feat: add fsnotify-based hot reload (#470)

.version

@@ -1 +1 @@
-0.2.546
+0.2.549

cmd/templ/generatecmd/cmd.go

@@ -0,0 +1,323 @@
+package generatecmd
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"path"
+	"path/filepath"
+	"runtime"
+	"sync"
+	"time"
+
+	"github.com/a-h/templ"
+	"github.com/a-h/templ/cmd/templ/generatecmd/modcheck"
+	"github.com/a-h/templ/cmd/templ/generatecmd/proxy"
+	"github.com/a-h/templ/cmd/templ/generatecmd/run"
+	"github.com/a-h/templ/cmd/templ/generatecmd/watcher"
+	"github.com/a-h/templ/generator"
+	"github.com/cenkalti/backoff/v4"
+	"github.com/cli/browser"
+	"github.com/fsnotify/fsnotify"
+)
+
+func NewGenerate(log *slog.Logger, args Arguments) (g *Generate) {
+	g = &Generate{
+		Log:  log,
+		Args: &args,
+	}
+	if g.Args.WorkerCount == 0 {
+		g.Args.WorkerCount = runtime.NumCPU()
+	}
+	return g
+}
+
+type Generate struct {
+	Log  *slog.Logger
+	Args *Arguments
+}
+
+type GenerationEvent struct {
+	Event       fsnotify.Event
+	GoUpdated   bool
+	TextUpdated bool
+}
+
+func (cmd Generate) Run(ctx context.Context) (err error) {
+	if cmd.Args.Watch && cmd.Args.FileName != "" {
+		return fmt.Errorf("cannot watch a single file, remove the -f or -watch flag")
+	}
+
+	if cmd.Args.PPROFPort > 0 {
+		go func() {
+			_ = http.ListenAndServe(fmt.Sprintf("localhost:%d", cmd.Args.PPROFPort), nil)
+		}()
+	}
+
+	// Use absolute path.
+	if !path.IsAbs(cmd.Args.Path) {
+		cmd.Args.Path, err = filepath.Abs(cmd.Args.Path)
+		if err != nil {
+			return fmt.Errorf("failed to get absolute path: %w", err)
+		}
+	}
+
+	// Configure generator.
+	var opts []generator.GenerateOpt
+	if cmd.Args.IncludeVersion {
+		opts = append(opts, generator.WithVersion(templ.Version()))
+	}
+	if cmd.Args.IncludeTimestamp {
+		opts = append(opts, generator.WithTimestamp(time.Now()))
+	}
+
+	// Check the version of the templ module.
+	if err := modcheck.Check(cmd.Args.Path); err != nil {
+		cmd.Log.Warn("templ version check: " + err.Error())
+	}
+
+	fseh := NewFSEventHandler(cmd.Log, cmd.Args.Path, cmd.Args.Watch, opts, cmd.Args.GenerateSourceMapVisualisations, cmd.Args.KeepOrphanedFiles)
+
+	// If we're processing a single file, don't bother setting up the channels/multithreaing.
+	if cmd.Args.FileName != "" {
+		_, _, err = fseh.HandleEvent(ctx, fsnotify.Event{
+			Name: cmd.Args.FileName,
+			Op:   fsnotify.Create,
+		})
+		return err
+	}
+
+	// Start timer.
+	start := time.Now()
+
+	// Create channels:
+	// For the initial filesystem walk and subsequent (optional) fsnotify events.
+	events := make(chan fsnotify.Event)
+	// count of events currently being processed by the event handler.
+	var eventsWG sync.WaitGroup
+	// Used to check that the event handler has completed.
+	var eventHandlerWG sync.WaitGroup
+	// For errs from the watcher.
+	errs := make(chan error)
+	// For triggering actions after generation has completed.
+	postGeneration := make(chan *GenerationEvent, 256)
+	// Used to check that the post-generation handler has completed.
+	var postGenerationWG sync.WaitGroup
+	var postGenerationEventsWG sync.WaitGroup
+
+	// Waitgroup for the push process.
+	var pushHandlerWG sync.WaitGroup
+
+	// Start process to push events into the channel.
