From 7324e28f0f0aa42a6790a7a41c988c5d7409d5bb Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 11 Mar 2026 15:48:47 +0300
Subject: [PATCH] js: Backend / unwraping Javascript Objects / TypeError:
 e.stack.contains is not a function (fixes #10393)

---
 vlib/v/gen/js/fn.v                            | 12 ++++++--
 vlib/v/gen/js/js.v                            | 29 +++++++++++++++++--
 .../tests/testdata/js_object_field_string.out |  3 ++
 .../tests/testdata/js_object_field_string.v   | 15 ++++++++++
 4 files changed, 54 insertions(+), 5 deletions(-)
 create mode 100644 vlib/v/gen/js/tests/testdata/js_object_field_string.out
 create mode 100644 vlib/v/gen/js/tests/testdata/js_object_field_string.v

diff --git a/vlib/v/gen/js/fn.v b/vlib/v/gen/js/fn.v
index e857ca341..d6ea52126 100644
--- a/vlib/v/gen/js/fn.v
+++ b/vlib/v/gen/js/fn.v
@@ -336,11 +336,16 @@ fn (mut g JsGen) method_call(node ast.CallExpr) {
 
 		name = g.generic_fn_name(node.concrete_types, name)
 		g.write('${name}(')
-		g.expr(it.left)
+		g.expr_with_expected_type(it.left, unwrapped_rec_type)
 		g.gen_deref_ptr(it.left_type)
 		g.write(',')
 		for i, arg in it.args {
-			g.expr(arg.expr)
+			expected_arg_type := if i < it.expected_arg_types.len {
+				it.expected_arg_types[i]
+			} else {
+				arg.typ
+			}
+			g.expr_with_expected_type(arg.expr, expected_arg_type)
 			if i != it.args.len - 1 {
 				g.write(', ')
 			}
@@ -441,7 +446,8 @@ fn (mut g JsGen) gen_call_expr(it ast.CallExpr) {
 
 	g.write('${name}(')
 	for i, arg in it.args {
-		g.expr(arg.expr)
+		expected_arg_type := if i < it.expected_arg_types.len { it.expected_arg_types[i] } else { arg.typ }
+		g.expr_with_expected_type(arg.expr, expected_arg_type)
 		if i != it.args.len - 1 {
 			g.write(', ')
 		}
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index 5455e0413..7c796976a 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -1882,7 +1882,7 @@ fn (mut g JsGen) gen_return_stmt(it ast.Return) {
 		g.write('${tmp}.state = new u8(0);')
 		g.write('${tmp}.data = ')
 		if it.exprs.len == 1 {
-			g.expr(it.exprs[0])
+			g.expr_with_expected_type(it.exprs[0], node.types[0])
 		} else { // Multi return
 			g.gen_array_init_values(it.exprs)
 		}
@@ -1900,7 +1900,7 @@ fn (mut g JsGen) gen_return_stmt(it ast.Return) {
 		g.write('throw new ReturnException(')
 	}
 	if it.exprs.len == 1 {
-		g.expr(it.exprs[0])
+		g.expr_with_expected_type(it.exprs[0], node.types[0])
 	} else { // Multi return
 		g.gen_array_init_values(it.exprs)
 	}
@@ -3032,6 +3032,31 @@ fn (mut g JsGen) expr_string(expr ast.Expr) string {
 	return g.out.cut_to(pos).trim_space()
 }
 
+fn (mut g JsGen) should_wrap_js_selector_rvalue(expr ast.Expr, expected_type ast.Type) bool {
+	if expected_type == 0 || expected_type.is_ptr() {
+		return false
+	}
+	match expr {
+		ast.SelectorExpr {}
+		else { return false }
+	}
+	target_sym := g.table.final_sym(g.unwrap_generic(expected_type))
+	if target_sym.language == .js || target_sym.name.starts_with('JS.') {
+		return false
+	}
+	return target_sym.kind in shallow_equatables
+}
+
+fn (mut g JsGen) expr_with_expected_type(expr ast.Expr, expected_type ast.Type) {
+	if g.should_wrap_js_selector_rvalue(expr, expected_type) {
+		g.write('new ${g.styp(expected_type)}(')
+		g.expr(expr)
+		g.write(')')
+		return
+	}
+	g.expr(expr)
+}
+
 fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 	l_sym := g.table.final_sym(it.left_type)
 	r_sym := g.table.final_sym(it.right_type)
diff --git a/vlib/v/gen/js/tests/testdata/js_object_field_string.out b/vlib/v/gen/js/tests/testdata/js_object_field_string.out
new file mode 100644
index 000000000..1dc73f774
--- /dev/null
+++ b/vlib/v/gen/js/tests/testdata/js_object_field_string.out
@@ -0,0 +1,3 @@
+false
+false
+false
diff --git a/vlib/v/gen/js/tests/testdata/js_object_field_string.v b/vlib/v/gen/js/tests/testdata/js_object_field_string.v
new file mode 100644
index 000000000..3731ed36b
--- /dev/null
+++ b/vlib/v/gen/js/tests/testdata/js_object_field_string.v
@@ -0,0 +1,15 @@
+fn contains_hello(s string) bool {
+	return s.contains('hello.v:')
+}
+
+fn get_stack() string {
+	e := JS.Error{}
+	return e.stack
+}
+
+fn main() {
+	e := JS.Error{}
+	println(e.stack.contains('hello.v:'))
+	println(contains_hello(e.stack))
+	println(get_stack().contains('hello.v:'))
+}
-- 
2.39.5