Revert "publisher: Make the HTML element collector more robust"

This reverts commit ef0f1a726901d6c614040cfc2d7e8f9a2ca97816.

3 files changed, 153 insertions, 286 deletions

diff --git a/common/text/transform.go b/common/text/transform.go
index 2d51f6c33..f59577803 100644
--- a/common/text/transform.go
+++ b/common/text/transform.go
@@ -45,25 +45,3 @@ func RemoveAccentsString(s string) string {
 	accentTransformerPool.Put(t)
 	return s
 }
-
-// Chunk splits s into strings of size.
-func Chunk(s string, size int) []string {
-	if size >= len(s) {
-		return []string{s}
-	}
-	var chunks []string
-	chunk := make([]rune, size)
-	l := 0
-	for _, r := range s {
-		chunk[l] = r
-		l++
-		if l == size {
-			chunks = append(chunks, string(chunk))
-			l = 0
-		}
-	}
-	if l > 0 {
-		chunks = append(chunks, string(chunk[:l]))
-	}
-	return chunks
-}
diff --git a/publisher/htmlElementsCollector.go b/publisher/htmlElementsCollector.go
index 1bc1a09bc..9dc28c4c2 100644
--- a/publisher/htmlElementsCollector.go
+++ b/publisher/htmlElementsCollector.go
@@ -19,51 +19,12 @@ import (
 	"sort"
 	"strings"
 	"sync"
-	"unicode"
-	"unicode/utf8"
 
 	"golang.org/x/net/html"
 
 	"github.com/gohugoio/hugo/helpers"
 )
 
-const eof = -1
-
-var (
-	htmlJsonFixer = strings.NewReplacer(", ", "\n")
-	jsonAttrRe    = regexp.MustCompile(`'?(.*?)'?:.*`)
-	classAttrRe   = regexp.MustCompile(`(?i)^class$|transition`)
-
-	skipInnerElementRe = regexp.MustCompile(`(?i)^(pre|textarea|script|style)`)
-	skipAllElementRe   = regexp.MustCompile(`(?i)^!DOCTYPE`)
-	endTagRe           = regexp.MustCompile(`(?i)<\/\s*([a-zA-Z]+)\s*>$`)
-
-	exceptionList = map[string]bool{
-		"thead": true,
-		"tbody": true,
-		"tfoot": true,
-		"td":    true,
-		"tr":    true,
-	}
-)
-
-func newHTMLElementsCollector() *htmlElementsCollector {
-	return &htmlElementsCollector{
-		elementSet: make(map[string]bool),
-	}
-}
-
-func newHTMLElementsCollectorWriter(collector *htmlElementsCollector) *htmlElementsCollectorWriter {
-	w := &htmlElementsCollectorWriter{
-		collector: collector,
-		state:     htmlLexStart,
-	}
-
-	w.defaultLexElementInside = w.lexElementInside(htmlLexStart)
-
-	return w
-}
-
 // HTMLElements holds lists of tags and attribute values for classes and id.
 type HTMLElements struct {
 	Tags    []string `json:"tags"`
@@ -87,12 +48,6 @@ func (h *HTMLElements) Sort() {
 	sort.Strings(h.IDs)
 }
 
-type htmlElement struct {
-	Tag     string
-	Classes []string
-	IDs     []string
-}
-
 type htmlElementsCollector struct {
 	// Contains the raw HTML string. We will get the same element
 	// several times, and want to avoid costly reparsing when this
@@ -104,6 +59,12 @@ type htmlElementsCollector struct {
 	mu sync.RWMutex
 }
 
+func newHTMLElementsCollector() *htmlElementsCollector {
+	return &htmlElementsCollector{
+		elementSet: make(map[string]bool),
+	}
+}
+
 func (c *htmlElementsCollector) getHTMLElements() HTMLElements {
 	var (
 		classes []string
@@ -132,118 +93,114 @@ func (c *htmlElementsCollector) getHTMLElements() HTMLElements {
 
 type htmlElementsCollectorWriter struct {
 	collector *htmlElementsCollector
+	buff      bytes.Buffer
 
-	r     rune   // Current rune
-	width int    // The width in bytes of r
-	input []byte // The current slice written to Write
-	pos   int    // The current position in input
-
-	err error
-
-	inQuote rune
-
-	buff bytes.Buffer
+	isCollecting bool
+	inPreTag     string
 
-	// Current state
-	state htmlCollectorStateFunc
+	inQuote    bool
+	quoteValue byte
+}
 
