Render mob_plugins.exs with sorted map keys (MOB-383)

AGENTS.md

@@ -525,6 +525,12 @@ Real fix: `sim_runtime_dir/0` should detect `ios/build.zig` and use
   shipping needs the user to wire the archive into ios/build.zig +
   android/jni/ themselves. Reach for `--type c` if static linking matters
   more than the source language.
+- **Generated files that print terms with `inspect` must pass
+  `custom_options: [sort_maps: true]`.** On OTP 26+ a map prints its keys in
+  atom-creation order, which differs between VMs, so a committed file that a
+  `--check` re-renders and compares byte-for-byte reports drift right after a
+  regen (MOB-383: `RuntimeManifest.render/1`, `priv/generated/mob_plugins.exs`).
+  Text built by iterating a map needs an explicit sort for the same reason.
 - **`mob.regen_driver_tab` reads `:static_nifs` from `mob.exs`** via
   `Config.Reader`, NOT from `Application.get_env`. mob.exs is not
   auto-imported into Mix application env (this matches every other

CHANGELOG.md

@@ -1,3 +1,18 @@
+## [Unreleased]
+
+### Fixed
+
+- **`mix mob.regen_plugin_manifest --check` no longer reports drift right
+  after a regen (MOB-383).** `priv/generated/mob_plugins.exs` printed each
+  map's keys in atom-creation order, which on OTP 26+ differs between VMs, so
+  the file a deploy wrote and the one `--check` (and `mix mob.doctor`)
+  rendered could differ in key order alone. Every map in the file, nested
+  ones included, is now printed with sorted keys, so the same plugins always
+  produce the same bytes. **Upgrading:** the first regen after updating
+  rewrites a committed `mob_plugins.exs` with its keys reordered (no content
+  change); run `mix mob.regen_plugin_manifest` once (or let the next deploy do
+  it) and commit the result, or `--check` reports drift until you do.
+
 ## [0.7.25] - 2026-10-13
 
 ### Added

lib/mob_dev/plugin/runtime_manifest.ex

@@ -164,15 +164,29 @@ defmodule MobDev.Plugin.RuntimeManifest do
   @doc """
   Renders the manifest map to the contents of `priv/generated/mob_plugins.exs` —
   a self-describing `.exs` that evaluates back to the map.
+
+  Every map, nested ones included, is printed with its keys sorted, so the same
+  manifest renders to the same bytes in any VM. Without that, a map's printed key
+  order follows atom-creation order (OTP 26+), which differs between runs, and
+  `mix mob.regen_plugin_manifest --check` reported drift right after a regen
+  (MOB-383).
   """
   @spec render(map()) :: String.t()
   def render(manifest) do
+    terms =
+      inspect(manifest,
+        limit: :infinity,
+        printable_limit: :infinity,
+        pretty: true,
+        custom_options: [sort_maps: true]
+      )
+
     """
     # Generated by `mix mob.regen_plugin_manifest` — do not edit by hand.
     #
     # The activated plugins' tier-3/4 contributions, read at boot by Mob.Plugins.
     # Regenerated whenever `config :mob, :plugins` changes (the deploy/regen hook).
-    #{inspect(manifest, limit: :infinity, printable_limit: :infinity, pretty: true)}
+    #{terms}
     """
   end
 

test/mob_dev/plugin/runtime_manifest_test.exs

@@ -32,6 +32,54 @@ defmodule MobDev.Plugin.RuntimeManifestTest do
   defp base(extra),
     do: Map.merge(%{name: :p, mob_version: "~> 0.6", plugin_spec_version: 1}, extra)
 
