Allow to read a plan file from stdin

cmd/filter.go

@@ -11,7 +11,7 @@ import (
 func init() {
 	filterCmd := newFilterCmd()
 	flags := filterCmd.PersistentFlags()
-	flags.StringP("file", "f", "-", "A path of input file")
+	flags.StringP("file", "f", "-", "A path to input Terraform configuration file")
 	flags.BoolP("update", "u", false, "Update files in-place")
 	_ = viper.BindPFlag("file", flags.Lookup("file"))
 	_ = viper.BindPFlag("update", flags.Lookup("update"))

cmd/migration.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"fmt"
+	"io"
 	"os"
 
 	"github.com/minamijoyo/tfedit/migration"
@@ -12,7 +13,9 @@ import (
 func init() {
 	migrationCmd := newMigrationCmd()
 	flags := migrationCmd.PersistentFlags()
+	flags.StringP("file", "f", "-", "A path to input Terraform plan file in JSON format")
 	flags.StringP("out", "o", "-", "Write a migration file to a given path")
+	_ = viper.BindPFlag("file", flags.Lookup("file"))
 	_ = viper.BindPFlag("out", flags.Lookup("out"))
 
 	RootCmd.AddCommand(migrationCmd)
@@ -36,17 +39,13 @@ func newMigrationCmd() *cobra.Command {
 
 func newMigrationAwsv4upgradeCmd() *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "awsv4upgrade <PATH>",
+		Use:   "awsv4upgrade",
 		Short: "Generate a migration file for awsv4upgrade",
 		Long: `Generate a migration file for awsv4upgrade
 
-Generate a migration file as a tfmigrate format.
+Read a Terraform plan file in JSON format and
+generate a migration file in tfmigrate HCL format.
 Only aws_s3_bucket refactor is supported.
-
-
-Arguments:
-  PATH               A path of Terraform plan file.
-                     Only JSON format is supported.
 `,
 		RunE: runMigrationAwsv4upgradeCmd,
 	}
@@ -55,19 +54,33 @@ Arguments:
 }
 
 func runMigrationAwsv4upgradeCmd(cmd *cobra.Command, args []string) error {
-	if len(args) != 1 {
-		return fmt.Errorf("expected 1 argument, but got %d arguments", len(args))
+	if len(args) != 0 {
+		return fmt.Errorf("expected 0 argument, but got %d arguments", len(args))
 	}
 
-	planFile := args[0]
+	planFile := viper.GetString("file")
 	migrationFile := viper.GetString("out")
-	output, err := migration.Generate(planFile)
+
+	var planJSON []byte
+	var err error
+	if planFile == "-" {
+		planJSON, err = io.ReadAll(cmd.InOrStdin())
+		if err != nil {
+			return fmt.Errorf("failed to read input from stdin: %s", err)
+		}
+	} else {
+		planJSON, err = os.ReadFile(planFile)
+		if err != nil {
+			return fmt.Errorf("failed to read file: %s", err)
+		}
+	}
+
+	output, err := migration.Generate(planJSON)
 	if err != nil {
 		return err
 	}
 
 	if migrationFile == "-" {
-		// Write to stdout
 		fmt.Fprintf(cmd.OutOrStdout(), string(output))
 	} else {
 		if err := os.WriteFile(migrationFile, output, os.ModePerm); err != nil {

migration/migration.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
-	"os"
 	"text/template"
 
 	tfjson "github.com/hashicorp/terraform-json"
@@ -29,14 +28,9 @@ func (r *AWSS3BucketACLFilterResource) ID() string {
 	return r.Bucket + "," + r.ACL
 }
 
-func Generate(planFile string) ([]byte, error) {
-	b, err := os.ReadFile(planFile)
-	if err != nil {
-		return nil, fmt.Errorf("failed to read file: %s", err)
-	}
-
+func Generate(planJSON []byte) ([]byte, error) {
 	var plan tfjson.Plan
-	if err := json.Unmarshal(b, &plan); err != nil {
+	if err := json.Unmarshal(planJSON, &plan); err != nil {
 		return nil, fmt.Errorf("failed to parse plan file: %s", err)
 	}