@@ -0,0 +1,22 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 Eric Chiang
+Copyright (c) 2021 Adrian Hesketh
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

@@ -0,0 +1,45 @@
+# htmlformat
+
+htmlformat is a Go package and CLI tool used to format HTML.
+
+It is forked and simplified from the https://github.com/ericchiang/pup package.
+
+It does not aim to:
+
+* Colorize output.
+* Modify the input HTML except for formatting (i.e. no HTML escaping will be applied).
+* Provide any facilities to query the content.
+
+## Installation
+
+To use the CLI, you can install with Go > 1.20.
+
+```
+go install github.com/a-h/htmlformat/cmd/htmlformat@latest
+```
+
+## Usage
+
+### CLI
+
+```bash
+echo '<ol><li style="&">A</li><li>B</li></ol>' | htmlformat
+<ol>
+ <li style="&">
+  A
+ </li>
+ <li>
+  B
+ </li>
+</ol>
+```
+
+### Package
+
+```go
+r := strings.NewReader(`<ol><li style="&">A</li><li>B</li></ol>`)
+w := os.Stdout
+if err := Fragment(w, r); err != nil {
+  log.Fatalf("failed to format: %v", err)
+}
+```

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+
+	"github.com/a-h/htmlformat"
+)
+
+var parseDocumentFlag = flag.Bool("document", false, "Set to true to parse a whole document")
+
+func main() {
+	flag.Parse()
+
+	var err error
+	if *parseDocumentFlag {
+		err = htmlformat.Document(os.Stdout, os.Stdin)
+	} else {
+		err = htmlformat.Fragment(os.Stdout, os.Stdin)
+	}
+	if err != nil {
+		log.Fatalf("failed to format: %v", err)
+	}
+}

