update wasmgen

go/cmd/wasmgen/main.go

@@ -0,0 +1,214 @@
+// Command wasmgen preprocesses component directives into glue code so that
+// server-component calls look identical to client-component calls, and routes
+// can opt into SSR with a tag.
+//
+// Directives (as doc comments on functions in the target package):
+//
+//	//gowasm:page <path> [static] [layout=<name>]
+//	                                a page factory `func(Deps) func() *vdom.VNode`.
+//	                                `static` => the server SSRs that route;
+//	                                `layout=` => wrap it in a named //gowasm:layout.
+//	//gowasm:layout <name>          a layout `func(Deps, *vdom.VNode) *vdom.VNode`.
+//	//gowasm:server                 a server component `func() func() *vdom.VNode`.
+//
+// It emits three files in the package:
+//   - routes.gen.go  (neutral)  Routes(Deps) + StaticPaths + RouteLayout/LayoutFor
+//   - server.gen.go  (native)   init() registering each server component
+//   - client.gen.go  (wasm)     a client stub per server component that
+//     mounts it over /rsc
+package main
+
+import (
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"text/template"
+)
+
+type page struct {
+	Func   string
+	Path   string
+	Static bool
+	Layout string // name of the //gowasm:layout wrapper (empty => default)
+}
+
+type layoutDecl struct {
+	Name string
+	Func string
+}
+
+type genData struct {
+	Pages         []page
+	Servers       []string
+	Layouts       []layoutDecl
+	DefaultLayout string // func name used when a page declares no layout
+}
+
+func main() {
+	dir := "app"
+	if len(os.Args) > 1 {
+		dir = os.Args[1]
+	}
+
+	fset := token.NewFileSet()
+	pkgs, err := parser.ParseDir(fset, dir, func(fi os.FileInfo) bool {
+		return !strings.HasSuffix(fi.Name(), ".gen.go")
+	}, parser.ParseComments)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "wasmgen: parse:", err)
+		os.Exit(1)
+	}
+
+	var data genData
+	for _, pkg := range pkgs {
+		for _, file := range pkg.Files {
+			for _, decl := range file.Decls {
+				fn, ok := decl.(*ast.FuncDecl)
+				if !ok || fn.Doc == nil {
+					continue
+				}
+				for _, c := range fn.Doc.List {
+					line := strings.TrimSpace(strings.TrimPrefix(c.Text, "//"))
+					switch {
+					case strings.HasPrefix(line, "gowasm:page "):
+						fields := strings.Fields(line[len("gowasm:page "):])
+						if len(fields) == 0 {
+							continue
+						}
+						p := page{Func: fn.Name.Name, Path: fields[0]}
+						for _, f := range fields[1:] {
+							switch {
+							case f == "static":
+								p.Static = true
+							case strings.HasPrefix(f, "layout="):
+								p.Layout = strings.TrimPrefix(f, "layout=")
+							}
+						}
+						data.Pages = append(data.Pages, p)
+					case strings.HasPrefix(line, "gowasm:layout "):
+						fields := strings.Fields(line[len("gowasm:layout "):])
+						if len(fields) == 0 {
+							continue
+						}
+						data.Layouts = append(data.Layouts, layoutDecl{Name: fields[0], Func: fn.Name.Name})
+					case line == "gowasm:server":
+						data.Servers = append(data.Servers, fn.Name.Name)
+					}
+				}
+			}
+		}
+	}
+	sort.Slice(data.Pages, func(i, j int) bool { return data.Pages[i].Path < data.Pages[j].Path })
+	sort.Strings(data.Servers)
+	sort.Slice(data.Layouts, func(i, j int) bool { return data.Layouts[i].Name < data.Layouts[j].Name })
+
+	// Default layout: prefer one literally named "app", else the first declared.
+	var defaultName string
+	if len(data.Layouts) > 0 {
+		data.DefaultLayout, defaultName = data.Layouts[0].Func, data.Layouts[0].Name
+		for _, l := range data.Layouts {
+			if l.Name == "app" {
+				data.DefaultLayout, defaultName = l.Func, l.Name
+				break
+			}
+		}
+	}
+	for i := range data.Pages {
+		if data.Pages[i].Layout == "" {
+			data.Pages[i].Layout = defaultName
+		}
+	}
+
+	write(filepath.Join(dir, "routes.gen.go"), routesTmpl, data)
+	write(filepath.Join(dir, "server.gen.go"), serverTmpl, data)
+	write(filepath.Join(dir, "client.gen.go"), clientTmpl, data)
+
+	fmt.Printf("wasmgen: %d page(s), %d server component(s)\n", len(data.Pages), len(data.Servers))
+}
+
+func write(path, tmpl string, data genData) {
+	var b strings.Builder
+	if err := template.Must(template.New("g").Parse(tmpl)).Execute(&b, data); err != nil {
+		panic(err)
+	}
+	src, err := format.Source([]byte(b.String()))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "wasmgen: format %s: %v\n---\n%s\n", path, err, b.String())
+		os.Exit(1)
+	}
+	// Only write when changed, so re-running codegen doesn't churn mtimes (which
+	// would make the dev server's file watcher loop).
+	if existing, err := os.ReadFile(path); err == nil && string(existing) == string(src) {
+		return
+	}
+	if err := os.WriteFile(path, src, 0o644); err != nil {
+		panic(err)
+	}
+}
+
+const routesTmpl = `// Code generated by wasmgen. DO NOT EDIT.
+package app
+
+import "kjol/vdom"
+
+// Routes maps each //gowasm:page path to its instantiated render function.
+func Routes(d Deps) map[string]func() *vdom.VNode {
+	return map[string]func() *vdom.VNode{
+{{range .Pages}}		"{{.Path}}": {{.Func}}(d),
+{{end}}	}
+}
+
+// StaticPaths are the routes the server pre-renders (SSR); others render client-side.
+var StaticPaths = map[string]bool{
+{{range .Pages}}{{if .Static}}	"{{.Path}}": true,
+{{end}}{{end}}}
+
+// RouteLayout maps each route to the name of the layout that wraps it.
+var RouteLayout = map[string]string{
+{{range .Pages}}	"{{.Path}}": "{{.Layout}}",
+{{end}}}
+
+// LayoutFor wraps a page's content in the layout declared for its route.
+func LayoutFor(d Deps, path string, content *vdom.VNode) *vdom.VNode {
+{{if .Layouts}}	switch RouteLayout[path] {
+{{range .Layouts}}	case "{{.Name}}":
+		return {{.Func}}(d, content)
+{{end}}	}
+	return {{.DefaultLayout}}(d, content)
+{{else}}	return content
+{{end}}}
+`
+
+const serverTmpl = `// Code generated by wasmgen. DO NOT EDIT.
+
+//go:build !(js && wasm)
+
+package app
+
+import "kjol/rsc"
+
+func init() {
+{{range .Servers}}	rsc.Register("{{.}}", {{.}})
+{{end}}}
+`
+
+const clientTmpl = `// Code generated by wasmgen. DO NOT EDIT.
+
+//go:build js && wasm
+
+package app
+
+import (
+	"kjol/rsc"
+	"kjol/vdom"
+)
+
+{{range .Servers}}// {{.}} is a generated client stub for the server component of the same name.
+func {{.}}() func() *vdom.VNode { return rsc.Mount("{{.}}") }
+{{end}}`