go-layerfs

This is a simple wrapper around multiple fs.FS instances, recursively merging them together dynamically.

If you have two directories, of which one is called examples/upper and the other examples/lower, you can layer upper over lower like this:

import (
	"os"
	"path/filepath"
	"github.com/dschmidt/go-layerfs"
)
upper, _ := filepath.Abs("examples/upper")
lower, _ := filepath.Abs("examples/lower")
fsys := layerfs.New(os.DirFS(upper), os.DirFS(lower))

If examples/upper looks like this

.
├── dir1
│   ├── f11.txt (content: foo)
│   └── f12.txt (content: foo)
├── f1.txt (content: foo)
└── f2.txt (content: foo)

and examples/lower looks like this

.
├── dir1
│   ├── f12.txt (content: bar)
│   └── f13.txt (content: bar)
├── f2.txt (content: bar)
└── f3.txt (content: bar)

then your fsys looks like this:

.
├── dir1
│   ├── f11.txt (content: foo)
│   ├── f12.txt (content: foo)
│   └── f13.txt (content: bar)
├── f1.txt (content: foo)
├── f2.txt (content: foo)
└── f3.txt (content: bar)

Example usage

You can run examples/file_server.go like this:

go run examples/file_server.go

2021/11/17 22:59:22 Listening on :8090...

Then requests via httpie should give you these results:

http GET http://localhost:8090/files
HTTP/1.1 200 OK
Content-Length: 123
Content-Type: text/html; charset=utf-8
Date: Wed, 17 Nov 2021 22:03:21 GMT
Last-Modified: Wed, 17 Nov 2021 21:55:53 GMT

<pre>
<a href="dir1/">dir1/</a>
<a href="f1.txt">f1.txt</a>
<a href="f2.txt">f2.txt</a>
<a href="f3.txt">f3.txt</a>
</pre>

http GET http://localhost:8090/files/f1.txt
HTTP/1.1 200 OK
Accept-Ranges: bytes
Content-Length: 3
Content-Type: text/plain; charset=utf-8
Date: Wed, 17 Nov 2021 22:05:29 GMT
Last-Modified: Wed, 17 Nov 2021 21:56:26 GMT

foo

http GET http://localhost:8090/files/f3.txt
HTTP/1.1 200 OK
Accept-Ranges: bytes
Content-Length: 3
Content-Type: text/plain; charset=utf-8
Date: Wed, 17 Nov 2021 22:05:56 GMT
Last-Modified: Wed, 17 Nov 2021 21:56:30 GMT

bar