Support 'optional' fields in proto3 (#34)

go.sum

@@ -4,7 +4,5 @@ github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 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 v1.26.0 h1:bxAC2xTBsZGibn2RTntX0oH50xLsqy1OxA9tTL3p/lk=
-google.golang.org/protobuf v1.26.0/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

@@ -1,63 +1,64 @@
 package main
 
 import (
+	"errors"
+	"flag"
 	"fmt"
-	"io"
 	"os"
-	"strings"
 
-	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/compiler/protogen"
 	"google.golang.org/protobuf/types/pluginpb"
 
 	"github.com/ckaznocha/protoc-gen-lint/linter"
 )
 
-// SortImports represents the parameter, which can be specified to the tool invocation
-// to enable checking, whether the proto file imports are sorted alphabetically.
-const SortImports = "sort_imports"
+type BoolFlag interface {
+	IsBoolFlag() bool
+}
+
+var errLint = errors.New("encountered lint errors")
 
 func main() {
-	var (
-		totalErrors      int
-		generatorRequest pluginpb.CodeGeneratorRequest
-		parameters       struct {
-			SortImports bool
-		}
-	)
-
-	data, err := io.ReadAll(os.Stdin)
-	if err != nil {
-		panic(err)
-	}
-
-	if err := proto.Unmarshal(data, &generatorRequest); err != nil {
-		panic(err)
-	}
-
-	for _, p := range strings.Split(generatorRequest.GetParameter(), ",") {
-		switch strings.TrimSpace(p) {
-		case "":
-			continue
-		case SortImports:
-			parameters.SortImports = true
-		default:
-			fmt.Fprintf(os.Stderr, "Unmatched parameter: %s", p)
-			os.Exit(1)
-		}
-	}
-
-	for _, file := range generatorRequest.GetProtoFile() {
-		numErrors, err := linter.LintProtoFile(linter.Config{
-			ProtoFile:   file,
-			OutFile:     os.Stderr,
-			SortImports: parameters.SortImports,
-		})
-		if err != nil {
-			panic(err)
+	var flags flag.FlagSet
+	sortImports := flags.Bool("sort_imports", false, "check whether or not the proto "+
+		"file imports are sorted alphabetically")
+
+	protogen.Options{
+		ParamFunc: func(param, value string) error {
+			// For backwards compatibility, treat a present flag with an empty
+			// string value as boolean true. The Go flag module parsing
+			// handles this, but the protogen flag parse behavior doesn't,
+			// because it doesn't parse flags the same way.
+			f := flags.Lookup(param)
+			if f != nil {
+				if _, ok := f.Value.(BoolFlag); ok {
+					value = "true"
+				}
+			}
+
+			return flags.Set(param, value)
+		},
+	}.Run(func(gen *protogen.Plugin) error {
+		gen.SupportedFeatures = uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)
+
+		totalErrors := 0
+		for _, f := range gen.Files {
+			numErrors, err := linter.LintProtoFile(linter.Config{
+				ProtoFile:   f.Proto,
+				OutFile:     os.Stderr,
+				SortImports: *sortImports,
+			})
+			if err != nil {
+				return err
+			}
+
+			totalErrors += numErrors
 		}
 
-		totalErrors += numErrors
-	}
+		if totalErrors > 0 {
+			return fmt.Errorf("%w: %d total", errLint, totalErrors)
+		}
 
-	os.Exit(totalErrors)
+		return nil
+	})
 }

optional.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+package test.optional;
+
+message WithOptional {
+	optional string test = 1;
+}