fix: generate_migrations --dev duplicating migration files (#173)

This issue was due to `get_existing_snapshot` ignoring dev migrations
because they don't comform to `{timestamp.json}`.

I fixed by making it closer to its postgres counterpart: not trying to
parse the timestamp and instead comparing the filenames, which
works the same until timestamps change their numbers of digits.


I'll think about how to introduce some reuse, because postgres has the
same feature except its getting more love.

Author: madjar

lib/migration_generator/migration_generator.ex

@@ -2006,25 +2006,13 @@ defmodule AshSqlite.MigrationGenerator do
       snapshot_folder
       |> File.ls!()
       |> Enum.filter(&String.ends_with?(&1, ".json"))
-      |> Enum.map(&String.trim_trailing(&1, ".json"))
-      |> Enum.map(&Integer.parse/1)
-      |> Enum.filter(fn
-        {_int, remaining} ->
-          remaining == ""
-
-        :error ->
-          false
-      end)
-      |> Enum.map(&elem(&1, 0))
       |> case do
         [] ->
           get_old_snapshot(folder, snapshot)
 
-        timestamps ->
-          timestamp = Enum.max(timestamps)
-          snapshot_file = Path.join(snapshot_folder, "#{timestamp}.json")
-
-          snapshot_file
+        snapshot_files ->
+          snapshot_folder
+          |> Path.join(Enum.max(snapshot_files))
           |> File.read!()
           |> load_snapshot()
       end

test/migration_generator_test.exs

@@ -192,6 +192,67 @@ defmodule AshSqlite.MigrationGeneratorTest do
     end
   end
 
+  describe "dev migrations" do
+    setup do
+      on_exit(fn ->
+        File.rm_rf!("test_snapshots_path")
+        File.rm_rf!("test_migration_path")
+      end)
+
+      defposts do
+        identities do
+          identity(:title, [:title])
+        end
+
+        attributes do
+          uuid_primary_key(:id)
+          attribute(:title, :string)
+        end
+      end
+
+      defdomain([Post])
+
+      Mix.shell(Mix.Shell.Process)
+
+      AshSqlite.MigrationGenerator.generate(Domain,
+        snapshot_path: "test_snapshots_path",
+        migration_path: "test_migration_path",
+        quiet: true,
+        format: false,
+        auto_name: true,
+        dev: true
+      )
+
+      :ok
+    end
+
+    test "running it again doesn't create a new file" do
+      defposts do
+        identities do
+          identity(:title, [:title])
+        end
+
+        attributes do
+          uuid_primary_key(:id)
+          attribute(:title, :string)
+        end
+      end
+
+      defdomain([Post])
+
+      AshSqlite.MigrationGenerator.generate(Domain,
+        snapshot_path: "test_snapshots_path",
+        migration_path: "test_migration_path",
+        quiet: true,
+        format: false,
+        auto_name: true,
+        dev: true
+      )
+
+      assert [_] = Path.wildcard("test_migration_path/**/*_migrate_resources*.exs")
+    end
+  end
+
   describe "creating follow up migrations" do
     setup do
       on_exit(fn ->
@@ -225,6 +286,31 @@ defmodule AshSqlite.MigrationGeneratorTest do
       :ok
     end
 
+    test "without change" do
+      defposts do
+        identities do
+          identity(:title, [:title])
+        end
+
+        attributes do
+          uuid_primary_key(:id)
+          attribute(:title, :string)
+        end
+      end
+
+      defdomain([Post])
+
+      AshSqlite.MigrationGenerator.generate(Domain,
+        snapshot_path: "test_snapshots_path",
+        migration_path: "test_migration_path",
+        quiet: true,
+        format: false,
+        auto_name: true
+      )
+
+      assert [_] = Path.wildcard("test_migration_path/**/*_migrate_resources*.exs")
+    end
+
     test "when renaming an index, it is properly renamed" do
       defposts do
         sqlite do