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

4 files changed, 380 insertions, 1 deletions

diff --git a/modules/collect.go b/modules/collect.go
index b82d395fd..8959572d6 100644
--- a/modules/collect.go
+++ b/modules/collect.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"time"
 
@@ -382,6 +383,11 @@ func (c *collector) applyMounts(moduleImport Import, mod *moduleAdapter) error {
 		return err
 	}
 
+	mounts, err = c.mountCommonJSConfig(mod, mounts)
+	if err != nil {
+		return err
+	}
+
 	mod.mounts = mounts
 	return nil
 }
@@ -549,6 +555,43 @@ func (c *collector) loadModules() error {
 	return nil
 }
 
+// Matches postcss.config.js etc.
+var commonJSConfigs = regexp.MustCompile(`(babel|postcss|tailwind)\.config\.js`)
+
+func (c *collector) mountCommonJSConfig(owner *moduleAdapter, mounts []Mount) ([]Mount, error) {
+	for _, m := range mounts {
+		if strings.HasPrefix(m.Target, files.JsConfigFolderMountPrefix) {
+			// This follows the convention of the other component types (assets, content, etc.),
+			// if one or more is specificed by the user, we skip the defaults.
+			// These mounts were added to Hugo in 0.75.
+			return mounts, nil
+		}
+	}
+
+	// Mount the common JS config files.
+	fis, err := afero.ReadDir(c.fs, owner.Dir())
+	if err != nil {
+		return mounts, err
+	}
+
+	for _, fi := range fis {
+		n := fi.Name()
+
+		should := n == files.FilenamePackageHugoJSON || n == files.FilenamePackageJSON
+		should = should || commonJSConfigs.MatchString(n)
+
+		if should {
+			mounts = append(mounts, Mount{
+				Source: n,
+				Target: filepath.Join(files.ComponentFolderAssets, files.FolderJSConfig, n),
+			})
+		}
+
+	}
+
+	return mounts, nil
+}
+
 func (c *collector) normalizeMounts(owner *moduleAdapter, mounts []Mount) ([]Mount, error) {
 	var out []Mount
 	dir := owner.Dir()
diff --git a/modules/config.go b/modules/config.go
index 1964479f4..e0a0ea060 100644
--- a/modules/config.go
+++ b/modules/config.go
@@ -56,7 +56,9 @@ func ApplyProjectConfigDefaults(cfg config.Provider, mod Module) error {
 	// the basic level.
 	componentsConfigured := make(map[string]bool)
 	for _, mnt := range moda.mounts {
-		componentsConfigured[mnt.Component()] = true
+		if !strings.HasPrefix(mnt.Target, files.JsConfigFolderMountPrefix) {
+			componentsConfigured[mnt.Component()] = true
+		}
 	}
 
 	type dirKeyComponent struct {
@@ -318,12 +320,21 @@ type Mount struct {
 	Target string // relative target path, e.g. "assets/bootstrap/scss"
 
 	Lang string // any language code associated with this mount.
+
 }
 
 func (m Mount) Component() string {
 	return strings.Split(m.Target, fileSeparator)[0]
 }
 
