feat(golang-rewrite): create asdf exec command

* Add `rogpeppe/go-internal` as a dependency
* Create `exec.Exec` function
* Create asdf exec command
* Address linter warnings

cmd/cmd.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"asdf/internal/config"
+	"asdf/internal/exec"
 	"asdf/internal/info"
 	"asdf/internal/installs"
 	"asdf/internal/plugins"
@@ -44,6 +45,15 @@ func Execute(version string) {
 		Usage:     "The multiple runtime version manager",
 		UsageText: usageText,
 		Commands: []*cli.Command{
+			{
+				Name: "exec",
+				Action: func(cCtx *cli.Context) error {
+					command := cCtx.Args().Get(0)
+					args := cCtx.Args().Slice()
+
+					return execCommand(logger, command, args)
+				},
+			},
 			{
 				Name: "info",
 				Action: func(_ *cli.Context) error {
@@ -159,6 +169,43 @@ func Execute(version string) {
 	}
 }
 
+func execCommand(logger *log.Logger, command string, args []string) error {
+	if command == "" {
+		logger.Printf("no command specified")
+		return fmt.Errorf("no command specified")
+	}
+
+	conf, err := config.LoadConfig()
+	if err != nil {
+		logger.Printf("error loading config: %s", err)
+		return err
+	}
+
+	currentDir, err := os.Getwd()
+	if err != nil {
+		logger.Printf("unable to get current directory: %s", err)
+		return err
+	}
+
+	executable, found, err := shims.FindExecutable(conf, command, currentDir)
+	if err != nil {
+		logger.Printf("executable not found due to reason: %s", err.Error())
+		return err
+	}
+
+	if !found {
+		logger.Print("executable not found")
+		return fmt.Errorf("executable not found")
+	}
+	if len(args) > 1 {
+		args = args[1:]
+	} else {
+		args = []string{}
+	}
+
+	return exec.Exec(executable, args, os.Environ())
+}
+
 func pluginAddCommand(_ *cli.Context, conf config.Config, logger *log.Logger, pluginName, pluginRepo string) error {
 	if pluginName == "" {
 		// Invalid arguments

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/go-git/go-git/v5 v5.11.0
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/otiai10/copy v1.14.0
+	github.com/rogpeppe/go-internal v1.11.0
 	github.com/sethvargo/go-envconfig v1.0.0
 	github.com/stretchr/testify v1.8.4
 	github.com/urfave/cli/v2 v2.27.1

internal/exec/exec.go

@@ -0,0 +1,12 @@
+// Package exec handles replacing the asdf go process with
+package exec
+
+import (
+	"syscall"
+)
+
+// Exec invokes syscall.Exec to exec an executable. Requires an absolute path to
+// executable.
+func Exec(executablePath string, args []string, env []string) error {
+	return syscall.Exec(executablePath, append([]string{executablePath}, args...), env)
+}

internal/exec/exec_test.go

@@ -0,0 +1,34 @@
+package exec
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"testing"
+
+	"github.com/rogpeppe/go-internal/testscript"
+)
+
+func execit() int {
+	// Exec only works with absolute path
+	cmdPath, _ := exec.LookPath(os.Args[1])
+	err := Exec(cmdPath, os.Args[2:], os.Environ())
+
+	if err != nil {
+		fmt.Printf("Err: %#+v\n", err.Error())
+	}
+
+	return 0
+}
+
+func TestMain(m *testing.M) {
+	os.Exit(testscript.RunMain(m, map[string]func() int{
+		"execit": execit,
+	}))
+}
+
+func TestExec(t *testing.T) {
+	testscript.Run(t, testscript.Params{
+		Dir: "testdata/script",
+	})
+}

internal/exec/testdata/script/exec-env.txtar

@@ -0,0 +1,3 @@
+env ENV=foo
+execit echo this is a $ENV
+stdout 'this is a foo\n'

internal/exec/testdata/script/exec-simple.txtar

@@ -0,0 +1,2 @@
+execit echo this is a test
+stdout 'this is a test\n'