feature: add support for source <(aws-sso completions --source)

Enables installing the completions at build time (aka during package building) and also simplifies the management of completions in the long run as the only required modification to the shell rc file can be a single line.

cmd/aws-sso/completions_cmd.go

@@ -27,6 +27,7 @@ import (
 )
 
 type CompleteCmd struct {
+	Source         bool   `kong:"help='Print out completions for sourcing in the active shell',xor='action'"`
 	Install        bool   `kong:"short='I',help='Install shell completions',xor='action'"`
 	Uninstall      bool   `kong:"short='U',help='Uninstall shell completions',xor='action'"`
 	UninstallPre19 bool   `kong:"help='Uninstall pre-v1.9 shell completion integration',xor='action',xor='shell,script'"`
@@ -37,7 +38,9 @@ type CompleteCmd struct {
 func (cc *CompleteCmd) Run(ctx *RunContext) error {
 	var err error
 
-	if ctx.Cli.Completions.Install {
+	if ctx.Cli.Completions.Source {
+		err = helper.SourceHelper(ctx.Cli.Completions.Shell)
+	} else if ctx.Cli.Completions.Install {
 		// install the current auto-complete helper
 		err = helper.InstallHelper(ctx.Cli.Completions.Shell, ctx.Cli.Completions.ShellScript)
 	} else if ctx.Cli.Completions.Uninstall {

internal/helper/helper.go

@@ -19,8 +19,10 @@ package helper
  */
 
 import (
+	"bytes"
 	"embed"
 	"fmt"
+	"io"
 	"os"
 	"path"
 
@@ -88,6 +90,16 @@ func getScript(shell string) ([]byte, string, error) {
 	return bytes, path, nil
 }
 
+// SourceHelper can be used to generate the completions script for immediate sourcing in the active shell
+func SourceHelper(shell string) error {
+	c, _, err := getScript(shell)
+	if err != nil {
+		return err
+	}
+
+	return printConfig(c)
+}
+
 // InstallHelper installs any helper code into our shell startup script(s)
 func InstallHelper(shell string, path string) error {
 	c, defaultPath, err := getScript(shell)
@@ -119,6 +131,27 @@ func UninstallHelper(shell string, path string) error {
 	return err
 }
 
+func printConfig(contents []byte) error {
+	var err error
+	var exec string
+	var source []byte
+
+	if exec, err = os.Executable(); err != nil {
+		return err
+	}
+
+	args := map[string]string{
+		"Executable": exec,
+	}
+
+	if source, err = utils.GenerateSource(string(contents), args); err != nil {
+		return err
+	}
+
+	_, err = io.Copy(os.Stdout, bytes.NewReader(source))
+	return err
+}
+
 // installConfigFile adds our blob to the given file
 func installConfigFile(path string, contents []byte) error {
 	var err error

internal/utils/fileedit.go

@@ -47,6 +47,21 @@ type FileEdit struct {
 
 var prompt = askUser
 
+func GenerateSource(fileTemplate string, vars interface{}) ([]byte, error) {
+	templ, err := template.New("template").Parse(fileTemplate)
+	if err != nil {
+		return nil, err
+	}
+
+	var buf bytes.Buffer
+	err = templ.Execute(&buf, vars)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
 func NewFileEdit(fileTemplate string, vars interface{}) (*FileEdit, error) {
 	var t string