+	pushHandlerWG.Add(1)
+	go func() {
+		defer pushHandlerWG.Done()
+		defer close(events)
+		defer close(errs)
+		cmd.Log.Debug("Walking directory", slog.String("path", cmd.Args.Path), slog.Bool("devMode", cmd.Args.Watch))
+		if err := watcher.WalkFiles(ctx, cmd.Args.Path, events); err != nil {
+			cmd.Log.Error("WalkFiles failed, exiting", slog.Any("error", err))
+			errs <- FatalError{Err: fmt.Errorf("failed to walk files: %w", err)}
+			return
+		}
+		if !cmd.Args.Watch {
+			cmd.Log.Debug("Dev mode not enabled, process can finish early")
+			return
+		}
+		cmd.Log.Info("Watching files")
+		rw, err := watcher.Recursive(ctx, cmd.Args.Path, events, errs)
+		if err != nil {
+			cmd.Log.Error("Recursive watcher setup failed, exiting", slog.Any("error", err))
+			errs <- FatalError{Err: fmt.Errorf("failed to setup recursive watcher: %w", err)}
+			return
+		}
+		cmd.Log.Debug("Waiting for context to be cancelled to stop watching files")
+		<-ctx.Done()
+		cmd.Log.Debug("Context cancelled, closing watcher")
+		if err := rw.Close(); err != nil {
+			cmd.Log.Error("Failed to close watcher", slog.Any("error", err))
+		}
+		cmd.Log.Debug("Waiting for events to be processed")
+		eventsWG.Wait()
+		cmd.Log.Debug("All pending events processed, waiting for pending post-generation events to complete")
+		postGenerationEventsWG.Wait()
+		cmd.Log.Debug("All post-generation events processed, running walk again, but in production mode")
+		fseh.DevMode = false
+		if err := watcher.WalkFiles(ctx, cmd.Args.Path, events); err != nil {
+			cmd.Log.Error("Post dev mode WalkFiles failed", slog.Any("error", err))
+			errs <- FatalError{Err: fmt.Errorf("failed to walk files: %w", err)}
+			return
+		}
+	}()
+
+	// Start process to handle events.
+	eventHandlerWG.Add(1)
+	sem := make(chan struct{}, cmd.Args.WorkerCount)
+	go func() {
+		defer eventHandlerWG.Done()
+		defer close(postGeneration)
+		cmd.Log.Debug("Starting event handler")
+		for event := range events {
+			eventsWG.Add(1)
+			sem <- struct{}{}
+			go func(event fsnotify.Event) {
+				cmd.Log.Debug("Processing file", slog.String("file", event.Name))
+				defer eventsWG.Done()
+				defer func() { <-sem }()
+				goUpdated, textUpdated, err := fseh.HandleEvent(ctx, event)
+				if err != nil {
+					cmd.Log.Error("Event handler failed", slog.Any("error", err))
+					errs <- err
+				}
+				if goUpdated || textUpdated {
+					postGeneration <- &GenerationEvent{
+						Event:       event,
+						GoUpdated:   goUpdated,
+						TextUpdated: textUpdated,
+					}
+				}
+			}(event)
+		}
+		// Wait for all events to be processed before closing.
+		eventsWG.Wait()
+	}()
+
+	// Start process to handle post-generation events.
+	var updates int
+	postGenerationWG.Add(1)
+	var firstPostGenerationExecuted bool
+	go func() {
+		defer postGenerationWG.Done()
+		cmd.Log.Debug("Starting post-generation handler")
+		timeout := time.NewTimer(time.Hour * 24 * 365)
+		var goUpdated, textUpdated bool
+		var p *proxy.Handler
+		for {
+			select {
+			case ge := <-postGeneration:
+				if ge == nil {
+					cmd.Log.Debug("Post-generation event channel closed, exiting")
+					return
+				}
+				goUpdated = goUpdated || ge.GoUpdated
+				textUpdated = textUpdated || ge.TextUpdated
+				if goUpdated || textUpdated {
+					updates++
+				}
+				// Reset timer.
+				if !timeout.Stop() {
+					<-timeout.C
+				}
+				timeout.Reset(time.Millisecond * 100)
+			case <-timeout.C:
+				if !goUpdated && !textUpdated {
+					// Nothing to process, reset timer and wait again.
