chore: don't cache errors in file cache (#18555)

coderd/files/cache_internal_test.go

@@ -0,0 +1,23 @@
+package files
+
+import (
+	"context"
+
+	"github.com/google/uuid"
+
+	"github.com/coder/coder/v2/coderd/database"
+)
+
+// LeakCache prevents entries from even being released to enable testing certain
+// behaviors.
+type LeakCache struct {
+	*Cache
+}
+
+func (c *LeakCache) Acquire(ctx context.Context, db database.Store, fileID uuid.UUID) (*CloseFS, error) {
+	// We need to call prepare first to both 1. leak a reference and 2. prevent
+	// the behavior of immediately closing on an error (as implemented in Acquire)
+	// from freeing the file.
+	c.prepare(db, fileID)
+	return c.Cache.Acquire(ctx, db, fileID)
+}