IT WORKS

Cargo.lock

@@ -158,6 +158,8 @@ dependencies = [
  "fs-err",
  "itertools",
  "libc",
+ "regex",
+ "regex-lite",
  "serde",
  "serde_json",
  "tap",
@@ -422,6 +424,18 @@ dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "regex"
+version = "1.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e10754a14b9137dd7b1e3e5b0493cc9171fdd105e0ab477f51b72e7f3ac0e276"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
 [[package]]
 name = "regex-automata"
 version = "0.4.14"
@@ -433,6 +447,12 @@ dependencies = [
  "regex-syntax",
 ]
 
+[[package]]
+name = "regex-lite"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cab834c73d247e67f4fae452806d17d3c7501756d98c8808d7c9c7aa7d18f973"
+
 [[package]]
 name = "regex-syntax"
 version = "0.8.9"

Cargo.toml

@@ -11,12 +11,19 @@ path = "src/main.rs"
 name = "dynix"
 path = "src/lib.rs"
 
+[features]
+default = ["regex-full"]
+regex-full = ["dep:regex"]
+regex-lite = ["dep:regex-lite"]
+
 [dependencies]
 clap = { version = "4.5.54", features = ["color", "derive"] }
 command-error = "0.8.0"
 fs-err = "3.2.2"
 itertools = "0.14.0"
 libc = { version = "0.2.180", features = ["extra_traits"] }
+regex = { version = "1.12.3", optional = true }
+regex-lite = { version = "0.1.9", optional = true }
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.149"
 tap = "1.0.1"

modules/dynamicism/dynamicism.nix

@@ -11,7 +11,6 @@ let
 
   inherit (import ./lib.nix { inherit lib; })
     typeCheck
-    convenientAttrPath
     concatFoldl
     recUpdateFoldl
     recUpdateFoldlAttrs
@@ -64,6 +63,13 @@ in
       default = { };
     };
 
+    finalEnabledSubmodules = mkOption {
+      type = options.dynamicism.for.type;
+      internal = true;
+      readOnly = true;
+      default = lib.filterAttrs (lib.const (lib.getAttr "enable")) config.dynamicism.for;
+    };
+
     finalSettings = mkOption {
       type = t.attrsOf t.raw;
       internal = true;
@@ -78,14 +84,6 @@ in
       type = t.functionTo t.raw;
       readOnly = true;
     };
-
-    doChange = mkOption {
-      type = t.functionTo t.pathInStore;
-      readOnly = true;
-      description = ''
-        The function to call to Do The Thing.
-      '';
-    };
   };
 
   # Assertions.
@@ -94,27 +92,49 @@ in
   #
   # Generic implementation.
   #
-  config.system.activationScripts."dynamicism-reset" = {
+
-    deps = [ "etc" "stdio" "specialfs" ];
+  config.system.activationScripts = config.dynamicism.for
-    text = ''
+  |> lib.filterAttrs (lib.const (lib.getAttr "enable"))
-      echo "DYNIX: removing existing systemd dropins"
+  |> lib.mapAttrs' (name: submod: let
-      # FIXME: do for each enabled submodule
+    forUnit = unitName: assert lib.isString unitName; let
-      if [[ -d /run/systemd/system ]]; then
+      dropinDir = "/run/systemd/system/${unitName}.d";
-        rm -v /run/systemd/system/*/dynix-*.conf || true
+      systemctl = lib.getExe' pkgs.systemd "systemctl";
+    in ''
+      if [[ -d "${dropinDir}" ]]; then
+        echo "Removing files in "${dropinDir}" >&2
+
+        rm -rvf "${dropinDir}/"*
+        rmdir "${dropinDir}"
+
+        ${systemctl} daemon-reload
+        ${systemctl} try-reload-or-restart "${unitName}"
       fi
     '';
-  };
+
+  in {
+    name = "dynix-reset-dynamicism-for-${name}";
+    value.deps = [ "etc" "stdio" "specialfs" "binsh" "usrbinenv" "var" "udevd" ];
+    value.text = ''
+      echo "Removing existing dynamic overrides for ${name}" >&2
+      ${submod.systemd-services-updated |> lib.map forUnit |> lib.concatStringsSep "\n"}
+    '';
+  });
+
   config.dynamicism = {
 
