Return an error when an unexpected state is provided

In order to avoid people relying in the state but not providing an encoder we now return an error.

Author: boekkooi-fresh

driver/sql/postgres/projector.go

@@ -3,6 +3,7 @@ package postgres
 import (
 	"context"
 	"database/sql/driver"
+	"errors"
 
 	"github.com/hellofresh/goengine/driver/sql"
 )
@@ -45,3 +46,12 @@ func resolveErrorAction(
 
 	return errorFallthrough
 }
+
+// defaultProjectionStateEncoder this `ProjectionStateEncoder` is used for a goeninge.Projection
+func defaultProjectionStateEncoder(state interface{}) ([]byte, error) {
+	if state == nil {
+		return []byte{'{', '}'}, nil
+	}
+
+	return nil, errors.New("unexpected state provided (Did you forget to implement goengine.ProjectionSaga?)")
+}

driver/sql/postgres/projector_aggregate_storage.go

@@ -53,6 +53,9 @@ func newAggregateProjectionStorage(
 	if logger == nil {
 		logger = goengine.NopLogger
 	}
+	if projectionStateEncoder == nil {
+		projectionStateEncoder = defaultProjectionStateEncoder
+	}
 
 	projectionTableQuoted := QuoteIdentifier(projectionTable)
 	projectionTableStr := QuoteString(projectionTable)
@@ -115,15 +118,9 @@ func (a *aggregateProjectionStorage) LoadOutOfSync(ctx context.Context, conn *sq
 }
 
 func (a *aggregateProjectionStorage) PersistState(conn *sql.Conn, notification *driverSQL.ProjectionNotification, state driverSQL.ProjectionState) error {
-	var (
-		err          error
-		encodedState = []byte{'{', '}'}
-	)
-	if a.projectionStateEncoder != nil {
-		encodedState, err = a.projectionStateEncoder(state.ProjectionState)
-		if err != nil {
-			return err
-		}
+	encodedState, err := a.projectionStateEncoder(state.ProjectionState)
+	if err != nil {
+		return err
 	}
 
 	_, err = conn.ExecContext(context.Background(), a.queryPersistState, notification.AggregateID, state.Position, encodedState)

driver/sql/postgres/projector_stream_storage.go

@@ -38,6 +38,13 @@ func newStreamProjectionStorage(
 	projectionStateEncoder driverSQL.ProjectionStateEncoder,
 	logger goengine.Logger,
 ) *streamProjectionStorage {
+	if logger == nil {
+		logger = goengine.NopLogger
+	}
+	if projectionStateEncoder == nil {
+		projectionStateEncoder = defaultProjectionStateEncoder
+	}
+
 	projectionTableQuoted := QuoteIdentifier(projectionTable)
 	projectionTableStr := QuoteString(projectionTable)
 
@@ -73,15 +80,9 @@ func newStreamProjectionStorage(
 }
 
 func (s *streamProjectionStorage) PersistState(conn *sql.Conn, notification *driverSQL.ProjectionNotification, state driverSQL.ProjectionState) error {
-	var (
-		err          error
-		encodedState = []byte{'{', '}'}
-	)
-	if s.projectionStateEncoder != nil {
-		encodedState, err = s.projectionStateEncoder(state.ProjectionState)
-		if err != nil {
-			return err
-		}
+	encodedState, err := s.projectionStateEncoder(state.ProjectionState)
+	if err != nil {
+		return err
 	}
 
 	_, err = conn.ExecContext(context.Background(), s.queryPersistState, state.Position, encodedState, s.projectionName)

driver/sql/postgres/projector_test.go

@@ -0,0 +1,38 @@
+// +build unit
+
+package postgres
+
+import (
+	"fmt"
+	"github.com/hellofresh/goengine"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestDefaultProjectionStateEncoder(t *testing.T) {
+	t.Run("Only accept nil values as valid", func(t *testing.T) {
+		res, err := defaultProjectionStateEncoder(nil)
+
+		assert.Equal(t, []byte{'{', '}'}, res)
+		assert.NoError(t, err)
+	})
+
+	t.Run("Reject any state this not nil", func(t *testing.T) {
+		var pointer *goengine.Projection
+		testCases := []interface{}{
+			struct{}{},
+			pointer,
+			"",
+			0,
+		}
+
+		for i, v := range testCases {
+			t.Run(fmt.Sprintf("case %d", i), func(t *testing.T) {
+				res, err := defaultProjectionStateEncoder(v)
+
+				assert.Error(t, err)
+				assert.Nil(t, res)
+			})
+		}
+	})
+}