add check constraint error handling for MyXQL

Author: petermueller

integration_test/myxql/constraints_test.exs

@@ -0,0 +1,91 @@
+defmodule Ecto.Integration.ConstraintsTest do
+  use ExUnit.Case, async: true
+
+  import Ecto.Migrator, only: [up: 4]
+  alias Ecto.Integration.PoolRepo
+
+  defmodule ConstraintMigration do
+    use Ecto.Migration
+
+    @table table(:constraints_test)
+
+    def change do
+      create @table do
+        add :price, :integer
+        add :from, :integer
+        add :to, :integer
+      end
+
+      execute(&positive_price_up/0, &positive_price_down/0)
+    end
+
+    defp positive_price_up do
+      # Only valid after MySQL 8.0.19
+      repo().query!("ALTER TABLE #{@table.name} ADD CONSTRAINT positive_price CHECK (price > 0);", [], [log: :info])
+    end
+
+    defp positive_price_down do
+      # Only valid after MySQL 8.0.19
+      repo().query!("ALTER TABLE #{@table.name} DROP CONSTRAINT positive_price;", [], [log: :info])
+    end
+  end
+
+  defmodule Constraint do
+    use Ecto.Integration.Schema
+
+    schema "constraints_test" do
+      field :price, :integer
+      field :from, :integer
+      field :to, :integer
+    end
+  end
+
+  @base_migration 2_000_000
+
+  setup_all do
+    ExUnit.CaptureLog.capture_log(fn ->
+      num = @base_migration + System.unique_integer([:positive])
+      up(PoolRepo, num, ConstraintMigration, log: false)
+    end)
+
+    :ok
+  end
+
+  test "check constraint" do
+    # When the changeset doesn't expect the db error
+    changeset = Ecto.Changeset.change(%Constraint{}, price: -10)
+    exception =
+      assert_raise Ecto.ConstraintError, ~r/constraint error when attempting to insert struct/, fn ->
+        PoolRepo.insert(changeset)
+      end
+
+    assert exception.message =~ "\"positive_price\" (check_constraint)"
+    assert exception.message =~ "The changeset has not defined any constraint."
+    assert exception.message =~ "call `check_constraint/3`"
+
+    # When the changeset does expect the db error, but doesn't give a custom message
+    {:error, changeset} =
+      changeset
+      |> Ecto.Changeset.check_constraint(:price, name: :positive_price)
+      |> PoolRepo.insert()
+    assert changeset.errors == [price: {"is invalid", [constraint: :check, constraint_name: "positive_price"]}]
+    assert changeset.data.__meta__.state == :built
+
+    # When the changeset does expect the db error and gives a custom message
+    changeset = Ecto.Changeset.change(%Constraint{}, price: -10)
+    {:error, changeset} =
+      changeset
+      |> Ecto.Changeset.check_constraint(:price, name: :positive_price, message: "price must be greater than 0")
+      |> PoolRepo.insert()
+    assert changeset.errors == [price: {"price must be greater than 0", [constraint: :check, constraint_name: "positive_price"]}]
+    assert changeset.data.__meta__.state == :built
+
+    # When the change does not violate the check constraint
+    changeset = Ecto.Changeset.change(%Constraint{}, price: 10, from: 100, to: 200)
+    {:ok, changeset} =
+      changeset
+      |> Ecto.Changeset.check_constraint(:price, name: :positive_price, message: "price must be greater than 0")
+      |> PoolRepo.insert()
+    assert is_integer(changeset.id)
+  end
+end

lib/ecto/adapters/myxql/connection.ex

@@ -78,6 +78,15 @@ if Code.ensure_loaded?(MyXQL) do
       end
     end
 
+    def to_constraints(%MyXQL.Error{mysql: %{name: :ER_CHECK_CONSTRAINT_VIOLATED}, message: message}, _opts) do
+      with [_, quoted] <- :binary.split(message, ["Check constraint "]),
+           [_, constraint | _] <- :binary.split(quoted, @quotes, [:global]) do
+        [check: constraint]
+      else
+        _ -> []
+      end
+    end
+
     def to_constraints(_, _),
       do: []