replace generator code with text/template

cmd/aws-sdk-client-gen-gen/main.go

@@ -1,47 +1,63 @@
 package main
 
 import (
-	"fmt"
+	"bytes"
 	"log"
 	"os"
+	"text/template"
 
 	"github.com/goccy/go-yaml"
 )
 
+const templateStr = `// Code generated by cmd/aws-sdk-client-gen-gen/main.go; DO NOT EDIT.
+package main
+
+import (
+	"reflect"
+{{ range $key, $value := .Services }}
+	"github.com/aws/aws-sdk-go-v2/service/{{ $key }}"
+{{- end }}
+)
+
+func generateAll() {
+{{ range $key, $value := .Services }}
+{{- if eq (len $value) 0 }}
+	gen("{{ $key }}", reflect.TypeOf({{ $key }}.New({{ $key }}.Options{})), nil)
+{{- else }}
+	gen("{{ $key }}", reflect.TypeOf({{ $key }}.New({{ $key }}.Options{})), {{ printf "%#v" $value }})
+{{- end }}
+{{ end }}
+}
+`
+
 type GenerateConfig struct {
 	Services map[string][]string `json:"services"`
 }
 
 func main() {
 	log.Println("generating gen.go")
-	o, err := os.Create("gen.go")
-	if err != nil {
-		log.Fatalf("failed to create gen.go: %v", err)
-	}
+
 	f, err := os.Open("../../gen.yaml")
 	if err != nil {
 		log.Fatalf("failed to open gen.yaml: %v", err)
 	}
 	defer f.Close()
+
 	cfg := GenerateConfig{}
 	if err := yaml.NewDecoder(f).Decode(&cfg); err != nil {
 		log.Fatalf("failed to decode gen.yaml: %v", err)
 	}
-
-	fmt.Fprintln(o, "// Code generated by cmd/aws-sdk-client-gen-gen/main.go; DO NOT EDIT.")
-	fmt.Fprintln(o, "package main")
-	fmt.Fprintln(o, "import \"reflect\"")
-	for k := range cfg.Services {
-		fmt.Fprintf(o, "import \"github.com/aws/aws-sdk-go-v2/service/%s\"\n", k)
+	tmpl, err := template.New("gen").Parse(templateStr)
+	if err != nil {
+		log.Fatalf("failed to parse template: %v", err)
+	}
+	buf := &bytes.Buffer{}
+	if err := tmpl.Execute(buf, cfg); err != nil {
+		log.Fatalf("failed to execute template: %v", err)
 	}
-	fmt.Fprintln(o, "func generateAll() {")
-	for k, v := range cfg.Services {
-		if len(v) == 0 {
-			fmt.Fprintf(o, "	gen(\"%s\", reflect.TypeOf(%s.New(%s.Options{})), nil)\n", k, k, k)
-		} else {
-			fmt.Fprintf(o, "	gen(\"%s\", reflect.TypeOf(%s.New(%s.Options{})), %#v)\n", k, k, k, v)
-		}
+
+	if err := os.WriteFile("gen.go", buf.Bytes(), 0644); err != nil {
+		log.Fatalf("failed to write gen.go: %v", err)
 	}
-	fmt.Fprintln(o, "}")
 	log.Println("generated gen.go")
 }

cmd/aws-sdk-client-gen/main.go

@@ -1,36 +1,57 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"log"
 	"os"
 	"reflect"
 	"strings"
+	"text/template"
 )
 
 //go:generate go run ../aws-sdk-client-gen-gen/main.go
 //go:generate go get ./...
 
+const templateStr = `// Code generated by cmd/aws-sdk-client-gen/main.go; DO NOT EDIT.
+package sdkclient
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/service/{{ .PkgName }}"
+)
+
+{{ range .Methods }}
+func {{ $.PkgName }}_{{ .Name }}(ctx context.Context, awsCfg aws.Config, b json.RawMessage) (any, error) {
+	svc := {{ $.PkgName }}.NewFromConfig(awsCfg)
+	var in {{ .Input }}
+	if err := json.Unmarshal(b, &in); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal request: %w", err)
+	}
+	return svc.{{ .Name }}(ctx, &in)
+}
+
+{{ end }}
+
+func init() {
+{{- range .Methods }}
+	clientMethods["{{ $.PkgName }}#Client.{{ .Name }}"] = {{ $.PkgName }}_{{ .Name }}
+{{- end }}
+}
+`
+
 func main() {
 	generateAll()
 }
 
 func gen(pkgName string, clientType reflect.Type, genNames []string) error {
 	log.Printf("generating %s_gen.go", pkgName)
-	buf := &strings.Builder{}
-	fmt.Fprintln(buf, "// Code generated by cmd/aws-sdk-client-gen/main.go; DO NOT EDIT.")
-	fmt.Fprintln(buf, "package sdkclient")
-	fmt.Fprintln(buf)
-	fmt.Fprintf(buf, `import (
-		"context"
-		"encoding/json"
-		"fmt"
 
-		"github.com/aws/aws-sdk-go-v2/aws"
-		"github.com/aws/aws-sdk-go-v2/service/%s"
-	)
-	`, pkgName)
-	var methodNames []string
+	methods := make([]map[string]string, 0)
 	for i := 0; i < clientType.NumMethod(); i++ {
 		method := clientType.Method(i)
 		if len(genNames) > 0 && !contains(genNames, method.Name) {
@@ -44,32 +65,27 @@ func gen(pkgName string, clientType reflect.Type, genNames []string) error {
 			log.Printf("no params func %s", method.Name)
 			continue
 		}
-		methodNames = append(methodNames, method.Name)
-		log.Printf("generating %s_%s", pkgName, method.Name)
-		fmt.Fprintf(buf, `func %s_%s(ctx context.Context, awsCfg aws.Config, b json.RawMessage) (any, error) {
-			svc := %s.NewFromConfig(awsCfg)
-			var in %s
-			if err := json.Unmarshal(b, &in); err != nil {
-				return nil, fmt.Errorf("failed to unmarshal request: %%w", err)
-			}
-			return svc.%s(ctx, &in)
-		}
-		`,
-			pkgName,
-			method.Name,
-			pkgName,
-			strings.TrimPrefix(params[2], "*"), // (receiver, context.Context, *Request, ...)
-			method.Name,
-		)
-		fmt.Fprintln(buf)
+		methods = append(methods, map[string]string{
+			"Name":  method.Name,
+			"Input": strings.TrimPrefix(params[2], "*"),
+		})
 	}
-	fmt.Fprintln(buf, `func init() {`)
-	for _, name := range methodNames {
-		fmt.Fprintf(buf, "	clientMethods[\"%s#Client.%s\"] = %s_%s\n", pkgName, name, pkgName, name)
+
+	tmpl, err := template.New("clientGen").Parse(templateStr)
+	if err != nil {
+		return fmt.Errorf("failed to parse template: %w", err)
+	}
+
+	data := map[string]interface{}{
+		"PkgName": pkgName,
+		"Methods": methods,
 	}
-	fmt.Fprintln(buf, "}")
 
-	if err := os.WriteFile(pkgName+"_gen.go", []byte(buf.String()), 0644); err != nil {
+	buf := &bytes.Buffer{}
+	if err := tmpl.Execute(buf, data); err != nil {
+		return fmt.Errorf("failed to execute template: %w", err)
+	}
+	if err := os.WriteFile(pkgName+"_gen.go", buf.Bytes(), 0644); err != nil {
 		return err
 	}
 	log.Printf("generated %s_gen.go", pkgName)