+					timeout.Reset(time.Hour * 24 * 365)
+					break
+				}
+				postGenerationEventsWG.Add(1)
+				if cmd.Args.Command != "" && goUpdated {
+					cmd.Log.Debug("Executing command", slog.String("command", cmd.Args.Command))
+					if _, err := run.Run(ctx, cmd.Args.Path, cmd.Args.Command); err != nil {
+						cmd.Log.Error("Error executing command", slog.Any("error", err))
+					}
+				}
+				if !firstPostGenerationExecuted {
+					cmd.Log.Debug("First post-generation event received, starting proxy")
+					firstPostGenerationExecuted = true
+					p, err = cmd.StartProxy(ctx)
+					if err != nil {
+						cmd.Log.Error("Failed to start proxy", slog.Any("error", err))
+					}
+				}
+				// Send server-sent event.
+				if p != nil && (textUpdated || goUpdated) {
+					cmd.Log.Debug("Sending reload event")
+					p.SendSSE("message", "reload")
+				}
+				postGenerationEventsWG.Done()
+				// Reset timer.
+				timeout.Reset(time.Millisecond * 100)
+				textUpdated = false
+				goUpdated = false
+			}
+		}
+	}()
+
+	// Read errors.
+	for err := range errs {
+		if err == nil {
+			continue
+		}
+		if errors.Is(err, FatalError{}) {
+			cmd.Log.Debug("Fatal error, exiting")
+			return err
+		}
+		cmd.Log.Error("Error received", slog.Any("error", err))
+	}
+
+	// Wait for everything to complete.
+	cmd.Log.Debug("Waiting for push handler to complete")
+	pushHandlerWG.Wait()
+	cmd.Log.Debug("Waiting for event handler to complete")
+	eventHandlerWG.Wait()
+	cmd.Log.Debug("Waiting for post-generation handler to complete")
+	postGenerationWG.Wait()
+	if cmd.Args.Command != "" {
+		cmd.Log.Debug("Killing command", slog.String("command", cmd.Args.Command))
+		if err := run.KillAll(); err != nil {
+			cmd.Log.Error("Error killing command", slog.Any("error", err))
+		}
+	}
+	cmd.Log.Info("Complete", slog.Int("updates", updates), slog.Duration("duration", time.Since(start)))
+
+	return nil
+}
+
+func (cmd *Generate) StartProxy(ctx context.Context) (p *proxy.Handler, err error) {
+	if cmd.Args.Proxy == "" {
+		cmd.Log.Debug("No proxy URL specified, not starting proxy")
+		return nil, nil
+	}
+	var target *url.URL
+	target, err = url.Parse(cmd.Args.Proxy)
+	if err != nil {
+		return nil, FatalError{Err: fmt.Errorf("failed to parse proxy URL: %w", err)}
+	}
+	if cmd.Args.ProxyPort == 0 {
+		cmd.Args.ProxyPort = 7331
+	}
+	p = proxy.New(cmd.Args.ProxyPort, target)
+	go func() {
+		cmd.Log.Info("Proxying", slog.String("from", p.URL), slog.String("to", p.Target.String()))
+		if err := http.ListenAndServe(fmt.Sprintf("127.0.0.1:%d", cmd.Args.ProxyPort), p); err != nil {
+			cmd.Log.Error("Proxy failed", slog.Any("error", err))
+		}
+	}()
+	if !cmd.Args.OpenBrowser {
+		cmd.Log.Debug("Not opening browser")
+		return p, nil
+	}
+	go func() {
+		cmd.Log.Debug("Waiting for proxy to be ready", slog.String("url", p.URL))
+		backoff := backoff.NewExponentialBackOff()
+		backoff.InitialInterval = time.Second
+		var client http.Client
+		client.Timeout = 1 * time.Second
+		for {
+			if _, err := client.Get(p.URL); err == nil {
+				break
+			}
+			d := backoff.NextBackOff()
+			cmd.Log.Debug("Proxy not ready, retrying", slog.String("url", p.URL), slog.Any("backoff", d))
+			time.Sleep(d)
+		}
+		if err := browser.OpenURL(p.URL); err != nil {
+			cmd.Log.Error("Failed to open browser", slog.Any("error", err))
+		}
+	}()
+	return p, nil
+}