Compare with Goverter

Author: sublee

README.md

@@ -73,10 +73,15 @@ generating type conversion code, it relies on comment-based directives that are
 not validated at compile time. Moreover, because it stops at the first error,
 refactoring becomes difficult when target types change. In contrast, Wire offers
 type-safe configuration and detailed diagnostics, but focuses on dependency
-injection. Convgen combines the best of both worlds, bringing **type-safe
-configuration** and **comprehensive diagnostics** to
+injection.
+
+Convgen combines the best of both worlds, bringing **type-safe configuration**
+and **comprehensive diagnostics** to
 **type conversion code generation**.
 
+To compare Convgen and goverter, see
+[cmd/vs-goverter/README.md](cmd/vs-goverter/README.md).
+
 ## Quick Start
 
 1. Install Convgen:

cmd/vs-goverter/README.md

@@ -0,0 +1,34 @@
+# Convgen vs. Goverter
+
+This directory contains code to compare
+[Convgen](https://github.com/sublee/convgen) and
+[Goverter](https://github.com/jmattheis/goverter).
+
+Generated code is already checked in. But you can regenerate it by running:
+
+```bash
+go run ./cmd/convgen ./cmd/vs-goverter
+go run github.com/jmattheis/goverter/cmd/goverter@v1.9.2 gen ./cmd/vs-goverter
+```
+
+The program output is:
+
+```
+# Case 1: Successful conversion
+
+Input:
+  {ID:499602d2 Name:John Doe URLs:[https://example.com] Role:2 CreateTime:2025-01-02 03:04:05 +0000 UTC}
+Convgen:
+  {"id":"499602d2","firstname":"John","lastname":"Doe","urls":["https://example.com"],"role":"member","createdAt":1735787045}
+Goverter:
+  {"id":"499602d2","firstname":"John","lastname":"Doe","urls":["https://example.com"],"role":"member","createdAt":1735787045}
+
+# Case 2: Comprehensive error message
+
+Input:
+  {ID:0 Name:Alice URLs:[] Role:0 CreateTime:0001-01-01 00:00:00 +0000 UTC}
+Convgen:
+  converting User.Name: need two parts to parse firstname: "Alice"
+Goverter:
+  need two parts to parse firstname: "Alice"
+```

cmd/vs-goverter/api/model.go

@@ -0,0 +1,40 @@
+package api
+
+import (
+	"encoding/json"
+)
+
+type User struct {
+	Id        string   `json:"id"`
+	Firstname string   `json:"firstname"`
+	Lastname  string   `json:"lastname"`
+	Urls      []string `json:"urls"`
+	Role      UserRole `json:"role"`
+	CreatedAt int64    `json:"createdAt"`
+}
+
+func (u User) String() string {
+	b, _ := json.Marshal(u)
+	return string(b)
+}
+
+type UserRole int
+
+const (
+	UserRoleUnspecified UserRole = iota
+	Admin
+	Member
+	Guest
+)
+
+func (r UserRole) MarshalJSON() ([]byte, error) {
+	switch r {
+	case Admin:
+		return json.Marshal("admin")
+	case Member:
+		return json.Marshal("member")
+	case Guest:
+		return json.Marshal("guest")
+	}
+	return json.Marshal(nil)
+}

cmd/vs-goverter/convgen.go

@@ -0,0 +1,31 @@
+//go:build convgen
+
+package main
+
+import (
+	"time"
+
+	"github.com/sublee/convgen"
+	"github.com/sublee/convgen/cmd/vs-goverter/api"
+)
+
+var mod = convgen.Module(
+	convgen.RenameReplace("", "", "Id", "ID"),
+	convgen.RenameReplace("", "", "Url", "URL"),
+	convgen.ImportFunc(func(u unique) string { return u.String() }),
+	convgen.ImportFunc(func(t time.Time) int64 { return t.Unix() }),
+)
+
+var ConvgenVersion = convgen.StructErr[User, api.User](mod,
+	convgen.MatchFuncErr(User{}.Name, api.User{}.Firstname, firstname),
+	convgen.MatchFuncErr(User{}.Name, api.User{}.Lastname, lastname),
+	convgen.Match(User{}.CreateTime, api.User{}.CreatedAt),
+)
+
+var convgenVersionUserRole = convgen.Enum[UserRole, api.UserRole](mod, api.UserRoleUnspecified,
+	convgen.RenameTrimPrefix("UserRole", ""),
+	convgen.MatchSkip(UserRoleUnknown, nil),
+)
+
+// avoid unused error
+var _ = convgenVersionUserRole

