Redirection to file doesn't work when snap program invokes another snap program via shell

Hi!

I'm using snap 2.49.1 on Debian 10. The issue is also reproducing on snap 2.49.1 on Ubuntu 20.04 in VirtualBox.

I'm experiencing a very strange bug with, apparently, all programs installed via snap --classic.

If I run program FOO, installed from snapcraft, and it runs a shell, which in turn runs program BAR, also installed from snapcraft, and BAR's output is redirected to a file, I always get zero exit code, but an EMPTY FILE.

If, instead of BAR, FOO runs some non-snap program, it works as expected. If FOO redirects BAR's output to cat's stdin, and redirects cat's stdout to a file, it also works as expected.

Here are some examples with "ruby" from snap:

$ sudo snap install ruby --classic
...

$ cat hello.rb
puts "hello from ruby"

GOOD:
$ /snap/bin/ruby hello.rb > out
$ cat out
hello from ruby

GOOD:
$ /snap/bin/ruby -e 'system("/snap/bin/ruby hello.rb | cat > out")'
$ cat out
hello from ruby

GOOD:
$ /snap/bin/ruby -e 'system("echo hello from shell > out")'
$ cat out
hello from shell

>>>>>>>> BAD <<<<<<<<
$ /snap/bin/ruby -e 'system("/snap/bin/ruby hello.rb > out")'
$ cat out
<nothing>

Here are similar examples with "go: from snap:

$ sudo snap install go --classic
...

$ cat hello.go
package main

import "fmt"

func main() {
    fmt.Println("hello from go")
}

$ cat exec.go
package main

import "syscall"
import "os"

func main() {
    syscall.Exec("/bin/sh", []string{"sh", "-c", os.Args[1]}, os.Environ())
}

GOOD:
$ /snap/bin/go run hello.go > out
$ cat out
hello from go

GOOD:
$ /snap/bin/go run exec.go "/snap/bin/go run hello.go | cat > out"
$ cat out
hello from go

GOOD:
$ /snap/bin/go run exec.go "echo hello from shell > out"
$ cat out
hello from shell

GOOD (non-snap go):
$ /usr/bin/go run exec.go "/usr/bin/go run hello.go > out"
$ cat out
hello from shell

>>>>>>>> BAD <<<<<<<<
$ /snap/bin/go run exec.go "/snap/bin/go run hello.go > out"
$ cat out
<nothing>

Please let me know if I can provide any further information!