add watcher struct for testing

cli.go

@@ -6,7 +6,6 @@ import (
 	"path/filepath"
 
 	"github.com/bmatcuk/doublestar/v4"
-	"github.com/fsnotify/fsnotify"
 	"github.com/labstack/echo/v4"
 	"github.com/labstack/echo/v4/middleware"
 )
@@ -31,28 +30,24 @@ func (c *CLI) Run() error {
 	}
 
 	if c.Serve {
-		watcher, err := fsnotify.NewWatcher()
-		if err != nil {
-			return fmt.Errorf("could not create file watcher: %w", err)
-		}
-		defer watcher.Close()
+		watcher := NewWatcher(c.SourcePath)
 
-		go func() {
-			for event := range watcher.Events {
-				matched, _ := doublestar.Match(filepath.Join(c.SourcePath, "**", "*.md"), event.Name)
+		//nolint:errcheck,unparam
+		go watcher.Execute(func(filename string) error {
+			glob := filepath.Join(c.SourcePath, "**", "*.md")
+			matched, _ := doublestar.Match(glob, filename)
 
-				if matched {
-					slog.Info("rebuilding markdown files")
+			if matched {
+				slog.Info("rebuilding markdown files")
 
-					_ = renderer.Execute()
+				err := renderer.Execute()
+				if err != nil {
+					slog.Error("could not rebuild markdown files", slog.String("error", err.Error()))
 				}
 			}
-		}()
 
-		err = watcher.Add(c.SourcePath)
-		if err != nil {
-			return fmt.Errorf("could add watching path: %w", err)
-		}
+			return nil
+		})
 
 		e := echo.New()
 		e.Use(middleware.Logger())

go.mod

@@ -35,6 +35,7 @@ require (
 	github.com/stretchr/testify v1.8.2 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
 	github.com/valyala/fasttemplate v1.2.2 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
 	golang.org/x/crypto v0.12.0 // indirect
 	golang.org/x/exp v0.0.0-20230817173708-d852ddb80c63 // indirect
 	golang.org/x/net v0.14.0 // indirect

go.sum

@@ -81,6 +81,8 @@ github.com/yuin/goldmark-highlighting v0.0.0-20220208100518-594be1970594 h1:yHfZ
 github.com/yuin/goldmark-highlighting v0.0.0-20220208100518-594be1970594/go.mod h1:U9ihbh+1ZN7fR5Se3daSPoz1CGF9IYtSvWwVQtnzGHU=
 go.abhg.dev/goldmark/mermaid v0.4.0 h1:yqwaYvNFbKwh9JByKzN0eDpxrUoYe8NUJvtSKY94S5M=
 go.abhg.dev/goldmark/mermaid v0.4.0/go.mod h1:L5SiQ7PedPuZY0+zaPoJ5ZnDitIYS0Obi5w7Pf02tPY=
+go.uber.org/atomic v1.11.0 h1:ZvwS0R+56ePWxUNi+Atn9dWONBPp/AUETXlHW0DxSjE=
+go.uber.org/atomic v1.11.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
 golang.org/x/crypto v0.12.0 h1:tFM/ta59kqch6LlvYnPa0yx5a83cL2nHflFhYKvv9Yk=
 golang.org/x/crypto v0.12.0/go.mod h1:NF0Gs7EO5K4qLn+Ylc+fih8BSTeIjAP05siRnAh98yw=
 golang.org/x/exp v0.0.0-20230817173708-d852ddb80c63 h1:m64FZMko/V45gv0bNmrNYoDEq8U5YUhetc9cBWKS1TQ=

watcher.go

@@ -0,0 +1,41 @@
+package builder
+
+import (
+	"fmt"
+
+	"github.com/fsnotify/fsnotify"
+)
+
+type Watcher struct {
+	sourceDir string
+}
+
+func NewWatcher(
+	sourceDir string,
+) *Watcher {
+	return &Watcher{
+		sourceDir: sourceDir,
+	}
+}
+
+func (w *Watcher) Execute(fn func(string) error) error {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return fmt.Errorf("could not create file watcher: %w", err)
+	}
+	defer watcher.Close()
+
+	err = watcher.Add(w.sourceDir)
+	if err != nil {
+		return fmt.Errorf("could add watching path: %w", err)
+	}
+
+	for event := range watcher.Events {
+		err := fn(event.Name)
+		if err != nil {
+			return fmt.Errorf("could not execute fn in watcher: %w", err)
+		}
+	}
+
+	return nil
+}

watcher_test.go

@@ -0,0 +1,81 @@
+package builder_test
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/jtarchie/builder"
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	"go.uber.org/atomic"
+)
+
+var _ = Describe("Watcher", func() {
+	When("a file gets updated", func() {
+		It("executes the callback with the affected filename", func() {
+			var foundFilename atomic.String
+
+			sourceDir, err := os.MkdirTemp("", "")
+			Expect(err).NotTo(HaveOccurred())
+
+			watcher := builder.NewWatcher(sourceDir)
+
+			//nolint:errcheck,unparam
+			go watcher.Execute(func(filename string) error {
+				foundFilename.Store(filename)
+
+				return nil
+			})
+
+			Consistently(foundFilename.Load).Should(Equal(""))
+
+			expectedFilename := filepath.Join(sourceDir, "file")
+
+			err = os.WriteFile(expectedFilename, []byte(""), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			Eventually(foundFilename.Load).Should(Equal(expectedFilename))
+		})
+	})
+
+	When("the source path does not exists", func() {
+		It("returns an error", func() {
+			watcher := builder.NewWatcher("asdf")
+
+			err := watcher.Execute(func(s string) error {
+				return nil
+			})
+			Expect(err).To(HaveOccurred())
+		})
+	})
+
+	When("the callback returns an error", func() {
+		It("stops watching altogether", func() {
+			var callbackCount atomic.Int32
+
+			sourceDir, err := os.MkdirTemp("", "")
+			Expect(err).NotTo(HaveOccurred())
+
+			watcher := builder.NewWatcher(sourceDir)
+
+			//nolint:errcheck,unparam
+			go watcher.Execute(func(filename string) error {
+				callbackCount.Add(1)
+
+				return fmt.Errorf("some error")
+			})
+
+			Consistently(callbackCount.Load).Should(BeEquivalentTo(0))
+
+			for i := 0; i < 10; i++ {
+				expectedFilename := filepath.Join(sourceDir, "file")
+
+				err = os.WriteFile(expectedFilename, []byte(fmt.Sprintf("%d", i)), os.ModePerm)
+				Expect(err).NotTo(HaveOccurred())
+			}
+
+			Consistently(callbackCount.Load).Should(BeEquivalentTo(1))
+		})
+	})
+})