wip: transaction support for Sqlite.

.gitignore

@@ -25,6 +25,6 @@ ash_sqlite-*.tar
 test_migration_path
 test_snapshots_path
 
-test/test.db
-test/test.db-shm
-test/test.db-wal
+test/*test.db
+test/*test.db-shm
+test/*test.db-wal

config/config.exs

@@ -28,8 +28,15 @@ if Mix.env() == :test do
     pool: Ecto.Adapters.SQL.Sandbox,
     migration_primary_key: [name: :id, type: :binary_id]
 
+  config :ash_sqlite, AshSqlite.TransactingRepo,
+    database: Path.join(__DIR__, "../test/transacting_test.db"),
+    pool_size: 1,
+    migration_lock: false,
+    pool: Ecto.Adapters.SQL.Sandbox,
+    migration_primary_key: [name: :id, type: :binary_id]
+
   config :ash_sqlite,
-    ecto_repos: [AshSqlite.TestRepo],
+    ecto_repos: [AshSqlite.TestRepo, AshSqlite.TransactingRepo],
     ash_domains: [
       AshSqlite.Test.Domain
     ]

lib/data_layer.ex

@@ -413,7 +413,14 @@ defmodule AshSqlite.DataLayer do
   def can?(_, :bulk_create), do: true
   def can?(_, {:lock, _}), do: false
 
-  def can?(_, :transact), do: false
+  # def can?(_, :transact), do: false
+
+  def can?(resource, :transact) do
+    repo = AshSqlite.DataLayer.Info.repo(resource)
+
+    repo.config()[:transactions_enabled?]
+  end
+
   def can?(_, :composite_primary_key), do: true
   def can?(_, {:atomic, :update}), do: true
   def can?(_, {:atomic, :upsert}), do: true

lib/repo.ex

@@ -16,6 +16,7 @@ defmodule AshSqlite.Repo do
 
   - `:tenant_migrations_path` - The path where your tenant migrations are stored (only relevant for a multitenant implementation)
   - `:snapshots_path` - The path where the resource snapshots for the migration generator are stored.
+  - `:transactions_enabled?` - Due to [SQLite's single writer paradigm](https://sqlite.org/lang_transaction.html#read_transactions_versus_write_transactions) they are disabled by default. See the [transactions guide](/documentation/topics/transactions.md) for more information.
   """
 
   @doc "Use this to inform the data layer about what extensions are installed"
@@ -56,6 +57,7 @@ defmodule AshSqlite.Repo do
           |> Keyword.put(:installed_extensions, installed_extensions())
           |> Keyword.put(:migrations_path, migrations_path())
           |> Keyword.put(:case_sensitive_like, :on)
+          |> Keyword.put_new(:transactions_enabled?, false)
 
         {:ok, new_config}
       end

priv/resource_snapshots/transacting_repo/transacting_posts/20250525053353.json

@@ -0,0 +1,47 @@
+{
+  "attributes": [
+    {
+      "default": "nil",
+      "size": null,
+      "type": "uuid",
+      "source": "id",
+      "references": null,
+      "allow_nil?": false,
+      "generated?": false,
+      "primary_key?": true
+    },
+    {
+      "default": "nil",
+      "size": null,
+      "type": "text",
+      "source": "title",
+      "references": null,
+      "allow_nil?": true,
+      "generated?": false,
+      "primary_key?": false
+    },
+    {
+      "default": "nil",
+      "size": null,
+      "type": "text",
+      "source": "subtitle",
+      "references": null,
+      "allow_nil?": true,
+      "generated?": false,
+      "primary_key?": false
+    }
+  ],
+  "table": "transacting_posts",
+  "hash": "56FE4F305257AC15BFA6AFA639A1D0A069C932004E89966DE7136AD9C96E1F93",
+  "repo": "Elixir.AshSqlite.TransactingRepo",
+  "identities": [],
+  "custom_indexes": [],
+  "base_filter": null,
+  "custom_statements": [],
+  "multitenancy": {
+    "global": null,
+    "attribute": null,
+    "strategy": null
+  },
+  "has_create_action": true
+}

