From 9c0ec1be0f3af528beb59b80d3b1b4eda5061a84 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 21 Apr 2026 14:55:41 +0300
Subject: [PATCH] tests: add test for assert with scoped defer cleanup and
 invisible chars (fixes #24727)

---
 vlib/v/tests/failing_tests_test.v             | 28 +++++++++++++++++++
 ...t_with_scoped_defer_cleanup_failing_test.v | 18 ++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/vlib/v/tests/failing_tests_test.v b/vlib/v/tests/failing_tests_test.v
index c7a6c1272..37e2299e3 100644
--- a/vlib/v/tests/failing_tests_test.v
+++ b/vlib/v/tests/failing_tests_test.v
@@ -2,6 +2,8 @@ import os
 
 const assert_failed_defer_cleanup_path = os.join_path(os.vtmp_dir(),
 	'v_assert_failed_defer_cleanup_test.txt')
+const assert_failed_deferred_file_close_path = os.join_path(os.vtmp_dir(),
+	'v_assert_failed_deferred_file_close_test.txt')
 
 fn vroot_path(relpath string) string {
 	return os.real_path(os.join_path(@VMODROOT, relpath))
@@ -13,6 +15,19 @@ fn vexecute(relpath string) os.Result {
 		os.quoted_path(vroot_path(relpath)))
 }
 
+fn deferred_file_flush_line(i int) string {
+	return '第${i:03}: {"code":200,"msg":"数据请求成功","word":"possible","meaning":"可能的；合适的","url":"https://dict.example/api?word=possible"}'
+}
+
+fn deferred_file_flush_expected() string {
+	line_sep := $if windows { '\r\n' } $else { '\n' }
+	mut lines := []string{cap: 160}
+	for i in 0 .. 160 {
+		lines << deferred_file_flush_line(i)
+	}
+	return lines.join(line_sep) + line_sep
+}
+
 fn testsuite_begin() {
 	os.setenv('VCOLORS', 'never', true)
 }
@@ -48,6 +63,19 @@ fn test_assert_failure_runs_scoped_defer_cleanup() {
 	assert !os.exists(assert_failed_defer_cleanup_path)
 }
 
+fn test_assert_failure_runs_deferred_file_close_flush() {
+	defer {
+		os.rm(assert_failed_deferred_file_close_path) or {}
+	}
+	os.rm(assert_failed_deferred_file_close_path) or {}
+	res := vexecute('vlib/v/tests/testdata/assert_with_scoped_defer_cleanup_failing_test.v')
+	assert res.exit_code == 1
+	assert res.output.contains('assert_with_scoped_defer_cleanup_failing_test.v')
+	assert res.output.contains('assert false')
+	content := os.read_file(assert_failed_deferred_file_close_path)!
+	assert content == deferred_file_flush_expected()
+}
+
 fn test_run_only_reports_filtered_failures() {
 	test_path := os.join_path(os.vtmp_dir(), 'issue_22778_run_only_${os.getpid()}_test.v')
 	defer {
diff --git a/vlib/v/tests/testdata/assert_with_scoped_defer_cleanup_failing_test.v b/vlib/v/tests/testdata/assert_with_scoped_defer_cleanup_failing_test.v
index 90dafaa6b..7942e21c3 100644
--- a/vlib/v/tests/testdata/assert_with_scoped_defer_cleanup_failing_test.v
+++ b/vlib/v/tests/testdata/assert_with_scoped_defer_cleanup_failing_test.v
@@ -1,9 +1,16 @@
 import os
 
 const cleanup_path = os.join_path(os.vtmp_dir(), 'v_assert_failed_defer_cleanup_test.txt')
+const deferred_file_close_path = os.join_path(os.vtmp_dir(),
+	'v_assert_failed_deferred_file_close_test.txt')
+
+fn deferred_file_close_line(i int) string {
+	return '第${i:03}: {"code":200,"msg":"数据请求成功","word":"possible","meaning":"可能的；合适的","url":"https://dict.example/api?word=possible"}'
+}
 
 fn testsuite_begin() {
 	os.rm(cleanup_path) or {}
+	os.rm(deferred_file_close_path) or {}
 }
 
 fn test_scoped_defer_cleanup_runs_on_assert_failure() {
@@ -15,3 +22,14 @@ fn test_scoped_defer_cleanup_runs_on_assert_failure() {
 		assert false
 	}
 }
+
+fn test_deferred_file_close_flushes_on_assert_failure() {
+	mut f := os.open_file(deferred_file_close_path, 'w+', 0o666)!
+	defer {
+		f.close()
+	}
+	for i in 0 .. 160 {
+		f.writeln(deferred_file_close_line(i))!
+	}
+	assert false
+}
-- 
2.39.5