From 0cc32a5cea613d3f657f97332fd287b82534515f Mon Sep 17 00:00:00 2001
From: Tyler Young <tyler@tylerayoung.com>
Date: Tue, 28 Jul 2026 13:08:29 -0500
Subject: [PATCH] fix (UnusedLiveViewAssign): Recognize `with` expression reads
 of assigns

Followup to #28. This fixes another oversight in the previous implementation where we didn't recognize pattern matches in `with` calls as a read from `assigns`.
---
 .../credo_checks/unused_live_view_assign.ex   |  4 ++
 .../unused_live_view_assign_test.exs          | 49 +++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/lib/jump/credo_checks/unused_live_view_assign.ex b/lib/jump/credo_checks/unused_live_view_assign.ex
index ec43f4f..1429141 100644
--- a/lib/jump/credo_checks/unused_live_view_assign.ex
+++ b/lib/jump/credo_checks/unused_live_view_assign.ex
@@ -338,6 +338,10 @@ defmodule Jump.CredoChecks.UnusedLiveViewAssign do
     if assigns_ast?(assigns_ast) or assigns_binding_ast?(assigns_ast), do: map_pattern_keys(map_pattern), else: []
   end
 
+  defp read_keys({:<-, _meta, [map_pattern, assigns_ast]}) do
+    if assigns_ast?(assigns_ast) or assigns_binding_ast?(assigns_ast), do: map_pattern_keys(map_pattern), else: []
+  end
+
   defp read_keys({:%{}, _meta, pairs}) do
     Enum.flat_map(pairs, fn
       {:assigns, nested_pattern} -> map_pattern_keys(nested_pattern)
diff --git a/test/jump/credo_checks/unused_live_view_assign_test.exs b/test/jump/credo_checks/unused_live_view_assign_test.exs
index 16d25d7..d516082 100644
--- a/test/jump/credo_checks/unused_live_view_assign_test.exs
+++ b/test/jump/credo_checks/unused_live_view_assign_test.exs
@@ -253,6 +253,7 @@ defmodule Jump.CredoChecks.UnusedLiveViewAssignTest do
         |> assign(:used_2, params)
         |> assign(:used_3, params)
         |> assign(:used_4, params)
+        |> assign(:used_5, params)
       end
 
       def handle_event("some_event", params, socket) do
@@ -261,6 +262,7 @@ defmodule Jump.CredoChecks.UnusedLiveViewAssignTest do
         |> read_from_assigns_2()
         |> read_from_assigns_3()
         |> read_from_assigns_4()
+        |> read_from_assigns_5()
       end
 
       defp read_from_assigns_1(%{assigns: assigns}) do
@@ -282,6 +284,53 @@ defmodule Jump.CredoChecks.UnusedLiveViewAssignTest do
       defp read_from_assigns_4(%{assigns: assigns}) do
         Map.get(assigns, :used_4, %{})
       end
+
+      defp read_from_assigns_5(socket) do
+        case Map.get(socket.assigns, :used_5) do
+          :ok -> :ok
+          _ -> :error
+        end
+      end
+    end
+    """
+    |> to_source_file()
+    |> run_check(UnusedLiveViewAssign)
+    |> refute_issues()
+  end
+
+  test "handles `with` matching on socket assigns" do
+    """
+    defmodule SampleLive do
+      use SampleWeb, :live_view
+
+      def mount(_params, _session, socket) do
+        socket
+        |> assign(:used_1, params)
+        |> assign(:used_2, params)
+      end
+
+      def handle_event("some_event", params, socket) do
+        socket
+        |> read_from_assigns_1()
+        |> read_from_assigns_2()
+      end
+
+      defp read_from_assigns_1(socket) do
+        with %{used_1: %AsyncResult{ok?: true, result: data}} <- socket.assigns,
+             true <- not is_nil(data) do
+          :ok
+        else
+          _ -> :error
+        end
+      end
+
+      defp read_from_assigns_2(socket) do
+        with %{used_2: %AsyncResult{ok?: true}} <- socket.assigns do
+          :ok
+        else
+          _ -> :error
+        end
+      end
     end
     """
     |> to_source_file()