From 84cd251933007f78b08e9cec1c46c256df0b5925 Mon Sep 17 00:00:00 2001
From: Malte Isberner <malte@redhat.com>
Date: Fri, 5 Aug 2022 21:24:07 -0700
Subject: [PATCH] allow using pointer receivers, always use pointers for
 passing structs for internally generated functions

---
 bootstrap/bootstrap.go | 12 ++++++++++--
 easyjson/main.go       |  2 ++
 gen/encoder.go         | 21 +++++++++++++++------
 gen/generator.go       |  6 ++++++
 4 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/bootstrap/bootstrap.go b/bootstrap/bootstrap.go
index 5755beea..1cfc982b 100644
--- a/bootstrap/bootstrap.go
+++ b/bootstrap/bootstrap.go
@@ -32,6 +32,7 @@ type Generator struct {
 	OmitEmpty                bool
 	DisallowUnknownFields    bool
 	SkipMemberNameUnescaping bool
+	PtrReceivers             bool
 
 	OutName       string
 	BuildTags     string
@@ -69,15 +70,19 @@ func (g *Generator) writeStub() error {
 		fmt.Fprintln(f, ")")
 	}
 
+	inPtrPrefix := ""
+	if g.PtrReceivers {
+		inPtrPrefix = "*"
+	}
 	sort.Strings(g.Types)
 	for _, t := range g.Types {
 		fmt.Fprintln(f)
 		if !g.NoStdMarshalers {
-			fmt.Fprintln(f, "func (", t, ") MarshalJSON() ([]byte, error) { return nil, nil }")
+			fmt.Fprintln(f, "func (", inPtrPrefix, t, ") MarshalJSON() ([]byte, error) { return nil, nil }")
 			fmt.Fprintln(f, "func (*", t, ") UnmarshalJSON([]byte) error { return nil }")
 		}
 
-		fmt.Fprintln(f, "func (", t, ") MarshalEasyJSON(w *jwriter.Writer) {}")
+		fmt.Fprintln(f, "func (", inPtrPrefix, t, ") MarshalEasyJSON(w *jwriter.Writer) {}")
 		fmt.Fprintln(f, "func (*", t, ") UnmarshalEasyJSON(l *jlexer.Lexer) {}")
 		fmt.Fprintln(f)
 		fmt.Fprintln(f, "type EasyJSON_exporter_"+t+" *"+t)
@@ -137,6 +142,9 @@ func (g *Generator) writeMain() (path string, err error) {
 	if g.SkipMemberNameUnescaping {
 		fmt.Fprintln(f, "  g.SkipMemberNameUnescaping()")
 	}
+	if g.PtrReceivers {
+		fmt.Fprintln(f, "  g.PtrReceivers()")
+	}
 
 	sort.Strings(g.Types)
 	for _, v := range g.Types {
diff --git a/easyjson/main.go b/easyjson/main.go
index d337c846..1153c5c1 100644
--- a/easyjson/main.go
+++ b/easyjson/main.go
@@ -31,6 +31,7 @@ var specifiedName = flag.String("output_filename", "", "specify the filename of
 var processPkg = flag.Bool("pkg", false, "process the whole package instead of just the given file")
 var disallowUnknownFields = flag.Bool("disallow_unknown_fields", false, "return error if any unknown field in json appeared")
 var skipMemberNameUnescaping = flag.Bool("disable_members_unescape", false, "don't perform unescaping of member names to improve performance")
+var ptrReceivers = flag.Bool("ptr_receivers", false, "use pointer receivers for all generated marshaling methods")
 
 func generate(fname string) (err error) {
 	fInfo, err := os.Stat(fname)
@@ -85,6 +86,7 @@ func generate(fname string) (err error) {
 		StubsOnly:                *stubs,
 		NoFormat:                 *noformat,
 		SimpleBytes:              *simpleBytes,
+		PtrReceivers:             *ptrReceivers,
 	}
 
 	if err := g.Run(); err != nil {
diff --git a/gen/encoder.go b/gen/encoder.go
index ed6d6ad5..d188bb94 100644
--- a/gen/encoder.go
+++ b/gen/encoder.go
@@ -203,7 +203,7 @@ func (g *Generator) genTypeEncoderNoCheck(t reflect.Type, in string, tags fieldT
 		enc := g.getEncoderName(t)
 		g.addType(t)
 
