Add Hugo Modules

This commit implements Hugo Modules.

This is a broad subject, but some keywords include:

* A new `module` configuration section where you can import almost anything. You can configure both your own file mounts nd the file mounts of the modules you import. This is the new recommended way of configuring what you earlier put in `configDir`, `staticDir` etc. And it also allows you to mount folders in non-Hugo-projects, e.g. the `SCSS` folder in the Bootstrap GitHub project.
* A module consists of a set of mounts to the standard 7 component types in Hugo: `static`, `content`, `layouts`, `data`, `assets`, `i18n`, and `archetypes`. Yes, Theme Components can now include content, which should be very useful, especially in bigger multilingual projects.
* Modules not in your local file cache will be downloaded automatically and even "hot replaced" while the server is running.
* Hugo Modules supports and encourages semver versioned modules, and uses the minimal version selection algorithm to resolve versions.
* A new set of CLI commands are provided to manage all of this: `hugo mod init`,  `hugo mod get`,  `hugo mod graph`,  `hugo mod tidy`, and  `hugo mod vendor`.

All of the above is backed by Go Modules.

Fixes #5973
Fixes #5996
Fixes #6010
Fixes #5911
Fixes #5940
Fixes #6074
Fixes #6082
Fixes #6092

5 files changed, 141 insertions, 152 deletions

diff --git a/source/fileInfo.go b/source/fileInfo.go
index 072b55b6c..a4cbf6fe6 100644
--- a/source/fileInfo.go
+++ b/source/fileInfo.go
@@ -14,11 +14,14 @@
 package source
 
 import (
-	"os"
 	"path/filepath"
 	"strings"
 	"sync"
 
+	"github.com/gohugoio/hugo/hugofs/files"
+
+	"github.com/pkg/errors"
+
 	"github.com/gohugoio/hugo/common/hugio"
 
 	"github.com/gohugoio/hugo/hugofs"
@@ -28,8 +31,7 @@ import (
 
 // fileInfo implements the File interface.
 var (
-	_ File         = (*FileInfo)(nil)
-	_ ReadableFile = (*FileInfo)(nil)
+	_ File = (*FileInfo)(nil)
 )
 
 // File represents a source file.
@@ -90,13 +92,7 @@ type FileWithoutOverlap interface {
 	// Hugo content files being one of them, considered to be unique.
 	UniqueID() string
 
-	FileInfo() os.FileInfo
-}
-
-// A ReadableFile is a File that is readable.
-type ReadableFile interface {
-	File
-	Open() (hugio.ReadSeekCloser, error)
+	FileInfo() hugofs.FileMetaInfo
 }
 
 // FileInfo describes a source file.
@@ -107,7 +103,7 @@ type FileInfo struct {
 
 	sp *SourceSpec
 
-	fi os.FileInfo
+	fi hugofs.FileMetaInfo
 
 	// Derived from filename
 	ext  string // Extension without any "."
@@ -179,13 +175,14 @@ func (fi *FileInfo) UniqueID() string {
 }
 
 // FileInfo returns a file's underlying os.FileInfo.
-func (fi *FileInfo) FileInfo() os.FileInfo { return fi.fi }
+func (fi *FileInfo) FileInfo() hugofs.FileMetaInfo { return fi.fi }
 
 func (fi *FileInfo) String() string { return fi.BaseFileName() }
 
 // Open implements ReadableFile.
 func (fi *FileInfo) Open() (hugio.ReadSeekCloser, error) {
-	f, err := fi.sp.SourceFs.Open(fi.Filename())
+	f, err := fi.fi.Meta().Open()
+
 	return f, err
 }
 
@@ -225,38 +222,45 @@ func NewTestFile(filename string) *FileInfo {
 	}
 }
 
-// NewFileInfo returns a new FileInfo structure.
-func (sp *SourceSpec) NewFileInfo(baseDir, filename string, isLeafBundle bool, fi os.FileInfo) *FileInfo {
+func (sp *SourceSpec) NewFileInfoFrom(path, filename string) (*FileInfo, error) {
+	meta := hugofs.FileMeta{
+		"filename": filename,
+		"path":     path,
+	}
 
-	var lang, translationBaseName, relPath string
+	return sp.NewFileInfo(hugofs.NewFileMetaInfo(nil, meta))
+}
 
-	if fp, ok := fi.(hugofs.FilePather); ok {
-		filename = fp.Filename()
-		baseDir = fp.BaseDir()
-		relPath = fp.Path()
-	}
+func (sp *SourceSpec) NewFileInfo(fi hugofs.FileMetaInfo) (*FileInfo, error) {
 
-	if fl, ok := fi.(hugofs.LanguageAnnouncer); ok {
-		lang = fl.Lang()
-		translationBaseName = fl.TranslationBaseName()
-	}
+	m := fi.Meta()
 
