Does go:embed embed.FS embeds directories or possible confusion with how it works

[Tajmeet Singh]

Hi there,

I have been testing the (relatively) new go:embed feature for a few days and I came across this situation which I wasn't quite sure what was causing it so I thought asking here would help.

Consider the following code:

```golang

package main

import (

"embed"

"fmt"

"log"

"net/http"

)

//go:embed files/static

var static embed.FS

func main() {

http.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.FS(static))))

log.Fatal(http.ListenAndServe(":8000", nil))

}

```

Now the files in directory files/static are very much accessible but the issue I seem to have is that it was accessible under the url /static/files/static/filename instead of just being accessible through /static/filename where filename exists inside the directory files/static/

I tried looking up some examples online and it seems that I have to use the fs.FS and fs.Sub and only expose (not sure if this is correct terminology) the new fs.Sub which would mitigate the issue I was having.

 

My question is about the reason why the Go team went with this implementation? Because in the above program I wasn't able to access the files in files/ directory even though there were files in it and was only able to access files inside the files/static files directory. So there doesn't seem to be a point in this implementation unless I'm missing something, and I'm sure its the latter case haha. If anyone knows about why they went with this implementation, I would be very grateful.

Best wishes

Taj

[Amnon]

What does

go list -f '{{ .EmbedFiles }}'

display?

[Sean Liao]

`embed` embeds the files with the path you specified, so if you look into your `static` variable, the files will be available as `files/static/yourfile`.

This means there won't be issues with filename collisions etc... if you specify multiple patterns

If you want to serve your files in your `files/static` directory under the `/static/` url, your handler should be : `http.Handle("/static/", http.FileServer(http.FS(static.Sub("files"))))`

That is, for everything under the `/static` url, serve from the embedded filesystem, skipping over the `files/` prefix in the embedded fs.

[Tajmeet Singh]

Ah okay, thanks seank. I was missing the fact that we can embed multiple files by specifying multiple patterns and assign it to a single `embed.FS`. Now it all makes sense. Thanks!

[Shammi Shailaj]

There is no function named Sub() for the variable static of type embed.FS. Hence, the handler: http.Handle("/static/", http.FileServer(http.FS(static. Sub("files")))) shall not work and throw an error like:

static.Sub undefined (type embed.FS has no field or method Sub)

Can anyone provide a solution to this? I am looking for the same

[Ian Lance Taylor]

On Mon, Jan 23, 2023 at 11:51 AM Shammi Shailaj <shammi...@gmail.com> wrote:
>
> There is no function named Sub() for the variable static of type embed.FS. Hence, the handler: http.Handle("/static/", http.FileServer(http.FS(static. Sub("files")))) shall not work and throw an error like:
>
> static.Sub undefined (type embed.FS has no field or method Sub)
>
> Can anyone provide a solution to this? I am looking for the same

Where it says static.Sub it should probably say fs.Sub(static, "files").

Ian

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[Shammi Shailaj]

Thanks Ian.

changing it to 

http.Handle("/static/", http.FileServer(http.FS(fs.Sub(static,"files"))))

did work.