Add support for (proto3) optional fields

Fixes #2

README.md

@@ -100,3 +100,9 @@ using this plugin.
 | generated_filename_suffix | filename suffix for all generated files, defaults to `_copy.pb.go` |
 | shallow_copy_method | method name generated for all message types unless set to an empty string, defaults to `Proto_ShallowCopy` |
 | shallow_clone_method | method name generated for all message types unless set to an empty string, defaults to `Proto_ShallowClone` |
+
+## Caveats
+
+- As the (`protoc-gen-go`) generated getters don't support field presence (e.g. returning `bool` not `*bool`), generated
+  shallow copy methods cannot support, and therefore ignore, optional fields, for sources of a different type to the
+  destination

examples/README.md

@@ -22,7 +22,9 @@ go install
 
 # generate the code, into the same directory as the proto file, see also the root readme, and google's reference docs
 find examples -type f -name '*.proto' -exec \
-    protoc --proto_path=. --go_out=. --go_opt=paths=source_relative --go-copy_out=. --go-copy_opt=paths=source_relative \
+    protoc \
+    --experimental_allow_proto3_optional \
+    --proto_path=. --go_out=. --go_opt=paths=source_relative --go-copy_out=. --go-copy_opt=paths=source_relative \
     {} +
 
 # validate the generated code

examples/addressbook/addressbook.proto

@@ -34,7 +34,7 @@
 // https://github.com/protocolbuffers/protobuf/blob/master/examples/addressbook.proto
 
 syntax = "proto3";
-package tutorial;
+package examples.addressbook;
 option go_package = "github.com/joeycumines/protoc-gen-go-copy/examples/addressbook";
 
 import "google/protobuf/timestamp.proto";

examples/oneoftypes/oneoftypes.proto

@@ -1,6 +1,6 @@
 syntax = "proto3";
 
-package example;
+package examples.oneoftypes;
 
 option go_package = "github.com/joeycumines/protoc-gen-go-copy/examples/oneoftypes";
 

examples/optionalfields/README.md

@@ -0,0 +1,7 @@
+# oneoftypes
+
+Example of all basic types using the `optional` field rule.
+
+This example was added as part of addressing [issue #2](https://github.com/joeycumines/protoc-gen-go-copy/issues/2).
+
+See [../README.md](../README.md) for how to generate.

examples/optionalfields/optionalfields.proto

@@ -0,0 +1,37 @@
+syntax = "proto3";
+
+package examples.optionalfields;
+
+option go_package = "github.com/joeycumines/protoc-gen-go-copy/examples/optionalfields";
+
+message Example {
+  message A {
+  }
+  enum B {
+    B_UNSPECIFIED = 0;
+  }
+
+  // https://developers.google.com/protocol-buffers/docs/proto3#scalar
+
+  optional double double = 1;
+  optional float float = 2;
+  optional int32 int32 = 3;
+  optional int64 int64 = 4;
+  optional uint32 uint32 = 5;
+  optional uint64 uint64 = 6;
+  optional sint32 sint32 = 7;
+  optional sint64 sint64 = 8;
+  optional fixed32 fixed32 = 9;
+  optional fixed64 fixed64 = 10;
+  optional sfixed32 sfixed32 = 11;
+  optional sfixed64 sfixed64 = 12;
+  optional bool bool = 13;
+  optional string string = 14;
+  optional bytes bytes = 15;
+
+  optional A message = 21;
+  optional B enum = 22;
+  optional Example recursive = 23;
+
+  string non_optional = 31;
+}

go.mod

@@ -4,6 +4,6 @@ go 1.16
 
 require (
 	github.com/jhump/gopoet v0.1.0
-	github.com/joeycumines/gopoet-protogen v0.1.0
-	google.golang.org/protobuf v1.27.1
+	github.com/joeycumines/gopoet-protogen v0.2.0
+	google.golang.org/protobuf v1.28.1
 )