-	dir, name := filepath.Split(filename)
-	if !strings.HasSuffix(dir, helpers.FilePathSeparator) {
-		dir = dir + helpers.FilePathSeparator
+	filename := m.Filename()
+	relPath := m.Path()
+	isLeafBundle := m.Classifier() == files.ContentClassLeaf
+
+	if relPath == "" || strings.Contains(relPath, "TODO") {
+		return nil, errors.Errorf("no Path provided by %v (%T)", m, m.Fs())
 	}
 
-	baseDir = strings.TrimSuffix(baseDir, helpers.FilePathSeparator)
+	if filename == "" || strings.Contains(filename, "TODO") {
+		return nil, errors.Errorf("no Filename provided by %v (%T)", m, m.Fs())
+	}
 
-	relDir := ""
-	if dir != baseDir {
-		relDir = strings.TrimPrefix(dir, baseDir)
+	relDir := filepath.Dir(relPath)
+	if relDir == "." {
+		relDir = ""
+	}
+	if !strings.HasSuffix(relDir, helpers.FilePathSeparator) {
+		relDir = relDir + helpers.FilePathSeparator
 	}
 
-	relDir = strings.TrimPrefix(relDir, helpers.FilePathSeparator)
+	lang := m.Lang()
+	translationBaseName := m.GetString("translationBaseName")
 
-	if relPath == "" {
-		relPath = filepath.Join(relDir, name)
+	dir, name := filepath.Split(relPath)
+	if !strings.HasSuffix(dir, helpers.FilePathSeparator) {
+		dir = dir + helpers.FilePathSeparator
 	}
 
 	ext := strings.ToLower(strings.TrimPrefix(filepath.Ext(name), "."))
@@ -277,14 +281,14 @@ func (sp *SourceSpec) NewFileInfo(baseDir, filename string, isLeafBundle bool, f
 		lang:                lang,
 		ext:                 ext,
 		dir:                 dir,
-		relDir:              relDir,
-		relPath:             relPath,
+		relDir:              relDir,  // Dir()
+		relPath:             relPath, // Path()
 		name:                name,
-		baseName:            baseName,
+		baseName:            baseName, // BaseFileName()
 		translationBaseName: translationBaseName,
 		isLeafBundle:        isLeafBundle,
 	}
 
-	return f
+	return f, nil
 
 }
diff --git a/source/fileInfo_test.go b/source/fileInfo_test.go
index 9390c6247..0c024de18 100644
--- a/source/fileInfo_test.go
+++ b/source/fileInfo_test.go
@@ -15,12 +15,9 @@ package source
 
 import (
 	"path/filepath"
+	"strings"
 	"testing"
 
-	"github.com/gohugoio/hugo/helpers"
-
-	"github.com/gohugoio/hugo/hugofs"
-	"github.com/spf13/afero"
 	"github.com/stretchr/testify/require"
 )
 
@@ -55,56 +52,10 @@ func TestFileInfo(t *testing.T) {
 
 		}},
 	} {
-		f := s.NewFileInfo(this.base, this.filename, false, nil)
+		path := strings.TrimPrefix(this.filename, this.base)
+		f, err := s.NewFileInfoFrom(path, this.filename)
+		assert.NoError(err)
 		this.assert(f)
 	}
 
 }
-
-func TestFileInfoLanguage(t *testing.T) {
-	assert := require.New(t)
-	langs := map[string]bool{
-		"sv": true,
-		"en": true,
-	}
-
-	m := afero.NewMemMapFs()
-	lfs := hugofs.NewLanguageFs("sv", langs, m)
-	v := newTestConfig()
-
-	fs := hugofs.NewFrom(m, v)
-
-	ps, err := helpers.NewPathSpec(fs, v)
-	assert.NoError(err)
-	s := SourceSpec{SourceFs: lfs, PathSpec: ps}
-	s.Languages = map[string]interface{}{
-		"en": true,
-	}
-
-	err = afero.WriteFile(lfs, "page.md", []byte("abc"), 0777)
-	assert.NoError(err)
-	err = afero.WriteFile(lfs, "page.en.md", []byte("abc"), 0777)
-	assert.NoError(err)
-
-	sv, _ := lfs.Stat("page.md")
-	en, _ := lfs.Stat("page.en.md")
-
-	fiSv := s.NewFileInfo("", "page.md", false, sv)
-	fiEn := s.NewFileInfo("", "page.en.md", false, en)
-
-	assert.Equal("sv", fiSv.Lang())
-	assert.Equal("en", fiEn.Lang())
-
-	// test contentBaseName implementation
-	fi := s.NewFileInfo("", "2018-10-01-contentbasename.md", false, nil)
-	assert.Equal("2018-10-01-contentbasename", fi.ContentBaseName())
-
-	fi = s.NewFileInfo("", "2018-10-01-contentbasename.en.md", false, nil)
-	assert.Equal("2018-10-01-contentbasename", fi.ContentBaseName())
-
-	fi = s.NewFileInfo("", filepath.Join("2018-10-01-contentbasename", "index.en.md"), true, nil)
-	assert.Equal("2018-10-01-contentbasename", fi.ContentBaseName())
-
-	fi = s.NewFileInfo("", filepath.Join("2018-10-01-contentbasename", "_index.en.md"), false, nil)
-	assert.Equal("_index", fi.ContentBaseName())
-}
diff --git a/source/filesystem.go b/source/filesystem.go
index 0c1a6ac7b..ce62c15a4 100644
--- a/source/filesystem.go
+++ b/source/filesystem.go
@@ -14,29 +14,25 @@
 package source
 
