Add :constraint_handler and Ecto.Adapters.SQL.Constraint

integration_test/myxql/constraints_test.exs

@@ -4,7 +4,30 @@ defmodule Ecto.Integration.ConstraintsTest do
   import Ecto.Migrator, only: [up: 4]
   alias Ecto.Integration.PoolRepo
 
-  defmodule ConstraintMigration do
+  defmodule CustomConstraintHandler do
+    @quotes ~w(" ' `)
+
+    # An example of a custom handler a user might write
+    def to_constraints(%MyXQL.Error{mysql: %{name: :ER_SIGNAL_EXCEPTION}, message: message}, opts) do
+      # Assumes this is the only use-case of `ER_SIGNAL_EXCEPTION` the user has implemented custom errors for
+      with [_, quoted] <- :binary.split(message, "Overlapping values for key "),
+           [_, index | _] <- :binary.split(quoted, @quotes, [:global]) do
+        [exclusion: strip_source(index, opts[:source])]
+      else
+        _ -> []
+      end
+    end
+
+    def to_constraints(err, opts) do
+      # Falls back to default `ecto_sql` handler for all others
+      Ecto.Adapters.MyXQL.Connection.to_constraints(err, opts)
+    end
+
+    defp strip_source(name, nil), do: name
+    defp strip_source(name, source), do: String.trim_leading(name, "#{source}.")
+  end
+
+  defmodule ConstraintTableMigration do
     use Ecto.Migration
 
     @table table(:constraints_test)
@@ -15,12 +38,64 @@ defmodule Ecto.Integration.ConstraintsTest do
         add :from, :integer
         add :to, :integer
       end
+    end
+  end
 
+  defmodule ConstraintMigration do
+    use Ecto.Migration
+
+    @table table(:constraints_test)
+
+    def change do
       # Only valid after MySQL 8.0.19
       create constraint(@table.name, :positive_price, check: "price > 0")
     end
   end
 
+  defmodule ProcedureEmulatingConstraintMigration do
+    use Ecto.Migration
+
+    @table_name :constraints_test
+
+    def up do
+      insert_trigger_sql = trigger_sql(@table_name, "INSERT")
+      update_trigger_sql = trigger_sql(@table_name, "UPDATE")
+
+      drop_triggers(@table_name)
+      repo().query!(insert_trigger_sql)
+      repo().query!(update_trigger_sql)
+    end
+
+    def down do
+      drop_triggers(@table_name)
+    end
+
+    defp trigger_sql(table_name, before_type) do
+      ~s"""
+      CREATE TRIGGER #{table_name}_#{String.downcase(before_type)}_overlap
+        BEFORE #{String.upcase(before_type)}
+        ON #{table_name} FOR EACH ROW
+      BEGIN
+        DECLARE v_rowcount INT;
+        DECLARE v_msg VARCHAR(200);
+
+        SELECT COUNT(*) INTO v_rowcount FROM #{table_name}
+        WHERE (NEW.from <= `to` AND NEW.to >= `from`);
+
+        IF v_rowcount > 0 THEN
+            SET v_msg = CONCAT('Overlapping values for key \\'#{table_name}.cannot_overlap\\'');
+            SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = v_msg, MYSQL_ERRNO = 1644;
+        END IF;
+      END;
+      """
+    end
+
+    defp drop_triggers(table_name) do
+      repo().query!("DROP TRIGGER IF EXISTS #{table_name}_insert_overlap")
+      repo().query!("DROP TRIGGER IF EXISTS #{table_name}_update_overlap")
+    end
+  end
+
   defmodule Constraint do
     use Ecto.Integration.Schema
 
@@ -36,20 +111,29 @@ defmodule Ecto.Integration.ConstraintsTest do
   setup_all do
     ExUnit.CaptureLog.capture_log(fn ->
       num = @base_migration + System.unique_integer([:positive])
-      up(PoolRepo, num, ConstraintMigration, log: false)
+      up(PoolRepo, num, ConstraintTableMigration, log: false)
+      up(PoolRepo, num + 1, ProcedureEmulatingConstraintMigration, log: false)
     end)
 
