Remove duplicate code to combine errors. (#422)

Author: Bogdan Drutu

internal/collector/processor/multi_processor.go

@@ -15,8 +15,7 @@
 package processor
 
 import (
-	"fmt"
-	"strings"
+	"github.com/census-instrumentation/opencensus-service/internal"
 
 	"github.com/spf13/cast"
 
@@ -124,18 +123,5 @@ func (msp *multiSpanProcessor) ProcessSpans(batch *agenttracepb.ExportTraceServi
 			maxFailures = failures
 		}
 	}
-
-	var err error
-	numErrors := len(errors)
-	if numErrors == 1 {
-		err = errors[0]
-	} else if numErrors > 1 {
-		errMsgs := make([]string, numErrors)
-		for _, err := range errors {
-			errMsgs = append(errMsgs, err.Error())
-		}
-		err = fmt.Errorf("[%s]", strings.Join(errMsgs, "; "))
-	}
-
-	return maxFailures, err
+	return maxFailures, internal.CombineErrors(errors)
 }

internal/internal.go

@@ -16,7 +16,6 @@ package internal
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -102,14 +101,15 @@ func TimeToTimestamp(t time.Time) *timestamp.Timestamp {
 
 // CombineErrors converts a list of errors into one error.
 func CombineErrors(errs []error) error {
-	if len(errs) == 0 {
-		return nil
-	}
-
-	// Otherwise
-	buf := new(strings.Builder)
-	for _, err := range errs {
-		fmt.Fprintf(buf, "%v\n", err)
+	numErrors := len(errs)
+	if numErrors == 1 {
+		return errs[0]
+	} else if numErrors > 1 {
+		errMsgs := make([]string, numErrors)
+		for _, err := range errs {
+			errMsgs = append(errMsgs, err.Error())
+		}
+		return fmt.Errorf("[%s]", strings.Join(errMsgs, "; "))
 	}
-	return errors.New(buf.String())
+	return nil
 }