Use Chroma as new default syntax highlighter

If you want to use Pygments, set `pygmentsUseClassic=true` in your site config. Fixes #3888
2025-08-28 22:19:59 +02:00 · 2017-09-25 08:59:02 +02:00
parent 81ed564793
commit fb33d8286d
18 changed files with 652 additions and 108 deletions
--- a/helpers/content.go
+++ b/helpers/content.go
@@ -48,19 +48,49 @@ type ContentSpec struct {
 	footnoteAnchorPrefix       string
 	footnoteReturnLinkContents string

+	Highlight            func(code, lang, optsStr string) (string, error)
+	defatultPygmentsOpts map[string]string
+
 	cfg config.Provider
 }

 // NewContentSpec returns a ContentSpec initialized
 // with the appropriate fields from the given config.Provider.
-func NewContentSpec(cfg config.Provider) *ContentSpec {
-	return &ContentSpec{
+func NewContentSpec(cfg config.Provider) (*ContentSpec, error) {
+	spec := &ContentSpec{
 		blackfriday:                cfg.GetStringMap("blackfriday"),
 		footnoteAnchorPrefix:       cfg.GetString("footnoteAnchorPrefix"),
 		footnoteReturnLinkContents: cfg.GetString("footnoteReturnLinkContents"),

 		cfg: cfg,
 	}
+
+	// Highlighting setup
+	options, err := parseDefaultPygmentsOpts(cfg)
+	if err != nil {
+		return nil, err
+	}
+	spec.defatultPygmentsOpts = options
+
+	// Use the Pygmentize on path if present
+	useClassic := false
+	h := newHiglighters(spec)
+
+	if cfg.GetBool("pygmentsUseClassic") {
+		if !hasPygments() {
+			jww.WARN.Println("Highlighting with pygmentsUseClassic set requires Pygments to be installed and in the path")
+		} else {
+			useClassic = true
+		}
+	}
+
+	if useClassic {
+		spec.Highlight = h.pygmentsHighlight
+	} else {
+		spec.Highlight = h.chromaHighlight
+	}
+
+	return spec, nil
 }

 // Blackfriday holds configuration values for Blackfriday rendering.
@@ -198,7 +228,7 @@ func BytesToHTML(b []byte) template.HTML {
 }

 // getHTMLRenderer creates a new Blackfriday HTML Renderer with the given configuration.
-func (c ContentSpec) getHTMLRenderer(defaultFlags int, ctx *RenderingContext) blackfriday.Renderer {
+func (c *ContentSpec) getHTMLRenderer(defaultFlags int, ctx *RenderingContext) blackfriday.Renderer {
 	renderParameters := blackfriday.HtmlRendererParameters{
 		FootnoteAnchorPrefix:       c.footnoteAnchorPrefix,
 		FootnoteReturnLinkContents: c.footnoteReturnLinkContents,
@@ -248,6 +278,7 @@ func (c ContentSpec) getHTMLRenderer(defaultFlags int, ctx *RenderingContext) bl
 	}

 	return &HugoHTMLRenderer{
+		cs:               c,
 		RenderingContext: ctx,
 		Renderer:         blackfriday.HtmlRendererWithParameters(htmlFlags, "", "", renderParameters),
 	}
@@ -299,7 +330,7 @@ func (c ContentSpec) markdownRender(ctx *RenderingContext) []byte {
 }

 // getMmarkHTMLRenderer creates a new mmark HTML Renderer with the given configuration.
-func (c ContentSpec) getMmarkHTMLRenderer(defaultFlags int, ctx *RenderingContext) mmark.Renderer {
+func (c *ContentSpec) getMmarkHTMLRenderer(defaultFlags int, ctx *RenderingContext) mmark.Renderer {
 	renderParameters := mmark.HtmlRendererParameters{
 		FootnoteAnchorPrefix:       c.footnoteAnchorPrefix,
 		FootnoteReturnLinkContents: c.footnoteReturnLinkContents,
@@ -320,8 +351,9 @@ func (c ContentSpec) getMmarkHTMLRenderer(defaultFlags int, ctx *RenderingContex
 	htmlFlags |= mmark.HTML_FOOTNOTE_RETURN_LINKS

 	return &HugoMmarkHTMLRenderer{
-		mmark.HtmlRendererWithParameters(htmlFlags, "", "", renderParameters),
-		c.cfg,
+		cs:       c,
+		Renderer: mmark.HtmlRendererWithParameters(htmlFlags, "", "", renderParameters),
+		Cfg:      c.cfg,
 	}
 }

