Use Chroma as new default syntax highlighter

Fixes gohugoio#3888

helpers/pygments.go

@@ -24,11 +24,25 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/alecthomas/chroma"
+	"github.com/alecthomas/chroma/formatters"
+	"github.com/alecthomas/chroma/formatters/html"
+	"github.com/alecthomas/chroma/lexers"
+	"github.com/alecthomas/chroma/styles"
+
 	"github.com/gohugoio/hugo/config"
 	"github.com/gohugoio/hugo/hugofs"
 	jww "github.com/spf13/jwalterweatherman"
 )
 
+func init() {
+	// TODO(bep) highlight
+	options := []html.Option{
+		html.TabWidth(4)}
+
+	formatters.Register("html", html.New(options...))
+}
+
 const pygmentsBin = "pygmentize"
 
 // HasPygments checks to see if Pygments is installed and available
@@ -42,6 +56,19 @@ func HasPygments() bool {
 
 // Highlight takes some code and returns highlighted code.
 func Highlight(cfg config.Provider, code, lang, optsStr string) string {
+	if true {
+		// TODO(bep) highlight
+		var buff bytes.Buffer
+		err := chromaHighlight(&buff, code, lang, "html", "trac")
+		if err != nil {
+			jww.ERROR.Print(err.Error())
+			return code
+		}
+
+		return buff.String()
+
+	}
+
 	if !HasPygments() {
 		jww.WARN.Println("Highlighting requires Pygments to be installed and in the path")
 		return code
@@ -131,6 +158,35 @@ func Highlight(cfg config.Provider, code, lang, optsStr string) string {
 	return str
 }
 
+func chromaHighlight(w io.Writer, source, lexer, formatter, style string) error {
+
+	l := lexers.Get(lexer)
+	if l == nil {
+		l = lexers.Analyse(source)
+	}
+	if l == nil {
+		l = lexers.Fallback
+	}
+	l = chroma.Coalesce(l)
+
+	f := formatters.Get(formatter)
+	if f == nil {
+		f = formatters.Fallback
+	}
+
+	s := styles.Get(style)
+	if s == nil {
+		s = styles.Fallback
+	}
+
+	writer, err := f.Format(w, s)
+	if err != nil {
+		return err
+	}
+
+	return l.Tokenise(nil, source, writer)
+}
+
 var pygmentsKeywords = make(map[string]bool)
 
 func init() {

vendor/vendor.json

@@ -20,6 +20,36 @@
 			"revision": "bbf7a2afc14f93e1e0a5c06df524fbd75e5031e5",
 			"revisionTime": "2017-03-24T14:02:28Z"
 		},
+		{
+			"checksumSHA1": "IW5IOamDS/QQOTJS55NPGeTkpok=",
+			"path": "github.com/alecthomas/chroma",
+			"revision": "b57f8a4b4b3e1acca1e97895d7ff9f1a105e5321",
+			"revisionTime": "2017-09-19T04:37:00Z"
+		},
+		{
+			"checksumSHA1": "hIBbm6T96GE6uexfQwDP7Xnop1g=",
+			"path": "github.com/alecthomas/chroma/formatters",
+			"revision": "b57f8a4b4b3e1acca1e97895d7ff9f1a105e5321",
+			"revisionTime": "2017-09-19T04:37:00Z"
+		},
+		{
+			"checksumSHA1": "LqBFWwE77eJUaIOMf9HBzpYj4No=",
+			"path": "github.com/alecthomas/chroma/formatters/html",
+			"revision": "b57f8a4b4b3e1acca1e97895d7ff9f1a105e5321",
+			"revisionTime": "2017-09-19T04:37:00Z"
+		},
+		{
+			"checksumSHA1": "k4iHIk4IrOcJwosB1UfXGKrLXrk=",
+			"path": "github.com/alecthomas/chroma/lexers",
+			"revision": "b57f8a4b4b3e1acca1e97895d7ff9f1a105e5321",
+			"revisionTime": "2017-09-19T04:37:00Z"
+		},
+		{
+			"checksumSHA1": "V+rAjRnac9zAcLTAuYBVQ1/UMMc=",
+			"path": "github.com/alecthomas/chroma/styles",
+			"revision": "b57f8a4b4b3e1acca1e97895d7ff9f1a105e5321",
+			"revisionTime": "2017-09-19T04:37:00Z"
+		},
 		{
 			"checksumSHA1": "7yrV1Gzr1ajco1xJ1gsyqRDTY2U=",
 			"path": "github.com/bep/gitmap",