fix: resolve Dgraph type name from DType tag in mutation validation

mutate.go

@@ -76,12 +76,12 @@ func (c client) process(ctx context.Context,
 			return fmt.Errorf("failed to get current schema: %w", err)
 		}
 
-		// Get the type name from the object
-		schemaObjVal := reflect.ValueOf(schemaObj)
-		if schemaObjVal.Kind() == reflect.Ptr {
-			schemaObjVal = schemaObjVal.Elem()
-		}
-		typeName := schemaObjVal.Type().Name()
+		// Resolve the Dgraph type name the same way mutations and schema
+		// generation do (the DType tag, falling back to the Go struct name).
+		// Using the raw Go struct name here would reject types whose Dgraph
+		// name differs from the struct name, e.g. a `migrationLock` struct
+		// declared as `dgraph:"MigrationLock"`.
+		typeName := getNodeType(schemaObj)
 
 		// When AutoSchema is disabled, validate that required schema exists
 		// Fail if user schema for the type doesn't exist, even if only system schema exists

mutate_dtype_validation_test.go

@@ -0,0 +1,43 @@
+/*
+ * SPDX-FileCopyrightText: © 2017-2026 Istari Digital, Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package modusgraph_test
+
+import (
+	"context"
+	"testing"
+
+	mg "github.com/matthewmcneely/modusgraph"
+	"github.com/stretchr/testify/require"
+)
+
+// lockLikeNode mirrors modusGraph-migrate's migrationLock: its Dgraph type
+// name (declared via the DType tag, "DTypeMismatchType") differs from its Go
+// struct name ("lockLikeNode").
+type lockLikeNode struct {
+	UID   string   `json:"uid,omitempty"`
+	DType []string `json:"dgraph.type,omitempty" dgraph:"DTypeMismatchType"`
+	Name  string   `json:"dtypeMismatchName,omitempty" dgraph:"predicate=dtype_mismatch_name index=exact"`
+}
+
+// TestMutateValidation_ResolvesDTypeName guards the AutoSchema-disabled mutation
+// path: it must resolve the type name from the DType tag (the same way schema
+// generation and getNodeType do), not from the raw Go struct name. Before the
+// fix, Insert rejected the row with "schema validation failed: database schema
+// does not contain type lockLikeNode" even though the schema held the (correctly
+// named) "type DTypeMismatchType".
+func TestMutateValidation_ResolvesDTypeName(t *testing.T) {
+	client, err := mg.NewClient("file://" + GetTempDir(t)) // autoSchema disabled by default
+	require.NoError(t, err)
+	defer client.Close()
+
+	ctx := context.Background()
+	// Register the type under its Dgraph name (derived from the DType tag).
+	require.NoError(t, client.UpdateSchema(ctx, &lockLikeNode{}))
+
+	// Insert must pass validation now that the type name resolves via DType.
+	err = client.Insert(ctx, &lockLikeNode{DType: []string{"DTypeMismatchType"}, Name: "x"})
+	require.NoError(t, err)
+}