fix: don't raise error on codegen with no domains

fixes #83

lib/mix/helpers.ex

@@ -30,49 +30,64 @@ defmodule AshSqlite.Mix.Helpers do
     |> Enum.map(&ensure_compiled(&1, args))
     |> case do
       [] ->
-        raise "must supply the --domains argument, or set `config :my_app, ash_domains: [...]` in config"
+        []
 
       domains ->
         domains
     end
   end
 
   def repos!(opts, args) do
-    domains = domains!(opts, args)
+    if opts[:domains] && opts[:domains] != "" do
+      domains = domains!(opts, args)
 
-    resources =
-      domains
-      |> Enum.flat_map(&Ash.Domain.Info.resources/1)
-      |> Enum.filter(&(Ash.DataLayer.data_layer(&1) == AshSqlite.DataLayer))
+      resources =
+        domains
+        |> Enum.flat_map(&Ash.Domain.Info.resources/1)
+        |> Enum.filter(&(Ash.DataLayer.data_layer(&1) == AshSqlite.DataLayer))
+        |> case do
+          [] ->
+            raise """
+            No resources with `data_layer: AshSqlite.DataLayer` found in the domains #{Enum.map_join(domains, ",", &inspect/1)}.
+
+            Must be able to find at least one resource with `data_layer: AshSqlite.DataLayer`.
+            """
+
+          resources ->
+            resources
+        end
+
+      resources
+      |> Enum.map(&AshSqlite.DataLayer.Info.repo/1)
+      |> Enum.uniq()
       |> case do
         [] ->
           raise """
-          No resources with `data_layer: AshSqlite.DataLayer` found in the domains #{Enum.map_join(domains, ",", &inspect/1)}.
-
-          Must be able to find at least one resource with `data_layer: AshSqlite.DataLayer`.
-          """
+          No repos could be found configured on the resources in the domains: #{Enum.map_join(domains, ",", &inspect/1)}
 
-        resources ->
-          resources
-      end
-
-    resources
-    |> Enum.map(&AshSqlite.DataLayer.Info.repo(&1))
-    |> Enum.uniq()
-    |> case do
-      [] ->
-        raise """
-        No repos could be found configured on the resources in the domains: #{Enum.map_join(domains, ",", &inspect/1)}
+          At least one resource must have a repo configured.
 
-        At least one resource must have a repo configured.
+          The following resources were found with `data_layer: AshSqlite.DataLayer`:
 
-        The following resources were found with `data_layer: AshSqlite.DataLayer`:
+          #{Enum.map_join(resources, "\n", &"* #{inspect(&1)}")}
+          """
 
-        #{Enum.map_join(resources, "\n", &"* #{inspect(&1)}")}
-        """
+        repos ->
+          repos
+      end
+    else
+      if Code.ensure_loaded?(Mix.Tasks.App.Config) do
+        Mix.Task.run("app.config", args)
+      else
+        Mix.Task.run("loadpaths", args)
+        "--no-compile" not in args && Mix.Task.run("compile", args)
+      end
 
-      repos ->
-        repos
+      Mix.Project.config()[:app]
+      |> Application.get_env(:ecto_repos, [])
+      |> Enum.filter(fn repo ->
+        Spark.implements_behaviour?(repo, AshSqlite.Repo)
+      end)
     end
   end
 

lib/mix/tasks/ash_sqlite.generate_migrations.ex

@@ -85,6 +85,13 @@ defmodule Mix.Tasks.AshSqlite.GenerateMigrations do
 
     domains = AshSqlite.Mix.Helpers.domains!(opts, args)
 
+    if Enum.empty?(domains) && !opts[:snapshots_only] do
+      IO.warn("""
+      No domains found, so no resource-related migrations will be generated.
+      Pass the `--domains` option or configure `config :your_app, ash_domains: [...]`
+      """)
+    end
+
     opts =
       opts
       |> Keyword.put(:format, !opts[:no_format])