fix: warn when resources are skipped due to migrate?: false during mi… (#792)

* fix: warn when resources are skipped due to migrate?: false during migration generation (#585)

* Changed the migrate?(false) bug fix error message
to only print that some resources were skipped without
printing a full list of them.

* Broke up the sentences for a better fit for the
terminal.

Author: Jsime34

lib/migration_generator/migration_generator.ex

@@ -85,9 +85,21 @@ defmodule AshPostgres.MigrationGenerator do
     case extension_migration_files ++ tenant_migration_files ++ migration_files do
       [] ->
         if !opts.check || opts.dry_run do
-          Mix.shell().info(
-            "No changes detected, so no migrations or snapshots have been created."
-          )
+          if Enum.empty?(unmanaged_resources) do
+            Mix.shell().info(
+              "No changes detected, so no migrations or snapshots have been created."
+            )
+          else
+            Mix.shell().info("""
+            No changes detected, so no migrations or snapshots have been created.
+
+            Note: Some resources have `migrate?` set to `false` and were skipped.
+
+            If you expected migrations to be generated for them, remove `migrate?(false)`
+            from their `postgres` block. Resources generated with `mix ash_postgres.gen.resources
+            --no-migrations` have `migrate?` set to `false` by default.
+            """)
+          end
         end
 
         :ok

test/migration_generator_test.exs

@@ -6816,4 +6816,55 @@ defmodule AshPostgres.MigrationGeneratorTest do
       refute up =~ "references(:referenced_schema_move_authors"
     end
   end
+  describe "resources with migrate? false (#585)" do
+    test "warns that resources were skipped due to migrate? false", %{
+      snapshot_path: snapshot_path,
+      migration_path: migration_path
+    } do
+      defresource SkippedMigrateResource do
+        postgres do
+          table "skipped_migrate_resource"
+          repo AshPostgres.TestRepo
+          migrate? false
+        end
+
+        actions do
+          defaults([:read, :create])
+        end
+
+        attributes do
+          uuid_primary_key(:id)
+        end
+      end
+
+      defdomain([SkippedMigrateResource])
+
+      # First run: creates extension migrations (unrelated to our resource)
+      AshPostgres.MigrationGenerator.generate(Domain,
+        snapshot_path: snapshot_path,
+        migration_path: migration_path,
+        quiet: false,
+        format: false,
+        auto_name: true
+      )
+
+      flush_mix_shell()
+
+      # Second run: extensions already exist, so only the migrate? false
+      # resource remains — which is skipped, producing "No changes detected"
+      AshPostgres.MigrationGenerator.generate(Domain,
+        snapshot_path: snapshot_path,
+        migration_path: migration_path,
+        quiet: false,
+        format: false,
+        auto_name: true
+      )
+
+      output = shell_output()
+
+      assert output =~ "No changes detected"
+      assert output =~ "migrate?"
+      assert output =~ "SkippedMigrateResource"
+    end
+  end
 end