nixos/tests: Test that Remote SSH can patch Node

nixos/tests/all-tests.nix

···
   victoriametrics = handleTest ./victoriametrics.nix {};
   vikunja = handleTest ./vikunja.nix {};
   virtualbox = handleTestOn ["x86_64-linux"] ./virtualbox.nix {};
+  vscode-remote-ssh = handleTestOn ["x86_64-linux"] ./vscode-remote-ssh.nix {};
   vscodium = discoverTests (import ./vscodium.nix);
   vsftpd = handleTest ./vsftpd.nix {};
   warzone2100 = handleTest ./warzone2100.nix {};

nixos/tests/vscode-remote-ssh.nix

···
+import ./make-test-python.nix ({ lib, ... }: let
+  pkgs = (import ../..) {
+    config.allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) [
+      "vscode" "vscode-with-extensions" "vscode-extension-ms-vscode-remote-remote-ssh"
+    ];
+  };
+
+  inherit (import ./ssh-keys.nix pkgs) snakeOilPrivateKey snakeOilPublicKey;
+
+  # Every VS Code server build corresponds to a specific commit of VS Code, so we
+  # want this to match the commit of VS Code in Nixpkgs.
+  # e.g. git rev-parse 1.77.0
+  rev = "7f329fe6c66b0f86ae1574c2911b681ad5a45d63";
+  shortRev = builtins.substring 0 8 rev;
+
+  # Our tests run without networking so the remote-ssh extension will always fail to
+  # download the VSCode server so we can copy it onto the server ourselves.
+  vscode-server = pkgs.srcOnly {
+    name = "vscode-server-${shortRev}";
+    src = pkgs.fetchurl {
+      name = "vscode-server-${shortRev}.tar.gz";
+      url = "https://update.code.visualstudio.com/commit:${rev}/server-linux-x64/stable";
+      sha256 = "11g234lwl3jn5q3637n9sxz5ghhzqvq137lk42vl2nbb57hgyqgq";
+    };
+  };
+in {
+  name = "vscode-remote-ssh";
+  meta.maintainers = with lib.maintainers; [ Enzime ];
+
+  nodes = let
+    serverAddress = "192.168.0.2";
+    clientAddress = "192.168.0.1";
+  in {
+    server = { ... }: {
+      networking.interfaces.eth1.ipv4.addresses = [ { address = serverAddress; prefixLength = 24; } ];
+      services.openssh.enable = true;
+      users.users.root.openssh.authorizedKeys.keys = [ snakeOilPublicKey ];
+      virtualisation.additionalPaths = [ pkgs.nodejs-14_x pkgs.nodejs-16_x ];
+    };
+    client = { ... }: {
+      imports = [ ./common/x11.nix ./common/user-account.nix ];
+      networking.interfaces.eth1.ipv4.addresses = [ { address = clientAddress; prefixLength = 24; } ];
+      networking.hosts.${serverAddress} = [ "server" ];
+      test-support.displayManager.auto.user = "alice";
+      environment.systemPackages = [
+        (pkgs.vscode-with-extensions.override {
+          vscodeExtensions = [
+            pkgs.vscode-extensions.ms-vscode-remote.remote-ssh
+          ];
+        })
+      ];
+    };
+  };
+
+  enableOCR = true;
+
+  testScript = let
+    jq = "${pkgs.jq}/bin/jq";
+
+    ssh-config = builtins.toFile "ssh.conf" ''
+      UserKnownHostsFile=/dev/null
+      StrictHostKeyChecking=no
+    '';
+
+    vscode-config = builtins.toFile "settings.json" ''
+      {
+        "window.zoomLevel": 1,
+        "security.workspace.trust.startupPrompt": "always"
+      }
+    '';
+  in ''
+    def connect_with_remote_ssh(screenshot, should_succeed):
+      print(f"connect_with_remote_ssh({screenshot=}, {should_succeed=})")
+
+      if server.execute("test -d ~/.vscode-server")[0] == 0:
+        server.succeed("rm -r ~/.vscode-server")
+
+      server.succeed("mkdir -p ~/.vscode-server/bin")
+      server.succeed("cp -r ${vscode-server} ~/.vscode-server/bin/${rev}")
+
+      client.succeed("sudo -u alice code --remote=ssh-remote+root@server /root")
+      client.wait_for_window("Visual Studio Code")
+
+      client.wait_for_text("Do you trust the authors" if should_succeed else "Disconnected from SSH")
+      client.screenshot(screenshot)
+
+      if should_succeed:
+        # Press the Don't Trust button
+        client.send_key("tab")
+        client.send_key("tab")
+        client.send_key("tab")
+        client.send_key("\n")
+      else:
+        # Close the error dialog
+        client.send_key("esc")
+
+      client.send_key("ctrl-q")
+      client.wait_until_fails("pidof code")
+
+
+    start_all()
+    server.wait_for_open_port(22)
+
+    VSCODE_COMMIT = server.execute("${jq} -r .commit ${pkgs.vscode}/lib/vscode/resources/app/product.json")[1].rstrip()
+    SERVER_COMMIT = server.execute("${jq} -r .commit ${vscode-server}/product.json")[1].rstrip()
+
+    print(f"{VSCODE_COMMIT=} {SERVER_COMMIT=}")
+    assert VSCODE_COMMIT == SERVER_COMMIT, "VSCODE_COMMIT and SERVER_COMMIT do not match"
+
+    client.wait_until_succeeds("ping -c1 server")
+    client.succeed("sudo -u alice mkdir ~alice/.ssh")
+    client.succeed("sudo -u alice install -Dm 600 ${snakeOilPrivateKey} ~alice/.ssh/id_ecdsa")
+    client.succeed("sudo -u alice install ${ssh-config} ~alice/.ssh/config")
+    client.succeed("sudo -u alice install -Dm 644 ${vscode-config} ~alice/.config/Code/User/settings.json")
+
+    client.wait_for_x()
+    client.wait_for_file("~alice/.Xauthority")
+    client.succeed("xauth merge ~alice/.Xauthority")
+    # Move the mouse out of the way
+    client.succeed("${pkgs.xdotool}/bin/xdotool mousemove 0 0")
+
+    with subtest("fails to connect when Node is broken"):
+      server.fail("node -v")
+      connect_with_remote_ssh(screenshot="no_node_installed", should_succeed=False)
+      server.succeed("test -e ~/.vscode-server/bin/*/node")
+      server.fail("~/.vscode-server/bin/*/node -v")
+
+    with subtest("fails to connect when server has the wrong Node installed"):
+      server.succeed("nix-env -i ${pkgs.nodejs-14_x}")
+      connect_with_remote_ssh(screenshot="wrong_node_installed", should_succeed=False)
+      server.fail("~/.vscode-server/bin/*/node -v")
+
+    with subtest("connects when server has the correct Node installed"):
+      server.succeed("nix-env -i ${pkgs.nodejs-16_x}")
+      connect_with_remote_ssh(screenshot="correct_node_installed", should_succeed=True)
+      server.succeed("~/.vscode-server/bin/*/node -v")
+      server.succeed("kill $(pgrep -f [v]scode-server)")
+      server.succeed("nix-env -e nodejs")
+
+    with subtest("connects when server can build Node from Nixpkgs"):
+      server.succeed("mkdir -p /nix/var/nix/profiles/per-user/root/channels")
+      server.succeed("ln -s ${pkgs.path} /nix/var/nix/profiles/per-user/root/channels/nixos")
+      connect_with_remote_ssh(screenshot="build_node_with_nix", should_succeed=True)
+  '';
+})

