Expose JSON codegen to external packages

cmd/mdl/main.go

@@ -10,7 +10,9 @@ import (
 	"path/filepath"
 	"strings"
 
-	"goa.design/goa/v3/codegen"
+	goacodegen "goa.design/goa/v3/codegen"
+
+	"goa.design/model/codegen"
 	"goa.design/model/mdl"
 	model "goa.design/model/pkg"
 )
@@ -24,7 +26,7 @@ func main() {
 		out    = genset.String("out", "design.json", "set path to generated JSON representation")
 
 		svrset = flag.NewFlagSet("serve", flag.ExitOnError)
-		dir    = svrset.String("dir", codegen.Gendir, "set output directory used by editor to save SVG files")
+		dir    = svrset.String("dir", goacodegen.Gendir, "set output directory used by editor to save SVG files")
 		port   = svrset.Int("port", 8080, "set local HTTP port used to serve diagram editor")
 
 		devmode = os.Getenv("DEVMODE") == "1"
@@ -81,7 +83,7 @@ func main() {
 			fail(`missing PACKAGE argument, use "--help" for usage`)
 		}
 		var b []byte
-		b, err = gen(pkg, *debug)
+		b, err = codegen.JSON(pkg, *debug)
 		if err == nil {
 			err = os.WriteFile(*out, b, 0644)
 		}
@@ -108,7 +110,7 @@ func main() {
 
 func serve(out, pkg string, port int, devmode, debug bool) error {
 	// Retrieve initial design and create server.
-	b, err := gen(pkg, debug)
+	b, err := codegen.JSON(pkg, debug)
 	if err != nil {
 		return err
 	}
@@ -120,7 +122,7 @@ func serve(out, pkg string, port int, devmode, debug bool) error {
 
 	// Update server whenever design changes on disk.
 	err = watch(pkg, func() {
-		b, err := gen(pkg, debug)
+		b, err := codegen.JSON(pkg, debug)
 		if err != nil {
 			fmt.Println("error parsing DSL:\n" + err.Error())
 			return

cmd/mdl/serve.go

@@ -60,13 +60,13 @@ func (s *Server) Serve(outDir string, devmode bool, port int) error {
 		http.Handle("/", http.FileServer(FS(false)))
 	}
 
-	http.HandleFunc("/data/model.json", func(w http.ResponseWriter, r *http.Request) {
+	http.HandleFunc("/data/model.json", func(w http.ResponseWriter, _ *http.Request) {
 		s.lock.Lock()
 		defer s.lock.Unlock()
 		_, _ = w.Write(s.design)
 	})
 
-	http.HandleFunc("/data/layout.json", func(w http.ResponseWriter, r *http.Request) {
+	http.HandleFunc("/data/layout.json", func(w http.ResponseWriter, _ *http.Request) {
 		s.lock.Lock()
 		defer s.lock.Unlock()
 

cmd/mdl/watch.go

@@ -10,6 +10,8 @@ import (
 	"github.com/fsnotify/fsnotify"
 	"github.com/jaschaephraim/lrserver"
 	"golang.org/x/tools/go/packages"
+
+	"goa.design/model/codegen"
 )
 
 // watch implements functionality to listen to changes in the model files
@@ -50,7 +52,7 @@ func watch(pkg string, reload func()) error {
 		for {
 			select {
 			case ev := <-watcher.Events:
-				if strings.HasPrefix(filepath.Base(ev.Name), tmpDirPrefix) {
+				if strings.HasPrefix(filepath.Base(ev.Name), codegen.TmpDirPrefix) {
 					continue
 				}
 

cmd/mdl/gen.go → codegen/json.go

@@ -1,4 +1,4 @@
-package main
+package codegen
 
 import (
 	"fmt"
@@ -10,9 +10,12 @@ import (
 	"golang.org/x/tools/go/packages"
 )
 
-const tmpDirPrefix = "mdl--"
+// TmpDirPrefix is the prefix used to create temporary directories.
+const TmpDirPrefix = "mdl--"
 
-func gen(pkg string, debug bool) ([]byte, error) {
+// JSON generates a JSON representation of the model described in pkg.
+// pkg must be a valid Go package import path.
+func JSON(pkg string, debug bool) ([]byte, error) {
 	// Validate package import path
 	if _, err := packages.Load(&packages.Config{Mode: packages.NeedName}, pkg); err != nil {
 		return nil, err
@@ -23,7 +26,7 @@ func gen(pkg string, debug bool) ([]byte, error) {
 	if err != nil {
 		cwd = "."
 	}
-	tmpDir, err := os.MkdirTemp(cwd, tmpDirPrefix)
+	tmpDir, err := os.MkdirTemp(cwd, TmpDirPrefix)
 	if err != nil {
 		return nil, err
 	}