fix(theme): #66 fail-closed theme-state errors at mkFlake/read

Missing, empty, or non-object theme-state.json now throws a short
message pointing at the template and `nomarchy-theme-sync validate`
instead of a raw readFile/fromJSON stack. Shared reader:
modules/theme-state-read.nix — wired in theme.nix, plymouth/timezone/
hardware, and lib.mkFlake (seq-forced early gate). Field-level schema
in theme.nix kept; unknown border roles still fail there; resolveColor
no longer falls through on missing palette keys. Defaults added for
settings.displayProfile / displayProfileAuto.

Verified: V0 nix flake check --no-build; negative evals (missing,
empty, [], bad border role); good-path template mode + displayProfile
defaults.

agent/MEMORY.md

@@ -71,6 +71,12 @@ iteration would otherwise rediscover.
 - `theme-state.json` is git-tracked inside an 86 MB flake tree, so every
   state write re-copies the source before eval — the wallpapers-artifact
   split (BACKLOG LATER) is the decided fix (§ Faster switches).
+- **Friendly theme-state load** (`modules/theme-state-read.nix`, #66):
+  `builtins.tryEval` does **not** catch `readFile`/`fromJSON` failures —
+  gate with `pathExists` + empty/non-object checks before `fromJSON`.
+  Subtle JSON syntax errors still surface from nlohmann (line/col);
+  field schema stays in `theme.nix`. mkFlake must `builtins.seq` the
+  check onto the whole return set or lazy attr access skips it.
 
 ## Design invariants
 - **Waybar status is never color-only** (item 28 sweep, iteration #69):

lib.nix

@@ -5,7 +5,16 @@
 # in flake.nix remain the escape hatch for power users.
 { nixpkgs, home-manager, nixos-hardware, nomarchy }:
 
+let
+  inherit (nixpkgs) lib;
+
+  # Shared pure reader (modules/theme-state-read.nix) — re-exported so
+  # power users composing without mkFlake can call it too.
+  readThemeState = import ./modules/theme-state-read.nix { inherit lib; };
+in
 {
+  inherit readThemeState;
+
   mkFlake =
     { src                      # the downstream flake directory (./.)
     , username                 # login name; also the homeConfigurations attr
@@ -13,8 +22,6 @@
     , system ? "x86_64-linux"
     }:
     let
-      inherit (nixpkgs) lib;
-
       # One profile or several (the installer's autodetection emits a few
       # common-* modules alongside the model-specific one).
       profileNames =
@@ -51,8 +58,17 @@
         # and the standalone HM desktop see the same package set.
         config.allowUnfree = true;
       };
+
+      # Early fail-closed gate: missing/empty/non-object theme-state.json
+      # throws here with a template + validate pointer, before module
+      # evaluation buries a raw readFile/fromJSON stack. Field-level
+      # schema still runs in modules/home/theme.nix after defaults merge.
+      # Forced via seq on the whole return set — attrNames alone must not
+      # skip the check (Nix is lazy on unused let bindings and attr values).
+      statePath = src + "/theme-state.json";
+      _themeState = readThemeState statePath;
     in
-    {
+    builtins.seq _themeState {
       # System layer — rebuilt rarely:
       #   sudo nixos-rebuild switch --flake .#default
       nixosConfigurations.default = nixpkgs.lib.nixosSystem {
@@ -67,7 +83,7 @@
             { environment.systemPackages = [ home-manager.packages.${system}.home-manager ]; }
             # System-side theme consumers (Plymouth splash background)
             # read the same JSON the desktop does.
-            { nomarchy.system.stateFile = src + "/theme-state.json"; }
+            { nomarchy.system.stateFile = statePath; }
           ]
           ++ hardwareModules
           ++ [
@@ -87,7 +103,7 @@
           {
             # Written by nomarchy-theme-sync; reading it is pure — the
             # file is part of the downstream flake's source.
-            nomarchy.stateFile = src + "/theme-state.json";
+            nomarchy.stateFile = statePath;
             home = {
               inherit username;
               homeDirectory = "/home/${username}";

modules/home/theme.nix

@@ -18,7 +18,11 @@
 let
   cfg = config.nomarchy;
 
-  themeState = builtins.fromJSON (builtins.readFile cfg.stateFile);
+  # Fail-closed load: missing / empty / non-object get a short pointer at
+  # the template + `nomarchy-theme-sync validate`, not a raw readFile stack
+  # from deep inside a consumer (nightlight, hyprland, …). Field-level
+  # checks below still run on the merged result.
+  themeState = import ../theme-state-read.nix { inherit lib; } cfg.stateFile;
 
   # Defaults guarantee evaluation succeeds on a sparse or older state
   # file (e.g. one written before a schema field was added). The shipped
@@ -64,6 +68,8 @@ let
     # rebuild. settings.monitors: per-output resolutions the Display menu
     # remembers (output-name -> "WxH@R"), overlaid onto nomarchy.monitors by
     # name in hyprland.nix — the monitor twin of the keyboard graduation.
+    # settings.displayProfile / displayProfileAuto: active named layout +
+    # auto-switch on plug events (hyprland.nix / Display menu).
     # Defaulted so a sparse/older state file still evaluates; nomarchy.settings
     # exposes them.
     settings = {
@@ -74,6 +80,8 @@ let
       # service, but the flag lives here so both sides read one source — the
       # home side gates the Waybar-refresh watcher (timezone.nix) on it.
       autoTimezone = false;
+      displayProfile = "";
+      displayProfileAuto = false;
     };
   };
 
@@ -135,11 +143,18 @@ let
       `nomarchy-theme-sync apply boreal`.'';
 
