feat: rebuild plugin on file changes while running dev server

cmd/cmd_run.go

@@ -1,17 +1,22 @@
 package main
 
 import (
+	"errors"
+	"log"
 	"os"
+	"path/filepath"
 
 	"github.com/customrealms/cli/internal/build"
 	"github.com/customrealms/cli/internal/project"
 	"github.com/customrealms/cli/internal/serve"
 	"github.com/customrealms/cli/internal/server"
+	"github.com/fsnotify/fsnotify"
+	"golang.org/x/sync/errgroup"
 )
 
 type RunCmd struct {
 	ProjectDir      string `name:"project" short:"p" usage:"plugin project directory" optional:""`
-	McVersion       string `name:"mc" short:"mc" usage:"Minecraft version number target" optional:""`
+	McVersion       string `name:"mc" usage:"Minecraft version number target" optional:""`
 	TemplateJarFile string `name:"jar" short:"t" usage:"template JAR file" optional:""`
 }
 
@@ -70,11 +75,77 @@ func (c *RunCmd) Run() error {
 		return err
 	}
 
-	// Create the serve runner
-	serveAction := serve.ServeAction{
-		MinecraftVersion: minecraftVersion,
-		PluginJarPath:    outputFile,
-		ServerJarFetcher: serverJarFetcher,
-	}
-	return serveAction.Run(ctx)
+	eg, ctx := errgroup.WithContext(ctx)
+
+	chanPluginUpdated := make(chan struct{})
+	chanServerStopped := make(chan struct{})
+	eg.Go(func() error {
+		// Create new watcher.
+		watcher, err := fsnotify.NewWatcher()
+		if err != nil {
+			return err
+		}
+		defer watcher.Close()
+
+		// Start listening for events.
+		go func() {
+			for {
+				select {
+				case event, ok := <-watcher.Events:
+					if !ok {
+						return
+					}
+					if event.Has(fsnotify.Write) {
+						// Rebuild the plugin JAR file
+						if err := buildAction.Run(ctx); err != nil {
+							log.Println("Error: ", err)
+						} else {
+							select {
+							case chanPluginUpdated <- struct{}{}:
+							case <-ctx.Done():
+								return
+							}
+						}
+					}
+				case err, ok := <-watcher.Errors:
+					if !ok {
+						return
+					}
+					log.Println("error:", err)
+				case <-ctx.Done():
+					return
+				case <-chanServerStopped:
+					return
+				}
+			}
+		}()
+
+		// Add the project directory and src directory to the watcher
+		if err := errors.Join(
+			watcher.Add(c.ProjectDir),
+			watcher.Add(filepath.Join(c.ProjectDir, "src")),
+		); err != nil {
+			return err
+		}
+
+		// Block until the server is stopped
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-chanServerStopped:
+			return nil
+		}
+	})
+	eg.Go(func() error {
+		defer close(chanServerStopped)
+
+		// Create the serve runner
+		serveAction := serve.ServeAction{
+			MinecraftVersion: minecraftVersion,
+			PluginJarPath:    outputFile,
+			ServerJarFetcher: serverJarFetcher,
+		}
+		return serveAction.Run(ctx, chanPluginUpdated)
+	})
+	return eg.Wait()
 }

cmd/cmd_yml.go

@@ -10,7 +10,7 @@ import (
 
 type YmlCmd struct {
 	ProjectDir string `name:"project" short:"p" usage:"plugin project directory" optional:""`
-	McVersion  string `name:"mc" short:"mc" usage:"Minecraft version number target" optional:""`
+	McVersion  string `name:"mc" usage:"Minecraft version number target" optional:""`
 }
 
 func (c *YmlCmd) Run() error {

cmd/main.go

@@ -12,11 +12,11 @@ import (
 )
 
 var cli struct {
-	VersionCmd VersionCmd `cmd:"" help:"Show the version of the CLI."`
-	InitCmd    InitCmd    `cmd:"" help:"Initialize a new plugin project."`
-	BuildCmd   BuildCmd   `cmd:"" help:"Build the plugin JAR file."`
-	RunCmd     RunCmd     `cmd:"" help:"Build and serve the plugin in a Minecraft server."`
-	YmlCmd     YmlCmd     `cmd:"" help:"Generate the plugin.yml file."`
+	VersionCmd VersionCmd `cmd:"" name:"version" help:"Show the version of the CLI."`
+	InitCmd    InitCmd    `cmd:"" name:"init" help:"Initialize a new plugin project."`
+	BuildCmd   BuildCmd   `cmd:"" name:"build" help:"Build the plugin JAR file."`
+	RunCmd     RunCmd     `cmd:"" name:"run" help:"Build and serve the plugin in a Minecraft server."`
+	YmlCmd     YmlCmd     `cmd:"" name:"yml" help:"Generate the plugin.yml file."`
 }
 
