Custom types

README.md

@@ -77,6 +77,63 @@ Then, in your project, add a dependency on the runtime library:
 
 `elm install tiziano88/elm-protobuf`
 
+
+## Options
+
+Options can be passed to the plugin in the --elm_out value, with the following
+syntax:
+
+`protoc "--elm_out=option=value;option=value1,value2:."`
+
+The valid options are:
+
+- `excludeFile`: A list of files that should be ignored. Usefull to ignore a
+  proto2 file that is a dependency of the compiled file.
+
+- `options`: A file to customize the output, see below
+
+## Customize the output
+
+The elm type used for each field is automatically determined, but can be
+overridden by passing an option file to the plugin.
+
+For example, if a message has a Uuid field, the proto definition will probably
+be something like this:
+
+```proto
+message MyObject {
+    string id = 1;
+    string name = 2;
+}
+```
+
+By adding an option file, it is possible to get a 'Maybe Uuid' field instead
+of a string.
+
+Write a yaml file with all the options, 'elm-proto-options.yaml':
+
+```yaml
+types:
+  Uuid.Uuid:
+    json:
+      encoder: Uuid.encode
+      decoder: Uuid.decoder
+
+files:
+  my_proto_file.proto:
+    imports:
+    - Uuid
+    fields:
+      MyObject.id:
+        type: Uuid.Uuid
+        required: false
+```
+
+Pass the option file as a parameter to the plugin:
+
+```
+`protoc --elm_out='options=./elm-proto-options.yaml:.' my_proto_file.proto`
+```
 ## References
 
 https://developers.google.com/protocol-buffers/

protoc-gen-elm/file_generator.go

@@ -7,19 +7,34 @@ import (
 )
 
 type FileGenerator struct {
-	w io.Writer
+	options Options
+	w       io.Writer
 	// Used to avoid qualifying names in the same file.
 	inFileName string
 	indent     uint
 }
 
-func NewFileGenerator(w io.Writer, inFileName string) *FileGenerator {
+func NewFileGenerator(options Options, w io.Writer, inFileName string) *FileGenerator {
 	return &FileGenerator{
+		options:    options,
 		w:          w,
 		inFileName: inFileName,
 	}
 }
 
+func (fg *FileGenerator) FileOptions() FileOptions {
+	o, _ := fg.options.Files[fg.inFileName]
+	return o
+}
+
+func (fg *FileGenerator) FieldOptions(name string) *FieldOptions {
+	o := fg.FileOptions()
+	if fo, ok := o.Fields[name]; ok {
+		return &fo
+	}
+	return nil
+}
+
 func (fg *FileGenerator) In() {
 	fg.indent++
 }

protoc-gen-elm/main.go

@@ -15,6 +15,7 @@ import (
 	"github.com/golang/protobuf/protoc-gen-go/descriptor"
 	"github.com/golang/protobuf/protoc-gen-go/generator"
 	plugin "github.com/golang/protobuf/protoc-gen-go/plugin"
+	"gopkg.in/yaml.v2"
 )
 
 var (
@@ -102,6 +103,38 @@ func main() {
 		inFile.SourceCodeInfo = nil
 	}
 
+	var options Options
+
+	if parameter := req.GetParameter(); parameter != "" {
+		list := strings.Split(parameter, ";")
+		for _, item := range list {
+			splitted := strings.Split(item, "=")
+			if len(splitted) != 2 {
+				log.Fatalf("Invalid parameter. Expected 'variable=value', got: '%s'", item)
+			}
+			switch splitted[0] {
+			case "excludeFile":
+				fileList := strings.Split(splitted[1], ",")
+				for _, name := range fileList {
+					excludedFiles[name] = true
+				}
+			case "options":
+				b, err := ioutil.ReadFile(splitted[1])
+				if err != nil {
+					log.Fatalf("Could not ready option file: %s", err)
+				}
+				if err := yaml.Unmarshal(b, &options); err != nil {
+					log.Fatalf("Could not decode the option file: %s", err)
+				}
+				log.Printf("Loaded options file: %s", splitted[1])
+
+			default:
+				log.Fatalf("Unknow parameter: %s", splitted[0])
+
+			}
+		}
+	}
+
 	log.Printf("Input data: %v", proto.MarshalTextString(req))
 
 	resp := &plugin.CodeGeneratorResponse{}
@@ -113,7 +146,7 @@ func main() {
 			log.Printf("Skipping well known type")
 			continue
 		}
-		outFile, err := processFile(inFile)
+		outFile, err := processFile(options, inFile)
 		if err != nil {
 			log.Fatalf("Could not process file: %v", err)
 		}
@@ -131,7 +164,7 @@ func main() {
 	}
 }
 
