Fix incorrect usage of os.Stat (#20125)

* Update main.go

* Fix incorrect stat for link

* add doc

Author: mustard-mh

components/ide/jetbrains/launcher/main.go

@@ -1186,10 +1186,13 @@ func linkRemotePlugin(launchCtx *LaunchContext) error {
 	return safeLink("/ide-desktop-plugins/gitpod-remote", remotePluginDir)
 }
 
+// safeLink creates a symlink from source to target, removing the old target if it exists
 func safeLink(source, target string) error {
-	if _, err := os.Stat(target); err == nil {
+	if _, err := os.Lstat(target); err == nil {
 		// unlink the old symlink
-		_ = os.RemoveAll(target)
+		if err2 := os.RemoveAll(target); err2 != nil {
+			log.WithError(err).Error("failed to unlink old symlink")
+		}
 	}
 	return os.Symlink(source, target)
 }

components/ide/jetbrains/launcher/main_test.go

@@ -5,6 +5,9 @@
 package main
 
 import (
+	"fmt"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -105,3 +108,42 @@ func TestUpdatePlatformProperties(t *testing.T) {
 		}
 	})
 }
+
+func Test_safeLink(t *testing.T) {
+	type args struct {
+		changeSource bool
+	}
+	t.Log("link folders twice")
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		{name: "happy path", args: args{changeSource: true}, wantErr: false},
+		{name: "happy path 2", args: args{changeSource: false}, wantErr: false},
+	}
+	for index, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			source := createTempDir(t, fmt.Sprintf("source_%d", index))
+			target := createTempDir(t, fmt.Sprintf("target_%d", index))
+			safeLink(source, target)
+			os.RemoveAll(source)
+			if tt.args.changeSource {
+				source = createTempDir(t, fmt.Sprintf("source_new_%d", index))
+			} else {
+				source = createTempDir(t, fmt.Sprintf("source_%d", index))
+			}
+			if err := safeLink(source, target); (err != nil) != tt.wantErr {
+				t.Errorf("safeLink() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+func createTempDir(t *testing.T, dir string) string {
+	path := filepath.Join(t.TempDir(), dir)
+	if err := os.Mkdir(path, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	return path
+}