fix(statements): restore Customer list button (merge listview_settings)

The list button was registered by reassigning
frappe.listview_settings['Customer'] in a globally-loaded script, but
ERPNext's own Customer list_js (loaded when the list opens) overwrote it,
so the button never appeared. Register it via doctype_list_js instead —
which Frappe appends after the doctype's own list_js — and merge into the
existing settings (wrapping onload, preserving ERPNext's add_fields)
rather than reassigning. The form button and shared ns_statements helpers
stay in customer_statements.js.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ns_app/hooks.py

@@ -16,6 +16,11 @@ doctype_js = {
     "Sales Invoice": "public/js/sales_invoice.js"
 }
 
+# Load on Customer list view (merges the "Generate Statements" action)
+doctype_list_js = {
+    "Customer": "public/js/customer_list.js"
+}
+
 # Ensure custom fields exist after every migrate
 after_migrate = "ns_app.setup.after_migrate"
 

ns_app/public/js/customer_list.js

@@ -0,0 +1,20 @@
+// Customer list action: "Generate Statements". Registered as a doctype_list_js
+// so it loads alongside ERPNext's own Customer list settings (in app order,
+// after them). We MERGE into listview_settings — preserving any existing
+// onload / add_fields — instead of reassigning the object, which would clobber
+// ERPNext's settings (and be clobbered by them). The shared generate/print
+// helpers live on `ns_statements` (public/js/customer_statements.js).
+
+frappe.listview_settings["Customer"] = frappe.listview_settings["Customer"] || {};
+
+(function () {
+    const settings = frappe.listview_settings["Customer"];
+    const original_onload = settings.onload;
+
+    settings.onload = function (listview) {
+        if (original_onload) original_onload(listview);
+        listview.page.add_inner_button(__("Generate Statements"), () => {
+            ns_statements.pick_and_generate();
+        });
+    };
+})();

ns_app/public/js/customer_statements.js

@@ -6,14 +6,9 @@
 
 frappe.provide("ns_statements");
 
-// ── Entry point: Customer list ───────────────────────────────────────────────
-frappe.listview_settings["Customer"] = {
-    onload(listview) {
-        listview.page.add_inner_button(__("Generate Statements"), () => {
-            ns_statements.pick_and_generate();
-        });
-    }
-};
+// The Customer list button is registered separately in customer_list.js
+// (a doctype_list_js) so it merges with — rather than overwrites — ERPNext's
+// own listview_settings["Customer"]. Shared helpers live here on ns_statements.
 
 // ── Entry point: Customer form ───────────────────────────────────────────────
 frappe.ui.form.on("Customer", {