     applyDynamicConfiguration = {
       baseConfiguration ? builtins.getEnv "NIXOS_CONFIG",
-      newConfiguration ? baseConfiguration + "/dynamic.nix",
+      newConfiguration ? (lib.filesystem.dirOf baseConfiguration) + "/dynamic.nix",
     }: let
       locFor = appendage: lib.concatLists [
         opts.applyDynamicConfiguration.loc
         [ "(function argument)" ]
         (lib.toList appendage)
       ];
+    in
+      assert seqTrue (typeCheck (locFor "baseConfiguration") t.deferredModule baseConfiguration);
+      assert seqTrue (typeCheck (locFor "newConfiguration") t.deferredModule newConfiguration);
+    let
 
       _file = "«inline module in ${showOption opts.applyDynamicConfiguration.loc}»";
 
@@ -132,49 +152,25 @@ in
         };
       };
 
-      submodulesChanged = lib.filter (submodName:
+      submodulesChanged = nixosAfter.config.dynamicism.finalEnabledSubmodules
+      |> lib.filterAttrs (submodName: _:
         nixosBefore.config.dynamicism.for.${submodName}.finalSettings
         !=
         nixosAfter.config.dynamicism.for.${submodName}.finalSettings
-      ) (lib.attrNames config.dynamicism.for);
+      );
-    in
-      assert seqTrue (typeCheck (locFor "baseConfiguration") t.deferredModule baseConfiguration);
-      assert seqTrue (typeCheck (locFor "newConfiguration") t.deferredModule newConfiguration);
-    {
-      inherit submodulesChanged;
-    };
 
-    doChange = {
+      runForSubmodCalled = name: ''
-      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
-          ];
-        };
-      };
-
-      runAllActivationScripts = nixosAfter.config.dynamicism.for
-      |> lib.filterAttrs (lib.const (lib.getAttr "enable"))
-      |> lib.mapAttrsToList (name: submod: ''
         echo "Activating dynamic configuration for ${name}"
-        ${lib.getExe submod.activate}
+        ${lib.getExe nixosAfter.config.dynamicism.for.${name}.activate}
-      '')
+      '';
+
+      runForChanged = submodulesChanged
+      |> lib.mapAttrsToList (name: _: runForSubmodCalled name)
       |> lib.concatStringsSep "\n";
 
     in pkgs.writeShellApplication {
       name = "dynamicism-activate";
-      text = runAllActivationScripts;
+      text = runForChanged;
       passthru.configuration = nixosAfter;
     };
 

modules/dynamicism/gotosocial.nix

@@ -12,7 +12,7 @@ in
       text = ''
         [Service]
         ExecStart=
-        ExecStart=${lib.getExe' pkgs.gotosocial "gotosocial"} --config-path ${configFile} start
+        ExecStart=${lib.getExe' pkgs.gotosocial "gotosocial"} --config-path ${configFile} server start
       '';
       passthru = { inherit configFile; };
     };

modules/dynamicism/lib.nix

@@ -18,6 +18,19 @@ in lib.fix (self: {
   /** Either a list of strings, or a dotted string that will be split. */
   convenientAttrPath = t.coercedTo t.str (lib.splitString ".") (t.listOf t.str);
 
+  executablePathInStore = lib.mkOptionType {
+    name = "exepath";
+    description = "executable path in the Nix store";
+    descriptionClass = "noun";
+    merge = lib.mergeEqualOption;
+    functor = lib.defaultFunctor "exepath";
+    check = x: if lib.isDerivation x then (
+      x.meta.mainProgram or null != null
+    ) else (
+      lib.pathInStore.check x
+    );
+  };
+
   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/dynamicism/submodule.nix

