build by env AWS_SDK_CLIENT_GO_GEN

README.md

@@ -26,22 +26,39 @@ $ brew install fujiwara/tap/aws-sdk-client-go
 
 You can build the client yourself, including only the needed services and methods. The optimized binary is small and boots up quickly.
 
-The client is built by a configuration file `gen.yaml`.
+The client is built by a configuration file `gen.yaml` or `AWS_SDK_CLIENT_GO_GEN` environment variable.
+
+### `AWS_SDK_CLIENT_GO_GEN` environment variable
+
+Set the environment variable `AWS_SDK_CLIENT_GO_GEN` to list the services joined by commas.
+
+For example, to build the client for ECS, Firehose, and S3:
+
+```console
+$ export AWS_SDK_CLIENT_GO_GEN="ecs,firehose,s3"
+```
+
+All methods of the specified services are generated. To build only specified methods, use the `gen.yaml` configuration file.
+
+### `gen.yaml` configuration file
 
 ```yaml
+# gen.yaml
 services:
   ecs:
     - DescribeClusters
     - DescribeTasks
   firehose:
     - DescribeDeliveryStream
     - ListDeliveryStreams
-  kinesis:
+  s3:
     # all methods of the service
 ```
 
 Keys of `services` are AWS service names (`github.com/aws/aws-sdk-go-v2/service/*`), and values are method names of the service client (for example, `s3` is [s3.Client](https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/service/s3#Client)). If you don't specify the method names, all methods of the service client are generated.
 
+### Build the client
+
 To build the client, run the following commands (or simply run `make`):
 
 ```console
@@ -52,6 +69,7 @@ $ go build -o your-client ./cmd/aws-sdk-client-go/main.go
 1. `go generate ./cmd/aws-sdk-client-gen .` generates the generator by `gen.yaml`.
 2. `go build -o your-client ./cmd/aws-sdk-client-go/main.go` builds your client.
 
+If you change the configuration, run `make clean` before `make` to purge the generated files.
 
 ## Performance comparison
 

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

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"log"
 	"os"
+	"strings"
 	"text/template"
 
 	"github.com/goccy/go-yaml"
@@ -41,16 +42,27 @@ type GenerateConfig struct {
 func main() {
 	log.Println("generating gen.go")
 
-	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)
+	e := os.Getenv("AWS_SDK_CLIENT_GO_GEN")
+	if e != "" {
+		log.Printf("AWS_SDK_CLIENT_GO_GEN is set, generating services: %s", e)
+		services := strings.Split(e, ",")
+		cfg.Services = make(map[string][]string, len(services))
+		for _, service := range services {
+			cfg.Services[service] = nil
+		}
+	} else {
+		log.Printf("AWS_SDK_CLIENT_GO_GEN is not set, reading gen.yaml")
+		f, err := os.Open("../../gen.yaml")
+		if err != nil {
+			log.Fatalf("failed to open gen.yaml: %v", err)
+		}
+		defer f.Close()
+		if err := yaml.NewDecoder(f).Decode(&cfg); err != nil {
+			log.Fatalf("failed to decode gen.yaml: %v", err)
+		}
 	}
+
 	tmpl, err := template.New("gen").Parse(templateStr)
 	if err != nil {
 		log.Fatalf("failed to parse template: %v", err)