--- a/helpers/content_renderer.go
+++ b/helpers/content_renderer.go
@@ -16,6 +16,7 @@ package helpers
 import (
 	"bytes"
 	"html"
+	"strings"

 	"github.com/gohugoio/hugo/config"
 	"github.com/miekg/mmark"
@@ -25,6 +26,7 @@ import (
 // HugoHTMLRenderer wraps a blackfriday.Renderer, typically a blackfriday.Html
 // Enabling Hugo to customise the rendering experience
 type HugoHTMLRenderer struct {
+	cs *ContentSpec
 	*RenderingContext
 	blackfriday.Renderer
 }
@@ -34,8 +36,9 @@ type HugoHTMLRenderer struct {
 func (r *HugoHTMLRenderer) BlockCode(out *bytes.Buffer, text []byte, lang string) {
 	if r.Cfg.GetBool("pygmentsCodeFences") && (lang != "" || r.Cfg.GetBool("pygmentsCodeFencesGuessSyntax")) {
 		opts := r.Cfg.GetString("pygmentsOptions")
-		str := html.UnescapeString(string(text))
-		out.WriteString(Highlight(r.RenderingContext.Cfg, str, lang, opts))
+		str := strings.Trim(html.UnescapeString(string(text)), "\n\r")
+		highlighted, _ := r.cs.Highlight(str, lang, opts)
+		out.WriteString(highlighted)
 	} else {
 		r.Renderer.BlockCode(out, text, lang)
 	}
@@ -88,6 +91,7 @@ func (r *HugoHTMLRenderer) List(out *bytes.Buffer, text func() bool, flags int)
 // HugoMmarkHTMLRenderer wraps a mmark.Renderer, typically a mmark.html,
 // enabling Hugo to customise the rendering experience.
 type HugoMmarkHTMLRenderer struct {
+	cs *ContentSpec
 	mmark.Renderer
 	Cfg config.Provider
 }
@@ -96,8 +100,9 @@ type HugoMmarkHTMLRenderer struct {
 // Pygments is used if it is setup to handle code fences.
 func (r *HugoMmarkHTMLRenderer) BlockCode(out *bytes.Buffer, text []byte, lang string, caption []byte, subfigure bool, callouts bool) {
 	if r.Cfg.GetBool("pygmentsCodeFences") && (lang != "" || r.Cfg.GetBool("pygmentsCodeFencesGuessSyntax")) {
-		str := html.UnescapeString(string(text))
-		out.WriteString(Highlight(r.Cfg, str, lang, ""))
+		str := strings.Trim(html.UnescapeString(string(text)), "\n\r")
+		highlighted, _ := r.cs.Highlight(str, lang, "")
+		out.WriteString(highlighted)
 	} else {
 		r.Renderer.BlockCode(out, text, lang, caption, subfigure, callouts)
 	}
--- a/helpers/content_renderer_test.go
+++ b/helpers/content_renderer_test.go
@@ -19,6 +19,7 @@ import (
 	"testing"

 	"github.com/spf13/viper"
+	"github.com/stretchr/testify/require"
 )

 // Renders a codeblock using Blackfriday
@@ -42,11 +43,7 @@ func (c ContentSpec) renderWithMmark(input string) string {
 }

 func TestCodeFence(t *testing.T) {
-
-	if !HasPygments() {
-		t.Skip("Skipping Pygments test as Pygments is not installed or available.")
-		return
-	}
+	assert := require.New(t)

 	type test struct {
 		enabled         bool
@@ -55,36 +52,39 @@ func TestCodeFence(t *testing.T) {

