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internal/storage/types/location_config.go

@@ -6,7 +6,6 @@ import (
 	"errors"
 	"fmt"
 	"net/url"
-	"reflect"
 
 	"github.com/aws/aws-sdk-go/aws/credentials"
 	"github.com/aws/aws-sdk-go/aws/session"
@@ -48,27 +47,28 @@ func (c LocationConfig) MarshalJSON() ([]byte, error) {
 }
 
 func (c *LocationConfig) UnmarshalJSON(blob []byte) error {
-	types := configTypes{}
+	// Raise an error if the doc describes multiple configs.
+	keys := map[string]json.RawMessage{}
+	err := json.Unmarshal(blob, &keys)
+	if err != nil {
+		return err
+	}
+	if len(keys) > 1 {
+		return errors.New("multiple config values have been assigned")
+	}
 
+	types := configTypes{}
 	if err := json.Unmarshal(blob, &types); err != nil {
 		return err
 	}
 
-	errMultipleConfig := errors.New("multiple config values have been assigned")
 	switch {
 	case types.S3 != nil:
 		c.Value = types.S3
 	case types.SFTPConfig != nil:
-		if reflect.ValueOf(c.Value).IsValid() {
-			return errMultipleConfig
-		}
 		c.Value = types.SFTPConfig
 	case types.URLConfig != nil:
-		if reflect.ValueOf(c.Value).IsValid() {
-			return errMultipleConfig
-		}
 		c.Value = types.URLConfig
-
 	default:
 		return errors.New("undefined configuration document")
 	}

internal/storage/types/location_config_test.go

@@ -109,6 +109,16 @@ func TestLocationConfig(t *testing.T) {
 		err = json.Unmarshal(blob, &cfg)
 		assert.Error(t, err, "undefined configuration document")
 		assert.DeepEqual(t, cfg, types.LocationConfig{})
+
+		// It rejects multiple configs.
+		blob = []byte(`{
+			"s3":{"bucket":"perma-aips-1","region":"eu-west-1"},
+			"sftp":{"address":"sftp:22","username":"user","password":"secret","directory":"upload"}
+		}`)
+		cfg = types.LocationConfig{}
+		err = json.Unmarshal(blob, &cfg)
+		assert.Error(t, err, "multiple config values have been assigned")
+		assert.DeepEqual(t, cfg, types.LocationConfig{})
 	})
 }