tests for PoC!

modules/dynamicism/default.nix

@@ -1,38 +1,42 @@
 { pkgs, lib, config, options, ... }:
 let
-  inherit (lib.modules)
-    mkIf
-  ;
   inherit (lib.options)
     mkOption
-    mkEnableOption
-    literalExpression
     showOption
   ;
   t = lib.types;
-  cfg = config.dynamicism;
+
+  inherit (import ./lib.nix { inherit lib; })
+    typeCheck
+    convenientAttrPath
+    concatFoldl
+    recUpdateFoldl
+    recUpdateFoldlAttrs
+  ;
+
+  evalNixos = import (pkgs.path + "/nixos");
+
   opts = options.dynamicism;
+
   subOpts = lib.mapAttrs (_: metaAttr: metaAttr.configuration.options) options.dynamicism.for.valueMeta.attrs;
   settingsFormat = pkgs.formats.yaml { };
 
-  concatFoldl = f: list: lib.foldl' (acc: value: acc ++ (f value)) [ ] list;
-  recUpdateFoldlAttrs = f: attrs: lib.foldlAttrs (acc: name: value: lib.recursiveUpdate acc (f name value)) { } attrs;
-
-  finalSettingsFor = { ... }@submod: lib.foldl (acc: optPath: let
-    next =
-      assert lib.isList optPath;
-      lib.setAttrByPath optPath (lib.getAttrFromPath optPath config);
-  in lib.recursiveUpdate acc next) { } submod.source-options;
+  finalSettingsFor = { ... }@submod: recUpdateFoldl (optPath:
+    lib.setAttrByPath optPath (lib.getAttrFromPath optPath config)
+  ) submod.source-options;
 
   ourAssertions = lib.concatAttrValues {
-    unitsExist = concatFoldl (submod: let
-      next = lib.map (unit: assert lib.isString unit; {
+    unitsExist = subOpts
+    |> lib.attrValues
+    |> concatFoldl (submod: submod.systemd-services-updated.value
+      |> lib.map (unit: {
         assertion = config.systemd.units.${unit}.enable or false;
         message = ''
-          '${showOption submod.systemd-services-updated.loc}' specified non-existent unit '${unit}'
+          ${showOption submod.systemd-services-updated.loc}' specified non-existent unit '${unit}'
         '';
-      }) submod.systemd-services-updated.value;
-    in lib.optionals submod.enable.value next) (lib.attrValues subOpts);
+      })
+      |> lib.optionals submod.enable.value
+    );
 
     optsExist = concatFoldl (submod: lib.optionals submod.enable.value (lib.map (optPath: {
       assertion = lib.hasAttrByPath optPath options;
@@ -62,6 +66,14 @@ in
         Attrset of each `source-options` tree to their actual values.
       '';
     };
+
+    doChange = mkOption {
+      type = t.functionTo t.pathInStore;
+      readOnly = true;
+      description = ''
+        The function to call to Do The Thing.
+      '';
+    };
   };
 
   # Assertions.
@@ -70,6 +82,39 @@ in
   #
   # Generic implementation.
   #
+  config.dynamicism.doChange = {
+    option,
+    value,
+    configuration ? builtins.getEnv "NIXOS_CONFIG",
+  }: let
+    loc = opts.doChange.loc ++ [ "(function argument)" "value" ];
+    option' = typeCheck loc convenientAttrPath option;
+    nixosAfter = evalNixos {
+      configuration = { config, ... }: {
+        imports = [
+          configuration
+          (lib.setAttrByPath option' (lib.mkOverride (-999) value))
+        ];
+
+        environment.systemPackages = [
+          config.dynamicism.for.gotosocial.activate
+        ];
+      };
+    };
+
+    allActivations = lib.mapAttrsToList (name: submod: submod.activate) config.dynamicism.for;
+    allActivationScripts = pkgs.writeShellApplication {
+      name = "dynamicism-activate";
+      runtimeInputs = allActivations;
+      text = nixosAfter.config.dynamicism.for
+      |> lib.mapAttrsToList (name: submod: ''
+        echo "Activating dynamicism for ${name}"
+        ${lib.getExe submod.activate}
+      '')
+      |> lib.concatStringsSep "\n";
+    };
+  in allActivationScripts;
+
   config.dynamicism.finalSettings = lib.asserts.checkAssertWarn ourAssertions [ ] (
     recUpdateFoldlAttrs (name: { ... }@submod: finalSettingsFor submod) config.dynamicism.for
   );

modules/dynamicism/lib.nix

@@ -0,0 +1,24 @@
+{
+  lib ? import <nixpkgs/lib>,
+}: let
+  t = lib.types;
+in lib.fix (self: {
+  /** Perform module-system type checking and resolving on a single option value. */
+  typeCheck = loc: option: value:
+    assert lib.isOptionType option;
+    assert lib.isList loc;
+    assert lib.all lib.isString loc;
+  let
+    merged = lib.modules.mergeDefinitions loc option [ {
+      inherit value;
+      file = "«inline»";
+    } ];
+  in merged.mergedValue;
+
+  /** Either a list of strings, or a dotted string that will be split. */
+  convenientAttrPath = t.coercedTo t.str (lib.splitString ".") (t.listOf t.str);
+
+  concatFoldl = f: list: lib.foldl' (acc: value: acc ++ (f value)) [ ] list;
+  recUpdateFoldl = f: list: lib.foldl' (acc: value: lib.recursiveUpdate acc (f value)) { } list;
+  recUpdateFoldlAttrs = f: attrs: lib.foldlAttrs (acc: name: value: lib.recursiveUpdate acc (f name value)) { } attrs;
+})