 func rootContext() (context.Context, context.CancelFunc) {

go.mod

@@ -2,4 +2,10 @@ module github.com/customrealms/cli
 
 go 1.22
 
-require github.com/alecthomas/kong v0.9.0
+require (
+	github.com/alecthomas/kong v0.9.0
+	github.com/fsnotify/fsnotify v1.7.0
+	golang.org/x/sync v0.7.0
+)
+
+require golang.org/x/sys v0.4.0 // indirect

go.sum

@@ -4,5 +4,11 @@ github.com/alecthomas/kong v0.9.0 h1:G5diXxc85KvoV2f0ZRVuMsi45IrBgx9zDNGNj165aPA
 github.com/alecthomas/kong v0.9.0/go.mod h1:Y47y5gKfHp1hDc7CH7OeXgLIpp+Q2m1Ni0L5s3bI8Os=
 github.com/alecthomas/repr v0.4.0 h1:GhI2A8MACjfegCPVq9f1FLvIBS+DrQ2KQBFZP1iFzXc=
 github.com/alecthomas/repr v0.4.0/go.mod h1:Fr0507jx4eOXV7AlPV6AVZLYrLIuIeSOWtW57eE/O/4=
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
+github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
 github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
 github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
+golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
+golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
+golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

internal/minecraft/versions.go

@@ -24,7 +24,7 @@ type paperMcBuild struct {
 
 func LookupVersion(ctx context.Context, versionStr string) (Version, error) {
 	// Lookup the version from PaperMC
-	builds, err := downloadJSON[paperMcBuilds](ctx, fmt.Sprintf("https://papermc.io/api/v2/projects/paper/versions/%s", versionStr))
+	builds, err := downloadJSON[paperMcBuilds](ctx, fmt.Sprintf("https://papermc.io/api/v2/projects/paper/versions/%s/builds", versionStr))
 	if err != nil {
 		return nil, fmt.Errorf("download builds list: %w", err)
 	}
@@ -48,6 +48,7 @@ func LookupVersion(ctx context.Context, versionStr string) (Version, error) {
 }
 
 func downloadJSON[T any](ctx context.Context, url string) (*T, error) {
+	fmt.Println(url)
 	// Create the HTTP request
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
 	if err != nil {

internal/serve/serve.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/customrealms/cli/internal/minecraft"
 	"github.com/customrealms/cli/internal/server"
+	"golang.org/x/sync/errgroup"
 )
 
 type ServeAction struct {
@@ -61,7 +62,7 @@ func copyFile(from, to string) error {
 	return nil
 }
 
-func (a *ServeAction) Run(ctx context.Context) error {
+func (a *ServeAction) Run(ctx context.Context, chanPluginUpdated <-chan struct{}) error {
 
 	// Check if Java is installed on the machine
 	if _, err := exec.LookPath("java"); err != nil {
@@ -126,12 +127,39 @@ func (a *ServeAction) Run(ctx context.Context) error {
 	fmt.Println("============================================================")
 	fmt.Println()
 
-	// Run the server
-	cmd := exec.CommandContext(ctx, "java", "-jar", jarBase, "-nogui")
-	cmd.Dir = dir
-	cmd.Stdin = os.Stdin
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	return cmd.Run()
-
+	eg, ctx := errgroup.WithContext(ctx)
+
+	chanServerStopped := make(chan struct{})
+	eg.Go(func() error {
+		for {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-chanServerStopped:
+				return nil
+			case _, ok := <-chanPluginUpdated:
+				if !ok {
+					return nil
+				}
+			}
+
+			// Copy the plugin file to the server
+			if err := copyFile(a.PluginJarPath, filepath.Join(pluginsDir, filepath.Base(a.PluginJarPath))); err != nil {
+				return err
+			}
+			fmt.Println("Plugin JAR updated. Run `/reload confirm` to reload the plugin.")
+		}
+	})
+	eg.Go(func() error {
+		defer close(chanServerStopped)
+
+		// Run the server
+		cmd := exec.CommandContext(ctx, "java", "-jar", jarBase, "-nogui")
+		cmd.Dir = dir
+		cmd.Stdin = os.Stdin
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		return cmd.Run()
+	})
+	return eg.Wait()
 }