Asset Etag is useless and invalid

[AtomicNibble]

The ETag sent back for assets (js,img,..) changes for every response making it useless.

https://github.com/gobuffalo/buffalo/blob/0ffd608c63439be1fc033ad7e48430528c96d2bc/route_mappings.go#L111-L115

This is because packd just returns the time you opened the file.
https://github.com/gobuffalo/packd/blob/128b5da43f114d0f9af8b4bba549b02e3496dfa8/file.go#L115

The ETag is also of invalid format and should be quoted as per RFC https://tools.ietf.org/html/rfc7232#section-2.3

Suggest the ETag is just removed as the info to make a sensible ETag is not avaliable and a very long max-age is already sent back.

[paganotoni]

Hey @AtomicNibble 👋, Thanks for reporting this. This seems only to happen in development mode due to a packr issue. I confirmed that this does not happen on compiled binaries where I see the ETag persist across requests .

[paganotoni]

I'm moving this one to the packr repository.

[AtomicNibble]

Thanks for investigating, does that mean the ETag will change after every deploy tho?

[paganotoni]

That's a good question. I think you're right. Here is what I did to prove it:

buffalo build -o bin/app # builds the app
bin/app # starts the app

# Requesting asset
curl -s -o /dev/null -D - http://localhost:3000/assets/application.463d2be36c4e069c72b5.css
HTTP/1.1 200 OK
Accept-Ranges: bytes
Cache-Control: max-age=31536000
Content-Length: 443539
Content-Type: text/css; charset=utf-8
Etag: 16120c74bb30a368
Last-Modified: Sun, 24 May 2020 19:08:33 GMT
Date: Sun, 24 May 2020 19:08:33 GMT

buffalo build -o bin/app # builds the app
bin/app # starts the app

curl -s -o /dev/null -D - http://localhost:3000/assets/application.463d2be36c4e069c72b5.css
HTTP/1.1 200 OK
Accept-Ranges: bytes
Cache-Control: max-age=31536000
Content-Length: 443539
Content-Type: text/css; charset=utf-8
Etag: 16120c9736764ce0
Last-Modified: Sun, 24 May 2020 19:11:02 GMT
Date: Sun, 24 May 2020 19:11:02 GMT

Notice how Etag changes without any modification to the file. I think Packr is using the compilation time as the last modification time of the file.