 	// Pygments 2.0 and 2.1 have slightly different outputs so only do partial matching
 	data := []test{
-		{true, "<html></html>", `(?s)^<div class="highlight"><pre><code class="language-html" data-lang="html">.*?</code></pre></div>\n$`},
-		{false, "<html></html>", `(?s)^<pre><code class="language-html">.*?</code></pre>\n$`},
+		{true, "<html></html>", `(?s)^<div class="highlight">\n?<pre.*><code class="language-html" data-lang="html">.*?</code></pre>\n?</div>\n?$`},
+		{false, "<html></html>", `(?s)^<pre.*><code class="language-html">.*?</code></pre>\n$`},
 	}

-	for i, d := range data {
-		v := viper.New()
+	for _, useClassic := range []bool{false, true} {
+		for i, d := range data {
+			v := viper.New()
+			v.Set("pygmentsStyle", "monokai")
+			v.Set("pygmentsUseClasses", true)
+			v.Set("pygmentsCodeFences", d.enabled)
+			v.Set("pygmentsUseClassic", useClassic)

-		v.Set("pygmentsStyle", "monokai")
-		v.Set("pygmentsUseClasses", true)
-		v.Set("pygmentsCodeFences", d.enabled)
+			c, err := NewContentSpec(v)
+			assert.NoError(err)

-		c := NewContentSpec(v)
+			result := c.render(d.input)

-		result := c.render(d.input)
+			expectedRe, err := regexp.Compile(d.expected)

-		expectedRe, err := regexp.Compile(d.expected)
+			if err != nil {
+				t.Fatal("Invalid regexp", err)
+			}
+			matched := expectedRe.MatchString(result)

-		if err != nil {
-			t.Fatal("Invalid regexp", err)
-		}
-		matched := expectedRe.MatchString(result)
+			if !matched {
+				t.Errorf("Test %d failed. BlackFriday enabled:%t, Expected:\n%q got:\n%q", i, d.enabled, d.expected, result)
+			}

-		if !matched {
-			t.Errorf("Test %d failed. BlackFriday enabled:%t, Expected:\n%q got:\n%q", i, d.enabled, d.expected, result)
-		}
-
-		result = c.renderWithMmark(d.input)
-		matched = expectedRe.MatchString(result)
-		if !matched {
-			t.Errorf("Test %d failed. Mmark enabled:%t, Expected:\n%q got:\n%q", i, d.enabled, d.expected, result)
+			result = c.renderWithMmark(d.input)
+			matched = expectedRe.MatchString(result)
+			if !matched {
+				t.Errorf("Test %d failed. Mmark enabled:%t, Expected:\n%q got:\n%q", i, d.enabled, d.expected, result)
+			}
 		}
 	}
 }
--- a/helpers/pygments.go
+++ b/helpers/pygments.go
@@ -21,9 +21,18 @@ import (
 	"io/ioutil"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"sort"
+	"strconv"
 	"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"
+	bp "github.com/gohugoio/hugo/bufferpool"
+
 	"github.com/gohugoio/hugo/config"
 	"github.com/gohugoio/hugo/hugofs"
 	jww "github.com/spf13/jwalterweatherman"
@@ -31,27 +40,62 @@ import (

 const pygmentsBin = "pygmentize"

-// HasPygments checks to see if Pygments is installed and available
+// TODO(bep) document chroma -s perldoc --html --html-styles
+// hasPygments checks to see if Pygments is installed and available
 // on the system.
-func HasPygments() bool {
+func hasPygments() bool {
 	if _, err := exec.LookPath(pygmentsBin); err != nil {
 		return false
 	}
 	return true
 }

