Add Type to bad args output

The changes the error message for invalid arguments to display 'Type (=
strvalue)' instead of just 'strvalue' for the given argument list.

Fixes #517.

Author: jagerman

include/pybind11/pybind11.h

@@ -509,7 +509,13 @@ class cpp_function : public function {
             msg += "\nInvoked with: ";
             auto args_ = reinterpret_borrow<tuple>(args);
             for (size_t ti = overloads->is_constructor ? 1 : 0; ti < args_.size(); ++ti) {
-                msg += static_cast<std::string>(pybind11::str(args_[ti]));
+                auto pytype = args_[ti].get_type();
+                pybind11::str value(args_[ti]);
+                msg += static_cast<std::string>(
+                    hasattr(pytype, "__name__")
+                        ? pybind11::str("{} (= {})").format(getattr(pytype, "__name__"), value)
+                        : value);
+
                 if ((ti + 1) != args_.size() )
                     msg += ", ";
             }

tests/test_inheritance.py

@@ -27,7 +27,7 @@ def test_inheritance(msg):
         dog_bark(): incompatible function arguments. The following argument types are supported:
             1. (arg0: m.Dog) -> str
 
-        Invoked with: <m.Pet object at 0>
+        Invoked with: Pet (= <m.Pet object at 0>)
     """
 
 

tests/test_issues.py

@@ -69,7 +69,7 @@ def test_no_id(msg):
         get_element(): incompatible function arguments. The following argument types are supported:
             1. (arg0: m.issues.ElementA) -> int
 
-        Invoked with: None
+        Invoked with: NoneType (= None)
     """
 
     with pytest.raises(TypeError) as excinfo:
@@ -78,7 +78,7 @@ def test_no_id(msg):
         expect_int(): incompatible function arguments. The following argument types are supported:
             1. (arg0: int) -> int
 
-        Invoked with: 5.2
+        Invoked with: float (= 5.2)
     """
     assert expect_float(12) == 12
 
@@ -96,7 +96,7 @@ def test_str_issue(msg):
             1. m.issues.StrIssue(arg0: int)
             2. m.issues.StrIssue()
 
-        Invoked with: no, such, constructor
+        Invoked with: str (= no), str (= such), str (= constructor)
     """
 
 

tests/test_opaque_types.py

@@ -38,7 +38,7 @@ def test_pointers(msg):
         get_void_ptr_value(): incompatible function arguments. The following argument types are supported:
             1. (arg0: capsule) -> int
 
-        Invoked with: [1, 2, 3]
+        Invoked with: list (= [1, 2, 3])
     """
 
     assert return_null_str() is None