From e5ea9f6171db5a79ac486c97f74126c5f42242e2 Mon Sep 17 00:00:00 2001
From: Peter Mueller <6015288+petermueller@users.noreply.github.com>
Date: Sun, 28 Jul 2024 23:20:32 -0400
Subject: [PATCH] add `Ecto.Adapters.SQL.Constraint`

---
 lib/ecto/adapters/sql.ex            |  1 +
 lib/ecto/adapters/sql/constraint.ex | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 lib/ecto/adapters/sql/constraint.ex

diff --git a/lib/ecto/adapters/sql.ex b/lib/ecto/adapters/sql.ex
index f30a1952..ffc11584 100644
--- a/lib/ecto/adapters/sql.ex
+++ b/lib/ecto/adapters/sql.ex
@@ -644,6 +644,7 @@ 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
diff --git a/lib/ecto/adapters/sql/constraint.ex b/lib/ecto/adapters/sql/constraint.ex
new file mode 100644
index 00000000..6e52524b
--- /dev/null
+++ b/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