pkgs/applications/editors/vscode/extensions/ms-vscode-remote.remote-ssh/default.nix

···
 { lib
+, nixosTests
 , vscode-utils
 , useLocalExtensions ? false
 }:
···
     substituteInPlace "out/extension.js" \
       --replace '# Start the server\n' '${patch}'
   '';
+
+  passthru.tests = { inherit (nixosTests) vscode-remote-ssh; };
 
   meta = {
     description = "Use any remote machine with a SSH server as your development environment.";

pkgs/applications/editors/vscode/vscode.nix

···
-{ stdenv, lib, callPackage, fetchurl
+{ stdenv
+, lib
+, callPackage
+, fetchurl
+, nixosTests
 , isInsiders ? false
 , commandLineArgs ? ""
 , useVSCodeRipgrep ? stdenv.isDarwin
···
     tests = {};
 
     sourceRoot = "";
+
+    tests = { inherit (nixosTests) vscode-remote-ssh; };
 
     updateScript = ./update-vscode.sh;
 

pkgs/build-support/src-only/default.nix

···
 { stdenv }:
 # srcOnly is a utility builder that only fetches and unpacks the given `src`,
-# maybe pathings it in the process with the optional `patches` and
-# `buildInputs` attributes.
+# and optionally patching with `patches` or adding build inputs.
 #
 # It can be invoked directly, or be used to wrap an existing derivation. Eg:
 #