fix(stdouttrace/observ): record error.type on opDuration when exportedSpans is disabled (#8432)

When `ExportOp.End` is called with a non-nil error and `exportedSpans`
metric is disabled but `opDuration` is enabled, the `error.type`
attribute is not included in the duration histogram record.

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -11,6 +11,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Fixed
 
 - Interpret HTTP `Retry-After` header values as seconds instead of nanoseconds when retrying OTLP HTTP exports in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`, `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`, `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8383)
+- Fix `go.opentelemetry.io/otel/exporters/stdout/stdouttrace` self-observability to record `error.type` on operation duration histogram when the `exportedSpans` metric is disabled. (#8432)
 
 <!-- Released section -->
 <!-- Don't change this section unless doing release -->

exporters/stdout/stdouttrace/internal/observ/instrumentation.go

@@ -205,7 +205,7 @@ func (e ExportOp) End(success int64, err error) {
 	}
 
 	mOpt := e.inst.setOpt
-	if err != nil && exportedSpansEnable {
+	if err != nil && (exportedSpansEnable || opDurationEnable) {
 		attrs := get[attribute.KeyValue](measureAttrsPool)
 		defer put(measureAttrsPool, attrs)
 		*attrs = append(*attrs, e.inst.attrs...)
@@ -216,10 +216,11 @@ func (e ExportOp) End(success int64, err error) {
 		set := attribute.NewSet(*attrs...)
 		mOpt = metric.WithAttributeSet(set)
 
-		// Reset addOpt with new attribute set.
-		*addOpt = append((*addOpt)[:0], mOpt)
-
-		e.inst.exportedSpans.Add(e.ctx, e.nSpans-success, *addOpt...)
+		if exportedSpansEnable {
+			// Reset addOpt with new attribute set.
+			*addOpt = append((*addOpt)[:0], mOpt)
+			e.inst.exportedSpans.Add(e.ctx, e.nSpans-success, *addOpt...)
+		}
 	}
 
 	if opDurationEnable {

exporters/stdout/stdouttrace/internal/observ/instrumentation_test.go

@@ -215,6 +215,101 @@ func TestInstrumentationExportSpansPartialErrored(t *testing.T) {
 	assertMetrics(t, collect(), n, success, assert.AnError)
 }
 
+func TestExportSpansErrorTypeRecorded(t *testing.T) {
+	exportedSpansName := otelconv.SDKExporterSpanExported{}.Name()
+	opDurationName := otelconv.SDKExporterOperationDuration{}.Name()
+	inflightSpansName := otelconv.SDKExporterSpanInflight{}.Name()
+
+	tests := []struct {
+		name              string
+		drop              string
+		errorOnExported   bool
+		errorOnOpDuration bool
+	}{
+		{
+			name:              "drop exportedSpans: opDuration still records error.type",
+			drop:              exportedSpansName,
+			errorOnOpDuration: true,
+		},
+		{
+			name:            "drop opDuration: exportedSpans still records error.type",
+			drop:            opDurationName,
+			errorOnExported: true,
+		},
+		{
+			name:              "drop inflightSpans: error.type still on exported and opDuration",
+			drop:              inflightSpansName,
+			errorOnExported:   true,
+			errorOnOpDuration: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Setenv("OTEL_GO_X_OBSERVABILITY", "true")
+
+			original := otel.GetMeterProvider()
+			t.Cleanup(func() { otel.SetMeterProvider(original) })
+
+			r := metric.NewManualReader()
+			mp := metric.NewMeterProvider(
+				metric.WithReader(r),
+				metric.WithView(metric.NewView(
+					metric.Instrument{Name: tt.drop},
+					metric.Stream{Aggregation: metric.AggregationDrop{}},
+				)),
+			)
+			otel.SetMeterProvider(mp)
+
+			inst, err := observ.NewInstrumentation(ID)
+			require.NoError(t, err)
+			require.NotNil(t, inst)
+
+			const n = 10
+			inst.ExportSpans(t.Context(), n).End(0, assert.AnError)
+
+			var rm metricdata.ResourceMetrics
+			require.NoError(t, r.Collect(t.Context(), &rm))
+			require.Len(t, rm.ScopeMetrics, 1)
+			got := rm.ScopeMetrics[0]
+
+			assert.Equal(t, Scope, got.Scope, "unexpected scope")
+
+			o := metricdatatest.IgnoreTimestamp()
+			seen := make(map[string]bool, 2)
+			for _, m := range got.Metrics {
+				seen[m.Name] = true
+				switch m.Name {
+				case exportedSpansName:
+					var exportedErr error
+					if tt.errorOnExported {
+						exportedErr = assert.AnError
+					}
+					metricdatatest.AssertEqual(t, spanExported(0, n, exportedErr), m, o)
+				case opDurationName:
+					var opErr error
+					if tt.errorOnOpDuration {
+						opErr = assert.AnError
+					}
+					metricdatatest.AssertEqual(
+						t, operationDuration(opErr), m, o, metricdatatest.IgnoreValue(),
+					)
+				case inflightSpansName:
+					metricdatatest.AssertEqual(t, spanInflight(), m, o)
+				}
+			}
+			// Verify the dropped instrument is absent and the other two are present.
+			assert.False(t, seen[tt.drop], "expected %q to be absent", tt.drop)
+			for _, name := range []string{exportedSpansName, opDurationName, inflightSpansName} {
+				if name == tt.drop {
+					continue
+				}
+				assert.True(t, seen[name], "expected %q to be present", name)
+			}
+		})
+	}
+}
+
 func BenchmarkInstrumentationExportSpans(b *testing.B) {
 	setup := func(b *testing.B) *observ.Instrumentation {
 		b.Helper()