Support watch scripts for serve (#478)

Author: malcolmholmes

cmd/grr/config.go

@@ -33,6 +33,7 @@ type Opts struct {
 	ProxyPort   int
 	CanSave     bool
 	Watch       bool
+	WatchScript string
 }
 
 func configPathCmd() *cli.Command {

cmd/grr/workflow.go

@@ -376,12 +376,16 @@ func serveCmd(registry grizzly.Registry) *cli.Command {
 		}
 
 		resourcesPath := ""
-		if len(args) > 0 {
-			resourcesPath = args[0]
-		}
 		watchPaths := []string{resourcesPath}
-		if len(args) > 1 {
-			watchPaths = args[1:]
+		if opts.WatchScript != "" {
+			watchPaths = args
+		} else {
+			if len(args) > 0 {
+				resourcesPath = args[0]
+			}
+			if len(args) > 1 {
+				watchPaths = args[1:]
+			}
 		}
 
 		targets := currentContext.GetTargets(opts.Targets)
@@ -405,6 +409,9 @@ func serveCmd(registry grizzly.Registry) *cli.Command {
 		server.SetFormatting(onlySpec, format)
 		if opts.Watch {
 			server.Watch(watchPaths)
+			if opts.WatchScript != "" {
+				server.WatchScript(opts.WatchScript)
+			}
 		}
 		if opts.OpenBrowser {
 			server.OpenBrowser()
@@ -414,6 +421,7 @@ func serveCmd(registry grizzly.Registry) *cli.Command {
 	cmd.Flags().BoolVarP(&opts.Watch, "watch", "w", false, "Watch filesystem for changes")
 	cmd.Flags().BoolVarP(&opts.OpenBrowser, "open-browser", "b", false, "Open Grizzly in default browser")
 	cmd.Flags().IntVarP(&opts.ProxyPort, "port", "p", 8080, "Port on which the server will listen")
+	cmd.Flags().StringVarP(&opts.WatchScript, "script", "S", "", "Script to execute on filesystem change")
 	cmd = initialiseOnlySpec(cmd, &opts)
 	return initialiseCmd(cmd, &opts)
 }

docs/content/server.md

@@ -64,19 +64,13 @@ grr serve -w examples/grr.jsonnet examples/*.*sonnet examples/vendor
 ### Reviewing changes to code in other languages in Grafana
 The [Grafana Foundation SDK](https://github.com/grafana/grafana-foundation-sdk) provides libraries in a
 range of languages that can be used to render Grafana dashboards. Watching changes to these with Grizzly
-is a two stage process, currently requiring an additional tool to watch for changes to source code and
-render your dashboard(s) to files. One such tool is [entr](https://github.com/eradman/entr), which can be
-used like so (with the Foundation SDK's TypeScript support):
+is also possible.
 
 ```
 git clone https://github.com/grafana/grafana-foundation-sdk
 cd grafana-foundation-sdk/examples/typescript/red-method
 npm install
-find . | entr -s 'npm run -s dev > ts.json'
-```
-Then, in another window:
-```
-grr serve -w ts.json
+grr serve -w -S 'npm run -s dev' .
 ```
 Finally, open the Grizzly server at [http://localhost:8080](http://localhost:8080) and select the Red
 Method dashboard.

examples/array-of-resources.jsonnet

@@ -0,0 +1,14 @@
+local dashboard(uid, title) = {
+  uid: uid,
+  title: title,
+  tags: ['templated'],
+  timezone: 'browser',
+  schemaVersion: 17,
+  panels: [],
+};
+
+[
+  dashboard("dashboard-1", "Dashboard 1"),
+  dashboard("dashboard-2", "Dashboard 2"),
+  dashboard("dashboard-3", "Dashboard 3"),
+]

pkg/grizzly/server.go

@@ -1,12 +1,14 @@
 package grizzly
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io/fs"
 	"net/http"
 	"net/http/httputil"
 	"os"
+	"os/exec"
 
