Include number of evicted entries when explicitly evicting

Update the implementation of `ghasum cache` to output the number of
entries that were removed when evicting. This gives some indication of
how much work was done. This may help users understand if future ghasum
operations will take more time because of cache misses as well as how
much disk space might have been saved.

This information is not outputted when other commands evict (by default)
in the background. This is because I believe it would be too noisy and
not as helpful in that context (e.g. the first benefit listed above does
not really apply). This is, however, open for debate, and I can see a
verbose mode or similar where this info would probably be included in
the output.

Author: ericcornelissen

cmd/ghasum/cache.go

@@ -46,13 +46,16 @@ func cmdCache(argv []string) error {
 		return errors.Join(errUnexpected, err)
 	}
 
-	msg := "Ok"
+	var msg string
 	command := args[0]
 	switch command {
 	case "clear":
 		err = c.Clear()
+		msg = "Ok"
 	case "evict":
-		err = c.Evict()
+		var cnt uint
+		cnt, err = c.Evict()
+		msg = fmt.Sprintf("Ok (%d evicted)", cnt)
 	case "path":
 		msg = c.Path()
 	default:

cmd/ghasum/init.go

@@ -54,7 +54,7 @@ func cmdInit(argv []string) error {
 	}
 
 	if !*flagNoEvict {
-		if err = c.Evict(); err != nil {
+		if _, err = c.Evict(); err != nil {
 			return errors.Join(errCache, err)
 		}
 	}

cmd/ghasum/list.go

@@ -55,7 +55,7 @@ func cmdList(argv []string) error {
 	}
 
 	if !*flagNoEvict {
-		if err = c.Evict(); err != nil {
+		if _, err = c.Evict(); err != nil {
 			return errors.Join(errCache, err)
 		}
 	}

cmd/ghasum/update.go

@@ -56,7 +56,7 @@ func cmdUpdate(argv []string) error {
 	}
 
 	if !*flagNoEvict {
-		if err = c.Evict(); err != nil {
+		if _, err = c.Evict(); err != nil {
 			return errors.Join(errCache, err)
 		}
 	}

cmd/ghasum/verify.go

@@ -77,7 +77,7 @@ func cmdVerify(argv []string) error {
 	}
 
 	if !*flagNoEvict {
-		if err = c.Evict(); err != nil {
+		if _, err = c.Evict(); err != nil {
 			return errors.Join(errCache, err)
 		}
 	}

internal/cache/cache.go

@@ -51,8 +51,10 @@ func (c *Cache) Clear() error {
 }
 
 // Evict removes old entries from the cache.
-func (c *Cache) Evict() error {
+func (c *Cache) Evict() (uint, error) {
 	deadline := time.Now().AddDate(0, 0, -5)
+
+	var count uint
 	walk := func(path string, entry fs.DirEntry, _ error) error {
 		depth := strings.Count(path, string(os.PathSeparator))
 		if depth < 2 {
@@ -65,6 +67,7 @@ func (c *Cache) Evict() error {
 		}
 
 		if info.ModTime().Before(deadline) {
+			count += 1
 			_ = os.RemoveAll(filepath.Join(c.path, path))
 			return fs.SkipDir
 		}
@@ -74,16 +77,16 @@ func (c *Cache) Evict() error {
 
 	fsys, err := os.OpenRoot(c.path)
 	if errors.Is(err, fs.ErrNotExist) {
-		return nil
+		return 0, nil
 	} else if err != nil {
-		return fmt.Errorf("could not open cache directory: %v", err)
+		return 0, fmt.Errorf("could not open cache directory: %v", err)
 	}
 
 	if err := fs.WalkDir(fsys.FS(), ".", walk); err != nil {
-		return fmt.Errorf("cache eviction failed: %v", err)
+		return 0, fmt.Errorf("cache eviction failed: %v", err)
 	}
 
-	return nil
+	return count, nil
 }
 
 // Init sets up the cache (if necessary).

testdata/cache/success.txtar

@@ -10,6 +10,18 @@ stdout 'Ok'
 ! stderr .
 ! exists .does-not-exist/
 
+# Evict - cache directory exists
+exec ghasum cache -cache .cache/ evict
+stdout 'Ok \(0 evicted\)'
+! stderr .
+! exists .cache/
+
+# Evict - cache directory does not exist
+exec ghasum cache -cache .does-not-exist/ evict
+stdout 'Ok \(0 evicted\)'
+! stderr .
+! exists .does-not-exist/
+
 # Path - no path specified
 exec ghasum cache path
 ! stdout 'Ok'