+func (m Mount) ComponentAndName() (string, string) {
+	k := strings.Index(m.Target, fileSeparator)
+	if k == -1 {
+		return m.Target, ""
+	}
+	return m.Target[:k], m.Target[k+1:]
+}
+
 func getStaticDirs(cfg config.Provider) []string {
 	var staticDirs []string
 	for i := -1; i <= 10; i++ {
diff --git a/modules/npm/package_builder.go b/modules/npm/package_builder.go
new file mode 100644
index 000000000..23aac7246
--- /dev/null
+++ b/modules/npm/package_builder.go
@@ -0,0 +1,230 @@
+// 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 npm
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+
+	"github.com/gohugoio/hugo/hugofs/files"
+
+	"github.com/pkg/errors"
+
+	"github.com/gohugoio/hugo/hugofs"
+	"github.com/spf13/afero"
+
+	"github.com/spf13/cast"
+
+	"github.com/gohugoio/hugo/helpers"
+)
+
+const (
+	dependenciesKey    = "dependencies"
+	devDependenciesKey = "devDependencies"
+
+	packageJSONName = "package.json"
+
+	packageJSONTemplate = `{
+  "name": "%s",
+  "version": "%s"
+}`
+)
+
+func Pack(fs afero.Fs, fis []hugofs.FileMetaInfo) error {
+
+	var b *packageBuilder
+
+	// Have a package.hugo.json?
+	fi, err := fs.Stat(files.FilenamePackageHugoJSON)
+	if err != nil {
+		// Have a package.json?
+		fi, err = fs.Stat(packageJSONName)
+		if err != nil {
+			// Create one.
+			name := "project"
+			// Use the Hugo site's folder name as the default name.
+			// The owner can change it later.
+			rfi, err := fs.Stat("")
+			if err == nil {
+				name = rfi.Name()
+			}
+			packageJSONContent := fmt.Sprintf(packageJSONTemplate, name, "0.1.0")
+			if err = afero.WriteFile(fs, files.FilenamePackageHugoJSON, []byte(packageJSONContent), 0666); err != nil {
+				return err
+			}
+			fi, err = fs.Stat(files.FilenamePackageHugoJSON)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	meta := fi.(hugofs.FileMetaInfo).Meta()
+	masterFilename := meta.Filename()
+	f, err := meta.Open()
+	if err != nil {
+		return errors.Wrap(err, "npm pack: failed to open package file")
+	}
+	b = newPackageBuilder(meta.Module(), f)
+	f.Close()
+
+	for _, fi := range fis {
+		if fi.IsDir() {
+			// We only care about the files in the root.
+			continue
+		}
+
+		if fi.Name() != files.FilenamePackageHugoJSON {
+			continue
+		}
+
+		meta := fi.(hugofs.FileMetaInfo).Meta()
+
+		if meta.Filename() == masterFilename {
+			continue
+		}
+
+		f, err := meta.Open()
+		if err != nil {
+			return errors.Wrap(err, "npm pack: failed to open package file")
+		}
+		b.Add(meta.Module(), f)
+		f.Close()
+	}
+
+	if b.Err() != nil {
+		return errors.Wrap(b.Err(), "npm pack: failed to build")
+	}
+
+	// Replace the dependencies in the original template with the merged set.
+	b.originalPackageJSON[dependenciesKey] = b.dependencies
+	b.originalPackageJSON[devDependenciesKey] = b.devDependencies
+	var commentsm map[string]interface{}
+	comments, found := b.originalPackageJSON["comments"]
+	if found {
+		commentsm = cast.ToStringMap(comments)
+	} else {
+		commentsm = make(map[string]interface{})
+	}
+	commentsm[dependenciesKey] = b.dependenciesComments
+	commentsm[devDependenciesKey] = b.devDependenciesComments
+	b.originalPackageJSON["comments"] = commentsm
+
+	// Write it out to the project package.json
+	packageJSONData, err := json.MarshalIndent(b.originalPackageJSON, "", " ")
+	if err != nil {
+		return errors.Wrap(err, "npm pack: failed to marshal JSON")
+	}
+
+	if err := afero.WriteFile(fs, packageJSONName, packageJSONData, 0666); err != nil {
+		return errors.Wrap(err, "npm pack: failed to write package.json")
+	}
+
+	return nil
+
+}
+
+func newPackageBuilder(source string, first io.Reader) *packageBuilder {
+	b := &packageBuilder{
+		devDependencies:         make(map[string]interface{}),
+		devDependenciesComments: make(map[string]interface{}),
+		dependencies:            make(map[string]interface{}),
+		dependenciesComments:    make(map[string]interface{}),
+	}
+
+	m := b.unmarshal(first)
+	if b.err != nil {
+		return b
+	}
+
+	b.addm(source, m)
+	b.originalPackageJSON = m