-	// Precompiled state funcs
-	defaultLexElementInside htmlCollectorStateFunc
+func newHTMLElementsCollectorWriter(collector *htmlElementsCollector) *htmlElementsCollectorWriter {
+	return &htmlElementsCollectorWriter{
+		collector: collector,
+	}
 }
 
-// Write collects HTML elements from p.
+// Write splits the incoming stream into single html element.
 func (w *htmlElementsCollectorWriter) Write(p []byte) (n int, err error) {
 	n = len(p)
-	w.input = p
-	w.pos = 0
-
-	for {
-		w.r = w.next()
-		if w.r == eof {
-			return
+	i := 0
+
+	for i < len(p) {
+		// If we are not collecting, cycle through byte stream until start bracket "<" is found.
+		if !w.isCollecting {
+			for ; i < len(p); i++ {
+				b := p[i]
+				if b == '<' {
+					w.startCollecting()
+					break
+				}
+			}
 		}
-		w.state = w.state(w)
-	}
-}
-
-func (l *htmlElementsCollectorWriter) backup() {
-	l.pos -= l.width
-	l.r, _ = utf8.DecodeRune(l.input[l.pos:])
-}
 
-func (w *htmlElementsCollectorWriter) consumeBuffUntil(condition func() bool, resolve htmlCollectorStateFunc) htmlCollectorStateFunc {
-	var s htmlCollectorStateFunc
-	s = func(*htmlElementsCollectorWriter) htmlCollectorStateFunc {
-		w.buff.WriteRune(w.r)
-		if condition() {
-			w.buff.Reset()
-			return resolve
+		if w.isCollecting {
+			// If we are collecting, cycle through byte stream until end bracket ">" is found,
+			// disregard any ">" if within a quote,
+			// write bytes until found to buffer.
+			for ; i < len(p); i++ {
+				b := p[i]
+				w.toggleIfQuote(b)
+				w.buff.WriteByte(b)
+
+				if !w.inQuote && b == '>' {
+					w.endCollecting()
+					break
+				}
+			}
 		}
-		return s
-	}
-	return s
-}
 
-func (w *htmlElementsCollectorWriter) consumeRuneUntil(condition func(r rune) bool, resolve htmlCollectorStateFunc) htmlCollectorStateFunc {
-	var s htmlCollectorStateFunc
-	s = func(*htmlElementsCollectorWriter) htmlCollectorStateFunc {
-		if condition(w.r) {
-			return resolve
-		}
-		return s
-	}
-	return s
-}
+		// If no end bracket ">" is found while collecting, but the stream ended
+		// this could mean we received chunks of a stream from e.g. the minify functionality
+		// next if loop will be skipped.
 
-// Starts with e.g. "<body " or "<div"
-func (w *htmlElementsCollectorWriter) lexElementInside(resolve htmlCollectorStateFunc) htmlCollectorStateFunc {
-	var s htmlCollectorStateFunc
-	s = func(w *htmlElementsCollectorWriter) htmlCollectorStateFunc {
-		w.buff.WriteRune(w.r)
-
-		// Skip any text inside a quote.
-		if w.r == '\'' || w.r == '"' {
-			if w.inQuote == w.r {
-				w.inQuote = 0
-			} else if w.inQuote == 0 {
-				w.inQuote = w.r
+		// At this point we have collected an element line between angle brackets "<" and ">".
+		if !w.isCollecting {
+			if w.buff.Len() == 0 {
+				continue
 			}
-		}
 
-		if w.inQuote != 0 {
-			return s
-		}
+			if w.inPreTag != "" { // within preformatted code block
+				s := w.buff.String()
+				w.buff.Reset()
+				if tagName, isEnd := parseEndTag(s); isEnd && w.inPreTag == tagName {
+					w.inPreTag = ""
+				}
+				continue
+			}
 
-		if w.r == '>' {
+			// First check if we have processed this element before.
+			w.collector.mu.RLock()
 
 			// Work with the bytes slice as long as it's practical,
 			// to save memory allocations.
 			b := w.buff.Bytes()
 
-			defer func() {
-				w.buff.Reset()
-			}()
-
-			// First check if we have processed this element before.
-			w.collector.mu.RLock()
-
+			// See https://github.com/dominikh/go-tools/issues/723
+			//lint:ignore S1030 This construct avoids memory allocation for the string.
 			seen := w.collector.elementSet[string(b)]
 			w.collector.mu.RUnlock()
 			if seen {
-				return resolve
+				w.buff.Reset()
+				continue
+			}
+
+			// Filter out unwanted tags
+			// if within preformatted code blocks <pre>, <textarea>, <script>, <style>
+			// comments and doctype tags
+			// end tags.
+			switch {
+			case bytes.HasPrefix(b, []byte("<!")): // comment or doctype tag
+				w.buff.Reset()
+				continue
+			case bytes.HasPrefix(b, []byte("</")): // end tag
+				w.buff.Reset()
+				continue
 			}
 
 			s := w.buff.String()
+			w.buff.Reset()
 
