Small improvements for transaction metadata

internal/datastore/crdb/crdb.go

@@ -338,7 +338,7 @@ func (cds *crdbDatastore) ReadWriteTx(
 		}
 
 		// If metadata is to be attached, write that row now.
-		if config.Metadata != nil {
+		if config.Metadata != nil && len(config.Metadata.GetFields()) > 0 {
 			expiresAt := time.Now().Add(cds.gcWindow).Add(1 * time.Minute)
 			insertTransactionMetadata := psql.Insert(tableTransactionMetadata).
 				Columns(colExpiresAt, colMetadata).

internal/datastore/memdb/memdb.go

@@ -205,7 +205,7 @@ func (mdb *memdbDatastore) ReadWriteTx(
 
 		tracked := common.NewChanges(revisions.TimestampIDKeyFunc, datastore.WatchRelationships|datastore.WatchSchema, 0)
 		if tx != nil {
-			if config.Metadata != nil {
+			if config.Metadata != nil && len(config.Metadata.GetFields()) > 0 {
 				if err := tracked.SetRevisionMetadata(ctx, newRevision, config.Metadata.AsMap()); err != nil {
 					return datastore.NoRevision, err
 				}

internal/datastore/postgres/postgres.go

@@ -438,7 +438,7 @@ func (pgd *pgDatastore) ReadWriteTx(
 		err = wrapError(pgx.BeginTxFunc(ctx, pgd.writePool, pgx.TxOptions{IsoLevel: pgx.Serializable}, func(tx pgx.Tx) error {
 			var err error
 			var metadata map[string]any
-			if config.Metadata != nil {
+			if config.Metadata != nil && len(config.Metadata.GetFields()) > 0 {
 				metadata = config.Metadata.AsMap()
 			}
 

internal/datastore/spanner/spanner.go

@@ -272,7 +272,7 @@ func (sd *spannerDatastore) ReadWriteTx(ctx context.Context, fn datastore.TxUser
 			return &traceableRTX{delegate: spannerRWT}
 		}
 
-		if config.Metadata != nil {
+		if config.Metadata != nil && len(config.Metadata.GetFields()) > 0 {
 			// Insert the metadata into the transaction metadata table.
 			mutation := spanner.Insert(tableTransactionMetadata,
 				[]string{colTransactionTag, colMetadata},

pkg/tuple/core_test.go

@@ -1,6 +1,7 @@
 package tuple
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -118,9 +119,13 @@ func TestCoreRelationToString(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			got, err := CoreRelationToString(tt.input)
 			require.NoError(t, err)
+
+			// Golang randomly injects spaces.
+			got = strings.ReplaceAll(got, " ", "")
 			require.Equal(t, tt.expected, got)
 
 			got = MustCoreRelationToString(tt.input)
+			got = strings.ReplaceAll(got, " ", "")
 			require.Equal(t, tt.expected, got)
 		})
 	}

pkg/tuple/strings.go

@@ -4,6 +4,7 @@ import (
 	"sort"
 	"strings"
 
+	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/types/known/structpb"
 
 	core "github.com/authzed/spicedb/pkg/proto/core/v1"
@@ -131,7 +132,10 @@ func StringCaveatContext(context *structpb.Struct) (string, error) {
 		return "", nil
 	}
 
-	contextBytes, err := context.MarshalJSON()
+	contextBytes, err := protojson.MarshalOptions{
+		Multiline: false,
+		Indent:    "",
+	}.Marshal(context)
 	if err != nil {
 		return "", err
 	}