priv/transacting_repo/migrations/20250525053353_add_transacting_repo.exs

@@ -0,0 +1,21 @@
+defmodule AshSqlite.TransactingRepo.Migrations.AddTransactingRepo do
+  @moduledoc """
+  Updates resources based on their most recent snapshots.
+
+  This file was autogenerated with `mix ash_sqlite.generate_migrations`
+  """
+
+  use Ecto.Migration
+
+  def up do
+    create table(:transacting_posts, primary_key: false) do
+      add :subtitle, :text
+      add :title, :text
+      add :id, :uuid, null: false, primary_key: true
+    end
+  end
+
+  def down do
+    drop table(:transacting_posts)
+  end
+end

test/support/domain.ex

@@ -1,5 +1,6 @@
 defmodule AshSqlite.Test.Domain do
   @moduledoc false
+
   use Ash.Domain
 
   resources do
@@ -15,6 +16,7 @@ defmodule AshSqlite.Test.Domain do
     resource(AshSqlite.Test.Account)
     resource(AshSqlite.Test.Organization)
     resource(AshSqlite.Test.Manager)
+    resource(AshSqlite.Test.TransactingPost)
   end
 
   authorization do

test/support/repo_case.ex

@@ -17,10 +17,11 @@ defmodule AshSqlite.RepoCase do
   end
 
   setup tags do
-    :ok = Sandbox.checkout(AshSqlite.TestRepo)
+    repo = tags[:repo] || AshSqlite.TestRepo
+    :ok = Sandbox.checkout(repo)
 
     unless tags[:async] do
-      Sandbox.mode(AshSqlite.TestRepo, {:shared, self()})
+      Sandbox.mode(repo, {:shared, self()})
     end
 
     :ok

test/support/transacting_post.ex

@@ -0,0 +1,21 @@
+defmodule AshSqlite.Test.TransactingPost do
+  @moduledoc false
+  use Ash.Resource,
+    domain: AshSqlite.Test.Domain,
+    data_layer: AshSqlite.DataLayer
+
+  sqlite do
+    table("transacting_posts")
+    repo AshSqlite.TransactingRepo
+  end
+
+  actions do
+    defaults([:read, :destroy, update: :*, create: :*])
+  end
+
+  attributes do
+    uuid_primary_key(:id, writable?: true)
+    attribute(:title, :string, public?: true)
+    attribute(:subtitle, :string, public?: true)
+  end
+end

test/support/transacting_repo.ex

@@ -0,0 +1,4 @@
+defmodule AshSqlite.TransactingRepo do
+  @moduledoc false
+  use AshSqlite.Repo, otp_app: :ash_sqlite, transactions_enabled?: true
+end

test/test_helper.exs

@@ -2,5 +2,7 @@ ExUnit.start()
 ExUnit.configure(stacktrace_depth: 100)
 
 AshSqlite.TestRepo.start_link()
-
 Ecto.Adapters.SQL.Sandbox.mode(AshSqlite.TestRepo, :manual)
+
+AshSqlite.TransactingRepo.start_link()
+Ecto.Adapters.SQL.Sandbox.mode(AshSqlite.TransactingRepo, :manual)

test/transaction_test.exs

@@ -0,0 +1,50 @@
+defmodule AshSqlite.TransactionTest do
+  @moduledoc false
+  use AshSqlite.RepoCase, async: false
+
+  describe "transactions are allowed when enabled" do
+    @describetag repo: AshSqlite.TransactingRepo
+
+    alias AshSqlite.Test.TransactingPost, as: Post
+
+    test "manual transaction" do
+      post_id = Ash.UUID.generate()
+
+      Ash.transaction(Post, fn ->
+        Post
+        |> Ash.create!(
+          %{
+            id: post_id,
+            title: "George McFly Murdered",
+            subtitle: "Local Author Shot Dead"
+          },
+          transaction?: true
+        )
+      end)
+
+      Ash.get!(Post, post_id)
+    end
+  end
+
+  describe "transactions are disallowed when disabled" do
+    @describetag repo: AshSqlite.TestRepo
+    alias AshSqlite.Test.Post
+
+    test "manual transaction" do
+      post_id = Ash.UUID.generate()
+
+      Ash.transaction(Post, fn ->
+        Post
+        |> Ash.create!(
+          %{
+            id: post_id,
+            title: "George McFly Murdered"
+          },
+          transaction?: true
+        )
+      end)
+
+      Ash.get!(Post, post_id)
+    end
+  end
+end