-			if s == "" {
-				return resolve
+			// Check if a preformatted code block started.
+			if tagName, isStart := parseStartTag(s); isStart && isPreFormatted(tagName) {
+				w.inPreTag = tagName
 			}
 
 			// Parse each collected element.
 			el, err := parseHTMLElement(s)
 			if err != nil {
-				w.err = err
-				return resolve
+				return n, err
 			}
 
 			// Write this tag to the element set.
@@ -251,137 +208,109 @@ func (w *htmlElementsCollectorWriter) lexElementInside(resolve htmlCollectorStat
 			w.collector.elementSet[s] = true
 			w.collector.elements = append(w.collector.elements, el)
 			w.collector.mu.Unlock()
-
-			return resolve
-
 		}
-
-		return s
 	}
 
-	return s
+	return
 }
 
-func (l *htmlElementsCollectorWriter) next() rune {
-	if l.pos >= len(l.input) {
-		l.width = 0
-		return eof
-	}
-
-	runeValue, runeWidth := utf8.DecodeRune(l.input[l.pos:])
-	l.width = runeWidth
-	l.pos += l.width
-	return runeValue
+func (c *htmlElementsCollectorWriter) startCollecting() {
+	c.isCollecting = true
 }
 
-// returns the next state in HTML element scanner.
-type htmlCollectorStateFunc func(*htmlElementsCollectorWriter) htmlCollectorStateFunc
+func (c *htmlElementsCollectorWriter) endCollecting() {
+	c.isCollecting = false
+	c.inQuote = false
+}
 
-// At "<", buffer empty.
-// Potentially starting a HTML element.
-func htmlLexElementStart(w *htmlElementsCollectorWriter) htmlCollectorStateFunc {
-	if w.r == '>' || unicode.IsSpace(w.r) {
-		if w.buff.Len() < 2 || bytes.HasPrefix(w.buff.Bytes(), []byte("</")) {
-			w.buff.Reset()
-			return htmlLexStart
+func (c *htmlElementsCollectorWriter) toggleIfQuote(b byte) {
+	if isQuote(b) {
+		if c.inQuote && b == c.quoteValue {
+			c.inQuote = false
+		} else if !c.inQuote {
+			c.inQuote = true
+			c.quoteValue = b
 		}
+	}
+}
 
-		tagName := w.buff.Bytes()[1:]
-
-		switch {
-		case skipInnerElementRe.Match(tagName):
-			// pre, script etc. We collect classes etc. on the surrounding
-			// element, but skip the inner content.
-			w.backup()
+func isQuote(b byte) bool {
+	return b == '"' || b == '\''
+}
 
-			// tagName will be overwritten, so make a copy.
-			tagNameCopy := make([]byte, len(tagName))
-			copy(tagNameCopy, tagName)
+func parseStartTag(s string) (string, bool) {
+	s = strings.TrimPrefix(s, "<")
+	s = strings.TrimSuffix(s, ">")
 
-			return w.lexElementInside(
-				w.consumeBuffUntil(
-					func() bool {
-						if w.r != '>' {
-							return false
-						}
-						m := endTagRe.FindSubmatch(w.buff.Bytes())
-						if m == nil {
-							return false
-						}
-						return bytes.EqualFold(m[1], tagNameCopy)
-					},
-					htmlLexStart,
-				))
-		case skipAllElementRe.Match(tagName):
-			// E.g. "<!DOCTYPE ..."
-			w.buff.Reset()
-			return w.consumeRuneUntil(func(r rune) bool {
-				return r == '>'
-			}, htmlLexStart)
-		default:
-			w.backup()
-			return w.defaultLexElementInside
-		}
+	spaceIndex := strings.Index(s, " ")
+	if spaceIndex != -1 {
+		s = s[:spaceIndex]
 	}
 
-	w.buff.WriteRune(w.r)
+	return strings.ToLower(strings.TrimSpace(s)), true
+}
 
-	// If it's a comment, skip to its end.
-	if w.r == '-' && bytes.Equal(w.buff.Bytes(), []byte("<!--")) {
-		w.buff.Reset()
-		return htmlLexToEndOfComment
+func parseEndTag(s string) (string, bool) {
+	if !strings.HasPrefix(s, "</") {
+		return "", false
 	}
 