-// Highlight takes some code and returns highlighted code.
-func Highlight(cfg config.Provider, code, lang, optsStr string) string {
-	if !HasPygments() {
-		jww.WARN.Println("Highlighting requires Pygments to be installed and in the path")
-		return code
+type highlighters struct {
+	cs          *ContentSpec
+	ignoreCache bool
+	cacheDir    string
+}
+
+func newHiglighters(cs *ContentSpec) highlighters {
+	return highlighters{cs: cs, ignoreCache: cs.cfg.GetBool("ignoreCache"), cacheDir: cs.cfg.GetString("cacheDir")}
+}
+
+func (h highlighters) chromaHighlight(code, lang, optsStr string) (string, error) {
+	opts, err := h.cs.parsePygmentsOpts(optsStr)
+	if err != nil {
+		jww.ERROR.Print(err.Error())
+		return code, err
 	}

-	options, err := parsePygmentsOpts(cfg, optsStr)
+	style, found := opts["style"]
+	if !found || style == "" {
+		style = "friendly"
+	}
+
+	f, err := h.cs.chromaFormatterFromOptions(opts)
+	if err != nil {
+		jww.ERROR.Print(err.Error())
+		return code, err
+	}
+
+	b := bp.GetBuffer()
+	defer bp.PutBuffer(b)
+
+	err = chromaHighlight(b, code, lang, style, f)
+	if err != nil {
+		jww.ERROR.Print(err.Error())
+		return code, err
+	}
+
+	return h.injectCodeTag(`<div class="highlight">`+b.String()+"</div>", lang), nil
+}
+
+func (h highlighters) pygmentsHighlight(code, lang, optsStr string) (string, error) {
+	options, err := h.cs.createPygmentsOptionsString(optsStr)

 	if err != nil {
 		jww.ERROR.Print(err.Error())
-		return code
+		return code, nil
 	}

 	// Try to read from cache first
@@ -62,32 +106,30 @@ func Highlight(cfg config.Provider, code, lang, optsStr string) string {

 	fs := hugofs.Os

-	ignoreCache := cfg.GetBool("ignoreCache")
-	cacheDir := cfg.GetString("cacheDir")
 	var cachefile string

-	if !ignoreCache && cacheDir != "" {
-		cachefile = filepath.Join(cacheDir, fmt.Sprintf("pygments-%x", hash.Sum(nil)))
+	if !h.ignoreCache && h.cacheDir != "" {
+		cachefile = filepath.Join(h.cacheDir, fmt.Sprintf("pygments-%x", hash.Sum(nil)))

 		exists, err := Exists(cachefile, fs)
 		if err != nil {
 			jww.ERROR.Print(err.Error())
-			return code
+			return code, nil
 		}
 		if exists {
 			f, err := fs.Open(cachefile)
 			if err != nil {
 				jww.ERROR.Print(err.Error())
-				return code
+				return code, nil
 			}

 			s, err := ioutil.ReadAll(f)
 			if err != nil {
 				jww.ERROR.Print(err.Error())
-				return code
+				return code, nil
 			}

-			return string(s)
+			return string(s), nil
 		}
 	}

@@ -109,26 +151,58 @@ func Highlight(cfg config.Provider, code, lang, optsStr string) string {

 	if err := cmd.Run(); err != nil {
 		jww.ERROR.Print(stderr.String())
-		return code
+		return code, err
 	}

 	str := string(normalizeExternalHelperLineFeeds([]byte(out.String())))

-	// inject code tag into Pygments output
-	if lang != "" && strings.Contains(str, "<pre>") {
-		codeTag := fmt.Sprintf(`<pre><code class="language-%s" data-lang="%s">`, lang, lang)
-		str = strings.Replace(str, "<pre>", codeTag, 1)
-		str = strings.Replace(str, "</pre>", "</code></pre>", 1)
-	}
+	str = h.injectCodeTag(str, lang)

-	if !ignoreCache && cachefile != "" {
+	if !h.ignoreCache && cachefile != "" {
 		// Write cache file
 		if err := WriteToDisk(cachefile, strings.NewReader(str), fs); err != nil {
 			jww.ERROR.Print(stderr.String())
 		}
 	}