 import (
-	"os"
 	"path/filepath"
-	"runtime"
 	"sync"
 
-	"github.com/gohugoio/hugo/helpers"
-	jww "github.com/spf13/jwalterweatherman"
-	"golang.org/x/text/unicode/norm"
+	"github.com/pkg/errors"
+
+	"github.com/gohugoio/hugo/hugofs"
 )
 
 // Filesystem represents a source filesystem.
 type Filesystem struct {
-	files     []ReadableFile
-	filesInit sync.Once
+	files        []File
+	filesInit    sync.Once
+	filesInitErr error
 
 	Base string
 
-	SourceSpec
-}
+	fi hugofs.FileMetaInfo
 
-// Input describes a source input.
-type Input interface {
-	Files() []ReadableFile
+	SourceSpec
 }
 
 // NewFilesystem returns a new filesytem for a given source spec.
@@ -44,76 +40,74 @@ func (sp SourceSpec) NewFilesystem(base string) *Filesystem {
 	return &Filesystem{SourceSpec: sp, Base: base}
 }
 
+func (sp SourceSpec) NewFilesystemFromFileMetaInfo(fi hugofs.FileMetaInfo) *Filesystem {
+	return &Filesystem{SourceSpec: sp, fi: fi}
+}
+
 // Files returns a slice of readable files.
-func (f *Filesystem) Files() []ReadableFile {
+func (f *Filesystem) Files() ([]File, error) {
 	f.filesInit.Do(func() {
-		f.captureFiles()
+		err := f.captureFiles()
+		if err != nil {
+			f.filesInitErr = errors.Wrap(err, "capture files")
+		}
 	})
-	return f.files
+	return f.files, f.filesInitErr
 }
 
 // add populates a file in the Filesystem.files
-func (f *Filesystem) add(name string, fi os.FileInfo) (err error) {
-	var file ReadableFile
+func (f *Filesystem) add(name string, fi hugofs.FileMetaInfo) (err error) {
+	var file File
 
-	if runtime.GOOS == "darwin" {
-		// When a file system is HFS+, its filepath is in NFD form.
-		name = norm.NFC.String(name)
+	file, err = f.SourceSpec.NewFileInfo(fi)
+	if err != nil {
+		return err
 	}
 
-	file = f.SourceSpec.NewFileInfo(f.Base, name, false, fi)
 	f.files = append(f.files, file)
 
 	return err
 }
 
-func (f *Filesystem) captureFiles() {
-	walker := func(filePath string, fi os.FileInfo, err error) error {
+func (f *Filesystem) captureFiles() error {
+	walker := func(path string, fi hugofs.FileMetaInfo, err error) error {
 		if err != nil {
+			return err
+		}
+
+		if fi.IsDir() {
 			return nil
 		}
 
-		b, err := f.shouldRead(filePath, fi)
+		meta := fi.Meta()
+		filename := meta.Filename()
+
+		b, err := f.shouldRead(filename, fi)
 		if err != nil {
 			return err
 		}
+
 		if b {
-			f.add(filePath, fi)
+			err = f.add(filename, fi)
 		}
+
 		return err
 	}
 
-	if f.SourceFs == nil {
-		panic("Must have a fs")
-	}
-	err := helpers.SymbolicWalk(f.SourceFs, f.Base, walker)
+	w := hugofs.NewWalkway(hugofs.WalkwayConfig{
+		Fs:     f.SourceFs,
+		Info:   f.fi,
+		Root:   f.Base,
+		WalkFn: walker,
+	})
 
-	if err != nil {
-		jww.ERROR.Println(err)
-	}
+	return w.Walk()
 