-	return htmlLexElementStart
+	s = strings.TrimPrefix(s, "</")
+	s = strings.TrimSuffix(s, ">")
+
+	return strings.ToLower(strings.TrimSpace(s)), true
 }
 
-// Entry state func.
-// Looks for a opening bracket, '<'.
-func htmlLexStart(w *htmlElementsCollectorWriter) htmlCollectorStateFunc {
-	if w.r == '<' {
-		w.backup()
-		w.buff.Reset()
-		return htmlLexElementStart
-	}
+// No need to look inside these for HTML elements.
+func isPreFormatted(s string) bool {
+	return s == "pre" || s == "textarea" || s == "script" || s == "style"
+}
 
-	return htmlLexStart
+type htmlElement struct {
+	Tag     string
+	Classes []string
+	IDs     []string
 }
 
-// After "<!--", buff empty.
-func htmlLexToEndOfComment(w *htmlElementsCollectorWriter) htmlCollectorStateFunc {
-	w.buff.WriteRune(w.r)
+var (
+	htmlJsonFixer = strings.NewReplacer(", ", "\n")
+	jsonAttrRe    = regexp.MustCompile(`'?(.*?)'?:.*`)
+	classAttrRe   = regexp.MustCompile(`(?i)^class$|transition`)
 
-	if w.r == '>' && bytes.HasSuffix(w.buff.Bytes(), []byte("-->")) {
-		// Done, start looking for HTML elements again.
-		return htmlLexStart
+	exceptionList = map[string]bool{
+		"thead": true,
+		"tbody": true,
+		"tfoot": true,
+		"td":    true,
+		"tr":    true,
 	}
-
-	return htmlLexToEndOfComment
-}
+)
 
 func parseHTMLElement(elStr string) (el htmlElement, err error) {
+	var tagBuffer string = ""
 
-	tagName := parseStartTag(elStr)
-
-	el.Tag = strings.ToLower(tagName)
-	tagNameToParse := el.Tag
+	tagName, ok := parseStartTag(elStr)
+	if !ok {
+		return
+	}
 
 	// The net/html parser does not handle single table elements as input, e.g. tbody.
 	// We only care about the element/class/ids, so just store away the original tag name
 	// and pretend it's a <div>.
-	if exceptionList[el.Tag] {
+	if exceptionList[tagName] {
+		tagBuffer = tagName
 		elStr = strings.Replace(elStr, tagName, "div", 1)
-		tagNameToParse = "div"
 	}
 
 	n, err := html.Parse(strings.NewReader(elStr))
 	if err != nil {
 		return
 	}
-
 	var walk func(*html.Node)
 	walk = func(n *html.Node) {
-		if n.Type == html.ElementNode && n.Data == tagNameToParse {
+		if n.Type == html.ElementNode && strings.Contains(elStr, n.Data) {
+			el.Tag = n.Data
+
 			for _, a := range n.Attr {
 				switch {
 				case strings.EqualFold(a.Key, "id"):
@@ -416,20 +345,10 @@ func parseHTMLElement(elStr string) (el htmlElement, err error) {
 
 	walk(n)
 
-	return
-}
-
-// Variants of s
-//    <body class="b a">
-//    <div>
-func parseStartTag(s string) string {
-	spaceIndex := strings.IndexFunc(s, func(r rune) bool {
-		return unicode.IsSpace(r)
-	})
-
-	if spaceIndex == -1 {
-		return s[1 : len(s)-1]
+	// did we replaced the start tag?
+	if tagBuffer != "" {
+		el.Tag = tagBuffer
 	}
 
-	return s[1:spaceIndex]
+	return
 }
diff --git a/publisher/htmlElementsCollector_test.go b/publisher/htmlElementsCollector_test.go
index 2eac31f73..0c8b2b65b 100644
--- a/publisher/htmlElementsCollector_test.go
+++ b/publisher/htmlElementsCollector_test.go
@@ -15,12 +15,8 @@ package publisher
 
 import (
 	"fmt"
-	"math/rand"
 	"strings"
 	"testing"
-	"time"
-
-	"github.com/gohugoio/hugo/common/text"
 