@@ -0,0 +1,187 @@
+package htmlformat
+
+import (
+	"fmt"
+	"io"
+	"strings"
+
+	"golang.org/x/net/html"
+	"golang.org/x/net/html/atom"
+)
+
+// Document formats a HTML document.
+func Document(w io.Writer, r io.Reader) (err error) {
+	node, err := html.Parse(r)
+	if err != nil {
+		return err
+	}
+	return Nodes(w, []*html.Node{node})
+}
+
+// Fragment formats a fragment of a HTML document.
+func Fragment(w io.Writer, r io.Reader) (err error) {
+	context := &html.Node{
+		Type: html.ElementNode,
+	}
+	nodes, err := html.ParseFragment(r, context)
+	if err != nil {
+		return err
+	}
+	return Nodes(w, nodes)
+}
+
+// Nodes formats a slice of HTML nodes.
+func Nodes(w io.Writer, nodes []*html.Node) (err error) {
+	for _, node := range nodes {
+		if err = printNode(w, node, 0); err != nil {
+			return
+		}
+	}
+	return
+}
+
+// The <pre> tag indicates that the text within it should always be formatted
+// as is. See https://github.com/ericchiang/pup/issues/33
+func printPre(w io.Writer, n *html.Node) (err error) {
+	switch n.Type {
+	case html.TextNode:
+		s := n.Data
+		if _, err = fmt.Fprint(w, s); err != nil {
+			return
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			if err = printPre(w, c); err != nil {
+				return
+			}
+		}
+	case html.ElementNode:
+		if _, err = fmt.Fprintf(w, "<%s", n.Data); err != nil {
+			return
+		}
+		for _, a := range n.Attr {
+			val := a.Val
+			if _, err = fmt.Fprintf(w, ` %s="%s"`, a.Key, val); err != nil {
+				return
+			}
+		}
+		if _, err = fmt.Fprint(w, ">"); err != nil {
+			return
+		}
+		if !isVoidElement(n) {
+			for c := n.FirstChild; c != nil; c = c.NextSibling {
+				if err = printPre(w, c); err != nil {
+					return
+				}
+			}
+			if _, err = fmt.Fprintf(w, "</%s>", n.Data); err != nil {
+				return
+			}
+		}
+	case html.CommentNode:
+		data := n.Data
+		if _, err = fmt.Fprintf(w, "<!--%s-->\n", data); err != nil {
+			return
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			if err = printPre(w, c); err != nil {
+				return
+			}
+		}
+	case html.DoctypeNode, html.DocumentNode:
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			if err = printPre(w, c); err != nil {
+				return
+			}
+		}
+	}
+	return
+}
+
+// Is this node a tag with no end tag such as <meta> or <br>?
+// http://www.w3.org/TR/html-markup/syntax.html#syntax-elements
+func isVoidElement(n *html.Node) bool {
+	switch n.DataAtom {
+	case atom.Area, atom.Base, atom.Br, atom.Col, atom.Command, atom.Embed,
+		atom.Hr, atom.Img, atom.Input, atom.Keygen, atom.Link,
+		atom.Meta, atom.Param, atom.Source, atom.Track, atom.Wbr:
+		return true
+	}
+	return false
+}
+
+func printNode(w io.Writer, n *html.Node, level int) (err error) {
+	switch n.Type {
+	case html.TextNode:
+		s := n.Data
+		s = strings.TrimSpace(s)
+		if s != "" {
+			if err = printIndent(w, level); err != nil {
+				return
+			}
+			if _, err = fmt.Fprintln(w, s); err != nil {
+				return
+			}
+		}
+	case html.ElementNode:
+		if err = printIndent(w, level); err != nil {
+			return
+		}
+		if _, err = fmt.Fprintf(w, "<%s", n.Data); err != nil {
+			return
+		}
+		for _, a := range n.Attr {
+			if _, err = fmt.Fprintf(w, ` %s="%s"`, a.Key, a.Val); err != nil {
+				return
+			}
+		}
+		if _, err = fmt.Fprintln(w, ">"); err != nil {
+			return
+		}
+		if !isVoidElement(n) {
+			if err = printChildren(w, n, level+1); err != nil {
+				return
+			}
+			if err = printIndent(w, level); err != nil {
+				return
+			}
+			if _, err = fmt.Fprintf(w, "</%s>\n", n.Data); err != nil {
+				return
+			}
+		}
+	case html.CommentNode:
+		if err = printIndent(w, level); err != nil {
+			return
+		}
+		if _, err = fmt.Fprintf(w, "<!--%s-->\n", n.Data); err != nil {
+			return
+		}
+		if err = printChildren(w, n, level); err != nil {
+			return
+		}
+	case html.DoctypeNode, html.DocumentNode:
+		if err = printChildren(w, n, level); err != nil {
+			return
+		}
+	}
+	return
+}
+
+func printChildren(w io.Writer, n *html.Node, level int) (err error) {
+	child := n.FirstChild
+	for child != nil {
+		if err = printNode(w, child, level); err != nil {
+			return
+		}
+		child = child.NextSibling
+	}
+	return
+}
+
+func printIndent(w io.Writer, level int) (err error) {
+	for ; level > 0; level-- {
+		if _, err = fmt.Fprint(w, " "); err != nil {
+			return
+		}
+	}
+	return
+}

@@ -0,0 +1,51 @@
+package htmlformat
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestFormat(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:  "html elements are indented",
+			input: `<ol> <li style="&"> A </li> <li> B </li> </ol> `,
+			expected: `<ol>
+ <li style="&">
+  A
+ </li>
+ <li>
+  B
+ </li>
+</ol>
+`,
+		},
+		{
+			name:     "text fragments are supported",
+			input:    `test 123`,
+			expected: `test 123` + "\n",
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			r := strings.NewReader(test.input)
+			w := new(strings.Builder)
+			if err := Fragment(w, r); err != nil {
+				t.Fatalf("failed to format: %v", err)
+			}
+			if diff := cmp.Diff(test.expected, w.String()); diff != "" {
+				t.Error(diff)
+			}
+		})
+	}
+}

@@ -0,0 +1,7 @@
+module github.com/a-h/htmlformat
+
+go 1.20
+
+require golang.org/x/net v0.9.0
+
+require github.com/google/go-cmp v0.5.9

@@ -0,0 +1,4 @@
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+golang.org/x/net v0.9.0 h1:aWJ/m6xSmxWBx+V0XRHTlrYrPG56jKsLdTFmsSsCzOM=
+golang.org/x/net v0.9.0/go.mod h1:d48xBJpPfHeWQsugry2m+kC02ZBRGRgulfHnEXEuWns=