 }
 
-func (f *Filesystem) shouldRead(filename string, fi os.FileInfo) (bool, error) {
-	if fi.Mode()&os.ModeSymlink == os.ModeSymlink {
-		link, err := filepath.EvalSymlinks(filename)
-		if err != nil {
-			jww.ERROR.Printf("Cannot read symbolic link '%s', error was: %s", filename, err)
-			return false, nil
-		}
-		linkfi, err := f.SourceFs.Stat(link)
-		if err != nil {
-			jww.ERROR.Printf("Cannot stat '%s', error was: %s", link, err)
-			return false, nil
-		}
-
-		if !linkfi.Mode().IsRegular() {
-			jww.ERROR.Printf("Symbolic links for directories not supported, skipping '%s'", filename)
-		}
-		return false, nil
-	}
+func (f *Filesystem) shouldRead(filename string, fi hugofs.FileMetaInfo) (bool, error) {
 
-	ignore := f.SourceSpec.IgnoreFile(filename)
+	ignore := f.SourceSpec.IgnoreFile(fi.Meta().Filename())
 
 	if fi.IsDir() {
 		if ignore {
diff --git a/source/filesystem_test.go b/source/filesystem_test.go
index 8c8e30413..33007c7e4 100644
--- a/source/filesystem_test.go
+++ b/source/filesystem_test.go
@@ -14,20 +14,31 @@
 package source
 
 import (
-	"os"
+	"fmt"
+	"path/filepath"
 	"runtime"
 	"testing"
 
+	"github.com/gohugoio/hugo/modules"
+
+	"github.com/gohugoio/hugo/langs"
+
+	"github.com/spf13/afero"
+
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/gohugoio/hugo/hugofs"
+	"github.com/stretchr/testify/require"
 
 	"github.com/spf13/viper"
 )
 
 func TestEmptySourceFilesystem(t *testing.T) {
+	assert := require.New(t)
 	ss := newTestSourceSpec()
-	src := ss.NewFilesystem("Empty")
-	if len(src.Files()) != 0 {
+	src := ss.NewFilesystem("")
+	files, err := src.Files()
+	assert.NoError(err)
+	if len(files) != 0 {
 		t.Errorf("new filesystem should contain 0 files.")
 	}
 }
@@ -38,6 +49,8 @@ func TestUnicodeNorm(t *testing.T) {
 		return
 	}
 
+	assert := require.New(t)
+
 	paths := []struct {
 		NFC string
 		NFD string
@@ -47,14 +60,18 @@ func TestUnicodeNorm(t *testing.T) {
 	}
 
 	ss := newTestSourceSpec()
-	var fi os.FileInfo
+	fi := hugofs.NewFileMetaInfo(nil, hugofs.FileMeta{})
 
-	for _, path := range paths {
-		src := ss.NewFilesystem("base")
+	for i, path := range paths {
+		base := fmt.Sprintf("base%d", i)
+		assert.NoError(afero.WriteFile(ss.Fs.Source, filepath.Join(base, path.NFD), []byte("some data"), 0777))
+		src := ss.NewFilesystem(base)
 		_ = src.add(path.NFD, fi)
-		f := src.Files()[0]
+		files, err := src.Files()
+		assert.NoError(err)
+		f := files[0]
 		if f.BaseFileName() != path.NFC {
-			t.Fatalf("file name in NFD form should be normalized (%s)", path.NFC)
+			t.Fatalf("file %q name in NFD form should be normalized (%s)", f.BaseFileName(), path.NFC)
 		}
 	}
 
@@ -70,12 +87,22 @@ func newTestConfig() *viper.Viper {
 	v.Set("resourceDir", "resources")
 	v.Set("publishDir", "public")
 	v.Set("assetDir", "assets")
+	_, err := langs.LoadLanguageSettings(v, nil)
+	if err != nil {
+		panic(err)
+	}
+	mod, err := modules.CreateProjectModule(v)
+	if err != nil {
+		panic(err)
+	}
+	v.Set("allModules", modules.Modules{mod})
+
 	return v
 }
 
 func newTestSourceSpec() *SourceSpec {
 	v := newTestConfig()
-	fs := hugofs.NewMem(v)
+	fs := hugofs.NewFrom(hugofs.NewBaseFileDecorator(afero.NewMemMapFs()), v)
 	ps, err := helpers.NewPathSpec(fs, v)
 	if err != nil {
 		panic(err)
diff --git a/source/sourceSpec.go b/source/sourceSpec.go
index 9731a8d8d..504a3a22d 100644
--- a/source/sourceSpec.go
+++ b/source/sourceSpec.go
@@ -17,6 +17,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"runtime"
 
 	"github.com/gohugoio/hugo/langs"
 	"github.com/spf13/afero"
@@ -107,6 +108,18 @@ func (s *SourceSpec) IgnoreFile(filename string) bool {
 		}
 	}
 
+	if runtime.GOOS == "windows" {
+		// Also check the forward slash variant if different.
+		unixFilename := filepath.ToSlash(filename)
+		if unixFilename != filename {
+			for _, re := range s.ignoreFilesRe {
+				if re.MatchString(unixFilename) {
+					return true
+				}
+			}
+		}
+	}
+
 	return false
 }