store/index: return error from UnTag

internal/store/index.go

@@ -39,10 +39,10 @@ func (i Index) Tag(reference string, tag string) (Index, error) {
 	return result, nil
 }
 
-func (i Index) UnTag(tag string) (name.Tag, Index) {
+func (i Index) UnTag(tag string) (name.Tag, Index, error) {
 	tagRef, err := name.NewTag(tag)
 	if err != nil {
-		return name.Tag{}, Index{}
+		return name.Tag{}, Index{}, err
 	}
 
 	result := Index{
@@ -52,7 +52,7 @@ func (i Index) UnTag(tag string) (name.Tag, Index) {
 		result.Models = append(result.Models, entry.UnTag(tagRef))
 	}
 
-	return tagRef, result
+	return tagRef, result, nil
 }
 
 func (i Index) Find(reference string) (IndexEntry, int, bool) {

internal/store/index_test.go

@@ -146,15 +146,26 @@ func TestUntag(t *testing.T) {
 				},
 			},
 		}
-		tag, idx := idx.UnTag("other-tag")
-		if len(idx.Models) != 2 {
-			t.Fatalf("Expected 2 models, got %d", len(idx.Models))
-		}
-		if len(idx.Models[0].Tags) != 1 {
-			t.Fatalf("Expected 1 tag, got %d", len(idx.Models[0].Tags))
-		}
-		if tag.String() != "other-tag" {
-			t.Fatalf("Expected tag 'other-tag', got '%s'", tag)
-		}
+		t.Run("UnTagging existing tag", func(t *testing.T) {
+			tag, idx, err := idx.UnTag("other-tag")
+			if err != nil {
+				t.Fatalf("Error untagging entry: %v", err)
+			}
+			if len(idx.Models) != 2 {
+				t.Fatalf("Expected 2 models, got %d", len(idx.Models))
+			}
+			if len(idx.Models[0].Tags) != 1 {
+				t.Fatalf("Expected 1 tag, got %d", len(idx.Models[0].Tags))
+			}
+			if tag.String() != "other-tag" {
+				t.Fatalf("Expected tag 'other-tag', got '%s'", tag)
+			}
+		})
+		t.Run("UnTagging invalid tag", func(t *testing.T) {
+			_, _, err := idx.UnTag("!@#$%^&*()")
+			if err == nil {
+				t.Fatal("Expected error when untagging non-existing tag, got nil")
+			}
+		})
 	})
 }

internal/store/store.go

@@ -7,7 +7,6 @@ import (
 	"path/filepath"
 
 	"github.com/docker/model-distribution/internal/progress"
-	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 )
 
@@ -165,11 +164,18 @@ func (s *LocalStore) RemoveTags(tags []string) ([]string, error) {
 	if err != nil {
 		return nil, fmt.Errorf("reading modelss index: %w", err)
 	}
-	var tagRef name.Tag
 	var tagRefs []string
 	for _, tag := range tags {
-		tagRef, index = index.UnTag(tag)
+		tagRef, newIndex, err := index.UnTag(tag)
+		if err != nil {
+			// Try to save progress before returning error.
+			if writeIndexErr := s.writeIndex(newIndex); writeIndexErr != nil {
+				return tagRefs, fmt.Errorf("untagging model: %w, also failed to save: %w", err, writeIndexErr)
+			}
+			return tagRefs, fmt.Errorf("untagging model: %w", err)
+		}
 		tagRefs = append(tagRefs, tagRef.Name())
+		index = newIndex
 	}
 	return tagRefs, s.writeIndex(index)
 }