@@ -14,32 +14,15 @@ let
     mkEnableOption
     literalExpression
   ;
-  inherit (lib.types)
-    mkOptionType
-  ;
   t = lib.types;
 
   inherit (import ./lib.nix { inherit lib; })
+    convenientAttrPath
+    executablePathInStore
     recUpdateFoldl
   ;
 
   pkgs = host.pkgs;
-
-  /** Either a list of strings, or a dotted string that will be split. */
-  convenientAttrPath = t.coercedTo t.str (lib.splitString ".") (t.listOf t.str);
-
-  executablePathInStore = mkOptionType {
-    name = "exepath";
-    description = "executable path in the Nix store";
-    descriptionClass = "noun";
-    merge = lib.mergeEqualOption;
-    functor = lib.defaultFunctor "exepath";
-    check = x: if lib.isDerivation x then (
-      x.meta.mainProgram or null != null
-    ) else (
-      lib.pathInStore.check x
-    );
-  };
 in
 {
   options = {
@@ -74,8 +57,9 @@ in
     };
 
     configFile = mkOption {
-      type = t.pathInStore;
+      type = t.nullOr t.pathInStore;
       internal = true;
+      default = null;
     };
 
     unitDropins = mkOption {

package.nix

@@ -122,9 +122,7 @@ in {
 		fenixToolchain,
 	}: let
 		mkShell' = mkShell.override { inherit stdenv; };
-		pyEnv = python3Packages.python.withPackages (p: [
+		pyEnv = python3Packages.python.withPackages (p: [ p.beartype ]);
-			p.beartype
-		]);
 	in mkShell' {
 		name = "devshell-for-${self.name}";
 		inputsFrom = [ self ];

src/args.rs

@@ -1,4 +1,7 @@
-use std::sync::Arc;
+use std::{
+    env,
+    sync::{Arc, LazyLock},
+};
 
 use clap::ColorChoice;
 
@@ -52,6 +55,7 @@ impl FromStr for NixOsOption {
 pub struct AppendCmd {
     #[arg(required = true)]
     pub name: Arc<str>,
+
     #[arg(required = true)]
     pub value: Arc<str>,
 }
@@ -67,6 +71,28 @@ pub enum Subcommand {
     Delta(DeltaCmd),
 }
 
+static DEFAULT_PATH: LazyLock<Box<OsStr>> = LazyLock::new(|| {
+    // This has to be in a let binding to keep the storage around.
+    let nixos_config = env::var_os("NIXOS_CONFIG");
+    let nixos_config = nixos_config
+        .as_deref()
+        .map(Path::new)
+        .unwrap_or(Path::new("/etc/nixos/configuration.nix"));
+
+    nixos_config
+        .parent()
+        .unwrap_or_else(|| {
+            error!(
+                "Your $NIXOS_CONFIG value doesn't make sense: {}. Ignoring.",
+                nixos_config.display(),
+            );
+            Path::new("/etc/nixos")
+        })
+        .join("dynamic.nix")
+        .into_os_string()
+        .into_boxed_os_str()
+});
+
 #[derive(Debug, Clone, PartialEq, clap::Parser)]
 #[command(version, about, author)]
 #[command(arg_required_else_help(true), args_override_self(true))]
@@ -75,8 +101,10 @@ pub struct Args {
     #[arg(long, global(true), default_value = "auto")]
     pub color: ColorChoice,
 
-    // FIXME: default to /etc/configuration.nix, or something?
+    /// The .nix file with dynamic overrides to modify.
-    #[arg(long, global(true), default_value = "./configuration.nix")]
+    /// [default: $(dirname ${NIXOS_CONFIG-/etc/nixos/configuration.nix})/dynamic.nix]
+    #[arg(long, global(true), default_value = &**DEFAULT_PATH)]
+    #[arg(hide_default_value(true))]
     pub file: Arc<OsStr>,
 
     #[command(subcommand)]

src/lib.rs

@@ -1,4 +1,7 @@
-use std::{iter, sync::Arc};
+use std::{
+    iter,
+    sync::{Arc, LazyLock},
+};
 
 pub(crate) mod prelude {
     #![allow(unused_imports)]
@@ -41,14 +44,38 @@ pub mod line;
 mod nixcmd;
 pub use line::Line;
 pub mod source;
-pub use source::SourceLine;
+pub use source::{SourceFile, SourceLine};
 
+#[cfg(all(not(feature = "regex-full"), not(feature = "regex-lite")))]
+compile_error!("At least one of features `regex-full` or `regex-lite` must be used");
+
+#[cfg(feature = "regex-full")]
+use regex as _regex;
+
+// Having both `regex-full` and `regex-lite` isn't an error; it's just wasteful.
+#[cfg(not(feature = "regex-full"))]
+use regex_lite as _regex;
+
+use _regex::Regex;
+
+use itertools::Itertools;
 use serde::{Deserialize, Serialize};
 