+  # A manifest with every map-bearing section, each map keyed partly by `a` and
+  # `z` (atoms the caller creates). Keys are written in sorted order here;
+  # @reverse_order_writer builds the same manifest with every key reversed.
+  defp every_section_manifest(a, z) do
+    %{
+      composites: [%{:atom => :card, :expand => {P.Card, :expand}, :plugin => :p, a => 1, z => 2}],
+      default_font: %{:android => "inter_regular", :ios => "Inter", a => 1, z => 2},
+      default_style: :brand,
+      lifecycle: [%{:on_start => {P, :start, []}, :plugin => :p, a => 1, z => 2}],
+      nifs: [P.Nif],
+      notification_handlers: [
+        %{:handler => {P, :h, 1}, :match => %{:type => "t", a => 1, z => 2}, :plugin => :p}
+      ],
+      plugins: [:p],
+      screens: [%{:default_route => "/p", :module => P.Home, :plugin => :p, a => 1, z => 2}],
+      settings: [
+        %{:plugin => :p, :schema => [%{:default => 3, :key => :x, a => 1, z => 2}]}
+      ],
+      styles: [%{:name => :brand, :theme => %{:colors => %{a => 1, z => 2}, a => 1, z => 2}}]
+    }
+  end
+
+  # Run in a fresh VM: creates `z` before `a` and writes every map literal in
+  # reverse key order, so each atom's creation order is the reverse of this
+  # VM's.
+  @reverse_order_writer """
+  [root, a_name, z_name] = System.argv()
+  z = String.to_atom(z_name)
+  a = String.to_atom(a_name)
+
+  manifest = %{
+    styles: [%{:theme => %{z => 2, a => 1, :colors => %{z => 2, a => 1}}, :name => :brand}],
+    settings: [%{:schema => [%{z => 2, a => 1, :key => :x, :default => 3}], :plugin => :p}],
+    screens: [%{z => 2, a => 1, :plugin => :p, :module => P.Home, :default_route => "/p"}],
+    plugins: [:p],
+    notification_handlers: [
+      %{:plugin => :p, :match => %{z => 2, a => 1, :type => "t"}, :handler => {P, :h, 1}}
+    ],
+    nifs: [P.Nif],
+    lifecycle: [%{z => 2, a => 1, :plugin => :p, :on_start => {P, :start, []}}],
+    default_style: :brand,
+    default_font: %{z => 2, a => 1, :ios => "Inter", :android => "inter_regular"},
+    composites: [%{z => 2, a => 1, :plugin => :p, :expand => {P.Card, :expand}, :atom => :card}]
+  }
+
+  MobDev.Plugin.RuntimeManifest.write(root, manifest)
+  """
+
   describe "build/1" do
     test "combines static and generated screens, each tagged with its plugin" do
       plugins = [
@@ -236,6 +284,46 @@ defmodule MobDev.Plugin.RuntimeManifestTest do
       {evaluated, _} = Code.eval_string(RuntimeManifest.render(manifest))
       assert evaluated == manifest
     end
+
+    # MOB-383: a map prints its keys in atom-creation order (OTP 26+), so a VM
+    # that created the atoms in another order rendered other bytes and
+    # `mix mob.regen_plugin_manifest --check` reported drift right after a regen.
+    # A fresh VM writes the manifest after creating every atom in reverse; this
+    # VM, which created them in forward order, runs the check's comparison.
+    test "a manifest written by a VM with another atom order passes the --check comparison" do
+      id = System.unique_integer([:positive])
+      {a_name, z_name} = {"mob383_alpha_#{id}", "mob383_zeta_#{id}"}
+      a = String.to_atom(a_name)
+      z = String.to_atom(z_name)
+      manifest = every_section_manifest(a, z)
+
+      root = Path.join(System.tmp_dir!(), "mob_rtm_order_#{id}")
+      on_exit(fn -> File.rm_rf!(root) end)
+
+      elixir = System.find_executable("elixir") || flunk("elixir not on PATH")
+
+      {out, status} =
+        System.cmd(
+          elixir,
+          [
+            "-pa",
+            Application.app_dir(:mob_dev, "ebin"),
+            "-e",
+            @reverse_order_writer,
+            root,
+            a_name,
+            z_name
+          ],
+          stderr_to_stdout: true
+        )
+
+      assert status == 0, out
+      path = Path.join([root, "priv", "generated", "mob_plugins.exs"])
+
+      {written, _} = Code.eval_file(path)
+      assert written == manifest
+      assert File.read!(path) == RuntimeManifest.render(manifest)
+    end
   end
 
   describe "write/1" do