Save auto-detected markup type in Page.Markup

If Page.Markup was not set by the user, it will now be set after
guessing from the file extension. This means, Page.Markup will be set in
any case. It can be used by a theme to differentiate between markup
types.

Fixes #1950

hugolib/page.go

@@ -264,7 +264,7 @@ func (p *Page) renderBytes(content []byte) []byte {
 		}
 	}
 	return helpers.RenderBytes(
-		&helpers.RenderingContext{Content: content, PageFmt: p.guessMarkupType(),
+		&helpers.RenderingContext{Content: content, PageFmt: p.determineMarkupType(),
 			DocumentID: p.UniqueID(), Config: p.getRenderingConfig(), LinkResolver: fn, FileResolver: fileFn})
 }
 
@@ -279,7 +279,7 @@ func (p *Page) renderContent(content []byte) []byte {
 			return p.Node.Site.SourceRelativeLinkFile(ref, p)
 		}
 	}
-	return helpers.RenderBytesWithTOC(&helpers.RenderingContext{Content: content, PageFmt: p.guessMarkupType(),
+	return helpers.RenderBytesWithTOC(&helpers.RenderingContext{Content: content, PageFmt: p.determineMarkupType(),
 		DocumentID: p.UniqueID(), Config: p.getRenderingConfig(), LinkResolver: fn, FileResolver: fileFn})
 }
 
@@ -801,16 +801,15 @@ func (p *Page) Render(layout ...string) template.HTML {
 	return tpl.ExecuteTemplateToHTML(p, l...)
 }
 
-func (p *Page) guessMarkupType() string {
-	// First try the explicitly set markup from the frontmatter
-	if p.Markup != "" {
-		format := helpers.GuessType(p.Markup)
-		if format != "unknown" {
-			return format
-		}
+func (p *Page) determineMarkupType() string {
+	// Try markup explicitly set in the frontmatter
+	p.Markup = helpers.GuessType(p.Markup)
+	if p.Markup == "unknown" {
+		// Fall back to file extension (might also return "unknown")
+		p.Markup = helpers.GuessType(p.Source.Ext())
 	}
 
-	return helpers.GuessType(p.Source.Ext())
+	return p.Markup
 }
 
 func (p *Page) parse(reader io.Reader) error {

hugolib/shortcode.go

@@ -234,7 +234,7 @@ func renderShortcode(sc shortcode, parent *ShortcodeWithPage, p *Page, t tpl.Tem
 
 		if sc.doMarkup {
 			newInner := helpers.RenderBytes(&helpers.RenderingContext{
-				Content: []byte(inner), PageFmt: p.guessMarkupType(),
+				Content: []byte(inner), PageFmt: p.determineMarkupType(),
 				DocumentID: p.UniqueID(), Config: p.getRenderingConfig()})
 
 			// If the type is “unknown” or “markdown”, we assume the markdown
@@ -250,7 +250,7 @@ func renderShortcode(sc shortcode, parent *ShortcodeWithPage, p *Page, t tpl.Tem
 			//     substitutions in <div>HUGOSHORTCODE-1</div> which prevents the
 			//     generation, but means that you can’t use shortcodes inside of
 			//     markdown structures itself (e.g., `[foo]({{% ref foo.md %}})`).
-			switch p.guessMarkupType() {
+			switch p.determineMarkupType() {
 			case "unknown", "markdown":
 				if match, _ := regexp.MatchString(innerNewlineRegexp, inner); !match {
 					cleaner, err := regexp.Compile(innerCleanupRegexp)