fix(bun): support extra generated model fields

cmd/relspec/convert.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	stdjson "encoding/json"
 	"fmt"
 	"os"
 	"strings"
@@ -54,6 +55,7 @@ var (
 	convertFlattenSchema   bool
 	convertNullableTypes   string
 	convertContinueOnError bool
+	convertExtraFields     string
 )
 
 var convertCmd = &cobra.Command{
@@ -179,6 +181,7 @@ func init() {
 	convertCmd.Flags().BoolVar(&convertFlattenSchema, "flatten-schema", false, "Flatten schema.table names to schema_table (useful for databases like SQLite that do not support schemas)")
 	convertCmd.Flags().StringVar(&convertNullableTypes, "types", "", "Nullable type package for code-gen writers (bun/gorm): 'baselib' (default, Go pointer types), 'stdlib' (database/sql), or 'sqltypes'")
 	convertCmd.Flags().BoolVar(&convertContinueOnError, "continue-on-error", false, "Prepend \\set ON_ERROR_STOP off to generated SQL so psql continues past errors (pgsql output only)")
+	convertCmd.Flags().StringVar(&convertExtraFields, "extra-fields", "", "JSON array of extra Bun model fields to inject (bun output only); fields support target_table, name, type, bun_tag, json_tag, comment")
 
 	err := convertCmd.MarkFlagRequired("from")
 	if err != nil {
@@ -245,7 +248,7 @@ func runConvert(cmd *cobra.Command, args []string) error {
 		fmt.Fprintf(os.Stderr, "      Schema: %s\n", convertSchemaFilter)
 	}
 
-	if err := writeDatabase(db, convertTargetType, convertTargetPath, convertPackageName, convertSchemaFilter, convertFlattenSchema, convertNullableTypes, convertContinueOnError); err != nil {
+	if err := writeDatabase(db, convertTargetType, convertTargetPath, convertPackageName, convertSchemaFilter, convertFlattenSchema, convertNullableTypes, convertContinueOnError, convertExtraFields); err != nil {
 		return fmt.Errorf("failed to write target: %w", err)
 	}
 
@@ -385,10 +388,25 @@ func readDatabaseForConvert(dbType, filePath, connString string) (*models.Databa
 	return db, nil
 }
 
-func writeDatabase(db *models.Database, dbType, outputPath, packageName, schemaFilter string, flattenSchema bool, nullableTypes string, continueOnError bool) error {
+func writeDatabase(db *models.Database, dbType, outputPath, packageName, schemaFilter string, flattenSchema bool, nullableTypes string, continueOnError bool, extraFields string) error {
 	var writer writers.Writer
 
 	writerOpts := newWriterOptions(outputPath, packageName, flattenSchema, nullableTypes, continueOnError)
+	if extraFields != "" {
+		if strings.ToLower(dbType) != "bun" {
+			return fmt.Errorf("--extra-fields is only supported for Bun output")
+		}
+		var parsed []wbun.ExtraFieldConfig
+		if err := stdjson.Unmarshal([]byte(extraFields), &parsed); err != nil {
+			return fmt.Errorf("invalid --extra-fields JSON: %w", err)
+		}
+		if len(parsed) == 0 {
+			return fmt.Errorf("--extra-fields must contain at least one field")
+		}
+		writerOpts.Metadata = map[string]interface{}{
+			"extra_fields": extraFields,
+		}
+	}
 
 	switch strings.ToLower(dbType) {
 	case "dbml":