NOLINT reduction (#3096)

* Copying from prework_no_rst branch (PR #3087): test_numpy_array.cpp, test_stl.cpp

* Manual changes reducing NOLINTs.

* clang-format-diff.py

* Minor adjustment to avoid MSVC warning C4702: unreachable code

Author: rwgk

tests/pybind11_cross_module_tests.cpp

@@ -132,7 +132,6 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_missing_header_message
     // The main module already includes stl.h, but we need to test the error message
     // which appears when this header is missing.
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("missing_header_arg", [](std::vector<float>) { });
+    m.def("missing_header_arg", [](const std::vector<float> &) {});
     m.def("missing_header_return", []() { return std::vector<float>(); });
 }

tests/test_buffers.cpp

@@ -79,8 +79,7 @@ TEST_SUBMODULE(buffers, m) {
     py::class_<Matrix>(m, "Matrix", py::buffer_protocol())
         .def(py::init<py::ssize_t, py::ssize_t>())
         /// Construct from a buffer
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        .def(py::init([](py::buffer const b) {
+        .def(py::init([](const py::buffer &b) {
             py::buffer_info info = b.request();
             if (info.format != py::format_descriptor<float>::format() || info.ndim != 2)
                 throw std::runtime_error("Incompatible buffer format!");

tests/test_builtin_casters.cpp

@@ -105,8 +105,7 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_bytes_to_string
     m.def("strlen", [](char *s) { return strlen(s); });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("string_length", [](std::string s) { return s.length(); });
+    m.def("string_length", [](const std::string &s) { return s.length(); });
 
 #ifdef PYBIND11_HAS_U8STRING
     m.attr("has_u8string") = true;
@@ -185,14 +184,11 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_none_deferred
     m.def("defer_none_cstring", [](char *) { return false; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("defer_none_cstring", [](py::none) { return true; });
+    m.def("defer_none_cstring", [](const py::none &) { return true; });
     m.def("defer_none_custom", [](UserType *) { return false; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("defer_none_custom", [](py::none) { return true; });
+    m.def("defer_none_custom", [](const py::none &) { return true; });
     m.def("nodefer_none_void", [](void *) { return true; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("nodefer_none_void", [](py::none) { return false; });
+    m.def("nodefer_none_void", [](const py::none &) { return false; });
 
     // test_void_caster
     m.def("load_nullptr_t", [](std::nullptr_t) {}); // not useful, but it should still compile
@@ -242,8 +238,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     }, "copy"_a);
 
     m.def("refwrap_iiw", [](const IncType &w) { return w.value(); });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("refwrap_call_iiw", [](IncType &w, py::function f) {
+    m.def("refwrap_call_iiw", [](IncType &w, const py::function &f) {
         py::list l;
         l.append(f(std::ref(w)));
         l.append(f(std::cref(w)));

tests/test_class.cpp

@@ -131,8 +131,7 @@ TEST_SUBMODULE(class_, m) {
     m.def("return_none", []() -> BaseClass* { return nullptr; });
 
     // test_isinstance
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("check_instances", [](py::list l) {
+    m.def("check_instances", [](const py::list &l) {
         return py::make_tuple(
             py::isinstance<py::tuple>(l[0]),
             py::isinstance<py::dict>(l[1]),
@@ -217,8 +216,7 @@ TEST_SUBMODULE(class_, m) {
     py::implicitly_convertible<UserType, ConvertibleFromUserType>();
 
     m.def("implicitly_convert_argument", [](const ConvertibleFromUserType &r) { return r.i; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("implicitly_convert_variable", [](py::object o) {
+    m.def("implicitly_convert_variable", [](const py::object &o) {
         // `o` is `UserType` and `r` is a reference to a temporary created by implicit
         // conversion. This is valid when called inside a bound function because the temp
         // object is attached to the same life support system as the arguments.
@@ -396,8 +394,7 @@ TEST_SUBMODULE(class_, m) {
     struct StringWrapper { std::string str; };
     m.def("test_error_after_conversions", [](int) {});
     m.def("test_error_after_conversions",
-          // NOLINTNEXTLINE(performance-unnecessary-value-param)
-          [](StringWrapper) -> NotRegistered { return {}; });
+          [](const StringWrapper &) -> NotRegistered { return {}; });
     py::class_<StringWrapper>(m, "StringWrapper").def(py::init<std::string>());
     py::implicitly_convertible<std::string, StringWrapper>();
 

tests/test_copy_move.cpp

@@ -126,7 +126,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
 
     // test_move_and_copy_casts
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("move_and_copy_casts", [](py::object o) {
+    m.def("move_and_copy_casts", [](const py::object &o) {
         int r = 0;
         r += py::cast<MoveOrCopyInt>(o).value; /* moves */
         r += py::cast<MoveOnlyInt>(o).value; /* moves */
@@ -141,8 +141,10 @@ TEST_SUBMODULE(copy_move_policies, m) {
 
