Add html2gomponents tool

.github/workflows/ci.yml

@@ -63,3 +63,24 @@ jobs:
         uses: golangci/golangci-lint-action@v6
         with:
           version: latest
+
+  test-html2gomponents:
+    name: Test html2gomponents
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: stable
+
+      - name: Build
+        run: go build -v ./...
+        working-directory: cmd/html2gomponents
+
+      - name: Test
+        run: go test -v -shuffle on ./...
+        working-directory: cmd/html2gomponents

cmd/html2gomponents/go.mod

@@ -0,0 +1,5 @@
+module maragu.dev/gomponents/cmd/html2gomponents
+
+go 1.23.2
+
+require golang.org/x/net v0.30.0

cmd/html2gomponents/go.sum

@@ -0,0 +1,2 @@
+golang.org/x/net v0.30.0 h1:AcW1SDZMkb8IpzCdQUaIq2sP4sZ4zw+55h6ynffypl4=
+golang.org/x/net v0.30.0/go.mod h1:2wGyMJ5iFasEhkwi13ChkO/t1ECNC4X4eBKkVFyYFlU=

cmd/html2gomponents/main.go

@@ -0,0 +1,211 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"go/format"
+	"io"
+	"log/slog"
+	"os"
+	"strings"
+
+	"golang.org/x/net/html"
+)
+
+var attrs = map[string]string{
+	"autocomplete": "AutoComplete",
+	"autofocus":    "AutoFocus",
+	"autoplay":     "AutoPlay",
+	"cite":         "CiteAttr",
+	"colspan":      "ColSpan",
+	"crossorigin":  "CrossOrigin",
+	"datetime":     "DateTime",
+	"enctype":      "EncType",
+	"form":         "FormAttr",
+	"id":           "ID",
+	"label":        "LabelAttr",
+	"maxlength":    "MaxLength",
+	"minlength":    "MinLength",
+	"playsinline":  "PlaysInline",
+	"readonly":     "ReadOnly",
+	"rowspan":      "RowSpan",
+	"srcset":       "SrcSet",
+	"tabindex":     "TabIndex",
+}
+
+var els = map[string]string{
+	"blockquote": "BlockQuote",
+	"colgroup":   "ColGroup",
+	"data":       "DataEl",
+	"datalist":   "DataList",
+	"fieldset":   "FieldSet",
+	"figcaption": "FigCaption",
+	"hgroup":     "HGroup",
+	"html":       "HTML",
+	"iframe":     "IFrame",
+	"noscript":   "NoScript",
+	"optgroup":   "OptGroup",
+	"style":      "StyleEl",
+	"svg":        "SVG",
+	"tbody":      "TBody",
+	"tfoot":      "TFoot",
+	"thead":      "THead",
+	"title":      "TitleEl",
+}
+
+func main() {
+	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
+	if err := start(os.Stdin, os.Stdout); err != nil {
+		log.Info("Error", "error", err)
+		os.Exit(1)
+	}
+}
+
+func start(r io.Reader, w2 io.Writer) error {
+	var b bytes.Buffer
+	w := &statefulWriter{w: &b}
+
+	w.Write("package html\n")
+	w.Write("\n")
+	w.Write("import (\n")
+	w.Write(". \"maragu.dev/gomponents\"\n")
+	w.Write(". \"maragu.dev/gomponents/html\"\n")
+	w.Write(")\n")
+	w.Write("\n")
+	w.Write("func Component() Node {\n")
+
+	z := html.NewTokenizer(r)
+
+	var hasContent bool
+	var depth int
+loop:
+	for {
+		tt := z.Next()
+
+		switch tt {
+		case html.ErrorToken:
+			if err := z.Err(); err != nil {
+				if errors.Is(err, io.EOF) {
+					if !hasContent {
+						w.Write("return nil")
+					}
+					break loop
+				}
+				return err
+			}
+
+		case html.TextToken:
+			text := strings.TrimSpace(string(z.Text()))
+			if text == "" {
+				continue
+			}
+
+			if !hasContent {
+				w.Write("return ")
+			}
+
+			hasContent = true
+			w.Write(fmt.Sprintf("Text(%q)", text))
+			if depth > 0 {
+				w.Write(",")
+			}
+
+		case html.StartTagToken, html.SelfClosingTagToken:
+			if !hasContent {
+				w.Write("return ")
+			}
+
+			if hasContent {
+				w.Write("\n")
+			}
+			hasContent = true
+
+			name, hasAttr := z.TagName()
+			if el, ok := els[string(name)]; ok {
+				w.Write(el)
+			} else {
+				w.Write(strings.ToTitle(string(name[0])))
+				w.Write(string(name[1:]))
+			}
+			w.Write("(")
+
+			if hasAttr {
+				for {
+					key, val, moreAttr := z.TagAttr()
+
+					if attr, ok := attrs[string(key)]; ok {
+						w.Write(attr)
+					} else {
+						w.Write(strings.ToTitle(string(key[0])))
+						w.Write(string(key[1:]))
+					}
+					w.Write("(")
+
+					if len(val) > 0 {
+						w.Write(`"` + string(val) + `"`)
+					}
+
+					w.Write("),")
+
+					if !moreAttr {
+						break
+					}
+				}
+				w.Write("\n")
+			}
+			depth++
+
+			if tt == html.SelfClosingTagToken {
+				depth--
+				w.Write("\n)")
+				if depth > 0 {
+					w.Write(",")
+				}
+			}
+
+		case html.EndTagToken:
+			depth--
+			w.Write("\n)")
+			if depth > 0 {
+				w.Write(",")
+			}
+
+		case html.CommentToken:
+			w.Write("// " + string(z.Text()) + "\n")
+
+		case html.DoctypeToken:
+			// TODO Ignore for now
+		}
+	}
+
+	w.Write("\n}\n")
+
+	if w.err != nil {
+		return w.err
+	}
+
+	formatted, err := format.Source(b.Bytes())
+	if err != nil {
+		return fmt.Errorf("error formatting output: %w", err)
+	}
+
+	if _, err = w2.Write(formatted); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// statefulWriter only writes if no errors have occurred earlier in its lifetime.
+type statefulWriter struct {
+	w   io.Writer
+	err error
+}
+
+func (w *statefulWriter) Write(s string) {
+	if w.err != nil {
+		return
+	}
+	_, w.err = w.w.Write([]byte(s))
+}

