Merge pull request #1111 from tdakkota/fix/set-proper-alias-nil-semantic

fix(gen): set proper nil semantic for aliased arrays

gen/_template/json/encoders_alias.tmpl

@@ -1,23 +1,30 @@
 {{- /*gotype: github.com/ogen-go/ogen/gen/ir.Type*/ -}}
 {{- define "json/encoders_alias" }}
+{{- $a := $.AliasTo }}
 // Encode encodes {{ $.Name }} as json.
 func (s {{ $.ReadOnlyReceiver }}) Encode(e *jx.Encoder) {
-	{{- if $.AliasTo.DoPassByPointer }}
-	unwrapped := (*{{ $.AliasTo.Go }})(s)
+	{{- if $a.DoPassByPointer }}
+		unwrapped := (*{{ $a.Go }})(s)
 	{{- else }}
-	unwrapped := {{ $.AliasTo.Go }}(s)
+		unwrapped := {{ $a.Go }}(s)
 	{{- end }}
-	{{ template "json/enc" elem $.AliasTo "unwrapped" -}}
+	{{- if and $a.IsArray $a.NilSemantic.Optional }}{{/* Prevents empty value encoding */}}
+		if unwrapped == nil {
+			e.ArrEmpty()
+			return
+		}
+	{{- end }}
+	{{ template "json/enc" elem $a "unwrapped" -}}
 }
 
 // Decode decodes {{ $.Name }} from json.
 func (s *{{ $.Name }}) Decode(d *jx.Decoder) error {
 	if s == nil {
 		return errors.New({{ printf "invalid: unable to decode %s to nil" $.Name | quote }})
 	}
-	var unwrapped {{ $.AliasTo.Go }}
+	var unwrapped {{ $a.Go }}
 	if err := func() error {
-		{{- template "json/dec" elem $.AliasTo "unwrapped" }}
+		{{- template "json/dec" elem $a "unwrapped" }}
 		return nil
 	}(); err != nil {
 		return errors.Wrap(err, "alias")

gen/generics.go

@@ -64,6 +64,7 @@ func boxType(t *ir.Type, v ir.GenericVariant) (*ir.Type, error) {
 	if dealiased.IsAlias() {
 		dealiased = dealiased.AliasTo
 	}
+
 	// Do not wrap if
 	//  * type is Any
 	//  * type is Stream
@@ -93,6 +94,7 @@ func boxType(t *ir.Type, v ir.GenericVariant) (*ir.Type, error) {
 			}
 			return ir.Generic(postfix, t, v), nil
 		}
+		dealiased.NilSemantic = t.NilSemantic
 
 		return t, nil
 	}