proposal: embed: treat `/` as module's root in `go:embed` directive

[gucio321]

Consider the following code:

//go:embed /example/path
var data embed.FS

f, err := data.Open("example/path/file.txt")

Since fs.ValidPath, sadly Open will not be able to handle this / at the beginning, but it could be treated as module's root (in go:embed directive) and than removed from embed.FS.

• ref: proposal: embed: allow embeding files in a parent directory #58519
• ref: //go:embed <path to file in parent directory> doesn't work #46056
• ref: https://go.googlesource.com/proposal/+/master/design/draft-embed.md

[00z20]

Consider the following code:

//go:embed /example/path
var data embed.FS

f, err := data.Open("example/path/file.txt")

Since fs.ValidPath, sadly Open will not be able to handle this / at the beginning, but it could be treated as module's root (in go:embed directive) and than removed from embed.FS.

• ref: proposal: embed: allow embeding files in a parent directory #58519
• ref: //go:embed <path to file in parent directory> doesn't work #46056
• ref: https://go.googlesource.com/proposal/+/master/design/draft-embed.md

[seankhliao]

what would this resolve to in non module mode?

[gucio321]

thre would be two options imao:

1. as the most common use-case of non-module programms is "scripting", the root dir same as script's root, so equal to .
2. disable this pattern in non-module mode

[rsc]

In general source files are not supposed to depend on where module boundaries are. We want to be able to split a module into two modules without having to go edit every single file in the module. The special meaning for "/" would break that property. It also complicates interpretation by other tools. It would also introduce ambiguity in that

//go:build /foo foo

would have two different foo being embedded, both laying claim to data.Open("foo").

The current limitation of embedded files being required to be in the current package directory or a subdirectory seems acceptable given the complexities we'd be introducing to try to remove it.

[rsc]

This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group

[rsc]

Based on the discussion above, this proposal seems like a likely decline.
— rsc for the proposal review group