store: GenerateName: optimize check if name is taken

The function was using NodeGroupByName, which validated the name to
be in the correct format, but also if the information on disk was
correct, obtained the last activity date, etc.

Given that names generated should always match the correct format,
and we're only looking  for _possible_ conflicts, we can simplify
the validation. The results of the generated name will still be
validated when used, as the Create function calls `NodeGroupByName`
as part of creating;
https://github.com/docker/buildx/blob/2d65b12a65ab5529c6eba55605a790580dad5f4b/builder/builder.go#L358-L387

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

store/store.go

@@ -98,6 +98,14 @@ func (t *Txn) NodeGroupByName(name string) (*NodeGroup, error) {
 	return &ng, nil
 }
 
+// nameExists checks if a nodeGroup with the given name was found on disk.
+// It does not validate the name, neither the information on disk to be
+// correct.
+func (t *Txn) nameExists(name string) bool {
+	_, err := os.Stat(filepath.Join(t.s.cfg.Dir(), instanceDir, name))
+	return err == nil
+}
+
 func (t *Txn) Save(ng *NodeGroup) error {
 	name, err := ValidateName(ng.Name)
 	if err != nil {

store/util.go

@@ -2,7 +2,6 @@ package store
 
 import (
 	"math/rand/v2"
-	"os"
 	"regexp"
 	"strings"
 
@@ -44,14 +43,9 @@ func GenerateName(txn *Txn) (string, error) {
 			nouns[rand.IntN(len(nouns))] + "_" +
 			themes[rand.IntN(len(themes))] // #nosec G404 -- ignore "Use of weak random number generator"
 
-		if _, err := txn.NodeGroupByName(name); err != nil {
-			if !os.IsNotExist(errors.Cause(err)) {
-				return "", err
-			}
-		} else {
-			continue
+		if !txn.nameExists(name) {
+			return name, nil
 		}
-		return name, nil
 	}
 	return "", errors.Errorf("failed to generate random name")
 }