feat: add --type-map to override SQL-to-Go types in bun and gorm writers

Adds WriterOptions.TypeMappings and a repeatable --type-map sqltype=gotype
flag. Defaults are unchanged when no mapping is given. Closes #36 (bun/gorm).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

cmd/relspec/prisma_options.go

@@ -27,6 +27,7 @@ func newWriterOptions(outputPath, packageName string, flattenSchema bool, nullab
 		FlattenSchema:    flattenSchema,
 		NullableTypes:    nullableTypes,
 		NullableArrays:   nullableArrays,
+		TypeMappings:     typeMappings,
 		Prisma7:          prisma7,
 		ContinueOnError:  continueOnError,
 		StrictDirectives: strictDirectives,

cmd/relspec/root.go

@@ -6,6 +6,7 @@ import (
 	"github.com/spf13/cobra"
 
 	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
 
 // version/buildDate mirror pkg/buildinfo so existing call sites keep working.
@@ -17,6 +18,8 @@ var (
 	noVersion        bool
 	silent           bool
 	strictDirectives bool
+	typeMapFlags     []string
+	typeMappings     map[string]string
 )
 
 var rootCmd = &cobra.Command{
@@ -28,6 +31,11 @@ bidirectional conversion between various database schema formats.
 It reads database schemas from multiple sources (live databases, DBML,
 DCTX, DrawDB, etc.) and writes them to various formats (GORM, Bun,
 JSON, YAML, SQL, etc.).`,
+	PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
+		var err error
+		typeMappings, err = writers.ParseTypeMappings(typeMapFlags)
+		return err
+	},
 }
 
 func init() {
@@ -44,6 +52,7 @@ func init() {
 	rootCmd.AddCommand(versionCmd)
 	rootCmd.AddCommand(reportCmd)
 	rootCmd.PersistentFlags().BoolVar(&prisma7, "prisma7", false, "Use Prisma 7 generator conventions when reading/writing Prisma schemas")
+	rootCmd.PersistentFlags().StringArrayVar(&typeMapFlags, "type-map", nil, "Override a SQL-to-Go type mapping for bun/gorm output as sqltype=gotype (repeatable), e.g. --type-map uuid=uuid.UUID --type-map numeric=decimal.Decimal")
 	rootCmd.PersistentFlags().BoolVar(&noVersion, "no-version", false, "Suppress the RelSpec version header")
 	rootCmd.PersistentFlags().BoolVar(&silent, "silent", false, "Suppress progress and status messages (errors are still shown)")
 	rootCmd.PersistentFlags().BoolVar(&strictDirectives, "strict-directives", false, "Fail on unknown or untranslatable DBML dialect directives (@postgres:, @sqlite:, …)")