test: assert line numbers of evaluated source

tests/test_eval.cpp

@@ -87,6 +87,31 @@ TEST_SUBMODULE(eval_, m) {
         return false;
     });
 
+    // Line numbers reported from evaluated source must match the source as given;
+    // before #6089 a prepended coding cookie shifted them by one.
+    m.def("test_eval_line_numbers", []() {
+        int syntax_lineno = -1;
+        try {
+            py::exec("x = 1\nx = = 2\n");
+            throw std::runtime_error("py::exec did not raise SyntaxError");
+        } catch (py::error_already_set &e) {
+            syntax_lineno = e.value().attr("lineno").cast<int>();
+        }
+        int traceback_lineno = -1;
+        try {
+            py::exec("x = 1\nraise RuntimeError('line two')\n");
+            throw std::runtime_error("py::exec did not raise RuntimeError");
+        } catch (py::error_already_set &e) {
+            py::object tb = e.trace();
+            for (py::object next = tb.attr("tb_next"); !next.is_none();
+                 next = tb.attr("tb_next")) {
+                tb = std::move(next);
+            }
+            traceback_lineno = tb.attr("tb_lineno").cast<int>();
+        }
+        return py::make_tuple(syntax_lineno, traceback_lineno);
+    });
+
     // test_eval_empty_globals
     m.def("eval_empty_globals", [](py::object global) {
         if (global.is_none()) {

tests/test_eval.py

@@ -27,6 +27,10 @@ def test_eval_file():
     assert m.test_eval_file_failure()
 
 
+def test_eval_line_numbers():
+    assert m.test_eval_line_numbers() == (2, 2)
+
+
 def test_eval_empty_globals():
     assert "__builtins__" in m.eval_empty_globals(None)