-use crate::source::SourceFile;
-
 pub const ASCII_WHITESPACE: &[char] = &['\t', '\n', '\x0C', '\r', ' '];
 
+/// Regex pattern to extract the priority in a `lib.mkOverride` call.
+static MK_OVERRIDE_RE: LazyLock<Regex> = LazyLock::new(|| {
+    // Named capture group: priority
+    // - Word boundary
+    // - Literal `mkOverride`
+    // - One or more whitespace characters
+    // - Literal open parenthesis
+    // - Named capture group "priority"
+    //   - One or more of: digit characters, or literal `-`
+    // - Literal close parenthesis
+    Regex::new(r"(?-u)\bmkOverride\s+\((?<priority>[\d-]+)\)").unwrap()
+});
+
 #[tracing::instrument(level = "debug")]
 pub fn do_delta(args: Arc<Args>, delta_args: DeltaCmd) -> Result<(), BoxDynError> {
     todo!();
@@ -65,17 +92,15 @@ pub fn do_append(args: Arc<Args>, append_args: AppendCmd) -> Result<(), BoxDynEr
         filepath.to_path_buf()
     };
 
-    // Get what file that thing is defined in.
-    let def_path = get_where(&append_args.name, &filepath)?;
-
     let mut opts = File::options();
     opts.read(true)
         .write(true)
         .create(false)
         .custom_flags(libc::O_CLOEXEC);
-    let source_file = SourceFile::open_from(Arc::from(def_path), opts)?;
 
-    let pri = get_highest_prio(&append_args.name, source_file.clone())?;
+    let source_file = SourceFile::open_from(Arc::from(filepath), opts)?;
+    let pri = get_where(source_file.clone())?;
+
     let new_pri = pri - 1;
 
     let new_pri_line = get_next_prio_line(
@@ -85,7 +110,7 @@ pub fn do_append(args: Arc<Args>, append_args: AppendCmd) -> Result<(), BoxDynEr
         append_args.value.into(),
     )?;
 
-    eprintln!("new_pri_line={new_pri_line}");
+    debug!("new_pri_line={new_pri_line}");
 
     write_next_prio(source_file, new_pri_line)?;
 
@@ -108,35 +133,30 @@ pub fn expr_for_configuration(source_file: &Path) -> OsString {
     .collect()
 }
 
-pub fn get_where(option_name: &str, configuration_nix: &Path) -> Result<Box<Path>, BoxDynError> {
+fn maybe_extract_prio_from_line(line: &SourceLine) -> Option<i64> {
-    let expr = expr_for_configuration(configuration_nix);
+    MK_OVERRIDE_RE
-    let attrpath = format!("options.{}.definitionsWithLocations", option_name);
+        .captures(line.text_ref())
-
+        .map(|caps| caps.name("priority").unwrap().as_str())
-    let output = nixcmd::NixEvalExpr { expr, attrpath }
+        .map(|prio_str| {
-        .into_command()
+            i64::from_str(prio_str).unwrap_or_else(|e| {
-        .output_checked_utf8()?;
+                panic!(
-    let stdout = output.stdout();
+                    "lib.mkOverride called with non-integer {}: {}. Nix source code is wrong!\n{}",
-
+                    prio_str, e, line,
-    let definitions: Box<[DefinitionWithLocation]> = serde_json::from_str(&stdout)?;
+                );
-    let last_location = definitions.into_iter().last().unwrap();
+            })
-
+        })
-    Ok(Box::from(last_location.file))
 }
 
-pub fn get_highest_prio(option_name: &str, source: SourceFile) -> Result<i64, BoxDynError> {
+pub fn get_where(dynamic_nix: SourceFile) -> Result<i64, BoxDynError> {
-    // Get the current highest priority.
+    let lines = dynamic_nix.lines()?;
+    let prio = lines
+        .into_iter()
+        .filter_map(maybe_extract_prio_from_line)
+        .sorted_unstable()
+        .next() // Priorities with lower integer values are "stronger" priorities.
+        .unwrap_or(0);
 
