all: Refactor to nonglobal file systems

Updates #2701
Fixes #2951

deps/deps.go

@@ -0,0 +1,115 @@
+package deps
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+
+	"github.com/spf13/hugo/helpers"
+	"github.com/spf13/hugo/hugofs"
+	"github.com/spf13/hugo/tplapi"
+	jww "github.com/spf13/jwalterweatherman"
+)
+
+// Deps holds dependencies used by many.
+// There will be normally be only one instance of deps in play
+// at a given time, i.e. one per Site built.
+type Deps struct {
+	// The logger to use.
+	Log *jww.Notepad `json:"-"`
+
+	// The templates to use.
+	Tmpl tplapi.Template `json:"-"`
+
+	// The file systems to use.
+	Fs *hugofs.Fs `json:"-"`
+
+	// The PathSpec to use
+	*helpers.PathSpec `json:"-"`
+
+	templateProvider TemplateProvider
+	WithTemplate     func(templ tplapi.Template) error
+
+	// TODO(bep) globals next in line: Viper
+
+}
+
+// Used to create and refresh, and clone the template.
+type TemplateProvider interface {
+	Update(deps *Deps) error
+	Clone(deps *Deps) error
+}
+
+func (d *Deps) LoadTemplates() error {
+	if err := d.templateProvider.Update(d); err != nil {
+		return err
+	}
+	d.Tmpl.PrintErrors()
+	return nil
+}
+
+func New(cfg DepsCfg) *Deps {
+	var (
+		logger = cfg.Logger
+		fs     = cfg.Fs
+	)
+
+	if cfg.TemplateProvider == nil {
+		panic("Must have a TemplateProvider")
+	}
+
+	if cfg.Language == nil {
+		panic("Must have a Language")
+	}
+
+	if logger == nil {
+		logger = jww.NewNotepad(jww.LevelError, jww.LevelError, os.Stdout, ioutil.Discard, "", log.Ldate|log.Ltime)
+	}
+
+	if fs == nil {
+		// Default to the most used file systems.
+		fs = hugofs.NewMem()
+	}
+
+	d := &Deps{
+		Fs:               fs,
+		Log:              logger,
+		templateProvider: cfg.TemplateProvider,
+		WithTemplate:     cfg.WithTemplate,
+		PathSpec:         helpers.NewPathSpec(fs, cfg.Language),
+	}
+
+	return d
+}
+
+// ForLanguage creates a copy of the Deps with the language dependent
+// parts switched out.
+func (d Deps) ForLanguage(l *helpers.Language) (*Deps, error) {
+
+	d.PathSpec = helpers.NewPathSpec(d.Fs, l)
+	if err := d.templateProvider.Clone(&d); err != nil {
+		return nil, err
+	}
+
+	return &d, nil
+
+}
+
+// DepsCfg contains configuration options that can be used to configure Hugo
+// on a global level, i.e. logging etc.
+// Nil values will be given default values.
+type DepsCfg struct {
+
+	// The Logger to use.
+	Logger *jww.Notepad
+
+	// The file systems to use
+	Fs *hugofs.Fs
+
+	// The language to use.
+	Language *helpers.Language
+
+	// Template handling.
+	TemplateProvider TemplateProvider
+	WithTemplate     func(templ tplapi.Template) error
+}