Prepare for Goldmark

This commmit prepares for the addition of Goldmark as the new Markdown renderer in Hugo.

This introduces a new `markup` package with some common interfaces and each implementation in its own package.

See #5963

2 files changed, 135 insertions, 0 deletions

diff --git a/markup/asciidoc/convert.go b/markup/asciidoc/convert.go
new file mode 100644
index 000000000..9e63911d8
--- /dev/null
+++ b/markup/asciidoc/convert.go
@@ -0,0 +1,97 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package asciidoc converts Asciidoc to HTML using Asciidoc or Asciidoctor
+// external binaries.
+package asciidoc
+
+import (
+	"os/exec"
+
+	"github.com/gohugoio/hugo/markup/internal"
+
+	"github.com/gohugoio/hugo/markup/converter"
+)
+
+// Provider is the package entry point.
+var Provider converter.NewProvider = provider{}
+
+type provider struct {
+}
+
+func (p provider) New(cfg converter.ProviderConfig) (converter.Provider, error) {
+	var n converter.NewConverter = func(ctx converter.DocumentContext) (converter.Converter, error) {
+		return &asciidocConverter{
+			ctx: ctx,
+			cfg: cfg,
+		}, nil
+	}
+	return n, nil
+}
+
+type asciidocConverter struct {
+	ctx converter.DocumentContext
+	cfg converter.ProviderConfig
+}
+
+func (a *asciidocConverter) Convert(ctx converter.RenderContext) (converter.Result, error) {
+	return converter.Bytes(a.getAsciidocContent(ctx.Src, a.ctx)), nil
+}
+
+// getAsciidocContent calls asciidoctor or asciidoc as an external helper
+// to convert AsciiDoc content to HTML.
+func (a *asciidocConverter) getAsciidocContent(src []byte, ctx converter.DocumentContext) []byte {
+	var isAsciidoctor bool
+	path := getAsciidoctorExecPath()
+	if path == "" {
+		path = getAsciidocExecPath()
+		if path == "" {
+			a.cfg.Logger.ERROR.Println("asciidoctor / asciidoc not found in $PATH: Please install.\n",
+				"                 Leaving AsciiDoc content unrendered.")
+			return src
+		}
+	} else {
+		isAsciidoctor = true
+	}
+
+	a.cfg.Logger.INFO.Println("Rendering", ctx.DocumentName, "with", path, "...")
+	args := []string{"--no-header-footer", "--safe"}
+	if isAsciidoctor {
+		// asciidoctor-specific arg to show stack traces on errors
+		args = append(args, "--trace")
+	}
+	args = append(args, "-")
+	return internal.ExternallyRenderContent(a.cfg, ctx, src, path, args)
+}
+
+func getAsciidocExecPath() string {
+	path, err := exec.LookPath("asciidoc")
+	if err != nil {
+		return ""
+	}
+	return path
+}
+
+func getAsciidoctorExecPath() string {
+	path, err := exec.LookPath("asciidoctor")
+	if err != nil {
+		return ""
+	}
+	return path
+}
+
+// Supports returns whether Asciidoc or Asciidoctor is installed on this computer.
+func Supports() bool {
+	return (getAsciidoctorExecPath() != "" ||
+		getAsciidocExecPath() != "")
+}
diff --git a/markup/asciidoc/convert_test.go b/markup/asciidoc/convert_test.go
new file mode 100644
index 000000000..1c53f4f25
--- /dev/null
+++ b/markup/asciidoc/convert_test.go
@@ -0,0 +1,38 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package asciidoc
+
+import (
+	"testing"
+
+	"github.com/gohugoio/hugo/common/loggers"
+
+	"github.com/gohugoio/hugo/markup/converter"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func TestConvert(t *testing.T) {
+	if !Supports() {
+		t.Skip("asciidoc/asciidoctor not installed")
+	}
+	c := qt.New(t)
+	p, err := Provider.New(converter.ProviderConfig{Logger: loggers.NewErrorLogger()})
+	c.Assert(err, qt.IsNil)
+	conv, err := p.New(converter.DocumentContext{})
+	c.Assert(err, qt.IsNil)
+	b, err := conv.Convert(converter.RenderContext{Src: []byte("testContent")})
+	c.Assert(err, qt.IsNil)
+	c.Assert(string(b.Bytes()), qt.Equals, "<div class=\"paragraph\">\n<p>testContent</p>\n</div>\n")
+}