-    let expr = expr_for_configuration(&source.path());
+    Ok(prio)
-
-    // Get the highest priority, and the file its defined in.
-    let attrpath = format!("options.{}.highestPrio", option_name);
-    let output = nixcmd::NixEvalExpr { expr, attrpath }
-        .into_command()
-        .output_checked_utf8()?;
-    let stdout = output.stdout();
-    let highest_prio = i64::from_str(stdout.trim())?;
-
-    Ok(highest_prio)
 }
 
 pub fn get_next_prio_line(
@@ -146,15 +166,19 @@ pub fn get_next_prio_line(
     new_value: Arc<str>,
 ) -> Result<SourceLine, BoxDynError> {
     let source_lines = source.lines()?;
-    let last_line = source_lines.last();
+    let penultimate = source_lines.get(source_lines.len() - 2);
-    assert_eq!(last_line.map(SourceLine::text).as_deref(), Some("]"));
+    // FIXME: don't rely on whitespace lol
-    let last_line = last_line.unwrap();
+    debug_assert_eq!(penultimate.map(SourceLine::text).as_deref(), Some("  ];"));
+    let penultimate = penultimate.unwrap();
+
+    let new_generation = 0 - new_prio;
 
     let new_line = SourceLine {
-        line: last_line.line,
+        line: penultimate.line,
         path: source.path(),
         text: Arc::from(format!(
-            "    {option_name} = lib.mkOverride ({new_prio}) ({new_value});",
+            "      {} = lib.mkOverride ({}) ({}); # DYNIX GENERATION {}",
+            option_name, new_prio, new_value, new_generation,
         )),
     };
 
@@ -165,12 +189,12 @@ pub fn write_next_prio(mut source: SourceFile, new_line: SourceLine) -> Result<(
     let new_mod_start = SourceLine {
         line: new_line.line.prev(),
         path: source.path(),
-        text: Arc::from("  {"),
+        text: Arc::from("    {"),
     };
     let new_mod_end = SourceLine {
         line: new_line.line.next(),
         path: source.path(),
-        text: Arc::from("  }"),
+        text: Arc::from("    }"),
     };
 
     source.insert_lines(&[new_mod_start, new_line, new_mod_end])?;

tests/default.nix

@@ -39,12 +39,17 @@
         enable = true;
         serviceConfig.Type = "oneshot";
         serviceConfig.RemainAfterExit = true;
-        serviceConfig.RequisteOf = [ "multi-user.target" ];
         path = [ config.system.path ];
         wantedBy = [ "multi-user.target" ];
+        requiredBy = [ "multi-user.target" ];
         after = [ "default.target" ];
         script = ''
-          nix profile install -vv "${dynix.modules}" # "
+          if [[ -e /etc/nixos/hardware-configuration.nix ]]; then
+            echo "install-dynix: configuration already copied; nothing to do"
+            exit 0
+          fi
+
+          nix profile install -vv "${dynix.drvPath}^*" # "
 
           mkdir -vp /etc/nixos
           nixos-generate-config
@@ -58,6 +63,8 @@
 
       passthru = { inherit options; };
 
+      environment.systemPackages = [ config.passthru.configurationDotNix ];
+
       # Just making something in this strict in `name`,
       # which is only present as an argument for nodes and I don't want to
       # confuse that with the test modules.

tests/distccd/test-script.py

@@ -4,7 +4,7 @@ import functools
 #from pprint import pformat
 import shlex
 import textwrap
-from typing import cast, TYPE_CHECKING
+from typing import Any, cast, TYPE_CHECKING
 
 from beartype import beartype
 
@@ -68,6 +68,27 @@ def get_cli_args() -> argparse.Namespace:
     args, rest = parser.parse_known_args(cmdline_args)
     return args
 
