Add array serialization to logging_exporter (#1994)

Bug fix - adds serialization of array attributes, including nested arrays, in the `logging_exporter`. This allows them to be printed like the primitive attribute types when debugging. AFAICT, there aren't any attributes with array values today, but they are permitted types in the [spec](https://github.com/open-telemetry/opentelemetry-specification/blob/master/semantic_conventions/syntax.md#attributes), and I will be contributing a resource detector that uses array attributes in the future.

exporter/loggingexporter/logging_exporter.go

@@ -278,11 +278,28 @@ func attributeValueToString(av pdata.AttributeValue) string {
  return strconv.FormatFloat(av.DoubleVal(), 'f', -1, 64)
  case pdata.AttributeValueINT:
  return strconv.FormatInt(av.IntVal(), 10)
+ case pdata.AttributeValueARRAY:
+ return attributeValueArrayToString(av.ArrayVal())
  default:
  return fmt.Sprintf("<Unknown OpenTelemetry attribute value type %q>", av.Type())
  }
 }
 
+func attributeValueArrayToString(av pdata.AnyValueArray) string {
+ var b strings.Builder
+ b.WriteByte('[')
+ for i := 0; i < av.Len(); i++ {
+ if i < av.Len()-1 {
+ fmt.Fprintf(&b, "%s, ", attributeValueToString(av.At(i)))
+ } else {
+ b.WriteString(attributeValueToString(av.At(i)))
+ }
+ }
+
+ b.WriteByte(']')
+ return b.String()
+}
+
 type loggingExporter struct {
  logger *zap.Logger
  debug bool

exporter/loggingexporter/logging_exporter_test.go

@@ -22,6 +22,7 @@ import (
  "go.uber.org/zap"
 
  "go.opentelemetry.io/collector/config/configmodels"
+ "go.opentelemetry.io/collector/consumer/pdata"
  "go.opentelemetry.io/collector/internal/data/testdata"
 )
 
@@ -69,3 +70,21 @@ func TestLoggingLogsExporterNoErrors(t *testing.T) {
 
  assert.NoError(t, lle.Shutdown(context.Background()))
 }
+
+func TestNestedArraySerializesCorrectly(t *testing.T) {
+ av := pdata.NewAnyValueArray()
+ ava := pdata.NewAttributeValueArray()
+ av.Append(pdata.NewAttributeValueString("foo"))
+ av.Append(pdata.NewAttributeValueInt(42))
+
+ av2 := pdata.NewAnyValueArray()
+ av2.Append(pdata.NewAttributeValueString("bar"))
+ ava2 := pdata.NewAttributeValueArray()
+ ava2.SetArrayVal(av2)
+
+ av.Append(ava2)
+ ava.SetArrayVal(av)
+
+ assert.Equal(t, 3, ava.ArrayVal().Len())
+ assert.Equal(t, "[foo, 42, [bar]]", attributeValueToString(ava))
+}