fix: restore symlink support for tool versions

Fixes a regression where symlink support for tool versions was inadvertently dropped.

Fixes asdf-vm#1873

Author: khmm12

internal/installs/installs.go

@@ -4,8 +4,10 @@
 package installs
 
 import (
+	"errors"
 	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 
 	"github.com/asdf-vm/asdf/internal/config"
@@ -19,19 +21,26 @@ func Installed(conf config.Config, plugin plugins.Plugin) (versions []string, er
 	installDirectory := data.InstallDirectory(conf.DataDir, plugin.Name)
 	files, err := os.ReadDir(installDirectory)
 	if err != nil {
-		if _, ok := err.(*fs.PathError); ok {
-			return versions, nil
+		if isFileNotFoundError(err) {
+			return nil, nil
 		}
 
-		return versions, err
+		return nil, err
 	}
 
 	for _, file := range files {
-		if !file.IsDir() {
-			continue
+		IsDir, err := resolveIsDirectory(installDirectory, file)
+		if err != nil {
+			if isFileNotFoundError(err) {
+				continue
+			}
+
+			return nil, err
 		}
 
-		versions = append(versions, file.Name())
+		if IsDir {
+			versions = append(versions, file.Name())
+		}
 	}
 
 	return versions, err
@@ -63,3 +72,38 @@ func IsInstalled(conf config.Config, plugin plugins.Plugin, version toolversions
 	_, err := os.Stat(installDir)
 	return !os.IsNotExist(err)
 }
+
+// isDirectory checks if a given file is a directory or a symbolic link to a directory.
+func resolveIsDirectory(parent string, file os.DirEntry) (bool, error) {
+	if file.IsDir() {
+		return true, nil
+	}
+
+	// Check if file is a symbolic link (which is a directory)
+	if file.Type()&os.ModeSymlink == 0 {
+		return false, nil
+	}
+
+	// Resolve symbolic link to determine if it points to a directory
+	linkTarget, err := os.Readlink(filepath.Join(parent, file.Name()))
+	if err != nil {
+		return false, err
+	}
+
+	// If the link target is relative, resolve it to an absolute path
+	if !path.IsAbs(linkTarget) {
+		linkTarget = filepath.Join(parent, linkTarget)
+	}
+
+	info, err := os.Stat(linkTarget)
+	if err != nil {
+		return false, err
+	}
+
+	return info.IsDir(), nil
+}
+
+func isFileNotFoundError(err error) bool {
+	var ferr *fs.PathError
+	return errors.As(err, &ferr) || errors.Is(err, fs.ErrNotExist)
+}

internal/installs/installs_test.go

@@ -48,35 +48,67 @@ func TestInstallPath(t *testing.T) {
 }
 
 func TestInstalled(t *testing.T) {
-	conf, plugin := generateConfig(t)
-
 	t.Run("returns empty slice for newly installed plugin", func(t *testing.T) {
+		conf, plugin := generateConfig(t)
 		installedVersions, err := Installed(conf, plugin)
 		assert.Nil(t, err)
 		assert.Empty(t, installedVersions)
 	})
 
 	t.Run("returns slice of all installed versions for a tool", func(t *testing.T) {
+		conf, plugin := generateConfig(t)
 		mockInstall(t, conf, plugin, "1.0.0")
 
 		installedVersions, err := Installed(conf, plugin)
 		assert.Nil(t, err)
 		assert.Equal(t, installedVersions, []string{"1.0.0"})
 	})
+
+	t.Run("returns installed versions including symlinks", func(t *testing.T) {
+		conf, plugin := generateConfig(t)
+		mockInstall(t, conf, plugin, "1.0.0")
+		aliasVersion(t, conf, plugin, "1.0.0", "latest")
+
+		installedVersions, err := Installed(conf, plugin)
+		assert.Nil(t, err)
+		assert.Equal(t, installedVersions, []string{"1.0.0", "latest"})
+	})
 }
 
 func TestIsInstalled(t *testing.T) {
-	conf, plugin := generateConfig(t)
-	installVersion(t, conf, plugin, "1.0.0")
-
 	t.Run("returns false when not installed", func(t *testing.T) {
+		conf, plugin := generateConfig(t)
+		installVersion(t, conf, plugin, "1.0.0")
+
 		version := toolversions.Version{Type: "version", Value: "4.0.0"}
 		assert.False(t, IsInstalled(conf, plugin, version))
 	})
+
 	t.Run("returns true when installed", func(t *testing.T) {
+		conf, plugin := generateConfig(t)
+		installVersion(t, conf, plugin, "1.0.0")
+
 		version := toolversions.Version{Type: "version", Value: "1.0.0"}
 		assert.True(t, IsInstalled(conf, plugin, version))
 	})
+
+	t.Run("returns true when aliased using symlinks", func(t *testing.T) {
+		conf, plugin := generateConfig(t)
+		installVersion(t, conf, plugin, "1.0.0")
+		aliasVersion(t, conf, plugin, "1.0.0", "latest")
+
+		version := toolversions.Version{Type: "alias", Value: "latest"}
+		assert.True(t, IsInstalled(conf, plugin, version))
+	})
+
+	t.Run("returns false when symlink broken", func(t *testing.T) {
+		conf, plugin := generateConfig(t)
+		installVersion(t, conf, plugin, "1.0.0")
+		aliasVersion(t, conf, plugin, "2.0.0", "latest")
+
+		version := toolversions.Version{Type: "alias", Value: "latest"}
+		assert.False(t, IsInstalled(conf, plugin, version))
+	})
 }
 
 // helper functions
@@ -101,6 +133,14 @@ func mockInstall(t *testing.T, conf config.Config, plugin plugins.Plugin, versio
 	assert.Nil(t, err)
 }
 
+func aliasVersion(t *testing.T, conf config.Config, plugin plugins.Plugin, versionStr, aliasStr string) {
+	t.Helper()
+	originPath := InstallPath(conf, plugin, toolversions.Version{Type: "version", Value: versionStr})
+	aliasPath := InstallPath(conf, plugin, toolversions.Version{Type: "version", Value: aliasStr})
+	err := os.Symlink(originPath, aliasPath)
+	assert.Nil(t, err)
+}
+
 func installVersion(t *testing.T, conf config.Config, plugin plugins.Plugin, version string) {
 	t.Helper()
 	err := installtest.InstallOneVersion(conf, plugin, "version", version)