From 16abc011ae90d5ecb5ec863db0df52ac34d9a7f7 Mon Sep 17 00:00:00 2001
From: Malte Rohde <maltoe@posteo.de>
Date: Sat, 1 Aug 2026 14:16:26 +0200
Subject: [PATCH] Add more lock_modes to Repo.fetch_by/3

---
 CHANGELOG.md                     |  5 +++--
 lib/bitcrowd_ecto/repo.ex        | 18 ++++++++++++++++--
 test/bitcrowd_ecto/repo_test.exs | 23 +++++++++++++++++++++--
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4759aa2..b9bb093 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,9 @@
 
 ### Added
 
-# [1.1.1] - 2026-01-27
+* Added lock modes `:share` and `:key_share` to `Repo.fetch_by/3` as well as the ability to pass a function.
+
+## [1.1.1] - 2026-01-27
 
 ### Fixed 
 
@@ -22,7 +24,6 @@
 
 * Ensure field/assoc/embed exists when listing errors in `flat_errors_on/3`. This prevents accidental test passes on typos in assertions like `refute_errors_on(cs, :sommtypo)`.
 
-
 ## [1.0.0] - 2023-12-21
 
 No changes from v0.17.0.
diff --git a/lib/bitcrowd_ecto/repo.ex b/lib/bitcrowd_ecto/repo.ex
index 519f51d..f389f58 100644
--- a/lib/bitcrowd_ecto/repo.ex
+++ b/lib/bitcrowd_ecto/repo.ex
@@ -18,7 +18,12 @@ defmodule BitcrowdEcto.Repo do
   import Ecto.Query, only: [lock: 2, preload: 2, where: 3]
   alias Ecto.Adapters.SQL
 
-  @type lock_mode :: :no_key_update | :update
+  @type lock_mode ::
+          :key_share
+          | :share
+          | :no_key_update
+          | :update
+          | (Ecto.Queryable.t() -> Ecto.Queryable.t())
 
   @type fetch_option ::
           {:lock, lock_mode | false}
@@ -94,7 +99,7 @@ defmodule BitcrowdEcto.Repo do
 
   ## Options
 
-  * `lock`               any of `[:no_key_update, :update]` (defaults to `false`)
+  * `lock`               any of `[:key_share, :share, :no_key_update, :update]` or a function (defaults to `false`)
   * `preload`            allows to preload associations
   * `error_tag`          allows to specify a custom "tag" value (instead of the queryable)
                          or `false` to disabled tagged error tuples
@@ -238,12 +243,21 @@ defmodule BitcrowdEcto.Repo do
 
   defp maybe_apply_lock(queryable, opts) do
     case Keyword.get(opts, :lock, false) do
+      :key_share ->
+        lock(queryable, "FOR KEY SHARE")
+
+      :share ->
+        lock(queryable, "FOR SHARE")
+
       :no_key_update ->
         lock(queryable, "FOR NO KEY UPDATE")
 
       :update ->
         lock(queryable, "FOR UPDATE")
 
+      fun when is_function(fun) ->
+        fun.(queryable)
+
       disabled when disabled in [nil, false] ->
         queryable
 
diff --git a/test/bitcrowd_ecto/repo_test.exs b/test/bitcrowd_ecto/repo_test.exs
index b0570e3..5d6535c 100644
--- a/test/bitcrowd_ecto/repo_test.exs
+++ b/test/bitcrowd_ecto/repo_test.exs
@@ -2,7 +2,7 @@
 
 defmodule BitcrowdEcto.RepoTest do
   use BitcrowdEcto.TestCase, async: true
-  require Ecto.Query
+  import Ecto.Query
   alias BitcrowdEcto.TestRepoWithUntaggedNotFoundErrors
 
   defp insert_test_schema(_) do
@@ -129,6 +129,25 @@ defmodule BitcrowdEcto.RepoTest do
       end)
     end
 
+    test "can lock for :share", %{resource: %{id: id} = resource} do
+      assert_lock_granted("relation = 'test_schema_pkey'::regclass::oid", fn ->
+        assert TestRepo.fetch_by(TestSchema, [id: id], lock: :share) == {:ok, resource}
+      end)
+    end
+
+    test "can lock for :key_share", %{resource: %{id: id} = resource} do
+      assert_lock_granted("relation = 'test_schema_pkey'::regclass::oid", fn ->
+        assert TestRepo.fetch_by(TestSchema, [id: id], lock: :key_share) == {:ok, resource}
+      end)
+    end
+
+    test "can lock with a function", %{resource: %{id: id} = resource} do
+      assert_lock_granted("relation = 'test_schema_pkey'::regclass::oid", fn ->
+        assert TestRepo.fetch_by(TestSchema, [id: id], lock: &lock(&1, "FOR SHARE")) ==
+                 {:ok, resource}
+      end)
+    end
+
     test "converts CastErrors for binary_id columns to not_found errors" do
       assert TestRepo.fetch_by(TestSchema, some_uuid: "doesnotcast") ==
                {:error, {:not_found, TestSchema}}
@@ -147,7 +166,7 @@ defmodule BitcrowdEcto.RepoTest do
     end
 
     test "returns the given error tag instead of the queryable" do
-      query = Ecto.Query.from(x in TestSchema, where: x.id == ^Ecto.UUID.generate())
+      query = from(x in TestSchema, where: x.id == ^Ecto.UUID.generate())
       assert TestRepo.fetch_by(query, []) == {:error, {:not_found, query}}
       assert TestRepo.fetch_by(query, [], error_tag: :foo) == {:error, {:not_found, :foo}}
     end