     // test_move_and_copy_loads
     m.def("move_only", [](MoveOnlyInt m) { return m.value; });
+    // Changing this breaks the existing test: needs careful review.
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("move_or_copy", [](MoveOrCopyInt m) { return m.value; });
+    // Changing this breaks the existing test: needs careful review.
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("copy_only", [](CopyOnlyInt m) { return m.value; });
     m.def("move_pair", [](std::pair<MoveOnlyInt, MoveOrCopyInt> p) {

tests/test_eigen.cpp

@@ -98,12 +98,13 @@ TEST_SUBMODULE(eigen, m) {
 
     // test_eigen_ref_to_python
     // Different ways of passing via Eigen::Ref; the first and second are the Eigen-recommended
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("cholesky1", [](Eigen::Ref<MatrixXdR> x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
+    m.def("cholesky1",
+          [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky2", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky3", [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("cholesky4", [](Eigen::Ref<const MatrixXdR> x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
+    m.def("cholesky4", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd {
+        return x.llt().matrixL();
+    });
 
     // test_eigen_ref_mutators
     // Mutators: these add some value to the given element using Eigen, but Eigen should be mapping into
@@ -248,12 +249,9 @@ TEST_SUBMODULE(eigen, m) {
     m.def("fixed_copy_r", [](const FixedMatrixR &m) -> FixedMatrixR { return m; });
     m.def("fixed_copy_c", [](const FixedMatrixC &m) -> FixedMatrixC { return m; });
     // test_mutator_descriptors
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("fixed_mutator_r", [](Eigen::Ref<FixedMatrixR>) {});
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("fixed_mutator_c", [](Eigen::Ref<FixedMatrixC>) {});
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("fixed_mutator_a", [](py::EigenDRef<FixedMatrixC>) {});
+    m.def("fixed_mutator_r", [](const Eigen::Ref<FixedMatrixR> &) {});
+    m.def("fixed_mutator_c", [](const Eigen::Ref<FixedMatrixC> &) {});
+    m.def("fixed_mutator_a", [](const py::EigenDRef<FixedMatrixC> &) {});
     // test_dense
     m.def("dense_r", [mat]() -> DenseMatrixR { return DenseMatrixR(mat); });
     m.def("dense_c", [mat]() -> DenseMatrixC { return DenseMatrixC(mat); });
@@ -284,9 +282,10 @@ TEST_SUBMODULE(eigen, m) {
     // that would allow copying (if types or strides don't match) for comparison:
     m.def("get_elem", &get_elem);
     // Now this alternative that calls the tells pybind to fail rather than copy:
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("get_elem_nocopy", [](Eigen::Ref<const Eigen::MatrixXd> m) -> double { return get_elem(m); },
-            py::arg{}.noconvert());
+    m.def(
+        "get_elem_nocopy",
+        [](const Eigen::Ref<const Eigen::MatrixXd> &m) -> double { return get_elem(m); },
+        py::arg{}.noconvert());
     // Also test a row-major-only no-copy const ref:
     m.def("get_elem_rm_nocopy", [](Eigen::Ref<const Eigen::Matrix<long, -1, -1, Eigen::RowMajor>> &m) -> long { return m(2, 1); },
             py::arg{}.noconvert());
@@ -301,20 +300,22 @@ TEST_SUBMODULE(eigen, m) {
     // test_issue1105
     // Issue #1105: when converting from a numpy two-dimensional (Nx1) or (1xN) value into a dense
     // eigen Vector or RowVector, the argument would fail to load because the numpy copy would
-    // fail: numpy won't broadcast a Nx1 into a 1-dimensional vector. NOLINTNEXTLINE
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("iss1105_col", [](Eigen::VectorXd) { return true; });
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("iss1105_row", [](Eigen::RowVectorXd) { return true; });
+    // fail: numpy won't broadcast a Nx1 into a 1-dimensional vector.
+    m.def("iss1105_col", [](const Eigen::VectorXd &) { return true; });
+    m.def("iss1105_row", [](const Eigen::RowVectorXd &) { return true; });
 
     // test_named_arguments
     // Make sure named arguments are working properly:
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("matrix_multiply", [](const py::EigenDRef<const Eigen::MatrixXd> A, const py::EigenDRef<const Eigen::MatrixXd> B)
-            -> Eigen::MatrixXd {
-        if (A.cols() != B.rows()) throw std::domain_error("Nonconformable matrices!");
-        return A * B;
-    }, py::arg("A"), py::arg("B"));
+    m.def(
+        "matrix_multiply",
+        [](const py::EigenDRef<const Eigen::MatrixXd> &A,
+           const py::EigenDRef<const Eigen::MatrixXd> &B) -> Eigen::MatrixXd {
+            if (A.cols() != B.rows())
+                throw std::domain_error("Nonconformable matrices!");
+            return A * B;
+        },
+        py::arg("A"),
+        py::arg("B"));
 