     :ok
   end
 
   @tag :create_constraint
   test "check constraint" do
+    num = @base_migration + System.unique_integer([:positive])
+    ExUnit.CaptureLog.capture_log(fn ->
+      :ok = up(PoolRepo, num, ConstraintMigration, log: false)
+    end)
+
     # 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_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."
@@ -60,24 +144,109 @@ defmodule Ecto.Integration.ConstraintsTest do
       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.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")
+      |> 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.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} =
+
+    {:ok, result} =
       changeset
-      |> Ecto.Changeset.check_constraint(:price, name: :positive_price, message: "price must be greater than 0")
+      |> Ecto.Changeset.check_constraint(:price,
+        name: :positive_price,
+        message: "price must be greater than 0"
+      )
+      |> PoolRepo.insert()
+
+    assert is_integer(result.id)
+  end
+
+  test "custom handled constraint" do
+    changeset = Ecto.Changeset.change(%Constraint{}, from: 0, to: 10)
+    {:ok, item} = PoolRepo.insert(changeset)
+
+    non_overlapping_changeset = Ecto.Changeset.change(%Constraint{}, from: 11, to: 12)
+    {:ok, _} = PoolRepo.insert(non_overlapping_changeset)
+
+    overlapping_changeset = Ecto.Changeset.change(%Constraint{}, from: 9, to: 12)
+
+    msg_re = ~r/constraint error when attempting to insert struct/
+
+    # When the changeset doesn't expect the db error
+    exception =
+      assert_raise Ecto.ConstraintError, msg_re, fn -> PoolRepo.insert(overlapping_changeset) end
+
+    assert exception.message =~ "\"cannot_overlap\" (exclusion_constraint)"
+    assert exception.message =~ "The changeset has not defined any constraint."
+    assert exception.message =~ "call `exclusion_constraint/3`"
+
+    # When the changeset does expect the db error
+    # but the key does not match the default generated by `exclusion_constraint`
+    exception =
+      assert_raise Ecto.ConstraintError, msg_re, fn ->
+        overlapping_changeset
+        |> Ecto.Changeset.exclusion_constraint(:from)
+        |> PoolRepo.insert()
+      end
+    assert exception.message =~ "\"cannot_overlap\" (exclusion_constraint)"
+
+    # When the changeset does expect the db error, but doesn't give a custom message
+    {:error, changeset} =
+      overlapping_changeset
+      |> Ecto.Changeset.exclusion_constraint(:from, name: :cannot_overlap)
+      |> PoolRepo.insert()
+    assert changeset.errors == [from: {"violates an exclusion constraint", [constraint: :exclusion, constraint_name: "cannot_overlap"]}]
+    assert changeset.data.__meta__.state == :built
+
+    # When the changeset does expect the db error and gives a custom message
+    {:error, changeset} =
+      overlapping_changeset
+      |> Ecto.Changeset.exclusion_constraint(:from, name: :cannot_overlap, message: "must not overlap")
+      |> PoolRepo.insert()
+    assert changeset.errors == [from: {"must not overlap", [constraint: :exclusion, constraint_name: "cannot_overlap"]}]
+    assert changeset.data.__meta__.state == :built
+
+
+    # When the changeset does expect the db error, but a different handler is used
+    exception =
+      assert_raise MyXQL.Error, fn ->
+        overlapping_changeset
+        |> Ecto.Changeset.exclusion_constraint(:from, name: :cannot_overlap)
+        |> PoolRepo.insert(constraint_handler: Ecto.Adapters.MyXQL.Connection)
+      end
+    assert exception.message =~ "Overlapping values for key 'constraints_test.cannot_overlap'"
+
+    # When custom error is coming from an UPDATE
+    overlapping_update_changeset = Ecto.Changeset.change(item, from: 0, to: 9)
+
+    {:error, changeset} =
+      overlapping_update_changeset
+      |> Ecto.Changeset.exclusion_constraint(:from, name: :cannot_overlap, message: "must not overlap")
       |> PoolRepo.insert()
-    assert is_integer(changeset.id)
+    assert changeset.errors == [from: {"must not overlap", [constraint: :exclusion, constraint_name: "cannot_overlap"]}]
+    assert changeset.data.__meta__.state == :loaded
   end
 end

