Rename transpileJS to babel

And add a test.

Updates #5764

resources/resource_transformers/babel/babel.go

@@ -0,0 +1,186 @@
+// Copyright 2020 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 babel
+
+import (
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+
+	"github.com/gohugoio/hugo/common/hugo"
+	"github.com/gohugoio/hugo/resources/internal"
+
+	"github.com/mitchellh/mapstructure"
+
+	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/hugofs"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/resource"
+	"github.com/pkg/errors"
+)
+
+// Options from https://babeljs.io/docs/en/options
+type Options struct {
+	Config string // Custom path to config file
+
+	Minified   bool
+	NoComments bool
+	Compact    *bool
+	Verbose    bool
+	NoBabelrc  bool
+}
+
+func DecodeOptions(m map[string]interface{}) (opts Options, err error) {
+	if m == nil {
+		return
+	}
+	err = mapstructure.WeakDecode(m, &opts)
+	return
+}
+func (opts Options) toArgs() []string {
+	var args []string
+
+	if opts.Minified {
+		args = append(args, "--minified")
+	}
+	if opts.NoComments {
+		args = append(args, "--no-comments")
+	}
+	if opts.Compact != nil {
+		args = append(args, "--compact="+strconv.FormatBool(*opts.Compact))
+	}
+	if opts.Verbose {
+		args = append(args, "--verbose")
+	}
+	if opts.NoBabelrc {
+		args = append(args, "--no-babelrc")
+	}
+	return args
+}
+
+// Client is the client used to do Babel transformations.
+type Client struct {
+	rs *resources.Spec
+}
+
+// New creates a new Client with the given specification.
+func New(rs *resources.Spec) *Client {
+	return &Client{rs: rs}
+}
+
+type babelTransformation struct {
+	options Options
+	rs      *resources.Spec
+}
+
+func (t *babelTransformation) Key() internal.ResourceTransformationKey {
+	return internal.NewResourceTransformationKey("babel", t.options)
+}
+
+// Transform shells out to babel-cli to do the heavy lifting.
+// For this to work, you need some additional tools. To install them globally:
+// npm install -g @babel/core @babel/cli
+// If you want to use presets or plugins such as @babel/preset-env
+// Then you should install those globally as well. e.g:
+// npm install -g @babel/preset-env
+// Instead of installing globally, you can also install everything as a dev-dependency (--save-dev instead of -g)
+func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
+	const localBabelPath = "node_modules/@babel/cli/bin/"
+	const binaryName = "babel.js"
+
+	// Try first in the project's node_modules.
+	csiBinPath := filepath.Join(t.rs.WorkingDir, localBabelPath, binaryName)
+
+	binary := csiBinPath
+
+	if _, err := exec.LookPath(binary); err != nil {
+		// Try PATH
+		binary = binaryName
+		if _, err := exec.LookPath(binary); err != nil {
+
+			// This may be on a CI server etc. Will fall back to pre-built assets.
+			return herrors.ErrFeatureNotAvailable
+		}
+	}
+
+	var configFile string
+	logger := t.rs.Logger
+
+	if t.options.Config != "" {
+		configFile = t.options.Config
+	} else {
+		configFile = "babel.config.js"
+	}
+
+	configFile = filepath.Clean(configFile)
+
+	// We need an abolute filename to the config file.
+	if !filepath.IsAbs(configFile) {
+		// We resolve this against the virtual Work filesystem, to allow
+		// this config file to live in one of the themes if needed.
+		fi, err := t.rs.BaseFs.Work.Stat(configFile)
+		if err != nil {
+			if t.options.Config != "" {
+				// Only fail if the user specificed config file is not found.
+				return errors.Wrapf(err, "babel config %q not found:", configFile)
+			}
+		} else {
+			configFile = fi.(hugofs.FileMetaInfo).Meta().Filename()
+		}
+	}
+
+	var cmdArgs []string
+
+	if configFile != "" {
+		logger.INFO.Println("babel: use config file", configFile)
+		cmdArgs = []string{"--config-file", configFile}
+	}
+
+	if optArgs := t.options.toArgs(); len(optArgs) > 0 {
+		cmdArgs = append(cmdArgs, optArgs...)
+	}
+	cmdArgs = append(cmdArgs, "--filename="+ctx.SourcePath)
+
+	cmd := exec.Command(binary, cmdArgs...)
+
+	cmd.Stdout = ctx.To
+	cmd.Stderr = os.Stderr
+	cmd.Env = hugo.GetExecEnviron(t.rs.Cfg)
+
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	go func() {
+		defer stdin.Close()
+		io.Copy(stdin, ctx.From)
+	}()
+
+	err = cmd.Run()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Process transforms the given Resource with the Babel processor.
+func (c *Client) Process(res resources.ResourceTransformer, options Options) (resource.Resource, error) {
+	return res.Transform(
+		&babelTransformation{rs: c.rs, options: options},
+	)
+}