+@beartype
+def dynix_append(option: str, value: Any):
+    machine.succeed(f'''
+        dynix append {shlex.quote(option)} {shlex.quote(str(value))}
+    '''.strip())
+
+@beartype
+def do_apply():
+    expr = textwrap.dedent("""
+        let
+            nixos = import <nixpkgs/nixos> { };
+        in nixos.config.dynamicism.applyDynamicConfiguration {
+            baseConfiguration = /etc/nixos/configuration.nix;
+            newConfiguration = /etc/nixos/dynamic.nix;
+        }
+    """).strip()
+
+    machine.succeed(rf"""
+        nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
+    """.strip())
+
 machine.wait_for_unit("default.target")
 assert "lix" in machine.succeed("nix --version").lower()
 machine.log("INIT")
@@ -89,17 +110,8 @@ args = get_cli_args()
 #assert int(args['max_connection_rate']) == 256, f"{args['max_connection_rate']=} != 256"
 #
 new_jobs = 4
-expr = textwrap.dedent(f"""
+dynix_append("services.distccd.maxJobs", new_jobs)
-    let
+do_apply()
-        nixos = import <nixpkgs/nixos> {{ }};
-    in nixos.config.dynamicism.doChange {{
-        option = "services.distccd.maxJobs";
-        value = {new_jobs};
-    }}
-""").strip()
-machine.succeed(rf"""
-    nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
-""".strip())
 
 args = get_cli_args()
 
@@ -109,17 +121,8 @@ assert args.job_lifetime == 900, f'{args.job_lifetime} != 900'
 assert args.log_level == 'warning', f'{args.log_level=} != warning'
 
 new_log_level = 'error'
-expr = textwrap.dedent(f"""
+dynix_append("services.distccd.logLevel", f'"{new_log_level}"')
-    let
+do_apply()
-        nixos = import <nixpkgs/nixos> {{ }};
-    in nixos.config.dynamicism.doChange {{
-        option = "services.distccd.logLevel";
-        value = "{new_log_level}";
-    }}
-""").strip()
-machine.succeed(rf"""
-    nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
-""".strip())
 
 args = get_cli_args()
 #assert args.jobs == new_jobs, f'{args.jobs=} != {new_jobs=}'

tests/distccd/test.nix

@@ -1,4 +1,7 @@
 { mkDynixConfigurationDotNix, config, ... }:
+let
+  testName = config.name;
+in
 {
   name = "nixos-test-dynamicism-distccd";
 
@@ -6,17 +9,13 @@
 
   extraPythonPackages = p: [ p.beartype ];
 
-  nodes.machine = { name, pkgs, ... }: {
+  nodes.machine = { ... }: {
     imports = [ ./configuration.nix ];
 
-    environment.systemPackages = let
+    passthru.configurationDotNix = mkDynixConfigurationDotNix {
-      configFileTree = mkDynixConfigurationDotNix {
+      name = testName;
-        inherit (config) name;
+      configuration = ./configuration.nix;
-        configuration = ./configuration.nix;
+    };
-      };
-    in [
-      configFileTree
-    ];
   };
 
   testScript = builtins.readFile ./test-script.py;

tests/gotosocial/test-script.py

@@ -46,37 +46,75 @@ def get_config_file() -> str:
 
     config_file_path = machine.out_dir / config_file.name
     with open(config_file_path, "r") as f:
-        return f.read()
+        data = f.read()
+
+    config_file_path.unlink()
+
+    return data
+
+@beartype
+def dynix_append(option: str, value: str):
+    machine.succeed(f'''
+        dynix append {shlex.quote(option)} {shlex.quote(value)}
+    '''.strip())
+
+@beartype
+def do_apply():
+    expr = textwrap.dedent("""
+        let
+            nixos = import <nixpkgs/nixos> { };
+        in nixos.config.dynamicism.applyDynamicConfiguration {
+            baseConfiguration = /etc/nixos/configuration.nix;
+            newConfiguration = /etc/nixos/dynamic.nix;
+        }
+    """).strip()
+
+    machine.succeed(rf"""
+        nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
+    """.strip())
 