+
+	return b
+}
+
+type packageBuilder struct {
+	err error
+
+	// The original package.hugo.json.
+	originalPackageJSON map[string]interface{}
+
+	devDependencies         map[string]interface{}
+	devDependenciesComments map[string]interface{}
+	dependencies            map[string]interface{}
+	dependenciesComments    map[string]interface{}
+}
+
+func (b *packageBuilder) Add(source string, r io.Reader) *packageBuilder {
+	if b.err != nil {
+		return b
+	}
+
+	m := b.unmarshal(r)
+	if b.err != nil {
+		return b
+	}
+
+	b.addm(source, m)
+
+	return b
+}
+
+func (b *packageBuilder) addm(source string, m map[string]interface{}) {
+	if source == "" {
+		source = "project"
+	}
+
+	// The version selection is currently very simple.
+	// We may consider minimal version selection or something
+	// after testing this out.
+	//
+	// But for now, the first version string for a given dependency wins.
+	// These packages will be added by order of import (project, module1, module2...),
+	// so that should at least give the project control over the situation.
+	if devDeps, found := m[devDependenciesKey]; found {
+		mm := cast.ToStringMapString(devDeps)
+		for k, v := range mm {
+			if _, added := b.devDependencies[k]; !added {
+				b.devDependencies[k] = v
+				b.devDependenciesComments[k] = source
+			}
+		}
+	}
+
+	if deps, found := m[dependenciesKey]; found {
+		mm := cast.ToStringMapString(deps)
+		for k, v := range mm {
+			if _, added := b.dependencies[k]; !added {
+				b.dependencies[k] = v
+				b.dependenciesComments[k] = source
+			}
+		}
+	}
+
+}
+
+func (b *packageBuilder) unmarshal(r io.Reader) map[string]interface{} {
+	m := make(map[string]interface{})
+	err := json.Unmarshal(helpers.ReaderToBytes(r), &m)
+	if err != nil {
+		b.err = err
+	}
+	return m
+}
+
+func (b *packageBuilder) Err() error {
+	return b.err
+}
diff --git a/modules/npm/package_builder_test.go b/modules/npm/package_builder_test.go
new file mode 100644
index 000000000..510a04776
--- /dev/null
+++ b/modules/npm/package_builder_test.go
@@ -0,0 +1,95 @@
+// 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 npm
+
+import (
+	"strings"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+)
+
+const templ = `{
+        "name": "foo",
+        "version": "0.1.1",
+        "scripts": {},
+         "dependencies": {
+                "react-dom": "1.1.1",
+                "tailwindcss": "1.2.0",
+                "@babel/cli": "7.8.4",
+                "@babel/core": "7.9.0",
+                "@babel/preset-env": "7.9.5"
+        },
+        "devDependencies": {
+                "postcss-cli": "7.1.0",
+                "tailwindcss": "1.2.0",
+                "@babel/cli": "7.8.4",
+                "@babel/core": "7.9.0",
+                "@babel/preset-env": "7.9.5"
+        }
+}`
+
+func TestPackageBuilder(t *testing.T) {
+	c := qt.New(t)
+
+	b := newPackageBuilder("", strings.NewReader(templ))
+	c.Assert(b.Err(), qt.IsNil)
+
+	b.Add("mymod", strings.NewReader(`{
+"dependencies": {
+	 "react-dom": "9.1.1",
+	 "add1": "1.1.1"
+},
+"devDependencies": {
+	 "tailwindcss": "error",
+	 "add2": "2.1.1"
+}	
+}`))
+
+	b.Add("mymod", strings.NewReader(`{
+"dependencies": {
+	 "react-dom": "error",
+	 "add1": "error",
+	 "add3": "3.1.1"
+},
+"devDependencies": {
+	 "tailwindcss": "error",
+	 "add2": "error",
+	 "add4": "4.1.1"
+	 
+}	
+}`))
+
+	c.Assert(b.Err(), qt.IsNil)
+
+	c.Assert(b.dependencies, qt.DeepEquals, map[string]interface{}{
+		"@babel/cli":        "7.8.4",
+		"add1":              "1.1.1",
+		"add3":              "3.1.1",
+		"@babel/core":       "7.9.0",
+		"@babel/preset-env": "7.9.5",
+		"react-dom":         "1.1.1",
+		"tailwindcss":       "1.2.0",
+	})
+
+	c.Assert(b.devDependencies, qt.DeepEquals, map[string]interface{}{
+		"tailwindcss":       "1.2.0",
+		"@babel/cli":        "7.8.4",
+		"@babel/core":       "7.9.0",
+		"add2":              "2.1.1",
+		"add4":              "4.1.1",
+		"@babel/preset-env": "7.9.5",
+		"postcss-cli":       "7.1.0",
+	})
+}