-func processFile(inFile *descriptor.FileDescriptorProto) (*plugin.CodeGeneratorResponse_File, error) {
+func processFile(options Options, inFile *descriptor.FileDescriptorProto) (*plugin.CodeGeneratorResponse_File, error) {
 	if inFile.GetSyntax() != "proto3" {
 		return nil, fmt.Errorf("Only proto3 syntax is supported")
 	}
@@ -158,7 +191,7 @@ func processFile(inFile *descriptor.FileDescriptorProto) (*plugin.CodeGeneratorR
 	outFile.Name = proto.String(outFileName)
 
 	b := &bytes.Buffer{}
-	fg := NewFileGenerator(b, inFileName)
+	fg := NewFileGenerator(options, b, inFileName)
 
 	fg.GenerateModule(fullModuleName)
 	fg.GenerateComments(inFile)
@@ -237,6 +270,13 @@ func (fg *FileGenerator) GenerateImports() {
 	fg.P("")
 	fg.P("import Json.Decode as JD")
 	fg.P("import Json.Encode as JE")
+	o := fg.FileOptions()
+	if len(o.Imports) != 0 {
+		fg.P("")
+		for _, name := range o.Imports {
+			fg.P("import " + name)
+		}
+	}
 }
 
 func (fg *FileGenerator) GenerateEverything(prefix string, inMessage *descriptor.DescriptorProto) error {

protoc-gen-elm/message.go

@@ -6,6 +6,15 @@ import (
 	"github.com/golang/protobuf/protoc-gen-go/descriptor"
 )
 
+func (fg *FileGenerator) isOptional(
+	msgName string, inField *descriptor.FieldDescriptorProto, fieldOptions *FieldOptions,
+) bool {
+	return (inField.GetLabel() == descriptor.FieldDescriptorProto_LABEL_OPTIONAL) &&
+		(inField.GetType() == descriptor.FieldDescriptorProto_TYPE_MESSAGE) ||
+		(fieldOptions != nil && !fieldOptions.Required)
+
+}
+
 func (fg *FileGenerator) GenerateMessageDefinition(prefix string, inMessage *descriptor.DescriptorProto) error {
 	typeName := prefix + inMessage.GetName()
 
@@ -26,12 +35,15 @@ func (fg *FileGenerator) GenerateMessageDefinition(prefix string, inMessage *des
 				// Handled in the oneof only.
 				continue
 			}
+			fieldOptions := fg.FieldOptions(typeName + "." + inField.GetName())
 
-			optional := (inField.GetLabel() == descriptor.FieldDescriptorProto_LABEL_OPTIONAL) &&
-				(inField.GetType() == descriptor.FieldDescriptorProto_TYPE_MESSAGE)
+			optional := fg.isOptional(inMessage.GetName(), inField, fieldOptions)
 			repeated := inField.GetLabel() == descriptor.FieldDescriptorProto_LABEL_REPEATED
 
 			fType := fieldElmType(inField)
+			if fieldOptions != nil {
+				fType = fieldOptions.Type
+			}
 
 			fName := elmFieldName(inField.GetName())
 			fNumber := inField.GetNumber()
@@ -90,12 +102,20 @@ func (fg *FileGenerator) GenerateMessageDecoder(prefix string, inMessage *descri
 					continue
 				}
 
-				optional := (inField.GetLabel() == descriptor.FieldDescriptorProto_LABEL_OPTIONAL) &&
-					(inField.GetType() == descriptor.FieldDescriptorProto_TYPE_MESSAGE)
+				fieldOptions := fg.FieldOptions(typeName + "." + inField.GetName())
+
+				optional := fg.isOptional(inMessage.GetName(), inField, fieldOptions)
+
 				repeated := inField.GetLabel() == descriptor.FieldDescriptorProto_LABEL_REPEATED
 				d := fieldDecoderName(inField)
 				def := fieldDefaultValue(inField)
 
+				if fieldOptions != nil {
+					if t, ok := fg.options.Types[fieldOptions.Type]; ok && t.JSON.Decoder != "" {
+						d = t.JSON.Decoder
+					}
+				}
+
 				if repeated {
 					fg.P("|> repeated %q %s", jsonFieldName(inField), d)
 				} else {
@@ -145,10 +165,16 @@ func (fg *FileGenerator) GenerateMessageEncoder(prefix string, inMessage *descri
 					continue
 				}
 
-				optional := (inField.GetLabel() == descriptor.FieldDescriptorProto_LABEL_OPTIONAL) &&
-					(inField.GetType() == descriptor.FieldDescriptorProto_TYPE_MESSAGE)
+				fieldOptions := fg.FieldOptions(typeName + "." + inField.GetName())
+
+				optional := fg.isOptional(inMessage.GetName(), inField, fieldOptions)
 				repeated := inField.GetLabel() == descriptor.FieldDescriptorProto_LABEL_REPEATED
 				d := fieldEncoderName(inField)
+				if fieldOptions != nil {
+					if t, ok := fg.options.Types[fieldOptions.Type]; ok && t.JSON.Encoder != "" {
+						d = t.JSON.Encoder
+					}
+				}
 				val := argName + "." + elmFieldName(inField.GetName())
 				def := fieldDefaultValue(inField)
 				if repeated {

protoc-gen-elm/options.go

@@ -0,0 +1,31 @@
+package main
+
+// EncDec defines a encoder and decoder
+type EncDec struct {
+	Encoder string
+	Decoder string
+}
+
+// CustomType defines a custom type
+type CustomType struct {
+	JSON    EncDec
+	Default string
+}
+
+// FieldOptions overrides the data type of a field
+type FieldOptions struct {
+	Type     string
+	Required bool
+}
+
+// FileOptions contains file-specific options
+type FileOptions struct {
+	Imports []string
+	Fields  map[string]FieldOptions
+}
+
+// Options contains the code generator options
+type Options struct {
+	Types map[string]CustomType
+	Files map[string]FileOptions
+}