Generalize some Pandoc options.

go.sum

@@ -364,7 +364,6 @@ github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
-github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/subosito/gotenv v1.2.0 h1:Slr1R9HxAlEKefgq5jn9U+DnETlIUa6HfgEzj0g5d7s=
 github.com/subosito/gotenv v1.2.0/go.mod h1:N0PQaV/YGNqwC0u51sEeR/aUtSLEXKX9iv69rRypqCw=

markup/markup_config/config.go

@@ -19,8 +19,8 @@ import (
 	"github.com/gohugoio/hugo/markup/asciidocext/asciidocext_config"
 	"github.com/gohugoio/hugo/markup/blackfriday/blackfriday_config"
 	"github.com/gohugoio/hugo/markup/goldmark/goldmark_config"
-	"github.com/gohugoio/hugo/markup/pandoc/pandoc_config"
 	"github.com/gohugoio/hugo/markup/highlight"
+	"github.com/gohugoio/hugo/markup/pandoc/pandoc_config"
 	"github.com/gohugoio/hugo/markup/tableofcontents"
 	"github.com/gohugoio/hugo/parser"
 	"github.com/mitchellh/mapstructure"
@@ -38,8 +38,7 @@ type Config struct {
 	// Content renderers
 	Goldmark    goldmark_config.Config
 	BlackFriday blackfriday_config.Config
-	Pandoc pandoc_config.Config
-
+	Pandoc      pandoc_config.Config
 	AsciidocExt asciidocext_config.Config
 }
 

markup/pandoc/convert.go

@@ -15,8 +15,6 @@
 package pandoc
 
 import (
-	"strings"
-	"fmt"
 	"os/exec"
 
 	"github.com/gohugoio/hugo/identity"
@@ -64,29 +62,7 @@ func (c *pandocConverter) getPandocContent(src []byte, ctx converter.DocumentCon
 		return src
 	}
 
-	args := []string{"--mathjax"}
-
-	if len(c.cfg.MarkupConfig.Pandoc.Filters) > 0 {
-		for _, filter := range c.cfg.MarkupConfig.Pandoc.Filters {
-			args = append(args, fmt.Sprintf("--filter=%s", filter))
-		}
-	}
-
-	if len(c.cfg.MarkupConfig.Pandoc.Extensions) > 0 {
-		var b strings.Builder
-		b.WriteString("--from=markdown")
-		for _, extension := range c.cfg.MarkupConfig.Pandoc.Extensions {
-			b.WriteString("+")
-			b.WriteString(extension)
-		}
-		args = append(args, b.String())
-	}
-
-	if len(c.cfg.MarkupConfig.Pandoc.ExtraArgs) > 0 {
-		args = append(args, c.cfg.MarkupConfig.Pandoc.ExtraArgs...)
-	}
-
-	return internal.ExternallyRenderContent(c.cfg, ctx, src, path, args)
+	return internal.ExternallyRenderContent(c.cfg, ctx, src, path, c.cfg.MarkupConfig.Pandoc.AsPandocArguments())
 }
 
 func getPandocExecPath() string {

markup/pandoc/pandoc_config/pandoc.go

@@ -1,5 +1,10 @@
 package pandoc_config
 
+import (
+	"fmt"
+	"strings"
+)
+
 // Config contains configuration settings for Pandoc.
 type Config struct {
 	// Input format. Use the 'Extensions' field to specify extensions thereof.
@@ -40,6 +45,89 @@ type Config struct {
 	// --from=markdown+foo+bar on the pandoc commandline.
 	Extensions []string
 
-	// Random extra arguments.
+	// List of input format extensions to use. Specifying ["foo", "bar"] is
+	// equivalent to specifying --from=markdown+foo+bar on the pandoc commandline
+	// assuming InputFormat is "markdown".
+	InputExtensions []string
+
+	// List of output format extensions to use. Specifying ["foo", "bar"] is
+	// equivalent to specifying --to=html5+foo+bar on the pandoc commandline,
+	// assuming UseLegacyHTML is false. Invoke "pandoc --list-extensions=html5" to
+	// or "pandoc --list-extensions=html5" to see the list of extensions that can
+	// be specified here.
+	OutputExtensions []string
+
+	// Extra commandline options passed to the pandoc invocation. These options
+	// are appended to the commandline after the format and filter options.
+	// Arguments are passed in literally. Hence must have the "--" or "-" prefix
+	// where applicable.
 	ExtraArgs []string
 }
+
+func (c *Config) getInputArg() string {
+	var b strings.Builder
+	b.WriteString("--from=")
+	if len(c.InputFormat) > 0 {
+		b.WriteString(c.InputFormat)
+	} else {
+		b.WriteString("markdown")
+	}
+
+	for _, extension := range c.InputExtensions {
+		b.WriteString("+")
+		b.WriteString(extension)
+	}
+	return b.String()
+}
+
+func (c *Config) getOutputArg() string {
+	var b strings.Builder
+	b.WriteString("--to=")
+	if c.UseLegacyHtml {
+		b.WriteString("html")
+	} else {
+		b.WriteString("html5")
+	}
+
+	for _, extension := range c.OutputExtensions {
+		b.WriteString("+")
+		b.WriteString(extension)
+	}
+	return b.String()
+}
+
+func (c *Config) getMathRenderingArg() string {
+	switch {
+	case c.UseMathml:
+		return "--mathml"
+	case c.UseWebtex:
+		return "--webtex"
+	case c.UseKatex:
+		return "--katex"
+	default:
+		return "--mathjax"
+	}
+}
+
+func (c *Config) getFilterArgs() []string {
+	var args []string
+	for _, filter := range c.Filters {
+		args = append(args, fmt.Sprintf("--filter=%s", filter))
+	}
+	return args
+}
+
+// AsPandocArguments returns a list of strings that can be used as arguments to
+// a "pandoc" invocation. All the settings contained in Config are represented
+// in the returned list of arguments.
+func (c *Config) AsPandocArguments() []string {
+	args := []string{
+		c.getInputArg(),
+		c.getOutputArg(),
+		c.getMathRenderingArg()}
+
+	args = append(args, c.getFilterArgs()...)
+	args = append(args, c.ExtraArgs...)
+
+	return args
+}