Add tests on proto3 optional fields

Let's add some tests on a message that contains proto3 optional
fields.

As I did not want to affect the compilation of all the test
protocol buffers with the --experimental_allow_proto3_optional
flag, compile the one .proto file intended to test this path
separately. Once the feature is no longer experimental (and
behind a flag), this .proto can be compiled along with the other
test fixtures.

Add a TODO on the single test that will be updated when we add
support for proto3 optional fields in the next commit.

fixtures/Cookie.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+package com.example;
+
+/**
+ * Represents a cookie.
+ */
+message Cookie {
+  string id = 1; // The id of the cookie.
+  optional string name = 2; // The name of the cookie.
+  repeated string ingredients = 3; // Ingredients in the cookie.
+}

fixtures/generate.go

@@ -1,3 +1,9 @@
 package fixtures
 
 //go:generate protoc --descriptor_set_out=fileset.pb --include_imports --include_source_info -I. -I../thirdparty Booking.proto Vehicle.proto
+
+// Compiling proto3 optional fields requires using protoc >=3.12.x and passing the --experimental_allow_proto3_optional flag.
+// Rather than use this flag to compile all of the protocol buffers (which would eliminate test coverage for descriptors
+// compiled without the flag), only pass this flag when compiling the one message explicitly testing proto3 optional fields.
+// Once this feature is no longer behind an experimental flag, compilation of Cookie.proto can be moved to the above protoc command.
+//go:generate protoc --experimental_allow_proto3_optional --descriptor_set_out=cookie.pb --include_imports --include_source_info -I. -I../thirdparty Cookie.proto

template_test.go

@@ -17,6 +17,9 @@ var (
 	template    *Template
 	bookingFile *File
 	vehicleFile *File
+
+	cookieTemplate *Template
+	cookieFile     *File
 )
 
 func TestMain(m *testing.M) {
@@ -30,6 +33,12 @@ func TestMain(m *testing.M) {
 	bookingFile = template.Files[0]
 	vehicleFile = template.Files[1]
 
+	set, _ = utils.LoadDescriptorSet("fixtures", "cookie.pb")
+	req = utils.CreateGenRequest(set, "Cookie.proto")
+	result = protokit.ParseCodeGenRequest(req)
+	cookieTemplate = NewTemplate(result)
+	cookieFile = cookieTemplate.Files[0]
+
 	os.Exit(m.Run())
 }
 
@@ -315,6 +324,41 @@ func TestFieldPropertiesProto3(t *testing.T) {
 	require.Empty(t, field.Options)
 }
 
+func TestFieldPropertiesProto3Optional(t *testing.T) {
+	msg := findMessage("Cookie", cookieFile)
+
+	field := findField("id", msg)
+	require.Equal(t, "id", field.Name)
+	require.Equal(t, "The id of the cookie.", field.Description)
+	require.Equal(t, "", field.Label)
+	require.Equal(t, "string", field.Type)
+	require.Equal(t, "string", field.LongType)
+	require.Equal(t, "string", field.FullType)
+	require.Empty(t, field.DefaultValue)
+	require.Empty(t, field.Options)
+
+	field = findField("name", msg)
+	require.Equal(t, "name", field.Name)
+	require.Equal(t, "The name of the cookie.", field.Description)
+	//TODO(ezimanyi): This is a proto3 optional field, and should have label "optional"
+	require.Equal(t, "", field.Label)
+	require.Equal(t, "string", field.Type)
+	require.Equal(t, "string", field.LongType)
+	require.Equal(t, "string", field.FullType)
+	require.Empty(t, field.DefaultValue)
+	require.Empty(t, field.Options)
+
+	field = findField("ingredients", msg)
+	require.Equal(t, "ingredients", field.Name)
+	require.Equal(t, "Ingredients in the cookie.", field.Description)
+	require.Equal(t, "repeated", field.Label)
+	require.Equal(t, "string", field.Type)
+	require.Equal(t, "string", field.LongType)
+	require.Equal(t, "string", field.FullType)
+	require.Empty(t, field.DefaultValue)
+	require.Empty(t, field.Options)
+}
+
 func TestServiceProperties(t *testing.T) {
 	service := findService("VehicleService", vehicleFile)
 	require.Equal(t, "VehicleService", service.Name)