-	return str
+	return str, nil
+}
+
+var preRe = regexp.MustCompile(`(?s)(.*?<pre.*?>)(.*?)(</pre>)`)
+
+func (h highlighters) injectCodeTag(code, lang string) string {
+	if lang == "" {
+		return code
+	}
+	codeTag := fmt.Sprintf(`<code class="language-%s" data-lang="%s">`, lang, lang)
+	return preRe.ReplaceAllString(code, fmt.Sprintf("$1%s$2</code>$3", codeTag))
+}
+
+func chromaHighlight(w io.Writer, source, lexer, style string, f chroma.Formatter) error {
+	l := lexers.Get(lexer)
+	if l == nil {
+		l = lexers.Analyse(source)
+	}
+	if l == nil {
+		l = lexers.Fallback
+	}
+	l = chroma.Coalesce(l)
+
+	if f == nil {
+		f = formatters.Fallback
+	}
+
+	s := styles.Get(style)
+	if s == nil {
+		s = styles.Fallback
+	}
+
+	it, err := l.Tokenise(nil, source)
+	if err != nil {
+		return err
+	}
+
+	return f.Format(w, s, it)
 }

 var pygmentsKeywords = make(map[string]bool)
@@ -158,23 +232,30 @@ func init() {
 	pygmentsKeywords["startinline"] = true
 }

-func parseOptions(options map[string]string, in string) error {
+func parseOptions(defaults map[string]string, in string) (map[string]string, error) {
 	in = strings.Trim(in, " ")
+	opts := make(map[string]string)
+
+	if defaults != nil {
+		for k, v := range defaults {
+			opts[k] = v
+		}
+	}

 	if in == "" {
-		return nil
+		return opts, nil
 	}

 	for _, v := range strings.Split(in, ",") {
 		keyVal := strings.Split(v, "=")
 		key := strings.ToLower(strings.Trim(keyVal[0], " "))
 		if len(keyVal) != 2 || !pygmentsKeywords[key] {
-			return fmt.Errorf("invalid Pygments option: %s", key)
+			return opts, fmt.Errorf("invalid Pygments option: %s", key)
 		}
-		options[key] = keyVal[1]
+		opts[key] = keyVal[1]
 	}

-	return nil
+	return opts, nil
 }

 func createOptionsString(options map[string]string) string {
@@ -196,8 +277,7 @@ func createOptionsString(options map[string]string) string {
 }

 func parseDefaultPygmentsOpts(cfg config.Provider) (map[string]string, error) {
-	options := make(map[string]string)
-	err := parseOptions(options, cfg.GetString("pygmentsOptions"))
+	options, err := parseOptions(nil, cfg.GetString("pygmentsOptions"))
 	if err != nil {
 		return nil, err
 	}
@@ -222,16 +302,100 @@ func parseDefaultPygmentsOpts(cfg config.Provider) (map[string]string, error) {
 	return options, nil
 }

-func parsePygmentsOpts(cfg config.Provider, in string) (string, error) {
-	options, err := parseDefaultPygmentsOpts(cfg)
-	if err != nil {
-		return "", err
+func (cs *ContentSpec) chromaFormatterFromOptions(pygmentsOpts map[string]string) (chroma.Formatter, error) {
+	var options = []html.Option{html.TabWidth(4)}
+
+	if pygmentsOpts["noclasses"] == "false" {
+		options = append(options, html.WithClasses())
 	}

-	err = parseOptions(options, in)
-	if err != nil {
-		return "", err
+	if pygmentsOpts["linenos"] != "" {
+		options = append(options, html.WithLineNumbers())
 	}

