cachefs: Add InvalidateCacheFS interface and extend cacheFS to implement it

Author: tmc

fs.go

@@ -34,6 +34,14 @@ import (
 	"github.com/mailgun/groupcache/v2"
 )
 
+// A InvalidateCacheFS is a file system with a InvalidateCache method.
+type InvalidateCacheFS interface {
+	fs.FS
+
+	// InvalidateCache invalidates the cache for a path on the FS.
+	InvalidateCache(ctx context.Context, path string) error
+}
+
 // Config stores the configuration settings of your cache.
 type Config struct {
 	GroupName   string        // Name of the groupcache group
@@ -49,6 +57,9 @@ type cacheFS struct {
 	cache    *groupcache.Group
 }
 
+// Statically declare that cacheFS satisfies InvalidateCacheFS.
+var _ InvalidateCacheFS = (*cacheFS)(nil)
+
 // Open opens the named file.
 //
 // When Open returns an error, it should be of type *fs.PathError
@@ -176,3 +187,8 @@ func New(innerFS fs.FS, config *Config) fs.FS {
 			})),
 	}
 }
+
+// InvalidateCache invalidates the cache for a path in the filesystem.
+func (cfs *cacheFS) InvalidateCache(ctx context.Context, path string) error {
+	return cfs.cache.Remove(ctx, path)
+}