pipes: Add external source map support to js.Build and Babel

Fixes #8132

4 files changed, 99 insertions, 2 deletions

diff --git a/resources/resource_transformers/babel/babel.go b/resources/resource_transformers/babel/babel.go
index 204153705..e291b210b 100644
--- a/resources/resource_transformers/babel/babel.go
+++ b/resources/resource_transformers/babel/babel.go
@@ -16,7 +16,11 @@ package babel
 import (
 	"bytes"
 	"io"
+	"io/ioutil"
+	"os"
+	"path"
 	"path/filepath"
+	"regexp"
 	"strconv"
 
 	"github.com/cli/safeexec"
@@ -43,8 +47,10 @@ type Options struct {
 	Compact    *bool
 	Verbose    bool
 	NoBabelrc  bool
+	SourceMap  string
 }
 
+// DecodeOptions decodes options to and generates command flags
 func DecodeOptions(m map[string]interface{}) (opts Options, err error) {
 	if m == nil {
 		return
@@ -56,6 +62,14 @@ func DecodeOptions(m map[string]interface{}) (opts Options, err error) {
 func (opts Options) toArgs() []string {
 	var args []string
 
+	// external is not a known constant on the babel command line
+	// .sourceMaps must be a boolean, "inline", "both", or undefined
+	switch opts.SourceMap {
+	case "external":
+		args = append(args, "--source-maps")
+	case "inline":
+		args = append(args, "--source-maps=inline")
+	}
 	if opts.Minified {
 		args = append(args, "--minified")
 	}
@@ -141,6 +155,8 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 		}
 	}
 
+	ctx.ReplaceOutPathExtension(".js")
+
 	var cmdArgs []string
 
 	if configFile != "" {
@@ -153,13 +169,24 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 	}
 	cmdArgs = append(cmdArgs, "--filename="+ctx.SourcePath)
 
+	// Create compile into a real temp file:
+	// 1. separate stdout/stderr messages from babel (https://github.com/gohugoio/hugo/issues/8136)
+	// 2. allow generation and retrieval of external source map.
+	compileOutput, err := ioutil.TempFile("", "compileOut-*.js")
+	if err != nil {
+		return err
+	}
+
+	cmdArgs = append(cmdArgs, "--out-file="+compileOutput.Name())
+	defer os.Remove(compileOutput.Name())
+
 	cmd, err := hexec.SafeCommand(binary, cmdArgs...)
 	if err != nil {
 		return err
 	}
 
-	cmd.Stdout = ctx.To
 	cmd.Stderr = io.MultiWriter(infoW, &errBuf)
+	cmd.Stdout = cmd.Stderr
 	cmd.Env = hugo.GetExecEnviron(t.rs.WorkingDir, t.rs.Cfg, t.rs.BaseFs.Assets.Fs)
 
 	stdin, err := cmd.StdinPipe()
@@ -177,6 +204,28 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 		return errors.Wrap(err, errBuf.String())
 	}
 
+	content, err := ioutil.ReadAll(compileOutput)
+	if err != nil {
+		return err
+	}
+
+	mapFile := compileOutput.Name() + ".map"
+	if _, err := os.Stat(mapFile); err == nil {
+		defer os.Remove(mapFile)
+		sourceMap, err := ioutil.ReadFile(mapFile)
+		if err != nil {
+			return err
+		}
+		if err = ctx.PublishSourceMap(string(sourceMap)); err != nil {
+			return err
+		}
+		targetPath := path.Base(ctx.OutPath) + ".map"
+		re := regexp.MustCompile(`//# sourceMappingURL=.*\n?`)
+		content = []byte(re.ReplaceAllString(string(content), "//# sourceMappingURL="+targetPath+"\n"))
+	}
+
+	ctx.To.Write(content)
+
 	return nil
 }
 
diff --git a/resources/resource_transformers/js/build.go b/resources/resource_transformers/js/build.go
index 5ff21cf02..0d70bdc33 100644
--- a/resources/resource_transformers/js/build.go
+++ b/resources/resource_transformers/js/build.go
@@ -18,6 +18,8 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"path"
+	"regexp"
 	"strings"
 
 	"github.com/spf13/afero"
@@ -92,6 +94,14 @@ func (t *buildTransformation) Transform(ctx *resources.ResourceTransformationCtx
 		return err
 	}
 
+	if buildOptions.Sourcemap == api.SourceMapExternal && buildOptions.Outdir == "" {
+		buildOptions.Outdir, err = ioutil.TempDir(os.TempDir(), "compileOutput")
+		if err != nil {
+			return err
+		}
+		defer os.Remove(buildOptions.Outdir)
+	}
+
 	result := api.Build(buildOptions)
 
 	if len(result.Errors) > 0 {
@@ -145,7 +155,25 @@ func (t *buildTransformation) Transform(ctx *resources.ResourceTransformationCtx
 		return errors[0]
 	}
 
-	ctx.To.Write(result.OutputFiles[0].Contents)
+	if buildOptions.Sourcemap == api.SourceMapExternal {
+		content := string(result.OutputFiles[1].Contents)
+		symPath := path.Base(ctx.OutPath) + ".map"
+		re := regexp.MustCompile(`//# sourceMappingURL=.*\n?`)
+		content = re.ReplaceAllString(content, "//# sourceMappingURL="+symPath+"\n")
+
+		if err = ctx.PublishSourceMap(string(result.OutputFiles[0].Contents)); err != nil {
+			return err
+		}
+		_, err := ctx.To.Write([]byte(content))
+		if err != nil {
+			return err
+		}
+	} else {
+		_, err := ctx.To.Write(result.OutputFiles[0].Contents)
+		if err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
diff --git a/resources/resource_transformers/js/options.go b/resources/resource_transformers/js/options.go
index 75daa0cad..5236fe126 100644
--- a/resources/resource_transformers/js/options.go
+++ b/resources/resource_transformers/js/options.go
@@ -338,6 +338,8 @@ func toBuildOptions(opts Options) (buildOptions api.BuildOptions, err error) {
 	switch opts.SourceMap {
 	case "inline":
 		sourceMap = api.SourceMapInline
+	case "external":
+		sourceMap = api.SourceMapExternal
 	case "":
 		sourceMap = api.SourceMapNone
 	default:
diff --git a/resources/resource_transformers/js/options_test.go b/resources/resource_transformers/js/options_test.go
index f07ccc26b..f425c3e75 100644
--- a/resources/resource_transformers/js/options_test.go
+++ b/resources/resource_transformers/js/options_test.go
@@ -109,4 +109,22 @@ func TestToBuildOptions(t *testing.T) {
 			Loader: api.LoaderJS,
 		},
 	})
+
+	opts, err = toBuildOptions(Options{
+		Target: "es2018", Format: "cjs", Minify: true, mediaType: media.JavascriptType,
+		SourceMap: "external",
+	})
+	c.Assert(err, qt.IsNil)
+	c.Assert(opts, qt.DeepEquals, api.BuildOptions{
+		Bundle:            true,
+		Target:            api.ES2018,
+		Format:            api.FormatCommonJS,
+		MinifyIdentifiers: true,
+		MinifySyntax:      true,
+		MinifyWhitespace:  true,
+		Sourcemap:         api.SourceMapExternal,
+		Stdin: &api.StdinOptions{
+			Loader: api.LoaderJS,
+		},
+	})
 }