feature/bug(renderer): Support chroma, fix source paragraph (#720)

This fixes three separate issues (it was natural to fix them all
at the same time).

Fixes #719 Should not panic on unrecognized source language
Fixes #706 Support "Chroma" as a syntax highlighter choice
Fixes #704 Source paragraph does not honor syntax highlighter

LIMITATIONS.adoc

@@ -128,9 +128,13 @@ See https://github.com/bytesparadise/libasciidoc/issues/679[Issue #679].
 The `favicon` document attribute is not recognized.
 See https://github.com/bytesparadise/libasciidoc/issues/681[Issue #681].
 
-== Syntax Highlighters
+== Syntax Highlighting
 
-Only the `pygments` highlighter is recognized.
+Libasciidoc highlights source code using https://github.com/alecthomas/chroma[Chroma].
+To use it, specify `chroma` for the `source-highlighter` attribute.  The value of `pygments`
+is treated as an alias.  Chroma supports all the standard pygments styles, as well as the vast
+majority of the same source code languages. However some more esoteric languages might not be supported.
+See https://github.com/alecthomas/chroma#supported-languages[Chroma's documentation] for details.
 
 == Math
 

README.adoc

@@ -19,7 +19,7 @@ Although it does not support the full Asciidoc/Asciidoctor syntax, Libasciidoc a
 * Attribute declaration and substitution
 * Paragraphs and admonition paragraphs
 * Delimited Blocks (fenced blocks, listing blocks, example blocks, comment blocks, quoted blocks, sidebar blocks, verse blocks)
-* Source code highlighting of delimited blocks
+* Source code highlighting of delimited blocks (use either `chroma` or `pygments` as the `source-highlighter`)
 * Literal blocks (paragraph starting with a space, with the `+++....+++` delimiter or with the `[literal]` attribute)
 * Quoted text (bold, italic, monospace, marked, superscript and subscript) and substitution prevention using the backslash (`\`) character
 * Single and double quoted typographic quotes (e.g. '`single`' and "`double`")

pkg/renderer/sgml/delimited_block.go

@@ -127,13 +127,17 @@ func (r *sgmlRenderer) renderSourceBlock(ctx *renderer.Context, b types.Delimite
 
 	highlighter, _ := ctx.Attributes.GetAsString(types.AttrSyntaxHighlighter)
 	language, found := b.Attributes.GetAsString(types.AttrLanguage)
-	if found && highlighter == "pygments" {
+	if found && (highlighter == "chroma" || highlighter == "pygments") {
 		// using github.com/alecthomas/chroma to highlight the content
 		contentBuf := &strings.Builder{}
 		lexer := lexers.Get(language)
+		if lexer == nil {
+			lexer = lexers.Fallback
+		}
 		lexer = chroma.Coalesce(lexer)
 		style := styles.Fallback
-		if s, found := ctx.Attributes.GetAsString("pygments-style"); found {
+
+		if s, found := ctx.Attributes.GetAsString(highlighter + "-style"); found {
 			style = styles.Get(s)
 		}
 		iterator, err := lexer.Tokenise(nil, content)
@@ -145,7 +149,7 @@ func (r *sgmlRenderer) renderSourceBlock(ctx *renderer.Context, b types.Delimite
 			html.PreventSurroundingPre(true),
 		}
 		// extra option: inline CSS instead of classes
-		if ctx.Attributes.GetAsStringWithDefault("pygments-css", "classes") == "style" {
+		if ctx.Attributes.GetAsStringWithDefault(highlighter+"-css", "classes") == "style" {
 			options = append(options, html.WithClasses(false))
 		} else {
 			options = append(options, html.WithClasses(true))

pkg/renderer/sgml/html5/delimited_block_test.go

@@ -302,6 +302,22 @@ end</code></pre>
 			Expect(RenderHTML(source)).To(MatchHTML(expected))
 		})
 
