cache/dynacache: Don't mark all evicted items as stale

Limit that to the evicted items that matches the given change set.

Currently this doesn't make any practical difference, but it would make the stale flag more general useful.

Author: bep

Diff for: cache/dynacache/dynacache.go

@@ -74,7 +74,6 @@ func New(opts Options) *Cache {
 			evictedIdentities.Push(id)
 			return false
 		})
-		resource.MarkStale(v)
 	}
 
 	c := &Cache{
@@ -434,11 +433,8 @@ func (p *Partition[K, V]) clearMatching(predicate func(k, v any) bool) {
 
 func (p *Partition[K, V]) clearOnRebuild(changeset ...identity.Identity) {
 	opts := p.getOptions()
-	if opts.ClearWhen == ClearNever {
-		return
-	}
 
-	if opts.ClearWhen == ClearOnRebuild {
+	if opts.ClearWhen == ClearOnRebuild && len(changeset) == 0 {
 		// Clear all.
 		p.Clear()
 		return
@@ -478,17 +474,23 @@ func (p *Partition[K, V]) clearOnRebuild(changeset ...identity.Identity) {
 	// Second pass needs to be done in a separate loop to catch any
 	// elements marked as stale in the other partitions.
 	p.c.DeleteFunc(func(key K, v V) bool {
-		if shouldDelete(key, v) {
-			p.trace.Log(
-				logg.StringFunc(
-					func() string {
-						return fmt.Sprintf("first pass: clearing cache key %v", key)
-					},
-				),
-			)
-			return true
+		match := shouldDelete(key, v)
+		clear := match || opts.ClearWhen == ClearOnRebuild
+
+		if match {
+			if clear {
+				p.trace.Log(
+					logg.StringFunc(
+						func() string {
+							return fmt.Sprintf("first pass: clearing cache key %v", key)
+						},
+					),
+				)
+			}
+			resource.MarkStale(v)
 		}
-		return false
+
+		return clear
 	})
 }
 
@@ -562,7 +564,6 @@ type PartitionManager interface {
 const (
 	ClearOnRebuild ClearWhen = iota + 1
 	ClearOnChange
-	ClearNever
 )
 
 type ClearWhen int