   # A border value is a palette key (look it up in colors) unless it's
-  # already a literal hex; unknown keys fall through to the raw string.
+  # already a literal hex. Unknown roles are rejected by the field checks
-  resolveColor = v: if lib.hasPrefix "#" v then v else parsed.colors.${v} or v;
+  # above; resolve only runs on a validated state.
+  resolveColor = v:
+    if lib.hasPrefix "#" v then v
+    else parsed.colors.${v} or (throw ''
+
+      Nomarchy: border role "${v}" is not in the palette (colors.*).
+      Use one of: ${lib.concatStringsSep ", " colorRoles}
+      or a literal "#RRGGBB". Validate with: nomarchy-theme-sync validate'');
   border = {
-    active = resolveColor parsed.border.active;
+    active = resolveColor checked.border.active;
-    inactive = resolveColor parsed.border.inactive;
+    inactive = resolveColor checked.border.inactive;
   };
 
   # Resolve the icon theme once and expose it on nomarchy.theme so both

modules/nixos/hardware.nix

@@ -16,10 +16,11 @@
 let
   cfg = config.nomarchy.hardware;
   # Fingerprint PAM can follow theme-state.json (menu toggle → next
-  # sys-rebuild), same bridge as autoTimezone (BACKLOG #55).
+  # sys-rebuild), same bridge as autoTimezone (BACKLOG #55). Missing or
+  # invalid JSON fails closed (theme-state-read.nix) instead of a raw stack.
   hwState =
     if config.nomarchy.system.stateFile != null
-    then builtins.fromJSON (builtins.readFile config.nomarchy.system.stateFile)
+    then import ../theme-state-read.nix { inherit lib; } config.nomarchy.system.stateFile
     else { };
   pamFromState = (hwState.settings or { }).fingerprint.pam or false;
 in

modules/nixos/plymouth.nix

@@ -12,7 +12,7 @@ let
 
   state =
     if cfg.stateFile != null
-    then builtins.fromJSON (builtins.readFile cfg.stateFile)
+    then import ../theme-state-read.nix { inherit lib; } cfg.stateFile
     else { };
   colorOf = key: fallback: lib.removePrefix "#" ((state.colors or { }).${key} or fallback);
   # Fallbacks match the distro default theme (Boreal) when stateFile is null.

modules/nixos/timezone.nix

@@ -15,10 +15,11 @@ let
   cfg = config.nomarchy.system;
 
   # Read the same state file the rest of the system side uses (Plymouth too),
-  # wired by lib.mkFlake. The flag defaults off when the file is absent/sparse.
+  # wired by lib.mkFlake. The flag defaults off when stateFile is null;
+  # a set-but-missing/invalid path fails closed via theme-state-read.nix.
   state =
     if cfg.stateFile != null
-    then builtins.fromJSON (builtins.readFile cfg.stateFile)
+    then import ../theme-state-read.nix { inherit lib; } cfg.stateFile
     else { };
   stateEnabled = (state.settings or { }).autoTimezone or false;
 

modules/theme-state-read.nix

@@ -0,0 +1,84 @@
+# Pure theme-state.json loader — fail closed with a short, actionable
+# message instead of a raw `readFile` / `fromJSON` stack buried in a
+# consumer. Used by modules/home/theme.nix (required path), the NixOS
+# stateFile consumers, and lib.mkFlake (early gate).
+#
+# Field-level schema checks stay in theme.nix (post-defaults). This file
+# only gates *existence* and *JSON-shape* so the first failure the user
+# sees points at the state file, not at nightlight.nix.
+{ lib }:
+
+path:
+
+let
+  pathStr = toString path;
+
+  tip = ''
+    Fix:
+      • Missing file → copy the template next to your flake.nix:
+          templates/downstream/theme-state.json
+        or regenerate from a preset:
+          nomarchy-theme-sync apply boreal
+      • Bad syntax / wrong shape → edit theme-state.json (trailing commas
+        are the usual culprit) or reset with `apply` as above.
+      • Field-level schema (colors, ui, border, …):
+          nomarchy-theme-sync validate
+        Eval-time field checks live in modules/home/theme.nix.'';
+
+  missingMsg = ''
+
+    Nomarchy: theme-state.json is missing:
+      ${pathStr}
+
+    This file is required (appearance + menu settings). Add it to your
+    flake checkout so evaluation stays pure.
+    ${tip}'';
+
+  emptyMsg = ''
+
+    Nomarchy: theme-state.json is empty:
+      ${pathStr}
+    ${tip}'';
+
+  notObjectMsg = ''
+
+    Nomarchy: theme-state.json must be a JSON object `{ ... }`:
+      ${pathStr}
+    ${tip}'';
+
+  # lib.trim / lib.strings.trim — strip leading/trailing whitespace so an
+  # all-whitespace file counts as empty and a BOM-less `{` is recognized.
+  strip = s:
+    let
+      # Prefer lib.trim when present (nixpkgs ≥ 23.11); fall back so a
+      # very old pin still gates missing/non-object.
+      trim =
+        if lib ? trim then lib.trim
+        else if lib.strings ? trim then lib.strings.trim
+        else (x: x);
+    in trim s;
+
+in
+if !(builtins.pathExists path) then
+  throw missingMsg
+else
+  let
+    raw = builtins.readFile path;
+    stripped = strip raw;
+  in
+  if stripped == "" then
+    throw emptyMsg
+  # Reject non-objects before fromJSON where we can (null / array / string
+  # literals). Subtle syntax errors still surface from fromJSON itself —
+  # those messages already include line/column; the path tip above is the
+  # part a raw stack used to bury.
+  else if builtins.match "[[:space:]]*\\{.*" stripped == null then
+    throw notObjectMsg
+  else
+    let
+      value = builtins.fromJSON raw;
+    in
+    if !(builtins.isAttrs value) then
+      throw notObjectMsg
+    else
+      value