cmd/vs-goverter/convgen_gen.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"time"
+
+	"github.com/sublee/convgen/cmd/vs-goverter/api"
+)
+
+// goverter:variables
+// goverter:extend uniqueToString
+// goverter:extend timeToUnix
+// goverter:matchIgnoreCase
+var (
+	// goverter:map Name Firstname | firstname
+	// goverter:map Name Lastname  | lastname
+	// goverter:map CreateTime CreatedAt
+	GoverterVersion func(User) (api.User, error)
+
+	// goverter:enum:unknown UserRoleUnspecified
+	// goverter:enum:transform regex UserRole(\w+) $1
+	// goverter:enum:map UserRoleUnknown UserRoleUnspecified
+	GoverterVersionUserRole func(UserRole) api.UserRole
+)
+
+func uniqueToString(u unique) string { return u.String() }
+
+func timeToUnix(t time.Time) int64 { return t.Unix() }
+
+var (
+	// avoid unused error
+	_ = uniqueToString
+	_ = timeToUnix
+)

cmd/vs-goverter/goverter.gen.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func main() {
+	fmt.Println("# Case 1: Successful conversion")
+	fmt.Println()
+
+	u1 := User{
+		ID:         unique(1234567890),
+		Name:       "John Doe",
+		URLs:       []string{"https://example.com"},
+		Role:       UserRoleMember,
+		CreateTime: time.Date(2025, 1, 2, 3, 4, 5, 0, time.UTC),
+	}
+	fmt.Println("Input:")
+	fmt.Printf("\t%+v\n", u1)
+
+	fmt.Println("Convgen:")
+	cgOut, _ := ConvgenVersion(u1)
+	fmt.Printf("\t%s\n", cgOut)
+
+	fmt.Println("Goverter:")
+	gvOut, _ := GoverterVersion(u1)
+	fmt.Printf("\t%s\n", gvOut)
+
+	fmt.Println()
+
+	fmt.Println("# Case 2: Comprehensive error message")
+	fmt.Println()
+
+	u2 := User{Name: "Alice"}
+	fmt.Println("Input:")
+	fmt.Printf("\t%+v\n", u2)
+
+	fmt.Println("Convgen:")
+	_, cgErr := ConvgenVersion(u2)
+	fmt.Printf("\t%s\n", cgErr.Error())
+
+	fmt.Println("Goverter:")
+	_, gvErr := GoverterVersion(u2)
+	fmt.Printf("\t%s\n", gvErr.Error())
+}

cmd/vs-goverter/goverter.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type User struct {
+	ID         unique
+	Name       string
+	URLs       []string
+	Role       UserRole
+	CreateTime time.Time
+}
+
+type unique int64
+
+func (u unique) String() string { return strconv.FormatInt(int64(u), 16) }
+
+func firstname(name string) (string, error) {
+	parts := strings.Split(name, " ")
+	if len(parts) != 2 {
+		return "", fmt.Errorf("need two parts to parse firstname: %q", name)
+	}
+	return parts[0], nil
+}
+
+func lastname(name string) (string, error) {
+	parts := strings.Split(name, " ")
+	if len(parts) != 2 {
+		return "", fmt.Errorf("need two parts to parse firstname: %q", name)
+	}
+	return parts[1], nil
+}
+
+type UserRole int
+
+const (
+	UserRoleUnknown UserRole = iota
+	UserRoleAdmin
+	UserRoleMember
+	UserRoleGuest
+)