Add "hugo mod npm pack"

This commit also introduces a convention where these common JS config files, including `package.hugo.json`, gets mounted into:

```
assets/_jsconfig
´``

These files mapped to their real filename will be added to the environment when running PostCSS, Babel etc., so you can do `process.env.HUGO_FILE_TAILWIND_CONFIG_JS` to resolve the real filename.

But do note that `assets` is a composite/union filesystem, so if your config file is not meant to be overridden, name them something specific.

This commit also adds adds `workDir/node_modules` to `NODE_PATH` and `HUGO_WORKDIR` to the env when running the JS tools above.

Fixes #7644
Fixes #7656
Fixes #7675

3 files changed, 10 insertions, 11 deletions

diff --git a/hugofs/files/classifier.go b/hugofs/files/classifier.go
index 5e26bbac0..35e416c8f 100644
--- a/hugofs/files/classifier.go
+++ b/hugofs/files/classifier.go
@@ -26,6 +26,13 @@ import (
 	"github.com/spf13/afero"
 )
 
+const (
+	// The NPM package.json "template" file.
+	FilenamePackageHugoJSON = "package.hugo.json"
+	// The NPM package file.
+	FilenamePackageJSON = "package.json"
+)
+
 var (
 	// This should be the only list of valid extensions for content files.
 	contentFileExtensions = []string{
@@ -163,9 +170,12 @@ const (
 	ComponentFolderI18n       = "i18n"
 
 	FolderResources = "resources"
+	FolderJSConfig  = "_jsconfig" // Mounted below /assets with postcss.config.js etc.
 )
 
 var (
+	JsConfigFolderMountPrefix = filepath.Join(ComponentFolderAssets, FolderJSConfig)
+
 	ComponentFolders = []string{
 		ComponentFolderArchetypes,
 		ComponentFolderStatic,
diff --git a/hugofs/rootmapping_fs.go b/hugofs/rootmapping_fs.go
index ea3ef003e..2c4f0df52 100644
--- a/hugofs/rootmapping_fs.go
+++ b/hugofs/rootmapping_fs.go
@@ -42,9 +42,6 @@ func NewRootMappingFs(fs afero.Fs, rms ...RootMapping) (*RootMappingFs, error) {
 		(&rm).clean()
 
 		fromBase := files.ResolveComponentFolder(rm.From)
-		if fromBase == "" {
-			panic("unrecognised component folder in" + rm.From)
-		}
 
 		if len(rm.To) < 2 {
 			panic(fmt.Sprintf("invalid root mapping; from/to: %s/%s", rm.From, rm.To))
diff --git a/hugofs/walk_test.go b/hugofs/walk_test.go
index 0c08968c6..c38c6044f 100644
--- a/hugofs/walk_test.go
+++ b/hugofs/walk_test.go
@@ -21,8 +21,6 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/gohugoio/hugo/common/hugo"
-
 	"github.com/pkg/errors"
 
 	"github.com/gohugoio/hugo/htesting"
@@ -129,12 +127,6 @@ func TestWalkSymbolicLink(t *testing.T) {
 	})
 
 	t.Run("BasePath Fs", func(t *testing.T) {
-		if hugo.GoMinorVersion() < 12 {
-			// https://github.com/golang/go/issues/30520
-			// This is fixed in Go 1.13 and in the latest Go 1.12
-			t.Skip("skip this for Go <= 1.11 due to a bug in Go's stdlib")
-
-		}
 		c := qt.New(t)
 
 		docsFs := afero.NewBasePathFs(fs, docsDir)