Add AppendLogicalError method to append a logical error if needed

helper/awsutil/error.go

@@ -2,6 +2,7 @@ package awsutil
 
 import (
 	awsRequest "github.com/aws/aws-sdk-go/aws/request"
+	multierror "github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/vault/logical"
 )
 
@@ -16,3 +17,15 @@ func CheckAWSError(err error) error {
 	}
 	return nil
 }
+
+// AppendLogicalError checks if the given error is a known AWS error we modify,
+// and if so then returns a go-multierror, appending the original and the
+// logical error.
+// If the error is not an AWS error, or not an error we wish to modify, then
+// return the original error.
+func AppendLogicalError(err error) error {
+	if awserr := CheckAWSError(err); awserr != nil {
+		err = multierror.Append(err, awserr)
+	}
+	return err
+}

helper/awsutil/error_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/aws/aws-sdk-go/aws/awserr"
+	multierror "github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/vault/logical"
 )
 
@@ -50,3 +51,44 @@ func Test_CheckAWSError(t *testing.T) {
 		})
 	}
 }
+
+func Test_AppendLogicalError(t *testing.T) {
+	awsErr := awserr.New("Throttling", "", nil)
+	testCases := []struct {
+		Name     string
+		Err      error
+		Expected error
+	}{
+		{
+			Name:     "Something not checked",
+			Err:      fmt.Errorf("something"),
+			Expected: fmt.Errorf("something"),
+		},
+		{
+			Name:     "Upstream throttle error",
+			Err:      awsErr,
+			Expected: multierror.Append(awsErr, logical.ErrUpstreamRateLimited),
+		},
+		{
+			Name: "Nil",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.Name, func(t *testing.T) {
+			err := AppendLogicalError(tc.Err)
+			if err == nil && tc.Expected != nil {
+				t.Fatalf("expected non-nil error (%#v), got nil", tc.Expected)
+			}
+			if err != nil && tc.Expected == nil {
+				t.Fatalf("expected nil error, got (%#v)", err)
+			}
+			if err == nil && tc.Expected == nil {
+				return
+			}
+			if err.Error() != tc.Expected.Error() {
+				t.Fatalf("expected error (%#v), got (%#v)", tc.Expected.Error(), err.Error())
+			}
+		})
+	}
+}