 
 machine.wait_for_unit("default.target")
 assert "lix" in machine.succeed("nix --version").lower()
-machine.log("INIT")
+machine.wait_for_unit("install-dynix.service")
+
+dynix_out = machine.succeed("dynix --version")
+assert "dynix" in dynix_out, f"dynix not in {dynix_out=}"
+
+machine.log("REBUILDING configuration inside VM")
+machine.succeed("env PAGER= nixos-rebuild switch --log-format raw-with-logs --fallback")
+machine.wait_for_unit("gotosocial.service")
+
+# Make sure the config before any dynamic changes is what we expect.
+config_text = get_config_file()
+lines = config_text.splitlines()
+try:
+    application_name = next(line for line in lines if line.startswith("application-name:"))
+except StopIteration:
+    raise AssertionError(f"no 'application-name:' found in config file: {textwrap.indent(config_text, "  ")}")
+assert "gotosocial-for-machine" in application_name, f"'gotosocial-for-machine' should be in {application_name=}"
+
+new_app_name = "yay!"
+dynix_append("services.gotosocial.settings.application-name", f'"{new_app_name}"')
+do_apply()
+
+config_text = get_config_file()
+lines = config_text.splitlines()
+try:
+    application_name = next(line for line in lines if line.startswith("application-name:"))
+except StopIteration:
+    raise AssertionError(f"no 'application-name:' found in config file: {textwrap.indent(config_text, "  ")}")
+assert new_app_name in application_name, f"'{new_app_name}' should be in {application_name=}"
 
 machine.log("REBUILDING configuration inside VM")
 machine.succeed("env PAGER= nixos-rebuild switch --log-format raw-with-logs --fallback")
 
+machine.wait_for_unit("gotosocial.service")
+
 config_text = get_config_file()
 lines = config_text.splitlines()
-application_name = next((line for line in lines if line.startswith("application-name:")), None)
+try:
-assert application_name is not None, f"no 'application-name:' found in config file: {textwrap.indent(config_text, "")}"
+    application_name = next(line for line in lines if line.startswith("application-name:"))
+except StopIteration:
+    raise AssertionError(f"no 'application-name:' found in config file: {textwrap.indent(config_text, "  ")}")
 assert "gotosocial-for-machine" in application_name, f"'gotosocial-for-machine' should be in {application_name=}"
-
-new_app_name = "yay!"
-expr = textwrap.dedent(f"""
-    let
-        nixos = import <nixpkgs/nixos> {{ }};
-    in nixos.config.dynamicism.doChange {{
-        option = "services.gotosocial.settings.application-name";
-        value = "{new_app_name}";
-    }}
-""").strip()
-machine.succeed(rf"""
-    nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
-""".strip())
-
-config_file_new = get_config_file()
-lines = config_file_new.splitlines()
-
-application_name = next(line for line in lines if line.startswith("application-name:"))
-assert new_app_name in application_name, f"'{new_app_name}' should be in {application_name=}"

tests/gotosocial/test.nix

@@ -1,5 +1,7 @@
 { mkDynixConfigurationDotNix, config, ... }:
-
+let
+  testName = config.name;
+in
 {
   name = "nixos-test-dynamicism-gotosocial";
 
@@ -9,21 +11,17 @@
     p.beartype
   ];
 
-  nodes.machine = { pkgs, ... }: {
+  nodes.machine = { ... }: {
     # NOTE: Anything in this `nodes.machine = ` module will not be included
     # in the VM's NixOS configuration once it does `nixos-rebuild switch`,
     # except for `./configuration.nix` which will be copied to `/etc/nixos/`.
     # dynix will also be statefully installed to root's user profile.
     imports = [ ./configuration.nix ];
 
-    environment.systemPackages = let
+    passthru.configurationDotNix = mkDynixConfigurationDotNix {
-      configFileTree = mkDynixConfigurationDotNix {
+      name = testName;
-        inherit (config) name;
+      configuration = ./configuration.nix;
-        configuration = ./configuration.nix;
+    };
-      };
-    in [
-      configFileTree
-    ];
   };
 
   testScript = builtins.readFile ./test-script.py;

tests/harmonia/test-script.py

@@ -55,6 +55,27 @@ def get_config_file() -> dict[str, Any]:
     config_file_path.unlink()
     return config_data
 
+@beartype
+def dynix_append(option: str, value: Any):
+    machine.succeed(f'''
+        dynix append {shlex.quote(option)} {shlex.quote(str(value))}
+    '''.strip())
+
+@beartype
+def do_apply():
+    expr = textwrap.dedent("""
+        let
+            nixos = import <nixpkgs/nixos> { };
+        in nixos.config.dynamicism.applyDynamicConfiguration {
+            baseConfiguration = /etc/nixos/configuration.nix;
+            newConfiguration = /etc/nixos/dynamic.nix;
+        }
+    """).strip()
+
+    machine.succeed(rf"""
+        nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
+    """.strip())
+
 machine.wait_for_unit("default.target")
 assert "lix" in machine.succeed("nix --version").lower()
 machine.log("INIT")
@@ -75,17 +96,8 @@ assert int(config_toml['workers']) == 4, f"{config_toml['workers']=} != 4"
 assert int(config_toml['max_connection_rate']) == 256, f"{config_toml['max_connection_rate']=} != 256"
 