 	"github.com/gohugoio/hugo/media"
 	"github.com/gohugoio/hugo/minifiers"
@@ -32,7 +28,6 @@ import (
 
 func TestClassCollector(t *testing.T) {
 	c := qt.New((t))
-	rnd := rand.New(rand.NewSource(time.Now().Unix()))
 
 	f := func(tags, classes, ids string) HTMLElements {
 		var tagss, classess, idss []string
@@ -62,20 +57,14 @@ func TestClassCollector(t *testing.T) {
 		expect HTMLElements
 	}{
 		{"basic", `<body class="b a"></body>`, f("body", "a b", "")},
-		{"duplicates", `<div class="b a b"></div><div class="b a b"></div>x'`, f("div", "a b", "")},
+		{"duplicates", `<div class="b a b"></div>`, f("div", "a b", "")},
 		{"single quote", `<body class='b a'></body>`, f("body", "a b", "")},
 		{"no quote", `<body class=b id=myelement></body>`, f("body", "b", "myelement")},
-		{"short", `<i>`, f("i", "", "")},
-		{"invalid", `< body class="b a"></body><div></div>`, f("div", "", "")},
 		// https://github.com/gohugoio/hugo/issues/7318
 		{"thead", `<table class="cl1">
     <thead class="cl2"><tr class="cl3"><td class="cl4"></td></tr></thead>
     <tbody class="cl5"><tr class="cl6"><td class="cl7"></td></tr></tbody>
 </table>`, f("table tbody td thead tr", "cl1 cl2 cl3 cl4 cl5 cl6 cl7", "")},
-		{"thead uppercase", `<TABLE class="CL1">
-    <THEAD class="CL2"><TR class="CL3"><TD class="CL4"></TD></TR></THEAD>
-    <TBODY class="CL5"><TR class="CL6"><TD class="CL7"></TD></TR></TBODY>
-</TABLE>`, f("table tbody td thead tr", "CL1 CL2 CL3 CL4 CL5 CL6 CL7", "")},
 		// https://github.com/gohugoio/hugo/issues/7161
 		{"minified a href", `<a class="b a" href=/></a>`, f("a", "a b", "")},
 		{"AlpineJS bind 1", `<body>
@@ -109,11 +98,6 @@ func TestClassCollector(t *testing.T) {
 		{"Textarea tags content should be skipped", `<textarea class="textareaclass"><span>foo</span><span>bar</span></textarea><div class="foo"></div>`, f("div textarea", "foo textareaclass", "")},
 		{"DOCTYPE should beskipped", `<!DOCTYPE html>`, f("", "", "")},
 		{"Comments should be skipped", `<!-- example comment -->`, f("", "", "")},
-		{"Comments with elements before and after", `<div></div><!-- example comment --><span><span>`, f("div span", "", "")},
-		// Issue #8530
-		{"Comment with single quote", `<!-- Hero Area Image d'accueil --><i class="foo">`, f("i", "foo", "")},
-		{"Uppercase tags", `<DIV></DIV>`, f("div", "", "")},
-		{"Predefined tags with distinct casing", `<script>if (a < b) { nothing(); }</SCRIPT><div></div>`, f("div script", "", "")},
 		// Issue #8417
 		{"Tabs inline", `<hr	id="a" class="foo"><div class="bar">d</div>`, f("div hr", "bar foo", "a")},
 		{"Tabs on multiple rows", `<form
@@ -124,29 +108,16 @@ func TestClassCollector(t *testing.T) {
 <div id="b" class="foo">d</div>`, f("div form", "foo", "a b")},
 	} {
 
-		for _, variant := range []struct {
-			minify bool
-			stream bool
-		}{
-			{minify: false, stream: false},
-			{minify: true, stream: false},
-			{minify: false, stream: true},
-		} {
-
-			c.Run(fmt.Sprintf("%s--minify-%t--stream-%t", test.name, variant.minify, variant.stream), func(c *qt.C) {
+		for _, minify := range []bool{false, true} {
+			c.Run(fmt.Sprintf("%s--minify-%t", test.name, minify), func(c *qt.C) {
 				w := newHTMLElementsCollectorWriter(newHTMLElementsCollector())
-				if variant.minify {
+				if minify {
 					if skipMinifyTest[test.name] {
 						c.Skip("skip minify test")
 					}
 					v := viper.New()
 					m, _ := minifiers.New(media.DefaultTypes, output.DefaultFormats, v)
 					m.Minify(media.HTMLType, w, strings.NewReader(test.html))
-				} else if variant.stream {
-					chunks := text.Chunk(test.html, rnd.Intn(41)+1)
-					for _, chunk := range chunks {
-						fmt.Fprint(w, chunk)
-					}
 				} else {
 					fmt.Fprint(w, test.html)
 				}
@@ -155,7 +126,6 @@ func TestClassCollector(t *testing.T) {
 			})
 		}
 	}
-
 }
 
 func BenchmarkElementsCollectorWriter(b *testing.B) {