Add R Markdown support

- Strip YAML front matter
- Parse and convert remaining Markdown document using Blackfriday

Code chunk delimiters like "```{r}" and chunk options are ignored by Blackfriday, so syntax highlighting will not be applied.

Glance/SupportedFilesWC.xib

@@ -61,7 +61,7 @@
  </fragment>
  <fragment>
  <string key="content">
-.md, .markdown, .mdown, .mkdn, .mkd
+.md, .markdown, .mdown, .mkdn, .mkd, .Rmd
 
 </string>
  <attributes>

HTMLConverter/htmlconverter.go

@@ -12,8 +12,12 @@ import (
  "github.com/microcosm-cc/bluemonday"
  "github.com/samuelmeuli/nbtohtml"
  "gopkg.in/russross/blackfriday.v2"
+ "regexp"
 )
 
+// Regex for YAML front matter in a Markdown document
+var markdownFrontMatterRegex = regexp.MustCompile(`---\n[\s\S]*?\n---\n`)
+
 // Functions for conversion between C and Go strings. Required here because cgo cannot be used in
 // tests.
 
@@ -81,6 +85,10 @@ func convertMarkdownToHTML(source *C.char) *C.char {
  bfchroma.ChromaOptions(htmlFormatter.WithClasses(true)),
  )
 
+ // Strip YAML front matter
+ sourceString = markdownFrontMatterRegex.ReplaceAllString(sourceString, "")
+
+ // Convert Markdown to HTML
  html := blackfriday.Run([]byte(sourceString), blackfriday.WithRenderer(renderer))
  htmlString := string(html)
  htmlStringSanitized := policy.Sanitize(htmlString)

HTMLConverter/htmlconverter_test.go

@@ -43,6 +43,20 @@ Text`
  assert.Equal(t, expected, minifyHTML(actual))
 }
 
+func TestConvertMarkdownToHTMLWithFrontMatter(t *testing.T) {
+ source := `---
+key: Value
+key2: Another value
+---
+
+# Heading
+
+Text`
+ expected := "<h1>Heading</h1><p>Text</p>"
+ actual := convertToGoString(convertMarkdownToHTML(convertToCString(source)))
+ assert.Equal(t, expected, minifyHTML(actual))
+}
+
 func TestConvertNotebookToHTML(t *testing.T) {
  source := `{"cells":[{"cell_type":"code","execution_count":1,"metadata":{},"outputs":[{"name":"stdout","output_type":"stream","text":["Hello world\n"]}],"source":["print(\"Hello world\")"]}],"metadata":{"kernelspec":{"display_name":"Python 3","language":"python","name":"python3"},"language_info":{"codemirror_mode":{"name":"ipython","version":3},"file_extension":".py","mimetype":"text/x-python","name":"python","nbconvert_exporter":"python","pygments_lexer":"ipython3","version":"3.8.2"}},"nbformat":4,"nbformat_minor":4}`
  actual := convertToGoString(convertNotebookToHTML(convertToCString(source)))

QLPlugin/Info.plist

@@ -50,6 +50,7 @@
  <string>dyn.ah62d4rv4ge80w6d3r3va</string> <!-- .ipynb -->
 
  <!-- Markdown -->
+ <string>dyn.ah62d4rv4ge81e5pe</string> <!-- .Rmd -->
  <string>io.caret.markdown</string> <!-- .markdown, .md, .mdown, .mkd, .mkdn -->
  <string>net.daringfireball.markdown</string> <!-- .markdown, .md, .mdown, .mkd, .mkdn -->
 

QLPlugin/Views/PreviewVCFactory.swift

@@ -8,7 +8,7 @@ class PreviewVCFactory {
  case "gz":
  // `gzip` is only supported for tarballs
  return fileURL.path.hasSuffix(".tar.gz") ? TARPreview.self : nil
- case "md", "markdown", "mdown", "mkdn", "mkd":
+ case "md", "markdown", "mdown", "mkdn", "mkd", "rmd":
  return MarkdownPreview.self
  case "ipynb":
  return JupyterPreview.self

README.md

@@ -20,7 +20,7 @@ TODO: Main app screenshot
 
  TODO: Add screenshot
 
-- **Markdown** (rendered using [Blackfriday](https://github.com/russross/blackfriday)): `.md`, `.markdown`, `.mdown`, `.mkdn`, `.mkd`
+- **Markdown** (rendered using [Blackfriday](https://github.com/russross/blackfriday)): `.md`, `.markdown`, `.mdown`, `.mkdn`, `.mkd`, `.Rmd`
 
  TODO: Add screenshot