Add tests for malformed selectors in readers (#4350)

CHANGELOG.md

@@ -44,6 +44,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Fix `resource.WithHostID()` to not set an empty `host.id`. (#4317)
 - Use the instrument identifying fields to cache aggregators and determine duplicate instrument registrations in `go.opentelemetry.io/otel/sdk/metric`. (#4337)
 - Detect duplicate instruments for case-insensitive names in `go.opentelemetry.io/otel/sdk/metric`. (#4338)
+- The `ManualReader` will not panic if `AggregationSelector` returns `nil`. (#4350)
+- If a Reader's AggregationSelector return nil or DefaultAggregation the pipeline will use the default aggregation. (#4350)
 - Log a suggested view that fixes instrument conflicts in `go.opentelemetry.io/otel/sdk/metric`. (#4349)
 - Fix possible panic, deadlock and race condition in batch span processor in `go.opentelemetry.io/otel/sdk/trace`. (#4353)
 

sdk/metric/manual_reader.go

@@ -227,6 +227,9 @@ func WithAggregationSelector(selector AggregationSelector) ManualReaderOption {
 	// Deep copy and validate before using.
 	wrapped := func(ik InstrumentKind) aggregation.Aggregation {
 		a := selector(ik)
+		if a == nil {
+			return nil
+		}
 		cpA := a.Copy()
 		if err := cpA.Err(); err != nil {
 			cpA = DefaultAggregationSelector(ik)

