cmd/twirp-openapi-gen: fix empty schema

Signed-off-by: Xe Iaso <me@xeiaso.net>

2 files changed, 43 insertions, 29 deletions

diff --git a/cmd/twirp-openapi-gen/internal/generator/aliases.go b/cmd/twirp-openapi-gen/internal/generator/aliases.go
index a8e29f3..660d345 100644
--- a/cmd/twirp-openapi-gen/internal/generator/aliases.go
+++ b/cmd/twirp-openapi-gen/internal/generator/aliases.go
@@ -74,9 +74,6 @@ var typeAliases = map[string]struct {
 		Type:   "boolean",
 		Format: "boolean",
 	},
-	"google.protobuf.Empty": {
-		Type: "object",
-	},
 
 	"google.type.DateTime": {
 		Type:   "string",
diff --git a/cmd/twirp-openapi-gen/internal/generator/handlers.go b/cmd/twirp-openapi-gen/internal/generator/handlers.go
index c11eb46..219000f 100644
--- a/cmd/twirp-openapi-gen/internal/generator/handlers.go
+++ b/cmd/twirp-openapi-gen/internal/generator/handlers.go
@@ -18,6 +18,7 @@ const (
 	googleListValueType = "google.protobuf.ListValue"
 	googleStructType    = "google.protobuf.Struct"
 	googleValueType     = "google.protobuf.Value"
+	googleEmptyType     = "google.protobuf.Empty"
 
 	googleMoneyType = "google.type.Money"
 )
@@ -92,40 +93,41 @@ func (gen *generator) RPC(rpc *proto.RPC) {
 	var reqMediaType *openapi3.MediaType
 	switch rpc.RequestType {
 	case "google.protobuf.Empty":
-		reqMediaType = openapi3.NewMediaType()
+		gen.addGoogleEmptySchema()
 	default:
-		if strings.Contains(rpc.RequestType, ".") {
-			reqMediaType = &openapi3.MediaType{
-				Schema: &openapi3.SchemaRef{
-					Ref: fmt.Sprintf("#/components/schemas/%s", rpc.RequestType),
-				},
-			}
-		} else {
-			reqMediaType = &openapi3.MediaType{
-				Schema: &openapi3.SchemaRef{
-					Ref: fmt.Sprintf("#/components/schemas/%s.%s", gen.packageName, rpc.RequestType),
-				},
-			}	
+	}
+	if strings.Contains(rpc.RequestType, ".") {
+		reqMediaType = &openapi3.MediaType{
+			Schema: &openapi3.SchemaRef{
+				Ref: fmt.Sprintf("#/components/schemas/%s", rpc.RequestType),
+			},
+		}
+	} else {
+		reqMediaType = &openapi3.MediaType{
+			Schema: &openapi3.SchemaRef{
+				Ref: fmt.Sprintf("#/components/schemas/%s.%s", gen.packageName, rpc.RequestType),
+			},
 		}
 	}
 
 	var resMediaType *openapi3.MediaType
 	switch rpc.ReturnsType {
 	case "google.protobuf.Empty":
-		resMediaType = openapi3.NewMediaType()
+		gen.addGoogleEmptySchema()
 	default:
-		if strings.Contains(rpc.ReturnsType, ".") {
-			resMediaType = &openapi3.MediaType{
-				Schema: &openapi3.SchemaRef{
-					Ref: fmt.Sprintf("#/components/schemas/%s", rpc.ReturnsType),
-				},
-			}
-		} else {
-			resMediaType = &openapi3.MediaType{
-				Schema: &openapi3.SchemaRef{
-					Ref: fmt.Sprintf("#/components/schemas/%s.%s", gen.packageName, rpc.ReturnsType),
-				},
-			}
+	}
+
+	if strings.Contains(rpc.ReturnsType, ".") {
+		resMediaType = &openapi3.MediaType{
+			Schema: &openapi3.SchemaRef{
+				Ref: fmt.Sprintf("#/components/schemas/%s", rpc.ReturnsType),
+			},
+		}
+	} else {
+		resMediaType = &openapi3.MediaType{
+			Schema: &openapi3.SchemaRef{
+				Ref: fmt.Sprintf("#/components/schemas/%s.%s", gen.packageName, rpc.ReturnsType),
+			},
 		}
 	}
 
@@ -283,6 +285,9 @@ func (gen *generator) addField(schemaPropsV3 openapi3.Schemas, field *proto.Fiel
 	case googleMoneyType:
 		slog.Debug("Money", "name", fieldName, "type", fieldType, "format", fieldFormat)
 		gen.addGoogleMoneySchema()
+	case googleEmptyType:
+		slog.Debug("Empty", "name", fieldName, "type", fieldType, "format", fieldFormat)
+		gen.addGoogleEmptySchema()
 	default:
 		slog.Debug("Default", "name", fieldName, "type", fieldType, "format", fieldFormat)
 	}
@@ -318,6 +323,18 @@ func (gen *generator) addField(schemaPropsV3 openapi3.Schemas, field *proto.Fiel
 	}
 }
 
+func (gen *generator) addGoogleEmptySchema() {
+	if _, ok := gen.openAPIV3.Components.Schemas[googleEmptyType]; ok {
+		return
+	}
+	gen.openAPIV3.Components.Schemas[googleEmptyType] = &openapi3.SchemaRef{
+		Value: &openapi3.Schema{
+			Description: "A generic empty message that you can re-use to avoid defining duplicated empty messages in your APIs. A typical example is to use it as the request or the response type of an API method. For instance:",
+			Type:        "object",
+		},
+	}
+}
+
 // addGoogleAnySchema adds a schema item for the google.protobuf.Any type.
 func (gen *generator) addGoogleAnySchema() {
 	if _, ok := gen.openAPIV3.Components.Schemas[googleAnyType]; ok {