feat: allow filtering by extension with -e flag

cmd/flags.go

@@ -8,6 +8,7 @@ import (
 )
 
 var types []string
+var extensions []string
 var allowFailing bool
 var defaultTypes = []string{"WRITE"}
 
@@ -20,6 +21,15 @@ func SetFlags(cmd *cobra.Command) {
 		fmt.Sprintf("Event types to watch, options: %s", event_types.EventTypes),
 	)
 
+	cmd.Flags().StringSliceVarP(
+		&extensions,
+		"extension",
+		"e",
+		[]string{},
+		`If provided, only files with the given extensions will trigger the command. E.g.:
+$ beholder . -e go -e yml -- go test ./...`,
+	)
+
 	cmd.Flags().BoolVarP(
 		&allowFailing,
 		"allow-failing",

cmd/root.go

@@ -46,6 +46,7 @@ func Run(cmd *cobra.Command, args []string) {
 		Paths:        paths,
 		Command:      command,
 		AllowedTypes: allowedTypes,
+		Extensions:   extensions,
 		AllowFailing: allowFailing,
 	}
 	use_case.Watch(watchConfig, infrastructure.FileWatcher, infrastructure.Command)

core/extension_filter.go

@@ -0,0 +1,15 @@
+package core
+
+func ExtensionFilter(path string, extensions []string) bool {
+	if len(extensions) == 0 {
+		return true
+	}
+
+	for _, extension := range extensions {
+		if extension == path[len(path)-len(extension):] {
+			return true
+		}
+	}
+
+	return false
+}

core/extension_filter_test.go

@@ -0,0 +1,22 @@
+package core_test
+
+import (
+	"testing"
+
+	"github.com/lucaschain/beholder/core"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExtensionFilter(t *testing.T) {
+	t.Run("should return true if no extensions passed", func(t *testing.T) {
+		assert.True(t, core.ExtensionFilter("foo.go", []string{}))
+	})
+
+	t.Run("should return true if path has one of the extensions", func(t *testing.T) {
+		assert.True(t, core.ExtensionFilter("foo.go", []string{".go", ".rb"}))
+	})
+
+	t.Run("should return false if the patch matches none of the extensions", func(t *testing.T) {
+		assert.False(t, core.ExtensionFilter("foo.go", []string{".rb", ".js"}))
+	})
+}

use_case/watch.go

@@ -12,6 +12,7 @@ type WatchConfig struct {
 	Paths        []string
 	Command      []string
 	AllowedTypes []event_types.EventType
+	Extensions   []string
 	AllowFailing bool
 }
 
@@ -24,7 +25,7 @@ func onFileChange(c WatchConfig, commandRunner CommandRunner) core.ChangeCallbac
 			return err
 		}
 
-		if event_types.Filter(event.Type, c.AllowedTypes) {
+		if event_types.Filter(event.Type, c.AllowedTypes) && core.ExtensionFilter(event.FileName, c.Extensions) {
 			command := core.CommandTokens(c.Command, event)
 			commandError := commandRunner(command)
 

use_case/watch_test.go

@@ -128,6 +128,7 @@ func buildWatchConfig() use_case.WatchConfig {
 	return use_case.WatchConfig{
 		Paths:        []string{"."},
 		Command:      []string{"echo", "hello"},
+		Extensions:   []string{".txt"},
 		AllowedTypes: []event_types.EventType{event_types.Create},
 		AllowFailing: false,
 	}