cmd/html2gomponents/main_test.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestStart(t *testing.T) {
+	entries, err := os.ReadDir("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, e := range entries {
+		name := e.Name()
+		if !strings.HasSuffix(name, ".html") {
+			continue
+		}
+		name = strings.TrimSuffix(name, ".html")
+
+		t.Run(name, func(t *testing.T) {
+			in := readTestData(t, name+".html")
+			out := readTestData(t, "_out/"+name+".go")
+
+			r := strings.NewReader(in)
+			var w strings.Builder
+			err := start(r, &w)
+
+			if err != nil {
+				t.Fatal(err)
+			}
+			if out != w.String() {
+				t.Fatalf("expected %v, got %v", out, w.String())
+			}
+		})
+	}
+}
+
+func readTestData(t *testing.T, path string) string {
+	t.Helper()
+
+	b, err := os.ReadFile("testdata/" + path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(b)
+}

cmd/html2gomponents/testdata/_out/attributes.go

@@ -0,0 +1,12 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	return A(Href("#"), Title("halløj"),
+		Text("Halløj!"),
+	)
+}

cmd/html2gomponents/testdata/_out/comment.go

@@ -0,0 +1,11 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	// halløj
+	return Div()
+}

cmd/html2gomponents/testdata/_out/complex.go

@@ -0,0 +1,20 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	return Div(
+		H1(ID("title"), Class("pretty"),
+			Text("Halløj!"),
+		),
+		H2(ID("subtitle"), Class("prettier"),
+			Text("What is this?"),
+		),
+		P(Class("prettiest"),
+			Text("It's a parser and converter for converting HTML to gomponents Go code."),
+		),
+	)
+}

cmd/html2gomponents/testdata/_out/div.go

@@ -0,0 +1,10 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	return Div()
+}

cmd/html2gomponents/testdata/_out/divspan.go

@@ -0,0 +1,12 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	return Div(
+		Span(),
+	)
+}

cmd/html2gomponents/testdata/_out/divspanspan.go

@@ -0,0 +1,13 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	return Div(
+		Span(),
+		Span(),
+	)
+}

cmd/html2gomponents/testdata/_out/divtext.go

@@ -0,0 +1,10 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	return Div(Text("halløj"))
+}

cmd/html2gomponents/testdata/_out/doctype.go

@@ -0,0 +1,10 @@
+package html
+
+import (
+	. "maragu.dev/gomponents"
+	. "maragu.dev/gomponents/html"
+)
+
+func Component() Node {
+	return nil
+}