add --output-stream(-o), --no-api-output(-n) option

README.md

@@ -80,11 +80,13 @@ Arguments:
   [<input>]      input JSON
 
 Flags:
-  -h, --help                   Show context-sensitive help.
-  -i, --input-stream=STRING    bind input filename or '-' to io.Reader field in the input struct
-  -c, --compact                compact JSON output
-  -q, --query=STRING           JMESPath query to apply to output
-  -v, --version                show version
+  -h, --help                    Show context-sensitive help.
+  -i, --input-stream=STRING     bind input filename or '-' to io.Reader field in the input struct
+  -o, --output-stream=STRING    bind output filename or '-' to io.ReadCloser field in the output struct
+  -n, --no-api-output           do not output API response into stdout
+  -c, --compact                 compact JSON output
+  -q, --query=STRING            JMESPath query to apply to output
+  -v, --version                 show version
 ```
 
 - `service`: AWS service name.
@@ -123,20 +125,34 @@ $ aws-sdk-client-go ecs describe-clusters '{"Cluster":"default"}'
 
 #### `--input-stream` option
 
-`--input-stream` option allows you to bind a file or stdin to the input struct.
+`--input-stream` (`-i`) option allows you to bind a file or stdin to the input struct.
 
 ```console
 $ aws-sdk-client-go s3 put-object '{"Bucket": "my-bucket", "Key": "my.txt"}' --input-stream my.txt
 ```
 
 [s3#PutObjectInput](https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/service/s3#PutObjectInput) has `Body` field of `io.Reader`. `--input-stream` option binds the file to the field.
 
-When the input struct has only one field of `io.Reader`, `aws-sdk-client-go` reads the file and binds it to the field automatically. (At now, all SDK input structs have only one field of `io.Reader`.)
+When the input struct has only one field of `io.Reader`, `aws-sdk-client-go` reads the file and binds it to the field automatically. (Currently, all SDK input structs have at most one io.Reader field.)
 
 When the input struct has a "\*Length" field for the size of the content, `aws-sdk-client-go` sets the size of the content to the field automatically. For example, [s3#PutObjectInput](https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/service/s3#PutObjectInput) has `ContentLength` field.
 
 If `--input-stream` is "-", `aws-sdk-client-go` reads from stdin. In this case, `aws-sdk-client-go` reads all contents into memory, so it is not suitable for large files. Consider using a file for large content.
 
+#### `--output-stream` option
+
+`--output-stream` (`-o`) option allows you to bind the `io.ReadCloser` of the API output to a file or stdout.
+
+```console
+$ aws-sdk-client-go s3 get-object '{"Bucket": "my-bucket", "Key": "my.txt"}' --output-stream my.txt
+```
+
+[s3#GetObjectOutput](https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/service/s3#PutObjectOutput) has `Body` field of `io.ReadeCloser`. `--output-stream` option binds the file to the field.
+
+When the output struct has only one field of `io.ReadCloser`, `aws-sdk-client-go` copies it to the file automatically. (Currently, all SDK output structs have at most one io.ReadCloser field.)
+
+If `--output-stream` is "-", `aws-sdk-client-go` writes into stdout. The result of the API also writes to stdout by default. If you don't want to output the result, use `--no-api-output` (`-n`).
+
 #### Query output by JMESPath
 
 `--query` option allows you to query the output by JMESPath like the AWS CLI.

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

@@ -20,12 +20,16 @@ import (
 )
 
 func generateAll() {
+	var err error
 {{ range $key, $value := .Services }}
 {{- if eq (len $value) 0 }}
-	gen("{{ $key }}", reflect.TypeOf({{ $key }}.New({{ $key }}.Options{})), nil)
+	err = gen("{{ $key }}", reflect.TypeOf({{ $key }}.New({{ $key }}.Options{})), nil)
 {{- else }}
-	gen("{{ $key }}", reflect.TypeOf({{ $key }}.New({{ $key }}.Options{})), {{ printf "%#v" $value }})
+	err = gen("{{ $key }}", reflect.TypeOf({{ $key }}.New({{ $key }}.Options{})), {{ printf "%#v" $value }})
 {{- end }}
+	if err != nil {
+		panic("failed to generate {{ $key }}" + err.Error())
+	}
 {{ end }}
 }
 `

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

@@ -28,21 +28,32 @@ import (
 func {{ $.PkgName }}_{{ .Name }}(ctx context.Context, p *clientMethodParam) (any, error) {
 	svc := {{ $.PkgName }}.NewFromConfig(p.awsCfg)
 	var in {{ .Input }}
-	{{ if .InputReaderLengthField }}
+	{{- if .InputReaderLengthField }}
 	p.mustInject("{{ .InputReaderLengthField }}", p.InputReaderLength)
-	{{ end }}
-
+	{{- end }}
 	if err := json.Unmarshal(p.InputBytes, &in); err != nil {
 		return nil, fmt.Errorf("failed to unmarshal request: %w", err)
 	}
-	if p.InputReader != nil {
+	if err := p.validate("{{ $.PkgName }}.{{ .Name }}", "{{ .InputReaderField }}", "{{ .OutputReadCloserField }}"); err != nil {
+		return nil, err
+	}
 	{{- if .InputReaderField }}
