html/js: Angle bracket inside script tag breaks minification

[bep]

Reopening of #396

package main

import (
	"os"
	"regexp"
	"strings"

	"github.com/tdewolff/minify/v2"
	"github.com/tdewolff/minify/v2/html"
	"github.com/tdewolff/minify/v2/js"
)

func main() {
	input := `<script><</script><div class="foo"></div>`
	m := minify.New()
	m.AddFunc("text/html", html.Minify)
	m.AddFuncRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"), js.Minify)

	if err := m.Minify("text/html", os.Stdout, strings.NewReader(input)); err != nil {
		panic(err)
	}
}

Fails with:

<script>panic: unexpected < in expression on line 1 and column 9
    1: <
       ^

[tdewolff]

What result were you expecting instead? You're trying to parse < as JavaScript, which clearly is invalid. See e.g. this demo in ESLint. In which case did this problem arise?

I assume this is from gohugoio/hugo#7567. However, parsing a script tag in HTML, there are only two special cases: finding </script> or <!-- inside JavaScript. The first case is actually not handled in minify yet (working on it now), the second case is. See relevant specification here: https://html.spec.whatwg.org/multipage/parsing.html#script-data-less-than-sign-state. This is not the problem of gohugoio/hugo#7567 hpwever, not sure what is the problem there...