sdk/metric/meter_test.go

@@ -28,6 +28,7 @@ import (
 
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/internal/global"
 	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
 	"go.opentelemetry.io/otel/sdk/metric/aggregation"
@@ -1811,3 +1812,148 @@ func BenchmarkInstrumentCreation(b *testing.B) {
 		sfHistogram, _ = meter.Float64Histogram("sync.float64.histogram")
 	}
 }
+
+func testNilAggregationSelector(InstrumentKind) aggregation.Aggregation {
+	return nil
+}
+func testDefaultAggregationSelector(InstrumentKind) aggregation.Aggregation {
+	return aggregation.Default{}
+}
+func testUndefinedTemporalitySelector(InstrumentKind) metricdata.Temporality {
+	return metricdata.Temporality(0)
+}
+func testInvalidTemporalitySelector(InstrumentKind) metricdata.Temporality {
+	return metricdata.Temporality(255)
+}
+
+type noErrorHandler struct {
+	t *testing.T
+}
+
+func (h noErrorHandler) Handle(err error) {
+	assert.NoError(h.t, err)
+}
+
+func TestMalformedSelectors(t *testing.T) {
+	type testCase struct {
+		name   string
+		reader Reader
+	}
+	testCases := []testCase{
+		{
+			name:   "nil aggregation selector",
+			reader: NewManualReader(WithAggregationSelector(testNilAggregationSelector)),
+		},
+		{
+			name:   "nil aggregation selector periodic",
+			reader: NewPeriodicReader(&fnExporter{aggregationFunc: testNilAggregationSelector}),
+		},
+		{
+			name:   "default aggregation selector",
+			reader: NewManualReader(WithAggregationSelector(testDefaultAggregationSelector)),
+		},
+		{
+			name:   "default aggregation selector periodic",
+			reader: NewPeriodicReader(&fnExporter{aggregationFunc: testDefaultAggregationSelector}),
+		},
+		{
+			name:   "undefined temporality selector",
+			reader: NewManualReader(WithTemporalitySelector(testUndefinedTemporalitySelector)),
+		},
+		{
+			name:   "undefined temporality selector periodic",
+			reader: NewPeriodicReader(&fnExporter{temporalityFunc: testUndefinedTemporalitySelector}),
+		},
+		{
+			name:   "invalid temporality selector",
+			reader: NewManualReader(WithTemporalitySelector(testInvalidTemporalitySelector)),
+		},
+		{
+			name:   "invalid temporality selector periodic",
+			reader: NewPeriodicReader(&fnExporter{temporalityFunc: testInvalidTemporalitySelector}),
+		},
+		{
+			name: "both aggregation and temporality selector",
+			reader: NewManualReader(
+				WithAggregationSelector(testNilAggregationSelector),
+				WithTemporalitySelector(testUndefinedTemporalitySelector),
+			),
+		},
+		{
+			name: "both aggregation and temporality selector periodic",
+			reader: NewPeriodicReader(&fnExporter{
+				aggregationFunc: testNilAggregationSelector,
+				temporalityFunc: testUndefinedTemporalitySelector,
+			}),
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			origErrorHandler := global.GetErrorHandler()
+			defer global.SetErrorHandler(origErrorHandler)
+			global.SetErrorHandler(noErrorHandler{t})
+
+			defer func() {
+				_ = tt.reader.Shutdown(context.Background())
+			}()
+
+			meter := NewMeterProvider(WithReader(tt.reader)).Meter("TestNilAggregationSelector")
+
+			// Create All instruments, they should not error
+			aiCounter, err := meter.Int64ObservableCounter("observable.int64.counter")
+			require.NoError(t, err)
+			aiUpDownCounter, err := meter.Int64ObservableUpDownCounter("observable.int64.up.down.counter")
+			require.NoError(t, err)
+			aiGauge, err := meter.Int64ObservableGauge("observable.int64.gauge")
+			require.NoError(t, err)
+
+			afCounter, err := meter.Float64ObservableCounter("observable.float64.counter")
+			require.NoError(t, err)
+			afUpDownCounter, err := meter.Float64ObservableUpDownCounter("observable.float64.up.down.counter")
+			require.NoError(t, err)
+			afGauge, err := meter.Float64ObservableGauge("observable.float64.gauge")
+			require.NoError(t, err)
+
+			siCounter, err := meter.Int64Counter("sync.int64.counter")
+			require.NoError(t, err)
+			siUpDownCounter, err := meter.Int64UpDownCounter("sync.int64.up.down.counter")
+			require.NoError(t, err)
+			siHistogram, err := meter.Int64Histogram("sync.int64.histogram")
+			require.NoError(t, err)
+
+			sfCounter, err := meter.Float64Counter("sync.float64.counter")
+			require.NoError(t, err)
+			sfUpDownCounter, err := meter.Float64UpDownCounter("sync.float64.up.down.counter")
+			require.NoError(t, err)
+			sfHistogram, err := meter.Float64Histogram("sync.float64.histogram")
+			require.NoError(t, err)
+
+			callback := func(ctx context.Context, obs metric.Observer) error {
+				obs.ObserveInt64(aiCounter, 1)
+				obs.ObserveInt64(aiUpDownCounter, 1)
+				obs.ObserveInt64(aiGauge, 1)
+				obs.ObserveFloat64(afCounter, 1)
+				obs.ObserveFloat64(afUpDownCounter, 1)
+				obs.ObserveFloat64(afGauge, 1)
+				return nil
+			}
+			_, err = meter.RegisterCallback(callback, aiCounter, aiUpDownCounter, aiGauge, afCounter, afUpDownCounter, afGauge)
+			require.NoError(t, err)
+
+			siCounter.Add(context.Background(), 1)
+			siUpDownCounter.Add(context.Background(), 1)
+			siHistogram.Record(context.Background(), 1)
+			sfCounter.Add(context.Background(), 1)
+			sfUpDownCounter.Add(context.Background(), 1)
+			sfHistogram.Record(context.Background(), 1)
+
+			var rm metricdata.ResourceMetrics
+			err = tt.reader.Collect(context.Background(), &rm)
+			require.NoError(t, err)
+
+			require.Len(t, rm.ScopeMetrics, 1)
+			require.Len(t, rm.ScopeMetrics[0].Metrics, 12)
+		})
+	}
+}

sdk/metric/pipeline.go

@@ -311,6 +311,11 @@ func (i *inserter[N]) cachedAggregator(scope instrumentation.Scope, kind Instrum
 	case nil, aggregation.Default:
 		// Undefined, nil, means to use the default from the reader.
 		stream.Aggregation = i.pipeline.reader.aggregation(kind)
+		switch stream.Aggregation.(type) {
+		case nil, aggregation.Default:
+			// If the reader returns default or nil use the default selector.
+			stream.Aggregation = DefaultAggregationSelector(kind)
+		}
 	}
 
 	if err := isAggregatorCompatible(kind, stream.Aggregation); err != nil {

sdk/metric/reader.go

@@ -145,6 +145,9 @@ func DefaultTemporalitySelector(InstrumentKind) metricdata.Temporality {
 
 // AggregationSelector selects the aggregation and the parameters to use for
 // that aggregation based on the InstrumentKind.
+//
+// If the Aggregation returned is nil or DefaultAggregation, the selection from
+// DefaultAggregationSelector will be used.
 type AggregationSelector func(InstrumentKind) aggregation.Aggregation
 
 // DefaultAggregationSelector returns the default aggregation and parameters