 new_workers = 20
-expr = textwrap.dedent(f"""
+dynix_append("services.harmonia.settings.workers", new_workers)
-    let
+do_apply()
-        nixos = import <nixpkgs/nixos> {{ }};
-    in nixos.config.dynamicism.doChange {{
-        option = "services.harmonia.settings.workers";
-        value = {new_workers};
-    }}
-""").strip()
-machine.succeed(rf"""
-    nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
-""".strip())
 
 # Workers, but not max connection rate, should have changed.
 config_toml = get_config_file()
@@ -94,17 +106,8 @@ assert int(config_toml['workers']) == new_workers, f"{config_toml['workers']=} !
 assert int(config_toml['max_connection_rate']) == 256, f"{config_toml['max_connection_rate']=} != 256"
 
 new_max_connection_rate = 100
-expr = textwrap.dedent(f"""
+dynix_append("services.harmonia.settings.max_connection_rate", new_max_connection_rate)
-    let
+do_apply()
-        nixos = import <nixpkgs/nixos> {{ }};
-    in nixos.config.dynamicism.doChange {{
-        option = [ "services" "harmonia" "settings" "max_connection_rate" ];
-        value = {new_max_connection_rate};
-    }}
-""").strip()
-machine.succeed(rf"""
-    nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
-""".strip())
 
 # Max connection rate should have changed, but workers should have reverted.
 config_toml = get_config_file()

tests/harmonia/test.nix

@@ -1,4 +1,7 @@
 { mkDynixConfigurationDotNix, config, ... }:
+let
+  testName = config.name;
+in
 {
   name = "nixos-test-dynamicism-harmonia";
 
@@ -6,21 +9,13 @@
 
   extraPythonPackages = p: [ p.beartype ];
 
-  nodes.machine = { name, pkgs, ... }: {
+  nodes.machine = { ... }: {
     imports = [ ./configuration.nix ];
 
-    environment.systemPackages = let
+    passthru.configurationDotNix = mkDynixConfigurationDotNix {
-      #configFileTree = pkgs.runCommand "${name}-configuration-dot-nix" { } ''
+      name = testName;
-      #  set -euo pipefail
+      configuration = ./configuration.nix;
-      #  install -Dm a=r ${./configuration.nix} "$out/share/nixos/configuration.nix"
+    };
-      #'';
-      configFileTree = mkDynixConfigurationDotNix {
-        inherit (config) name;
-        configuration = ./configuration.nix;
-      };
-    in [
-      configFileTree
-    ];
   };
 
   testScript = builtins.readFile ./test-script.py;

tests/mk-test-configuration-dot-nix.nix

@@ -44,6 +44,15 @@
       echo "  ];" >> "$modulesOut/configuration.nix"
       echo "}" >> "$modulesOut/configuration.nix"
 
+      echo "/** GENERATED BY mk-test-configuration-dot-nix! */" >> "$modulesOut/dynamic.nix"
+      echo "{ lib, ... }:" >> "$modulesOut/dynamic.nix"
+      echo >> "$modulesOut/dynamic.nix"
+      echo >> "$modulesOut/dynamic.nix"
+      echo "{" >> "$modulesOut/dynamic.nix"
+      echo "  imports = [ ./configuration.nix ];" >> "$modulesOut/dynamic.nix"
+      echo "  config = lib.mkMerge [" >> "$modulesOut/dynamic.nix"
+      echo "  ];" >> "$modulesOut/dynamic.nix"
+      echo "}" >> "$modulesOut/dynamic.nix"
       runHook postInstall
     '';
 

tests/module-allow-rebuild-in-vm.nix

@@ -13,8 +13,8 @@
     installBootLoader = true;
 
     # With how much memory Nix eval uses, this is essentially required.
-    memorySize = 4096;
+    memorySize = 8192;
-    cores = 4;
+    cores = 8;
 
   };