-		fmt.Fprintln(g.out, ws+enc+"(out, "+in+")")
+		fmt.Fprintln(g.out, ws+enc+"(out, &"+in+")")
 
 	case reflect.Ptr:
 		if !assumeNonEmpty {
@@ -406,7 +406,7 @@ func (g *Generator) genStructEncoder(t reflect.Type) error {
 	fname := g.getEncoderName(t)
 	typ := g.getType(t)
 
-	fmt.Fprintln(g.out, "func "+fname+"(out *jwriter.Writer, in "+typ+") {")
+	fmt.Fprintln(g.out, "func "+fname+"(out *jwriter.Writer, in *"+typ+") {")
 	fmt.Fprintln(g.out, "  out.RawByte('{')")
 	fmt.Fprintln(g.out, "  first := true")
 	fmt.Fprintln(g.out, "  _ = first")
@@ -449,18 +449,27 @@ func (g *Generator) genStructMarshaler(t reflect.Type) error {
 	fname := g.getEncoderName(t)
 	typ := g.getType(t)
 
+	ptrPrefix := ""
+	addrOfPrefix := ""
+	if t.Kind() == reflect.Struct {
+		if g.ptrReceivers {
+			ptrPrefix = "*"
+		} else {
+			addrOfPrefix = "&"
+		}
+	}
 	if !g.noStdMarshalers {
 		fmt.Fprintln(g.out, "// MarshalJSON supports json.Marshaler interface")
-		fmt.Fprintln(g.out, "func (v "+typ+") MarshalJSON() ([]byte, error) {")
+		fmt.Fprintln(g.out, "func (v "+ptrPrefix+typ+") MarshalJSON() ([]byte, error) {")
 		fmt.Fprintln(g.out, "  w := jwriter.Writer{}")
-		fmt.Fprintln(g.out, "  "+fname+"(&w, v)")
+		fmt.Fprintln(g.out, "  "+fname+"(&w, "+addrOfPrefix+"v)")
 		fmt.Fprintln(g.out, "  return w.Buffer.BuildBytes(), w.Error")
 		fmt.Fprintln(g.out, "}")
 	}
 
 	fmt.Fprintln(g.out, "// MarshalEasyJSON supports easyjson.Marshaler interface")
-	fmt.Fprintln(g.out, "func (v "+typ+") MarshalEasyJSON(w *jwriter.Writer) {")
-	fmt.Fprintln(g.out, "  "+fname+"(w, v)")
+	fmt.Fprintln(g.out, "func (v "+ptrPrefix+typ+") MarshalEasyJSON(w *jwriter.Writer) {")
+	fmt.Fprintln(g.out, "  "+fname+"(w, "+addrOfPrefix+"v)")
 	fmt.Fprintln(g.out, "}")
 
 	return nil
diff --git a/gen/generator.go b/gen/generator.go
index 79f4d6f7..59510157 100644
--- a/gen/generator.go
+++ b/gen/generator.go
@@ -39,6 +39,7 @@ type Generator struct {
 	fieldNamer               FieldNamer
 	simpleBytes              bool
 	skipMemberNameUnescaping bool
+	ptrReceivers             bool
 
 	// package path to local alias map for tracking imports
 	imports map[string]string
@@ -123,6 +124,11 @@ func (g *Generator) SkipMemberNameUnescaping() {
 	g.skipMemberNameUnescaping = true
 }
 
+// PtrReceivers instructs to use pointer receivers for marshaling methods of structs.
+func (g *Generator) PtrReceivers() {
+	g.ptrReceivers = true
+}
+
 // OmitEmpty triggers `json=",omitempty"` behaviour by default.
 func (g *Generator) OmitEmpty() {
 	g.omitEmpty = true