modules/tests-common.nix

@@ -0,0 +1,4 @@
+{ pkgs, ... }:
+{
+	nix.package = pkgs.lixPackageSets.latest.lix;
+}

modules/tests-main.py

@@ -0,0 +1,76 @@
+#import re
+from pathlib import Path
+from typing import cast, TYPE_CHECKING
+
+from test_driver.machine import Machine
+from test_driver.errors import RequestedAssertionFailed
+
+DEFAULT_NIX = "@DEFAULT_NIX@"
+CONFIGURATION_NIX = "@CONFIGURATION_NIX@"
+DYNAMICISM = "@DYNAMICISM@"
+
+if TYPE_CHECKING:
+    global machine
+    machine = cast(Machine, ...)
+
+def run_log(machine: Machine, *commands: str, timeout: int | None = 60) -> str:
+    output = ""
+    for command in commands:
+        with machine.nested(f"must succeed: {command}"):
+            (status, out) = machine.execute(f"{command} | tee /dev/stderr", timeout=timeout)
+            if status != 0:
+                machine.log(f"output: {out}")
+                raise RequestedAssertionFailed(
+                    f"command `{command}` failed (exit code {status})",
+                )
+            output += out
+
+    return output
+
+def get_config_file() -> Path:
+    machine.wait_for_unit("gotosocial.service")
+    gotosocial_pid = int(machine.get_unit_property("gotosocial.service", "MainPID"))
+    print(f"{gotosocial_pid=}")
+
+    cmdline = machine.succeed(f"cat /proc/{gotosocial_pid}/cmdline")
+    cmdline_args = cmdline.split("\0")
+
+    config_file_idx = cmdline_args.index("--config-path") + 1
+    config_file = Path(cmdline_args[config_file_idx])
+
+    machine.log(f"copying from VM: {config_file=}")
+    machine.copy_from_vm(config_file.as_posix())
+
+    return machine.out_dir / config_file.name
+
+
+machine.wait_for_unit("default.target")
+assert "lix" in run_log(machine, "nix --version").lower()
+
+print(f"{CONFIGURATION_NIX=}")
+machine.succeed("mkdir -vp /etc/nixos")
+machine.copy_from_host(CONFIGURATION_NIX, "/etc/nixos")
+machine.copy_from_host(DYNAMICISM, "/etc/nixos")
+
+run_log(machine, f"nix build --log-format multiline-with-logs --impure -E 'import <nixpkgs/nixos> {{ configuration = {CONFIGURATION_NIX}; }}'")
+run_log(machine, f"nixos-rebuild switch --file {CONFIGURATION_NIX} --verbose --print-build-logs")
+
+config_file_local = get_config_file()
+machine.log(f"opening copied file: {config_file_local=}")
+with open(config_file_local, "r") as f:
+    text = f.read()
+    lines = text.splitlines()
+    application_name = next(line for line in lines if line.startswith("application-name:"))
+    assert "gotosocial-for-machine" in application_name, f"'gotosocial-for-machine' should be in {application_name=}"
+
+print(f"{DEFAULT_NIX=}")
+
+run_log(machine, "eza -lah --color=always --group-directories-first --tree /etc/")
+
+#exec_start = machine.succeed("systemctl show gotosocial.service --property=ExecStart --value")
+#exec_start = machine.succeed("systemctl show gotosocial.service --property=ExecStart --value")
+
+#service_text = machine.succeed("systemctl show gotosocial.service")
+#service_props = dict(line.split("=", maxsplit=1) for line in service_text.splitlines())
+#exec_start = service_props['ExecStart']
+#print(f"{exec_start=}")

modules/tests.nix

@@ -0,0 +1,52 @@
+{
+  pkgs,
+  lib,
+  testers,
+}:
+ let
+  inherit (testers) runNixOSTest;
+in lib.makeScope lib.callPackageWith (self: {
+  main = runNixOSTest {
+    name = "nixos-test-dynamicism-main";
+
+    defaults = { pkgs, ... }: {
+      imports = [ ./dynamicism ];
+
+      nix = {
+        package = pkgs.lixPackageSets.latest.lix;
+        settings.experimental-features = [ "nix-command" ];
+        nixPath = [ "nixpkgs=${pkgs.path}" ];
+      };
+
+      environment.shellAliases = {
+        ls = "eza --long --header --group --group-directories-first --classify --binary";
+      };
+      environment.systemPackages = with pkgs; [
+        eza
+        fd
+        ripgrep
+      ];
+    };
+
+    nodes.machine = { name, ... }: {
+      #services.gotosocial = {
+      #  enable = true;
+      #  setupPostgresqlDB = true;
+      #  settings = {
+      #    application-name = "gotosocial-for-${name}";
+      #    host = "${name}.local";
+      #  };
+      #};
+      #
+      #dynamicism.for.gotosocial.enable = true;
+    };
+
+    # What's a little IFD between friends?
+    testScript = pkgs.replaceVars ./tests-main.py {
+      DEFAULT_NIX = ../default.nix;
+      CONFIGURATION_NIX = ./tests-configuration.nix;
+      DYNAMICISM = ./dynamicism;
+    }
+    |> builtins.readFile;
+  };
+})