integration_test/myxql/test_helper.exs

@@ -57,7 +57,9 @@ Application.put_env(:ecto_sql, PoolRepo,
   url: Application.get_env(:ecto_sql, :mysql_test_url) <> "/ecto_test",
   pool_size: 5,
   pool_count: String.to_integer(System.get_env("POOL_COUNT", "1")),
-  show_sensitive_data_on_connection_error: true
+  show_sensitive_data_on_connection_error: true,
+  # Passes through into adapter_meta
+  constraint_handler: Ecto.Integration.ConstraintsTest.CustomConstraintHandler
 )
 
 defmodule Ecto.Integration.PoolRepo do
@@ -84,6 +86,9 @@ _ = Ecto.Adapters.MyXQL.storage_down(TestRepo.config())
 :ok = Ecto.Adapters.MyXQL.storage_up(TestRepo.config())
 
 {:ok, _pid} = TestRepo.start_link()
+
+# Passes through into adapter_meta, overrides Application config
+# {:ok, _pid} = PoolRepo.start_link([constraint_handler: Ecto.Integration.ConstraintsTest.CustomConstraintHandler])
 {:ok, _pid} = PoolRepo.start_link()
 
 %{rows: [[version]]} = TestRepo.query!("SELECT @@version", [])

lib/ecto/adapters/myxql.ex

@@ -314,7 +314,7 @@ defmodule Ecto.Adapters.MyXQL do
         {:ok, last_insert_id(key, last_insert_id)}
 
       {:error, err} ->
-        case @conn.to_constraints(err, source: source) do
+        case Ecto.Adapters.SQL.to_constraints(adapter_meta, opts, err, source: source) do
           [] -> raise err
           constraints -> {:invalid, constraints}
         end

lib/ecto/adapters/sql.ex

@@ -658,6 +658,13 @@ defmodule Ecto.Adapters.SQL do
     sql_call(adapter_meta, :query_many, [sql], params, opts)
   end
 
+  @doc false
+  def to_constraints(adapter_meta, opts, err, err_opts) do
+    %{constraint_handler: constraint_handler} = adapter_meta
+    constraint_handler = Keyword.get(opts, :constraint_handler) || constraint_handler
+    constraint_handler.to_constraints(err, err_opts)
+  end
+
   defp sql_call(adapter_meta, callback, args, params, opts) do
     %{pid: pool, telemetry: telemetry, sql: sql, opts: default_opts} = adapter_meta
     conn = get_conn_or_pool(pool, adapter_meta)
@@ -872,6 +879,7 @@ defmodule Ecto.Adapters.SQL do
       """
     end
 
+    constraint_handler = Keyword.get(config, :constraint_handler, connection)
     stacktrace = Keyword.get(config, :stacktrace, nil)
     telemetry_prefix = Keyword.fetch!(config, :telemetry_prefix)
     telemetry = {config[:repo], log, telemetry_prefix ++ [:query]}
@@ -884,6 +892,7 @@ defmodule Ecto.Adapters.SQL do
     meta = %{
       telemetry: telemetry,
       sql: connection,
+      constraint_handler: constraint_handler,
       stacktrace: stacktrace,
       opts: Keyword.take(config, @pool_opts)
     }
@@ -1130,7 +1139,7 @@ defmodule Ecto.Adapters.SQL do
   @doc false
   def struct(
         adapter_meta,
-        conn,
+        _conn,
         sql,
         operation,
         source,
@@ -1165,7 +1174,7 @@ defmodule Ecto.Adapters.SQL do
           operation: operation
 
       {:error, err} ->
-        case conn.to_constraints(err, source: source) do
+        case to_constraints(adapter_meta, opts, err, source: source) do
           [] -> raise_sql_call_error(err)
           constraints -> {:invalid, constraints}
         end

lib/ecto/adapters/sql/constraint.ex

@@ -0,0 +1,19 @@
+defmodule Ecto.Adapters.SQL.Constraint do
+  @moduledoc """
+  Specifies the constraint handling API
+  """
+
+  @doc """
+  Receives the exception returned by `c:Ecto.Adapters.SQL.Connection.query/4`.
+
+  The constraints are in the keyword list and must return the
+  constraint type, like `:unique`, and the constraint name as
+  a string, for example:
+
+      [unique: "posts_title_index"]
+
+  Must return an empty list if the error does not come
+  from any constraint.
+  """
+  @callback to_constraints(exception :: Exception.t(), options :: Keyword.t()) :: Keyword.t()
+end