+	if p.InputReader != nil {
 		in.{{ .InputReaderField }} = p.InputReader
-	{{- else }}
-		return nil, fmt.Errorf("{{ $.PkgName }}.{{ .Name }}Input has no io.Reader field")
+	}
 	{{- end }}
+	{{- if .OutputReadCloserField }}
+	if out, err := svc.{{ .Name }}(ctx, &in); err != nil {
+		return nil, err
+	} else {
+		if err := p.Output(out.{{ .OutputReadCloserField }}); err != nil {
+			return nil, err
+		}
+		return out, nil
 	}
+	{{- else }}
 	return svc.{{ .Name }}(ctx, &in)
+	{{- end }}
 }
 
 {{ end }}
@@ -99,24 +110,26 @@ func gen(pkgName string, clientType reflect.Type, genNames []string) error {
 				}
 			}
 		}
+
+		var outputReadCloserField string
+		output := method.Type.Out(0).Elem()
+		for j := 0; j < output.NumField(); j++ {
+			field := output.Field(j)
+			if t := field.Type.String(); t == "io.ReadCloser" {
+				log.Printf("found %s field in %s.%sOutput %s %s", t, pkgName, method.Name, field.Name, t)
+				if outputReadCloserField != "" {
+					return fmt.Errorf("found multiple io.ReadCloser fields in %s.%sOutput", pkgName, method.Name)
+				}
+				outputReadCloserField = field.Name
+			}
+		}
 		methods = append(methods, map[string]string{
 			"Name":                   method.Name,
 			"Input":                  strings.TrimPrefix(params[2], "*"),
 			"InputReaderField":       inputReaderField,
 			"InputReaderLengthField": inputReaderLengthField,
+			"OutputReadCloserField":  outputReadCloserField,
 		})
-		/*
-			output := method.Type.Out(0)
-			if output.Kind() == reflect.Ptr {
-				output = output.Elem()
-			}
-			for j := 0; j < output.NumField(); j++ {
-				field := output.Field(j)
-				if t := field.Type.String(); strings.Contains(t, "io.") {
-					log.Printf("found %s field in %s.%sOutput %s %s", t, pkgName, method.Name, field.Name, t)
-				}
-			}
-		*/
 	}
 
 	tmpl, err := template.New("clientGen").Parse(templateStr)

main.go

@@ -27,10 +27,12 @@ type CLI struct {
 	Method  string `arg:"" help:"method name" default:""`
 	Input   string `arg:"" help:"input JSON" default:"{}"`
 
-	InputStream string `short:"i" help:"bind input filename or '-' to io.Reader field in the input struct"`
-	Compact     bool   `short:"c" help:"compact JSON output"`
-	Query       string `short:"q" help:"JMESPath query to apply to output"`
-	Version     bool   `short:"v" help:"show version"`
+	InputStream  string `short:"i" help:"bind input filename or '-' to io.Reader field in the input struct"`
+	OutputStream string `short:"o" help:"bind output filename or '-' to io.ReadCloser field in the output struct"`
+	NoAPIOutput  bool   `short:"n" help:"do not output API response into stdout"`
+	Compact      bool   `short:"c" help:"compact JSON output"`
+	Query        string `short:"q" help:"JMESPath query to apply to output"`
+	Version      bool   `short:"v" help:"show version"`
 
 	w io.Writer
 }
@@ -82,6 +84,10 @@ func (c *CLI) CallMethod(ctx context.Context) error {
 		return err
 	}
 
+	if c.NoAPIOutput {
+		return nil
+	}
+
 	if c.Query != "" {
 		out, err = jmespath.Search(c.Query, out)
 		if err != nil {
@@ -110,9 +116,10 @@ func (c *CLI) clientMethodParam(ctx context.Context) (*clientMethodParam, error)
 		return nil, err
 	}
 	p := &clientMethodParam{
-		awsCfg:      awsCfg,
-		InputBytes:  json.RawMessage(c.Input),
-		InputReader: nil,
+		awsCfg:       awsCfg,
+		InputBytes:   json.RawMessage(c.Input),
+		InputReader:  nil,
+		OutputWriter: nil,
 	}
 
 	switch c.InputStream {
@@ -140,6 +147,21 @@ func (c *CLI) clientMethodParam(ctx context.Context) (*clientMethodParam, error)
 		}
 		p.InputReaderLength = aws.Int64(st.Size())
 	}
+
+	switch c.OutputStream {
+	case "":
+		// do nothing
+	case "-": // stdout
+		p.OutputWriter = os.Stdout
+	default:
+		f, err := os.Create(c.OutputStream)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create output file: %w", err)
+		}
+		p.OutputWriter = f
+		p.cleanup = append(p.cleanup, f.Close)
+	}
+
 	return p, nil
 }
 

param.go

@@ -14,6 +14,7 @@ type clientMethodParam struct {
 	InputBytes        json.RawMessage
 	InputReader       io.Reader
 	InputReaderLength *int64
+	OutputWriter      io.Writer
 
 	awsCfg  aws.Config
 	cleanup []func() error
@@ -27,6 +28,25 @@ func (p *clientMethodParam) Cleanup() {
 	}
 }
 
+func (p *clientMethodParam) Output(src io.ReadCloser) error {
+	if p.OutputWriter == nil {
+		return nil
+	}
+	defer src.Close()
+	_, err := io.Copy(p.OutputWriter, src)
+	return err
+}
+
+func (p *clientMethodParam) validate(name, inputReaderField, outputReadCloserField string) error {
+	if p.InputReader != nil && inputReaderField == "" {
+		return fmt.Errorf("%sInput has not io.Reader field", name)
+	}
+	if p.OutputWriter != nil && outputReadCloserField == "" {
+		return fmt.Errorf("%sOutput has not io.ReadCloser field", name)
+	}
+	return nil
+}
+
 func (p *clientMethodParam) mustInject(field string, value *int64) {
 	v := make(map[string]any)
 	if err := json.Unmarshal(p.InputBytes, &v); err != nil {