cmd/go: go:embed fails with special characters in module parent directory

[ryanjoneil]

What version of Go are you using (go version)?

$ go version
go version go1.18.3 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOVERSION="go1.18.3"

What did you do?

I have a simple file structure for a main package under a directory foo.

% tree foo
foo
└── example
    ├── baz.txt
    ├── go.mod
    └── main.go

go.mod is just the model name and Go version.

module example

go 1.18

The main.go embeds baz.txt and prints its contents.

package main

import (
	_ "embed"
	"fmt"
)

//go:embed baz.txt
var baz string

func main() {
	fmt.Println(baz)
}

baz.txt contains a simple string,

xyzzy

This works as expected.

% cd foo/example/
example % go build
example % ./example 
xyzzy

If I change the parent directory of the module from foo to [foo], go build cannot find baz.txt.

example % cd ../../
% mv foo '[foo]'
% cd \[foo\]/example 
example % go build
main.go:8:12: pattern baz.txt: no matching files found

What did you expect to see?

I expected the same behavior in both cases (go build succeeding).

What did you see instead?

go build cannot resolve the embed if a parent directory of the module contains square brackets. It doesn't seem like this should matter, since it is outside the module itself and is a valid directory name.

[cherrymui]

There may be a restriction on the file path. But I couldn't find the documentation.

cc @rsc @bcmills

[gopherbot]

Change https://go.dev/cl/411696 mentions this issue: cmd/go: quote package directory when calling glob