 	"github.com/go-chi/chi"
 	"github.com/go-chi/chi/middleware"
@@ -31,6 +33,7 @@ type Server struct {
 	UserAgent      string
 	ResourcePath   string
 	WatchPaths     []string
+	watchScript    string
 	OnlySpec       bool
 	OutputFormat   string
 	watch          bool
@@ -85,6 +88,10 @@ func (s *Server) Watch(watchPaths []string) {
 	s.WatchPaths = watchPaths
 }
 
+func (s *Server) WatchScript(script string) {
+	s.watchScript = script
+}
+
 func (s *Server) SetFormatting(onlySpec bool, outputFormat string) {
 	s.OnlySpec = onlySpec
 	s.OutputFormat = outputFormat
@@ -174,10 +181,19 @@ func (s *Server) Start() error {
 	r.Get("/grizzly/{kind}/{name}", s.IframeHandler)
 	r.Get("/api/live/ws", livereload.LiveReloadHandlerFunc(upgrader))
 
-	if _, err := s.ParseResources(s.ResourcePath); err != nil {
+	if s.watchScript != "" {
+		var b []byte
+		b, err = s.executeWatchScript()
+		if err != nil {
+			return err
+		}
+		_, err = s.ParseBytes(b)
+	} else {
+		_, err = s.ParseResources(s.ResourcePath)
+	}
+	if err != nil {
 		fmt.Print(err)
 	}
-
 	if s.openBrowser {
 		browser, err := NewBrowserInterface(s.Registry, s.ResourcePath, s.port)
 		if err != nil {
@@ -217,6 +233,26 @@ func (s *Server) ParseResources(resourcePath string) (Resources, error) {
 	return resources, err
 }
 
+func (s *Server) ParseBytes(b []byte) (Resources, error) {
+	f, err := os.CreateTemp(".", fmt.Sprintf("*.%s", s.OutputFormat))
+	if err != nil {
+		return Resources{}, err
+	}
+	defer os.Remove(f.Name())
+	_, err = f.Write(b)
+	if err != nil {
+		return Resources{}, err
+	}
+	err = f.Close()
+	if err != nil {
+		return Resources{}, err
+	}
+	resources, err := s.parser.Parse(f.Name(), s.parserOpts)
+	s.parserErr = err
+	s.Resources.Merge(resources)
+	return resources, err
+}
+
 func (s *Server) URL(path string) string {
 	if len(path) == 0 || path[0] != '/' {
 		path = "/" + path
@@ -226,10 +262,19 @@ func (s *Server) URL(path string) string {
 }
 
 func (s *Server) updateWatchedResource(name string) error {
-	if !s.parser.Accept(name) {
-		return nil
+	var resources Resources
+	var err error
+
+	if s.watchScript != "" {
+		var b []byte
+		b, err = s.executeWatchScript()
+		if err != nil {
+			return err
+		}
+		resources, err = s.ParseBytes(b)
+	} else {
+		resources, err = s.ParseResources(s.ResourcePath)
 	}
-	resources, err := s.ParseResources(s.ResourcePath)
 	if errors.As(err, &UnrecognisedFormatError{}) {
 		uerr := err.(UnrecognisedFormatError)
 		log.Printf("Skipping %s", uerr.File)
@@ -239,6 +284,7 @@ func (s *Server) updateWatchedResource(name string) error {
 		log.Error("Error: ", err)
 		return err
 	}
+
 	for _, resource := range resources.AsList() {
 		handler, err := s.Registry.GetHandler(resource.Kind())
 		if err != nil {
@@ -257,6 +303,22 @@ func (s *Server) updateWatchedResource(name string) error {
 	return nil
 }
 
+func (s *Server) executeWatchScript() ([]byte, error) {
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	cmd := exec.Command("sh", "-c", s.watchScript)
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	err := cmd.Run()
+	if err != nil {
+		return nil, err
+	}
+	if stderr.Len() > 0 {
+		log.Errorf("%s", stderr.String())
+	}
+	return stdout.Bytes(), nil
+}
+
 func (s *Server) blockHandler(response string) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")