-	return createOptionsString(options), nil
+	startLineStr := pygmentsOpts["linenostart"]
+	var startLine = 1
+	if startLineStr != "" {
+
+		line, err := strconv.Atoi(strings.TrimSpace(startLineStr))
+		if err == nil {
+			startLine = line
+			options = append(options, html.BaseLineNumber(startLine))
+		}
+	}
+
+	hlLines := pygmentsOpts["hl_lines"]
+
+	if hlLines != "" {
+		ranges, err := hlLinesToRanges(startLine, hlLines)
+
+		if err == nil {
+			options = append(options, html.HighlightLines(ranges))
+		}
+	}
+
+	return html.New(options...), nil
+}
+
+func (cs *ContentSpec) parsePygmentsOpts(in string) (map[string]string, error) {
+	opts, err := parseOptions(cs.defatultPygmentsOpts, in)
+	if err != nil {
+		return nil, err
+	}
+	return opts, nil
+
+}
+
+func (cs *ContentSpec) createPygmentsOptionsString(in string) (string, error) {
+	opts, err := cs.parsePygmentsOpts(in)
+	if err != nil {
+		return "", err
+	}
+	return createOptionsString(opts), nil
+}
+
+// startLine compansates for https://github.com/alecthomas/chroma/issues/30
+func hlLinesToRanges(startLine int, s string) ([][2]int, error) {
+	var ranges [][2]int
+	s = strings.TrimSpace(s)
+
+	if s == "" {
+		return ranges, nil
+	}
+
+	// Variants:
+	// 1 2 3 4
+	// 1-2 3-4
+	// 1-2 3
+	// 1 3-4
+	// 1    3-4
+	fields := strings.Split(s, " ")
+	for _, field := range fields {
+		field = strings.TrimSpace(field)
+		if field == "" {
+			continue
+		}
+		numbers := strings.Split(field, "-")
+		var r [2]int
+		first, err := strconv.Atoi(numbers[0])
+		if err != nil {
+			return ranges, err
+		}
+		first = first + startLine - 1
+		r[0] = first
+		if len(numbers) > 1 {
+			second, err := strconv.Atoi(numbers[1])
+			if err != nil {
+				return ranges, err
+			}
+			second = second + startLine - 1
+			r[1] = second
+		} else {
+			r[1] = first
+		}
+
+		ranges = append(ranges, r)
+	}
+	return ranges, nil
+
 }
--- a/helpers/pygments_test.go
+++ b/helpers/pygments_test.go
@@ -14,12 +14,19 @@
 package helpers

 import (
+	"fmt"
+	"reflect"
 	"testing"

+	"github.com/alecthomas/chroma/formatters/html"
+
 	"github.com/spf13/viper"
+	"github.com/stretchr/testify/require"
 )

 func TestParsePygmentsArgs(t *testing.T) {
+	assert := require.New(t)
+
 	for i, this := range []struct {
 		in                 string
 		pygmentsStyle      string
@@ -38,8 +45,10 @@ func TestParsePygmentsArgs(t *testing.T) {
 		v := viper.New()
 		v.Set("pygmentsStyle", this.pygmentsStyle)
 		v.Set("pygmentsUseClasses", this.pygmentsUseClasses)
+		spec, err := NewContentSpec(v)
+		assert.NoError(err)

-		result1, err := parsePygmentsOpts(v, this.in)
+		result1, err := spec.createPygmentsOptionsString(this.in)
 		if b, ok := this.expect1.(bool); ok && !b {
 			if err == nil {
 				t.Errorf("[%d] parsePygmentArgs didn't return an expected error", i)
@@ -58,6 +67,8 @@ func TestParsePygmentsArgs(t *testing.T) {
 }

 func TestParseDefaultPygmentsArgs(t *testing.T) {
+	assert := require.New(t)
+
 	expect := "encoding=utf8,noclasses=false,style=foo"

 	for i, this := range []struct {
@@ -83,7 +94,10 @@ func TestParseDefaultPygmentsArgs(t *testing.T) {
 			v.Set("pygmentsUseClasses", b)
 		}

