Add configuration options for pandoc

Current options are:

  markup:
    pandoc:
      filters:
        - list
        - of
        - filters
      extensions:
        - list
        - of
        - extensions
      extraArgs:
        - --extra-arguments
        - --one-per-line

Author: asankah

go.sum

@@ -367,6 +367,7 @@ 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

@@ -19,6 +19,7 @@ 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/tableofcontents"
 	"github.com/gohugoio/hugo/parser"
@@ -37,6 +38,7 @@ type Config struct {
 	// Content renderers
 	Goldmark    goldmark_config.Config
 	BlackFriday blackfriday_config.Config
+	Pandoc pandoc_config.Config
 
 	AsciidocExt asciidocext_config.Config
 }

markup/pandoc/convert.go

@@ -15,6 +15,8 @@
 package pandoc
 
 import (
+	"strings"
+	"fmt"
 	"os/exec"
 
 	"github.com/gohugoio/hugo/identity"
@@ -36,7 +38,6 @@ func (p provider) New(cfg converter.ProviderConfig) (converter.Provider, error)
 			cfg: cfg,
 		}, nil
 	}), nil
-
 }
 
 type pandocConverter struct {
@@ -57,11 +58,34 @@ func (c *pandocConverter) getPandocContent(src []byte, ctx converter.DocumentCon
 	logger := c.cfg.Logger
 	path := getPandocExecPath()
 	if path == "" {
-		logger.ERROR.Println("pandoc not found in $PATH: Please install.\n",
+		logger.ERROR.Println(
+			"pandoc not found in $PATH: Please install.\n",
 			"                 Leaving pandoc content unrendered.")
 		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)
 }
 

markup/pandoc/pandoc_config/pandoc.go

@@ -0,0 +1,45 @@
+package pandoc_config
+
+// Config contains configuration settings for Pandoc.
+type Config struct {
+	// Input format. Use the 'Extensions' field to specify extensions thereof.
+	// Only specify the bare format here. Defaults to 'markdown' if empty. Invoke
+	// "pandoc --list-input-formats" to see the list of supported input formats
+	// including various Markdown dialects.
+	InputFormat string
+
+	// If true, the output format is HTML (i.e. "--to=html"). Otherwise the output
+	// format is HTML5 (i.e. "--to=html5").
+	UseLegacyHtml bool
+
+	// Equivalent to specifying "--mathjax". For compatibility, this option is
+	// always true if none of the other math options are used.
+	// See https://pandoc.org/MANUAL.html#math-rendering-in-html
+	UseMathjax bool
+
+	// Equivalent to specifying "--mathml".
+	// See https://pandoc.org/MANUAL.html#math-rendering-in-html
+	UseMathml bool
+
+	// Equivalent to specifying "--webtex".
+	// See https://pandoc.org/MANUAL.html#math-rendering-in-html. Uses the default
+	// Webtex rendering URL.
+	UseWebtex bool
+
+	// Equivalent to specifying "--katex".
+	// See https://pandoc.org/MANUAL.html#math-rendering-in-html
+	UseKatex bool
+
+	// List of filters to use. These translate to '--filter=' arguments to the
+	// pandoc invocation.  The order of elements in `Filters` is preserved when
+	// constructing the `pandoc` commandline.
+	Filters []string
+
+	// List of Pandoc Markdown extensions to use. No need to include default
+	// extensions. Specifying ["foo", "bar"] is equivalent to specifying
+	// --from=markdown+foo+bar on the pandoc commandline.
+	Extensions []string
+
+	// Random extra arguments.
+	ExtraArgs []string
+}