     // test_custom_operator_new
     py::class_<CustomOperatorNew>(m, "CustomOperatorNew")
@@ -326,8 +327,7 @@ TEST_SUBMODULE(eigen, m) {
     // In case of a failure (the caster's temp array does not live long enough), creating
     // a new array (np.ones(10)) increases the chances that the temp array will be garbage
     // collected and/or that its memory will be overridden with different values.
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("get_elem_direct", [](Eigen::Ref<const Eigen::VectorXd> v) {
+    m.def("get_elem_direct", [](const Eigen::Ref<const Eigen::VectorXd> &v) {
         py::module_::import("numpy").attr("ones")(10);
         return v(5);
     });

tests/test_exceptions.cpp

@@ -201,17 +201,16 @@ TEST_SUBMODULE(exceptions, m) {
         throw py::error_already_set();
     });
 
-    // Changing this broke things. Don't know why
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("python_call_in_destructor", [](py::dict d) {
+    m.def("python_call_in_destructor", [](const py::dict &d) {
+        bool retval = false;
         try {
             PythonCallInDestructor set_dict_in_destructor(d);
             PyErr_SetString(PyExc_ValueError, "foo");
             throw py::error_already_set();
         } catch (const py::error_already_set&) {
-            return true;
+            retval = true;
         }
-        return false;
+        return retval;
     });
 
     m.def("python_alreadyset_in_destructor", [](const py::str &s) {

tests/test_kwargs_and_defaults.cpp

@@ -65,9 +65,10 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     #endif
     m.def("arg_refcount_h", [](py::handle h) { GC_IF_NEEDED; return h.ref_count(); });
     m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) { GC_IF_NEEDED; return h.ref_count(); });
-    // TODO replace the following nolints as appropriate
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("arg_refcount_o", [](py::object o) { GC_IF_NEEDED; return o.ref_count(); });
+    m.def("arg_refcount_o", [](const py::object &o) {
+        GC_IF_NEEDED;
+        return o.ref_count();
+    });
     m.def("args_refcount", [](py::args a) {
         GC_IF_NEEDED;
         py::tuple t(a.size());
@@ -76,8 +77,7 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
             t[i] = (int) Py_REFCNT(PyTuple_GET_ITEM(a.ptr(), static_cast<py::ssize_t>(i)));
         return t;
     });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("mixed_args_refcount", [](py::object o, py::args a) {
+    m.def("mixed_args_refcount", [](const py::object &o, py::args a) {
         GC_IF_NEEDED;
         py::tuple t(a.size() + 1);
         t[0] = o.ref_count();

tests/test_methods_and_attributes.cpp

@@ -294,20 +294,17 @@ TEST_SUBMODULE(methods_and_attributes, m) {
             "static_rw_func", py::cpp_function(static_get2, rvp_copy), static_set2)
         // test_property_rvalue_policy
         .def_property_readonly("rvalue", &TestPropRVP::get_rvalue)
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        .def_property_readonly_static("static_rvalue", [](py::object) { return UserType(1); });
+        .def_property_readonly_static("static_rvalue",
+                                      [](const py::object &) { return UserType(1); });
 
     // test_metaclass_override
     struct MetaclassOverride { };
     py::class_<MetaclassOverride>(m, "MetaclassOverride", py::metaclass((PyObject *) &PyType_Type))
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        .def_property_readonly_static("readonly", [](py::object) { return 1; });
+        .def_property_readonly_static("readonly", [](const py::object &) { return 1; });
 
     // test_overload_ordering
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("overload_order", [](std::string) { return 1; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("overload_order", [](std::string) { return 2; });
+    m.def("overload_order", [](const std::string &) { return 1; });
+    m.def("overload_order", [](const std::string &) { return 2; });
     m.def("overload_order", [](int) { return 3; });
     m.def("overload_order", [](int) { return 4; }, py::prepend{});
 

tests/test_multiple_inheritance.cpp

@@ -141,8 +141,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def(py::init<int, int>());
 
     m.def("bar_base2a", [](Base2a *b) { return b->bar(); });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("bar_base2a_sharedptr", [](std::shared_ptr<Base2a> b) { return b->bar(); });
+    m.def("bar_base2a_sharedptr", [](const std::shared_ptr<Base2a> &b) { return b->bar(); });
 
     // test_mi_unaligned_base
     // test_mi_base_return