+		It("with title, source and unknown languages attributes", func() {
+			source := `[source,brainfart]
+.Source block title
+----
+int main(int argc, char **argv);
+----`
+			expected := `<div class="listingblock">
+<div class="title">Source block title</div>
+<div class="content">
+<pre class="highlight"><code class="language-brainfart" data-lang="brainfart">int main(int argc, char **argv);</code></pre>
+</div>
+</div>
+`
+			Expect(RenderHTML(source)).To(MatchHTML(expected))
+		})
+
 		It("with id, title, source and languages attributes", func() {
 			source := `[#id-for-source-block]
 [source,ruby]

pkg/renderer/sgml/html5/paragraph.go

@@ -20,15 +20,6 @@ const (
 
 	delimitedBlockParagraphTmpl = "<p>{{ .CheckStyle }}{{ .Content }}</p>\n"
 
-	sourceParagraphTmpl = "<div class=\"listingblock\">\n" +
-		"<div class=\"content\">\n" +
-		"<pre class=\"highlight\">" +
-		`<code{{ if .Language }} class="language-{{ .Language }}" data-lang="{{ .Language }}"{{ end }}>` +
-		"{{ .Content }}" +
-		"</code></pre>\n" +
-		"</div>\n" +
-		"</div>\n"
-
 	verseParagraphTmpl = "<div {{ if .ID }}id=\"{{ .ID }}\" {{ end }}class=\"verseblock\">\n" +
 		"{{ if .Title }}<div class=\"title\">{{ .Title }}</div>\n{{ end }}" +
 		"<pre class=\"content\">{{ .Content }}</pre>\n" +

pkg/renderer/sgml/html5/paragraph_test.go

@@ -477,4 +477,21 @@ image::foo.png[]`
 		})
 	})
 
+	Context("source paragraphs", func() {
+
+		It("with source and languages attributes", func() {
+			source := `:source-highlighter: chroma
+
+[source,c]
+int main(int argc, char **argv);
+`
+			expected := `<div class="listingblock">
+<div class="content">
+<pre class="chroma highlight"><code data-lang="c"><span class="tok-kt">int</span> <span class="tok-nf">main</span><span class="tok-p">(</span><span class="tok-kt">int</span> <span class="tok-n">argc</span><span class="tok-p">,</span> <span class="tok-kt">char</span> <span class="tok-o">**</span><span class="tok-n">argv</span><span class="tok-p">);</span></code></pre>
+</div>
+</div>
+`
+			Expect(RenderHTML(source)).To(MatchHTML(expected))
+		})
+	})
 })

pkg/renderer/sgml/html5/templates.go

@@ -63,7 +63,6 @@ var templates = sgml.Templates{
 	SectionHeader:             sectionHeaderTmpl,
 	SidebarBlock:              sidebarBlockTmpl,
 	SourceBlock:               sourceBlockTmpl,
-	SourceParagraph:           sourceParagraphTmpl,
 	StringElement:             stringTmpl,
 	SubscriptText:             subscriptTextTmpl,
 	SuperscriptText:           superscriptTextTmpl,

pkg/renderer/sgml/paragraph.go

@@ -93,30 +93,11 @@ func (r *sgmlRenderer) renderAdmonitionParagraph(ctx *renderer.Context, p types.
 }
 
 func (r *sgmlRenderer) renderSourceParagraph(ctx *renderer.Context, p types.Paragraph) (string, error) {
-	log.Debug("rendering source paragraph...")
-	result := &strings.Builder{}
-
-	content, err := r.renderLines(ctx, p.Lines)
-	if err != nil {
-		return "", errors.Wrap(err, "unable to render source paragraph lines")
-	}
-	err = r.sourceParagraph.Execute(result, struct {
-		Context  *renderer.Context
-		ID       sanitized
-		Title    sanitized
-		Language string
-		Content  sanitized
-		Lines    []interface{}
-	}{
-
-		Context:  ctx,
-		ID:       r.renderElementID(p.Attributes),
-		Title:    r.renderElementTitle(p.Attributes),
-		Language: p.Attributes.GetAsStringWithDefault(types.AttrLanguage, ""),
-		Content:  sanitized(content),
-		Lines:    p.Lines,
+	return r.renderSourceBlock(ctx, types.DelimitedBlock{
+		Kind:       types.Source,
+		Attributes: p.Attributes,
+		Elements:   p.Lines,
 	})
-	return result.String(), err
 }
 
