improvement: don't install sat solver in initial installation

improvement: ask user to install sat solver when extending with policies
improvement: validate that a solver exists at compile time when using policies

lib/ash/policy/authorizer/authorizer.ex

@@ -410,7 +410,8 @@ defmodule Ash.Policy.Authorizer do
   ]
 
   @verifiers [
-    Ash.Policy.Authorizer.Verifiers.VerifyInAuthorizers
+    Ash.Policy.Authorizer.Verifiers.VerifyInAuthorizers,
+    Ash.Policy.Authorizer.Verifiers.VerifySatSolverImplementation
   ]
 
   use Spark.Dsl.Extension,
@@ -453,6 +454,38 @@ defmodule Ash.Policy.Authorizer do
     )
   end
 
+  def install(igniter, module, type, _path, _argv) do
+    igniter =
+      with nil <- Igniter.Project.Deps.get_dependency_declaration(igniter, :picosat_elixir),
+           nil <- Igniter.Project.Deps.get_dependency_declaration(igniter, :simple_sat) do
+        solver =
+          Owl.IO.select(
+            [
+              {:picosat_elixir, "~> 0.2"},
+              {:simple_sat, "~> 0.1"}
+            ],
+            label:
+              "Which sat solver would you like to use? If on windows, use `simple_sat`, otherwise, use `picosat_elixir`.",
+            render_as: &to_string(elem(&1, 0))
+          )
+
+        igniter
+        |> Igniter.Project.Deps.add_dep(solver)
+        |> Igniter.apply_and_fetch_dependencies()
+      else
+        _ ->
+          igniter
+      end
+
+    igniter
+    |> Spark.Igniter.add_extension(
+      module,
+      type,
+      :authorizers,
+      Ash.Policy.Authorizer
+    )
+  end
+
   @doc false
   # We can't actually validate that they are check modules here
   # without causing compile time dependencies

lib/ash/policy/authorizer/verifiers/verify_sat_solver_implementation.ex

@@ -0,0 +1,9 @@
+defmodule Ash.Policy.Authorizer.Verifiers.VerifySatSolverImplementation do
+  @moduledoc false
+  use Spark.Dsl.Verifier
+
+  def verify(_dsl) do
+    Ash.SatSolver.Implementation.check!()
+    :ok
+  end
+end

lib/mix/tasks/install/ash.install.ex

@@ -36,8 +36,7 @@ defmodule Mix.Tasks.Ash.Install do
   @impl Igniter.Mix.Task
   def info(_argv, _source) do
     %Igniter.Mix.Task.Info{
-      composes: ["spark.install"],
-      adds_deps: [picosat_elixir: "~> 0.2"]
+      composes: ["spark.install"]
     }
   end
 

lib/sat_solver/implementation.ex

@@ -5,6 +5,8 @@ cond do
       def solve_expression(cnf) do
         Module.concat([System.get_env("SAT_SOLVER") || "Picosat"]).solve(cnf)
       end
+
+      def check!, do: :ok
     end
 
   Code.ensure_loaded?(Picosat) ->
@@ -13,6 +15,8 @@ cond do
       def solve_expression(cnf) do
         Picosat.solve(cnf)
       end
+
+      def check!, do: :ok
     end
 
   Code.ensure_loaded?(SimpleSat) ->
@@ -21,31 +25,41 @@ cond do
       def solve_expression(cnf) do
         SimpleSat.solve(cnf)
       end
+
+      def check!, do: :ok
     end
 
   true ->
     defmodule Ash.SatSolver.Implementation do
       @moduledoc false
       def solve_expression(_cnf) do
+        check!()
+
+        :ok
+      end
+
+      def check! do
         if Code.ensure_loaded?(Picosat) || Code.ensure_loaded?(SimpleSat) do
           raise """
-          No SAT solver available, although one was loaded. This typically means you need to run `mix deps.compile ash --force`
+          No SAT solver available, although one was loaded.
+
+          This typically means that you need to run `mix deps.compile ash --force`
 
           If that doesn't work, please ensure that one of the following dependencies is present in your application to use sat solver features:
 
-          * `:picosat_elixir` (recommended) - A NIF wrapper around the PicoSAT SAT solver. Fast, production ready, battle tested.
-          * `:simple_sat` - A pure Elixir SAT solver. Slower than PicoSAT, but no NIF dependency.
-          """
-        else
-          raise """
-          No SAT solver available.
-
-          Please add one of the following dependencies to your application to use sat solver features:
-
           * `:picosat_elixir` (recommended) - A NIF wrapper around the PicoSAT SAT solver. Fast, production ready, battle tested.
           * `:simple_sat` - A pure Elixir SAT solver. Slower than PicoSAT, but no NIF dependency.
           """
         end
+
+        raise """
+        No SAT solver available.
+
+        Please add one of the following dependencies to your application to use sat solver features:
+
+        * `:picosat_elixir` (recommended) - A NIF wrapper around the PicoSAT SAT solver. Fast, production ready, battle tested.
+        * `:simple_sat` - A pure Elixir SAT solver. Slower than PicoSAT, but no NIF dependency.
+        """
       end
     end
 end