should take precedence over all others.
+change_logs: [user]

processor/tailsamplingprocessor/internal/sampling/and.go

@@ -30,14 +30,14 @@ func NewAnd(
 // Evaluate looks at the trace data and returns a corresponding SamplingDecision.
 func (c *And) Evaluate(ctx context.Context, traceID pcommon.TraceID, trace *TraceData) (Decision, error) {
 	// The policy iterates over all sub-policies and returns Sampled if all sub-policies returned a Sampled Decision.
-	// If any subpolicy returns NotSampled, it returns NotSampled Decision.
+	// If any subpolicy returns NotSampled or InvertNotSampled it returns that
 	for _, sub := range c.subpolicies {
 		decision, err := sub.Evaluate(ctx, traceID, trace)
 		if err != nil {
 			return Unspecified, err
 		}
 		if decision == NotSampled || decision == InvertNotSampled {
-			return NotSampled, nil
+			return decision, nil
 		}
 
 	}

processor/tailsamplingprocessor/internal/sampling/and_test.go

@@ -113,6 +113,6 @@ func TestAndEvaluatorStringInvertNotSampled(t *testing.T) {
 	}
 	decision, err := and.Evaluate(context.Background(), traceID, trace)
 	require.NoError(t, err, "Failed to evaluate and policy: %v", err)
-	assert.Equal(t, decision, NotSampled)
+	assert.Equal(t, decision, InvertNotSampled)
 
 }