-		result, err := parsePygmentsOpts(v, this.in)
+		spec, err := NewContentSpec(v)
+		assert.NoError(err)
+
+		result, err := spec.createPygmentsOptionsString(this.in)
 		if err != nil {
 			t.Errorf("[%d] parsePygmentArgs failed: %s", i, err)
 			continue
@@ -93,3 +107,186 @@ func TestParseDefaultPygmentsArgs(t *testing.T) {
 		}
 	}
 }
+
+type chromaInfo struct {
+	classes            bool
+	lineNumbers        bool
+	highlightRangesLen int
+	highlightRangesStr string
+	baseLineNumber     int
+}
+
+func formatterChromaInfo(f *html.Formatter) chromaInfo {
+	v := reflect.ValueOf(f).Elem()
+	c := chromaInfo{}
+	// Hack:
+	c.classes = v.FieldByName("classes").Bool()
+	c.lineNumbers = v.FieldByName("lineNumbers").Bool()
+	c.baseLineNumber = int(v.FieldByName("baseLineNumber").Int())
+	vv := v.FieldByName("highlightRanges")
+	c.highlightRangesLen = vv.Len()
+	c.highlightRangesStr = fmt.Sprint(vv)
+
+	return c
+}
+
+func TestChromaHTMLHighlight(t *testing.T) {
+	assert := require.New(t)
+
+	v := viper.New()
+	v.Set("pygmentsUseClasses", true)
+	spec, err := NewContentSpec(v)
+	assert.NoError(err)
+
+	result, err := spec.Highlight(`echo "Hello"`, "bash", "")
+	assert.NoError(err)
+
+	assert.Contains(result, `<code class="language-bash" data-lang="bash"><span class="s7d2">echo</span> <span class="sc1c">&#34;Hello&#34;</span></code>`)
+
+}
+
+func TestChromaHTMLFormatterFromOptions(t *testing.T) {
+	assert := require.New(t)
+
+	for i, this := range []struct {
+		in                 string
+		pygmentsStyle      interface{}
+		pygmentsUseClasses interface{}
+		pygmentsOptions    string
+		assert             func(c chromaInfo)
+	}{
+		{"", "monokai", true, "style=manni,noclasses=true", func(c chromaInfo) {
+			assert.True(c.classes)
+			assert.False(c.lineNumbers)
+			assert.Equal(0, c.highlightRangesLen)
+
+		}},
+		{"", nil, nil, "style=monokai,noclasses=false", func(c chromaInfo) {
+			assert.True(c.classes)
+		}},
+		{"linenos=sure,hl_lines=1 2 3", nil, nil, "style=monokai,noclasses=false", func(c chromaInfo) {
+			assert.True(c.classes)
+			assert.True(c.lineNumbers)
+			assert.Equal(3, c.highlightRangesLen)
+			assert.Equal("[[1 1] [2 2] [3 3]]", c.highlightRangesStr)
+			assert.Equal(1, c.baseLineNumber)
+		}},
+		{"linenos=sure,hl_lines=1,linenostart=4", nil, nil, "style=monokai,noclasses=false", func(c chromaInfo) {
+			assert.True(c.classes)
+			assert.True(c.lineNumbers)
+			assert.Equal(1, c.highlightRangesLen)
+			// This compansates for https://github.com/alecthomas/chroma/issues/30
+			assert.Equal("[[4 4]]", c.highlightRangesStr)
+			assert.Equal(4, c.baseLineNumber)
+		}},
+		{"style=monokai,noclasses=false", nil, nil, "style=manni,noclasses=true", func(c chromaInfo) {
+			assert.True(c.classes)
+		}},
+		{"style=monokai,noclasses=true", "friendly", false, "style=manni,noclasses=false", func(c chromaInfo) {
+			assert.False(c.classes)
+		}},
+	} {
+		v := viper.New()
+
+		v.Set("pygmentsOptions", this.pygmentsOptions)
+
