feat: add DebugWith option

encode.go

@@ -3,6 +3,7 @@ package json
 import (
 	"context"
 	"io"
+	"os"
 	"unsafe"
 
 	"github.com/goccy/go-json/internal/encoder"
@@ -62,6 +63,7 @@ func (e *Encoder) encodeWithOption(ctx *encoder.RuntimeContext, v interface{}, o
 		ctx.Option.Flag |= encoder.HTMLEscapeOption
 	}
 	ctx.Option.Flag |= encoder.NormalizeUTF8Option
+	ctx.Option.DebugOut = os.Stdout
 	for _, optFunc := range optFuncs {
 		optFunc(ctx.Option)
 	}

encode_test.go

@@ -477,7 +477,8 @@ func TestDebugMode(t *testing.T) {
 			t.Fatal("expected error")
 		}
 	}()
-	json.MarshalWithOption(mustErrTypeForDebug{}, json.Debug())
+	var buf bytes.Buffer
+	json.MarshalWithOption(mustErrTypeForDebug{}, json.Debug(), json.DebugWith(&buf))
 }
 
 func TestIssue116(t *testing.T) {

internal/encoder/option.go

@@ -1,6 +1,9 @@
 package encoder
 
-import "context"
+import (
+	"context"
+	"io"
+)
 
 type OptionFlag uint8
 
@@ -19,6 +22,7 @@ type Option struct {
 	Flag        OptionFlag
 	ColorScheme *ColorScheme
 	Context     context.Context
+	DebugOut    io.Writer
 }
 
 type EncodeFormat struct {

internal/encoder/vm/debug_vm.go

@@ -16,16 +16,17 @@ func DebugRun(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet)
 		}
 
 		if err := recover(); err != nil {
-			fmt.Println("=============[DEBUG]===============")
-			fmt.Println("* [TYPE]")
-			fmt.Println(codeSet.Type)
-			fmt.Printf("\n")
-			fmt.Println("* [ALL OPCODE]")
-			fmt.Println(code.Dump())
-			fmt.Printf("\n")
-			fmt.Println("* [CONTEXT]")
-			fmt.Printf("%+v\n", ctx)
-			fmt.Println("===================================")
+			w := ctx.Option.DebugOut
+			fmt.Fprintln(w, "=============[DEBUG]===============")
+			fmt.Fprintln(w, "* [TYPE]")
+			fmt.Fprintln(w, codeSet.Type)
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [ALL OPCODE]")
+			fmt.Fprintln(w, code.Dump())
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [CONTEXT]")
+			fmt.Fprintf(w, "%+v\n", ctx)
+			fmt.Fprintln(w, "===================================")
 			panic(err)
 		}
 	}()

internal/encoder/vm_color/debug_vm.go

@@ -16,16 +16,17 @@ func DebugRun(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet)
 
 	defer func() {
 		if err := recover(); err != nil {
-			fmt.Println("=============[DEBUG]===============")
-			fmt.Println("* [TYPE]")
-			fmt.Println(codeSet.Type)
-			fmt.Printf("\n")
-			fmt.Println("* [ALL OPCODE]")
-			fmt.Println(code.Dump())
-			fmt.Printf("\n")
-			fmt.Println("* [CONTEXT]")
-			fmt.Printf("%+v\n", ctx)
-			fmt.Println("===================================")
+			w := ctx.Option.DebugOut
+			fmt.Fprintln(w, "=============[DEBUG]===============")
+			fmt.Fprintln(w, "* [TYPE]")
+			fmt.Fprintln(w, codeSet.Type)
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [ALL OPCODE]")
+			fmt.Fprintln(w, code.Dump())
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [CONTEXT]")
+			fmt.Fprintf(w, "%+v\n", ctx)
+			fmt.Fprintln(w, "===================================")
 			panic(err)
 		}
 	}()

internal/encoder/vm_color_indent/debug_vm.go

@@ -16,16 +16,17 @@ func DebugRun(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet)
 
 	defer func() {
 		if err := recover(); err != nil {
-			fmt.Println("=============[DEBUG]===============")
-			fmt.Println("* [TYPE]")
-			fmt.Println(codeSet.Type)
-			fmt.Printf("\n")
-			fmt.Println("* [ALL OPCODE]")
-			fmt.Println(code.Dump())
-			fmt.Printf("\n")
-			fmt.Println("* [CONTEXT]")
-			fmt.Printf("%+v\n", ctx)
-			fmt.Println("===================================")
+			w := ctx.Option.DebugOut
+			fmt.Fprintln(w, "=============[DEBUG]===============")
+			fmt.Fprintln(w, "* [TYPE]")
+			fmt.Fprintln(w, codeSet.Type)
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [ALL OPCODE]")
+			fmt.Fprintln(w, code.Dump())
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [CONTEXT]")
+			fmt.Fprintf(w, "%+v\n", ctx)
+			fmt.Fprintln(w, "===================================")
 			panic(err)
 		}
 	}()

internal/encoder/vm_indent/debug_vm.go

@@ -16,16 +16,17 @@ func DebugRun(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet)
 
 	defer func() {
 		if err := recover(); err != nil {
-			fmt.Println("=============[DEBUG]===============")
-			fmt.Println("* [TYPE]")
-			fmt.Println(codeSet.Type)
-			fmt.Printf("\n")
-			fmt.Println("* [ALL OPCODE]")
-			fmt.Println(code.Dump())
-			fmt.Printf("\n")
-			fmt.Println("* [CONTEXT]")
-			fmt.Printf("%+v\n", ctx)
-			fmt.Println("===================================")
+			w := ctx.Option.DebugOut
+			fmt.Fprintln(w, "=============[DEBUG]===============")
+			fmt.Fprintln(w, "* [TYPE]")
+			fmt.Fprintln(w, codeSet.Type)
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [ALL OPCODE]")
+			fmt.Fprintln(w, code.Dump())
+			fmt.Fprintf(w, "\n")
+			fmt.Fprintln(w, "* [CONTEXT]")
+			fmt.Fprintf(w, "%+v\n", ctx)
+			fmt.Fprintln(w, "===================================")
 			panic(err)
 		}
 	}()

option.go

@@ -1,6 +1,8 @@
 package json
 
 import (
+	"io"
+
 	"github.com/goccy/go-json/internal/decoder"
 	"github.com/goccy/go-json/internal/encoder"
 )
@@ -39,6 +41,13 @@ func Debug() EncodeOptionFunc {
 	}
 }
 
+// DebugWith sets the destination to write debug messages.
+func DebugWith(w io.Writer) EncodeOptionFunc {
+	return func(opt *EncodeOption) {
+		opt.DebugOut = w
+	}
+}
+
 // Colorize add an identifier for coloring to the string of the encoded result.
 func Colorize(scheme *ColorScheme) EncodeOptionFunc {
 	return func(opt *EncodeOption) {