Prevent double escaping of image alt-text in Goldmar typographer

Fixes gohugoio#11045

markup/goldmark/convert_test.go

@@ -584,6 +584,29 @@ rightDoubleQuote = "»"
 	c.Assert(got, qt.Contains, "<p>A &laquo;quote&raquo; and &lsquo;another quote&rsquo; and a &laquo;quote with a &rsquo;nested&rsquo; quote&raquo; and a &lsquo;quote with a &laquo;nested&raquo; quote&rsquo; and an ellipsis&hellip;</p>\n")
 }
 
+// Issue #11045
+func TestTypographerImageAltText(t *testing.T) {
+	c := qt.New(t)
+
+	content := `
+!["They didn't even say 'hello'!" I exclaimed.](https://example.com/image.jpg)
+`
+
+	confStr := `
+[markup]
+[markup.goldmark]
+
+`
+
+	cfg := config.FromTOMLConfigString(confStr)
+	conf := testconfig.GetTestConfig(nil, cfg)
+
+	b := convert(c, conf, content)
+	got := string(b.Bytes())
+
+	c.Assert(got, qt.Contains, "&ldquo;They didn&rsquo;t even say &lsquo;hello&rsquo;!&rdquo; I exclaimed.")
+}
+
 func unsafeConf() config.AllProvider {
 	cfg := config.FromTOMLConfigString(`
 [markup]

markup/goldmark/render_hooks.go

@@ -225,7 +225,7 @@ func (r *hookedRenderer) renderImageDefault(w util.BufWriter, source []byte, nod
 		_, _ = w.Write(util.EscapeHTML(util.URLEscape(n.Destination, true)))
 	}
 	_, _ = w.WriteString(`" alt="`)
-	_, _ = w.Write(util.EscapeHTML(n.Text(source)))
+	_, _ = w.Write(nodeToHTMLText(n, source))
 	_ = w.WriteByte('"')
 	if n.Title != nil {
 		_, _ = w.WriteString(` title="`)
@@ -475,3 +475,18 @@ func (e *links) Extend(m goldmark.Markdown) {
 		util.Prioritized(newLinkRenderer(e.cfg), 100),
 	))
 }
+
+// Borrowed from Goldmark.
+func nodeToHTMLText(n ast.Node, source []byte) []byte {
+	var buf bytes.Buffer
+	for c := n.FirstChild(); c != nil; c = c.NextSibling() {
+		if s, ok := c.(*ast.String); ok && s.IsCode() {
+			buf.Write(s.Text(source))
+		} else if !c.HasChildren() {
+			buf.Write(util.EscapeHTML(c.Text(source)))
+		} else {
+			buf.Write(nodeToHTMLText(c, source))
+		}
+	}
+	return buf.Bytes()
+}