schema/fields: validate for slices builder (ent#3566)

This PR changes the way slice types are built and adds the possibility to add a custom validation function to json slice types.

entc/gen/template/meta.tmpl

@@ -87,9 +87,12 @@ const (
 			{{- end }}
 			{{- with $f.Validators }}
 				{{- $name := $f.Validator }}
-				{{- $type :=  printf "func (%s) error" $f.Type.Type }}
+				{{- $type := $f.Type.Type.String }}
+				{{- if $f.IsJSON }}
+					{{- $type = $f.Type.String }}
+				{{- end }}
 				// {{ $name }} is a validator for the "{{ $f.Name }}" field. It is called by the builders before save.
-				{{ $name }} {{ $type }}
+				{{ $name }} {{ printf "func (%s) error" $type }}
 			{{- end }}
 		{{- end }}
 		{{- if $.HasValueScanner }}

entc/gen/template/runtime.tmpl

@@ -195,12 +195,15 @@ func init() {
 			{{- end }}
 			{{- with $f.Validators }}
 				{{- $name := print $pkg "." $f.Validator }}
-				{{- $type :=  printf "func (%s) error" $f.Type.Type }}
+				{{- $type := $f.Type.Type.String }}
+				{{- if $f.IsJSON }}
+					{{- $type = $f.Type.String }}
+				{{- end }}
 				// {{ $name }} is a validator for the "{{ $f.Name }}" field. It is called by the builders before save.
 				{{- if eq $f.Validators 1 }}
-					{{ $name }} = {{ $desc }}.Validators[0].({{ $type }})
+					{{ $name }} = {{ $desc }}.Validators[0].({{ printf "func (%s) error" $type }})
 				{{- else }}
-					{{ $name }} = func() {{ $type }} {
+					{{ $name }} = func() {{ printf "func (%s) error" $type }} {
 						validators := {{ $desc }}.Validators
 						fns := [...]func({{ $f.Type.Type }}) error {
 							{{- range $j, $n := xrange $f.Validators }}

entc/gen/type.go

@@ -1039,7 +1039,7 @@ func (t *Type) checkField(tf *Field, f *load.Field) (err error) {
 			// Enum types should be named as follows: typepkg.Field.
 			f.Info.Ident = fmt.Sprintf("%s.%s", t.PackageDir(), pascal(f.Name))
 		}
-	case tf.Validators > 0 && !tf.ConvertedToBasic():
+	case tf.Validators > 0 && !tf.ConvertedToBasic() && f.Info.Type != field.TypeJSON:
 		err = fmt.Errorf("GoType %q for field %q must be converted to the basic %q type for validators", tf.Type, f.Name, tf.Type.Type)
 	case ant != nil && ant.Default != "" && (ant.DefaultExpr != "" || ant.DefaultExprs != nil):
 		err = fmt.Errorf("field %q cannot have both default value and default expression annotations", f.Name)
@@ -1804,6 +1804,8 @@ func (f Field) BasicType(ident string) (expr string) {
 		case rt.TypeEqual(nullStringType) || rt.TypeEqual(nullStringPType):
 			expr = fmt.Sprintf("%s.String", ident)
 		}
+	case field.TypeJSON:
+		expr = ident
 	default:
 		if t.Numeric() && rt.Kind >= reflect.Int && rt.Kind <= reflect.Float64 {
 			expr = fmt.Sprintf("%s(%s)", rt.Kind, ident)