run() command fails if environment variable value contains an ampersand (&)

[dtenenba]

ETA: I've been able to pass an environment variable with a & in it in Invoke and paramiko, so it does seem like a Fabric issue.

Describe the bug

run() on a connection fails if you pass an environment variable (with the env= argument) whose value contains an ampersand (&).

To Reproduce
Steps to reproduce the behaviour (please attach a minimal example):

Run this. Change the hostname, username (if necessary) and key or password:

#!/usr/bin/env python3

import fabric

# TODO - edit this to match your system
conn = fabric.Connection('my.host.name', user="root", connect_kwargs={"key_filename": "ssh_key"})  

env = {"FOO": "has an ampersand & iamnotacommand blah"}

try:
    conn.run("hostname", env=env)
except Exception as e:
     print(e)

Prints out this:

bash: iamnotacommand: command not found
Encountered a bad command exit code!

Command: 'hostname'

Exit code: 127

Stdout: already printed

Stderr: already printed

Remove the & and it works fine.

Expected behaviour

It should print out the hostname.

Environment

• What version of the Python interpreter are you using? Are you using an
  alternative interpreter such as PyPy?

Python 3.12.0 (main, Nov 21 2023, 17:38:35) [GCC 12.2.0] on linux

• What operating system are you using both client & server-side?

Client:

PRETTY_NAME="Debian GNU/Linux 12 (bookworm)"
NAME="Debian GNU/Linux"
VERSION_ID="12"
VERSION="12 (bookworm)"
VERSION_CODENAME=bookworm
ID=debian

Server:

DISTRIB_DESCRIPTION="Ubuntu 18.04.6 LTS"
NAME="Ubuntu"
VERSION="18.04.6 LTS (Bionic Beaver)"

• Are you using OpenSSH server or something else?

yes

• Which version or versions of the software are you using?

3.2.2

• Have you already tried the latest release?

yes

• Have you, or can you, try some older releases to pin down where the bug
  appeared?

I have not

• How can the developers recreate the bug on their end? If possible, include a
  copy of your code, the command you used to invoke it, and the full output of
  your run (if applicable.)

see above

• A common tactic is to pare down your code until a simple (but still
  bug-causing) “base case” remains. Not only can this help you identify
  problems which aren’t real bugs, but it means the developer can get to fixing
  the bug faster.

see above

[auioe]

Add parameter inline_ssh_env=False while initializing your connection. Or fabric only add a simple export command in front of hostname command.

[dtenenba]

When I set inline_ssh_env=False I don't get an error, but the variable is not set in the remote shell.
This works, but only when inline_ssh_env=False:

conn.run("export 'FOO=b&ar' && echo $FOO")

This still seems like a bug and your suggestion is a workaround.
Thanks.