Extension is not compatible with an SSH Config `RemoteCommand` option

[ethanndickson]

An SSH config can be written such that all connections to workspaces using the Coder VS Code hostname also run a RemoteCommand when connecting:

# --- START CODER VSCODE example.coder.com ---
Host coder-vscode.example.coder.com--*
  ConnectTimeout 0
  LogLevel ERROR
  ProxyCommand "/path/to/coder ssh [....] %h"
  SetEnv  CODER_SSH_SESSION_TYPE=vscode
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null
# --- END CODER VSCODE example.coder.com ---

Host  coder-vscode.example.coder.com--*
  RequestTTY yes
  RemoteCommand echo "test"; exec /bin/bash -l

This works fine with OpenSSH in /usr/bin/ssh:

$ ssh coder-vscode.example.coder.com--ethan--dev
test
coder@dev $

However, there's a comment on remote.SSH.EnableRemoteCommand that says:

Experimental: Enable using RemoteCommands from ssh config entries. This is only enabled if #remote.SSH.useLocalServer# is enabled as well and the remote you are trying to connect to is not listed under the #remote.SSH.remotePlatform# setting.

(From my, and the customer's, testing, RemoteCommand seems to work regardless of the value of remote.SSH.EnableRemoteCommand.)

What appears to be breaking RemoteCommand is whether the host being connected to has a platform specified in remote.SSH.RemotePlatform.

If I have, in my settings.json:

"remote.SSH.remotePlatform": {"coder-vscode.example.coder.com--ethan--dev":"linux"}

and a RemoteCommand (as above), VS Code fails to connect to the workspace:

Running ssh connection command: ssh -v -T -D 55444 -o ConnectTimeout=1800 coder-vscode.example.coder.com--ethan--dev bash
Cannot execute command-line and remote command.

If I remove that remotePlatform entry, bash is removed from that ssh command string, and you're able to connect, and the RemoteCommand is ran.

However, our VS Code extension creates this remotePlatform entry if it doesn't exist, each time a workspace is connected to:

vscode-coder/src/remote.ts

Lines 445 to 463 in e0adfb8

	// Add the remote platform for this host to bypass a step where VS Code asks
	// the user for the platform.
	let mungedPlatforms = false;
	if (
	!remotePlatforms[parts.host] ||
	remotePlatforms[parts.host] !== agent.operating_system
	) {
	remotePlatforms[parts.host] = agent.operating_system;
	settingsContent = jsonc.applyEdits(
	settingsContent,
	jsonc.modify(
	settingsContent,
	["remote.SSH.remotePlatform"],
	remotePlatforms,
	{},
	),
	);
	mungedPlatforms = true;
	}

This makes it impossible to connect to a workspace via the Coder VS Code extension if a RemoteCommand option is set on the host config.

This issue can be worked around by bypassing the Coder VS Code extension, and instead connecting to workspace.coder in Remote - SSH after having run coder config-ssh, and ensuring there's no entry for workspace.coder in remote.SSH.remotePlatform.