+		if s, ok := this.pygmentsStyle.(string); ok {
+			v.Set("pygmentsStyle", s)
+		}
+
+		if b, ok := this.pygmentsUseClasses.(bool); ok {
+			v.Set("pygmentsUseClasses", b)
+		}
+
+		spec, err := NewContentSpec(v)
+		assert.NoError(err)
+
+		opts, err := spec.parsePygmentsOpts(this.in)
+		if err != nil {
+			t.Fatalf("[%d] parsePygmentsOpts failed: %s", i, err)
+		}
+
+		chromaFormatter, err := spec.chromaFormatterFromOptions(opts)
+		if err != nil {
+			t.Fatalf("[%d] chromaFormatterFromOptions failed: %s", i, err)
+		}
+
+		this.assert(formatterChromaInfo(chromaFormatter.(*html.Formatter)))
+	}
+}
+
+func TestHlLinesToRanges(t *testing.T) {
+	var zero [][2]int
+
+	for _, this := range []struct {
+		in        string
+		startLine int
+		expected  interface{}
+	}{
+		{"", 1, zero},
+		{"1 4", 1, [][2]int{[2]int{1, 1}, [2]int{4, 4}}},
+		{"1 4", 2, [][2]int{[2]int{2, 2}, [2]int{5, 5}}},
+		{"1-4 5-8", 1, [][2]int{[2]int{1, 4}, [2]int{5, 8}}},
+		{" 1   4 ", 1, [][2]int{[2]int{1, 1}, [2]int{4, 4}}},
+		{"1-4    5-8 ", 1, [][2]int{[2]int{1, 4}, [2]int{5, 8}}},
+		{"1-4 5", 1, [][2]int{[2]int{1, 4}, [2]int{5, 5}}},
+		{"4 5-9", 1, [][2]int{[2]int{4, 4}, [2]int{5, 9}}},
+		{" 1 -4 5 - 8  ", 1, true},
+		{"a b", 1, true},
+	} {
+		got, err := hlLinesToRanges(this.startLine, this.in)
+
+		if expectErr, ok := this.expected.(bool); ok && expectErr {
+			if err == nil {
+				t.Fatal("No error")
+			}
+		} else if err != nil {
+			t.Fatalf("Got error: %s", err)
+		} else if !reflect.DeepEqual(this.expected, got) {
+			t.Fatalf("Expected\n%v but got\n%v", this.expected, got)
+		}
+	}
+}
+
+func BenchmarkChromaHighlight(b *testing.B) {
+	assert := require.New(b)
+	v := viper.New()
+
+	v.Set("pygmentsstyle", "trac")
+	v.Set("pygmentsuseclasses", false)
+	v.Set("pygmentsuseclassic", false)
+
+	code := `// GetTitleFunc returns a func that can be used to transform a string to
+// title case.
+//
+// The supported styles are
+//
+// - "Go" (strings.Title)
+// - "AP" (see https://www.apstylebook.com/)
+// - "Chicago" (see http://www.chicagomanualofstyle.org/home.html)
+//
+// If an unknown or empty style is provided, AP style is what you get.
+func GetTitleFunc(style string) func(s string) string {
+  switch strings.ToLower(style) {
+  case "go":
+    return strings.Title
+  case "chicago":
+    tc := transform.NewTitleConverter(transform.ChicagoStyle)
+    return tc.Title
+  default:
+    tc := transform.NewTitleConverter(transform.APStyle)
+    return tc.Title
+  }
+}
+`
+
+	spec, err := NewContentSpec(v)
+	assert.NoError(err)
+
+	for i := 0; i < b.N; i++ {
+		_, err := spec.Highlight(code, "go", "linenos=inline,hl_lines=8 15-17")
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
--- a/helpers/testhelpers_test.go
+++ b/helpers/testhelpers_test.go
@@ -34,5 +34,9 @@ func newTestCfg(fs *hugofs.Fs) *viper.Viper {

 func newTestContentSpec() *ContentSpec {
 	v := viper.New()
-	return NewContentSpec(v)
+	spec, err := NewContentSpec(v)
+	if err != nil {
+		panic(err)
+	}
+	return spec
 }