go.sum

@@ -3,10 +3,10 @@ github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/jhump/gopoet v0.1.0 h1:gYjOPnzHd2nzB37xYQZxj4EIQNpBrBskRqQQ3q4ZgSg=
 github.com/jhump/gopoet v0.1.0/go.mod h1:me9yfT6IJSlOL3FCfrg+L6yzUEZ+5jW6WHt4Sk+UPUI=
-github.com/joeycumines/gopoet-protogen v0.1.0 h1:90o8BVwcIQJOvoGksGJpP/w2h5zoYuM0eQwEqLGOxVM=
-github.com/joeycumines/gopoet-protogen v0.1.0/go.mod h1:xoERQVyp/Zw3/mRxPL+QKWpmFelsFCOncyGaG2JIhVk=
+github.com/joeycumines/gopoet-protogen v0.2.0 h1:ht9tJtB0Gh86DDcDrH7x4NBaAavTMe9K/vygj7WSShc=
+github.com/joeycumines/gopoet-protogen v0.2.0/go.mod h1:4WpQOy18ktTEG63rFFAmJP1e++0IuRnLrpTcDn7qmuc=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
-google.golang.org/protobuf v1.27.1 h1:SnqbnDw1V7RiZcXPx5MEeqPv2s79L9i7BJUlG/+RurQ=
-google.golang.org/protobuf v1.27.1/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
+google.golang.org/protobuf v1.28.1 h1:d0NfwRgPtno5B1Wa6L2DAG+KivqkdutMf1UhdNx175w=
+google.golang.org/protobuf v1.28.1/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=

main.go

@@ -22,6 +22,7 @@ import (
 	"github.com/joeycumines/gopoet-protogen"
 	"google.golang.org/protobuf/compiler/protogen"
 	"google.golang.org/protobuf/reflect/protoreflect"
+	"google.golang.org/protobuf/types/pluginpb"
 	"path"
 )
 
@@ -70,6 +71,8 @@ func (x *Generator) NewFlagSet() *flag.FlagSet {
 }
 
 func (x Generator) Generate() error {
+	x.Plugin.SupportedFeatures = uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)
+
 	for _, file := range x.Plugin.Files {
 		x.Cache.AddFile(file)
 
@@ -98,16 +101,41 @@ func (x Generator) Generate() error {
 				elem.SetComment(fmt.Sprintf(`%s copies fields, from v to the receiver, using field getters.
 Note that v is of an arbitrary type, which may implement any number of the
 field getters, which are defined as any methods of the same signature as those
-generated for the receiver type, with a name starting with Get.`, x.ShallowCopyMethod))
+generated for the receiver type, with a name starting with Get.
+WARNING: Optional fields may be ignored, if v is not the receiver type.`, x.ShallowCopyMethod))
 				elem.AddArg(`v`, gopoet.InterfaceType(nil))
 				if len(fields) != 0 {
 					elem.Printlnf(`switch v := v.(type) {`)
 					elem.Printlnf(`case %s:`, gopoet.PointerType(t))
+					var hasOptional bool
 					for _, field := range fields {
+						if gopoet_protogen.FieldIsOptional(field) {
+							hasOptional = true
+							continue
+						}
 						elem.Printlnf(`x.%s = v.%s()`, field.Name(), field.Getter().Name)
 					}
+					if hasOptional {
+						elem.Println(`if v != nil {`)
+						for _, field := range fields {
+							if gopoet_protogen.FieldIsOptional(field) {
+								elem.Printlnf(`x.%s = v.%s`, field.Name(), field.Name())
+							}
+						}
+						elem.Println(`} else {`)
+						for _, field := range fields {
+							if gopoet_protogen.FieldIsOptional(field) {
+								elem.Printlnf(`x.%s = nil`, field.Name())
+							}
+						}
+						elem.Println(`}`)
+					}
 					elem.Println(`default:`)
 					for _, field := range fields {
+						if gopoet_protogen.FieldIsOptional(field) {
+							// special case: the generated getters don't support presence, so we can't use them
+							continue
+						}
 						elem.Printlnf(`if v, ok := v.(%s); ok {`, gopoet.InterfaceType(nil, field.Getter()))
 						elem.Printlnf(`x.%s = v.%s()`, field.Name(), field.Getter().Name)
 						if field.OneOf() != nil {
@@ -154,6 +182,7 @@ generated for the receiver type, with a name starting with Get.`, x.ShallowCopyM
 				genMsg(msg)
 			}
 		}
+
 		for _, msg := range file.Messages {
 			genMsg(msg)
 		}