 func (r *sgmlRenderer) renderVerseParagraph(ctx *renderer.Context, p types.Paragraph) (string, error) {

pkg/renderer/sgml/sgml_renderer.go

@@ -63,7 +63,6 @@ type sgmlRenderer struct {
 	sectionHeader             *textTemplate
 	sidebarBlock              *textTemplate
 	sourceBlock               *textTemplate
-	sourceParagraph           *textTemplate
 	stringElement             *textTemplate
 	subscriptText             *textTemplate
 	superscriptText           *textTemplate
@@ -144,7 +143,6 @@ func (r *sgmlRenderer) prepareTemplates() error {
 		r.stringElement, err = r.newTemplate("string-element", tmpls.StringElement, err)
 		r.sidebarBlock, err = r.newTemplate("sidebar-block", tmpls.SidebarBlock, err)
 		r.sourceBlock, err = r.newTemplate("source-block", tmpls.SourceBlock, err)
-		r.sourceParagraph, err = r.newTemplate("source-paragraph", tmpls.SourceParagraph, err)
 		r.subscriptText, err = r.newTemplate("subscript", tmpls.SubscriptText, err)
 		r.superscriptText, err = r.newTemplate("superscript", tmpls.SuperscriptText, err)
 		r.table, err = r.newTemplate("table", tmpls.Table, err)

pkg/renderer/sgml/templates.go

@@ -56,7 +56,6 @@ type Templates struct {
 	SectionHeader             string
 	SidebarBlock              string
 	SourceBlock               string
-	SourceParagraph           string
 	StringElement             string
 	SubscriptText             string
 	SuperscriptText           string

pkg/renderer/sgml/xhtml5/delimited_block_test.go

@@ -327,6 +327,22 @@ end</code></pre>
 			Expect(RenderXHTML(source)).To(MatchHTML(expected))
 		})
 
+		It("with title, source and unknown languages attributes", func() {
+			source := `[source,brainfart]
+.Source block title
+----
+int main(int argc, char **argv);
+----`
+			expected := `<div class="listingblock">
+<div class="title">Source block title</div>
+<div class="content">
+<pre class="highlight"><code class="language-brainfart" data-lang="brainfart">int main(int argc, char **argv);</code></pre>
+</div>
+</div>
+`
+			Expect(RenderXHTML(source)).To(MatchHTML(expected))
+		})
+
 		It("with html content", func() {
 			source := `[source]
 ----

pkg/renderer/sgml/xhtml5/paragraph_test.go

@@ -466,6 +466,24 @@ image::foo.png[]`
 <img src="foo.png" alt="quote" width="john doe" height="quote title"/>
 </div>
 </div>
+`
+			Expect(RenderXHTML(source)).To(MatchHTML(expected))
+		})
+	})
+
+	Context("source paragraphs", func() {
+
+		It("with source and languages attributes", func() {
+			source := `:source-highlighter: chroma
+
+[source,c]
+int main(int argc, char **argv);
+`
+			expected := `<div class="listingblock">
+<div class="content">
+<pre class="chroma highlight"><code data-lang="c"><span class="tok-kt">int</span> <span class="tok-nf">main</span><span class="tok-p">(</span><span class="tok-kt">int</span> <span class="tok-n">argc</span><span class="tok-p">,</span> <span class="tok-kt">char</span> <span class="tok-o">**</span><span class="tok-n">argv</span><span class="tok-p">);</span></code></pre>
+</div>
+</div>
 `
 			Expect(RenderXHTML(source)).To(MatchHTML(expected))
 		})