From 8206ee7c181da9940aa533555b3ef47aa93a7f0c Mon Sep 17 00:00:00 2001
From: Daniel Pupius <dan@pupi.us>
Date: Sat, 27 Apr 2024 10:01:35 -0700
Subject: [PATCH] Use field_name?: field_type for optional fields, instead of
 OneOf extension, see #5 (#13)

---
 data/message.go       | 2 ++
 generator/template.go | 8 ++++++--
 registry/field.go     | 6 +++++-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/data/message.go b/data/message.go
index 3552547..ebb421c 100644
--- a/data/message.go
+++ b/data/message.go
@@ -14,6 +14,8 @@ type Message struct {
 	Fields []*Field
 	// NonOneOfFields contains a subset of fields that are not in the one-of groups
 	NonOneOfFields []*Field
+	// OptionalFields contains a subset of fields that are optional
+	OptionalFields []*Field
 	// Message is the nested messages defined inside the message
 	Messages []*Message
 	// OneOfFieldsGroups is the grouped list of one of fields with same index. so that renderer can render the clearing of other fields on set.
diff --git a/generator/template.go b/generator/template.go
index f04f084..f6f6b4b 100644
--- a/generator/template.go
+++ b/generator/template.go
@@ -37,6 +37,9 @@ type Base{{.Name}} = {
 {{- range .NonOneOfFields}}
   {{tsTypeKey .}}: {{tsTypeDef .}}
 {{- end}}
+{{- range .OptionalFields}}
+  {{tsTypeKey .}}: {{tsTypeDef .}}
+{{- end}}
 }
 
 export type {{.Name}} = Base{{.Name}}
@@ -541,9 +544,10 @@ func include(t *template.Template) func(name string, data interface{}) (string,
 func tsTypeKey(r *registry.Registry) func(field *data.Field) string {
 	return func(field *data.Field) string {
 		name := fieldName(r)(field.Name)
-		if !r.EmitUnpopulated {
+		if !r.EmitUnpopulated || field.IsOptional {
 			// When EmitUnpopulated is false, the gateway will return undefined for
-			// any zero value, so all fields may be undefined.
+			// any zero value, so all fields may be undefined. Optional fields, may
+			// also be undefined if unset.
 			return name + "?"
 		}
 		// When it is false, only optional fields can be undefined, however they are
diff --git a/registry/field.go b/registry/field.go
index 53390e4..d84740b 100644
--- a/registry/field.go
+++ b/registry/field.go
@@ -74,6 +74,9 @@ func (r *Registry) analyseField(fileData *data.File, msgData *data.Message, pack
 	if !fieldData.IsOneOfField {
 		msgData.NonOneOfFields = append(msgData.NonOneOfFields, fieldData)
 	}
+	if fieldData.IsOptional {
+		msgData.OptionalFields = append(msgData.OptionalFields, fieldData)
+	}
 
 	// if it's an external dependencies. store in the file data so that they can be collected when every file's finished
 	if isExternal {
@@ -81,7 +84,8 @@ func (r *Registry) analyseField(fileData *data.File, msgData *data.Message, pack
 	}
 
 	// if it's a one of field. register the field data in the group of the same one of index.
-	if fieldData.IsOneOfField { // one of field
+	// internally, optional fields are modeled as OneOf, however, we don't want to include them here.
+	if fieldData.IsOneOfField && !fieldData.IsOptional {
 		index := f.GetOneofIndex()
 		fieldData.OneOfIndex = index
 		_, ok := msgData.OneOfFieldsGroups[index]