Adding support for Go 1.16's FS interface

[advdv]

Go 1.16 introduces the fs package and a FS interface. Implementing a Jet loader for this seems like an ideal use case. Are there any plans for this, would it be easy?

EDIT: actually, maybe it is as simple as this?

type StdFileSystemLoader struct{ fs.FS }

func (l StdFileSystemLoader) Open(templatePath string) (io.ReadCloser, error) {
	return l.FS.Open(templatePath)
}

func (l StdFileSystemLoader) Exists(templatePath string) bool {
	_, err := l.Open(templatePath)
	return err == nil && !os.IsNotExist(err)
}

[sauerbraten]

Yes, that adapter should be all you need to use 1.16's FS interface!
Let me know if it works, It probably makes sense to have this boilerplate directly in Jet.

[advdv]

I actually just found a way to do this without an extra type by using jets loaders/httpfs package:

//go:embed *.html
var tfs embed.FS

// loader allows for loading templates
func loader() (jet.Loader, error) {
	return httpfs.NewLoader(http.FS(tfs))
}

it is a bit weird to require a "httpfs/http" package for something that just have to deal with filesystems but it works as expected.

[replay111]

@advanderveer How did you pass this func loader to Jet Engine so it is loading files from tfs ?

I have someting like this:
main.go:

//go:embed templates
var assets embed.FS //stored in: Repo.App.TemplatesFS

handlers.go:

var view = jet.NewSet(
	jet.NewOSFileSystemLoader("./templates"),
	jet.InDevelopmentMode(), // remove in production
)

func loader() (jet.Loader, error) {
	return httpfs.NewLoader(http.FS(Repo.App.TemplatesFS))
}

but I have no idea how to link this together :-)

[replay111]

Hello again,

I've tried this way:

var view *jet.Set

func init() {
	httpFsLoader, err := loader()
	if err != nil {
		log.Panicln("error: ", err)
	}
	view = jet.NewSet(
		httpFsLoader,
		jet.InDevelopmentMode(),
	)
}

func loader() (jet.Loader, error) {
	return httpfs.NewLoader(http.FS(Repo.App.TemplatesFS))
}

where Repo.App.TemplatesFS stores:

type ApplicationConfig struct {
	InfoLog       *log.Logger
	ErrorLog      *log.Logger
	InDevelopment bool
	Session       *scs.SessionManager
	TemplatesFS   embed.FS
}

//go:embed templates
var assets embed.FS
var app config.ApplicationConfig

app.TemplatesFS = assets

But compiler does not like this part:

func loader() (jet.Loader, error) {
	return httpfs.NewLoader(http.FS(Repo.App.TemplatesFS))
}

error:
cannot use httpfs.NewLoader(http.FS(Repo.App.TemplatesFS)) (value of type jet.Loader) as jet.Loader value in return statement: wrong type for method Open (have func(templatePath string) (io.ReadCloser, error), want func(templatePath string) (io.ReadCloser, error))compilerInvalidIfaceAssign

but Repo.App.TemplatesFS is embed.FS so it is the same type as in example from @advanderveer

[replay111]

Ok I also found solution for my case:

func InitTemplateSystem(assets embed.FS) *jet.Set {
	httpFsLoader, err := httpfs.NewLoader(http.FS(assets))
	if err != nil {
		log.Panicln("error: ", err)
	}
	return jet.NewSet(httpFsLoader, jet.InDevelopmentMode())
}

the error was caused by wrong import - VSCode is suggesting:

	"github.com/CloudyKit/jet/v6"
	"github.com/CloudyKit/jet/loaders/httpfs"

instead of:

	"github.com/CloudyKit/jet/v6"
	"github.com/CloudyKit/jet/v6/loaders/httpfs"

Now I am calling: app.View = handlers.InitTemplateSystem(web.WebFiles) in my main.go file and initialize once Jet engine. Web files are loaded in "./web/web.go" module:

import "embed"

//go:embed templates
var WebFiles embed.FS

which is on the same level as templates directory.

Maybe not the best solution (because of passing Jet engine to app config - which I do not like very much for now) but for the beginning I think it is ok. When I learn more then problably will change that to maybe something more sophisticated.