Adding a get_slot_fields_and_types method to python msg classes

rosidl_generator_py/resource/_msg.py.em

@@ -14,6 +14,7 @@
 @#  - value_to_py (function)
 @#######################################################################
 @
+from copy import copy
 import logging
 import traceback
 
@@ -114,6 +115,28 @@ class @(spec.base_type.type)(metaclass=Metaclass):
         '_@(field.name)',
 @[end for]@
     ]
+
+    _fields_and_field_types = {
+@[for field in spec.fields]@
+@[  if field.type.is_primitive_type() ]@
+        '@(field.name)': '@(field.type)',
+@[  else ]@
+@[    if field.type.is_array ]@
+@[      if field.type.array_size ]@
+@[        if field.type.is_upper_bound ]@
+        '@(field.name)': '@(field.type.pkg_name)/@(field.type.type)[<=@(field.type.array_size)]',
+@[        else ]@
+        '@(field.name)': '@(field.type.pkg_name)/@(field.type.type)[@(field.type.array_size)]',
+@[        end if ]@
+@[      else ]@
+        '@(field.name)': '@(field.type.pkg_name)/@(field.type.type)[]',
+@[      end if ]@
+@[    else ]@
+        '@(field.name)': '@(field.type.pkg_name)/@(field.type.type)',
+@[    end if ]@
+@[  end if ]@
+@[end for]@
+    }
 @
 @[if len(spec.fields) > 0]@
 
@@ -175,6 +198,10 @@ class @(spec.base_type.type)(metaclass=Metaclass):
             return False
 @[end for]@
         return True
+
+    @@classmethod
+    def get_fields_and_field_types(cls):
+        return copy(cls._fields_and_field_types)
 @[for field in spec.fields]@
 
 @{

rosidl_generator_py/test/test_interfaces.py

@@ -257,3 +257,60 @@ def test_out_of_range():
         setattr(b, 'unbounded_uint64_values', [2**64])
     with pytest.raises(AssertionError):
         setattr(b, 'unbounded_uint64_values', [-1])
+
+
+def test_slot_attributes():
+    a = Nested()
+    assert hasattr(a, 'get_fields_and_field_types')
+    assert hasattr(a, '__slots__')
+    nested_slot_types_dict = getattr(a, 'get_fields_and_field_types')()
+    nested_slots = getattr(a, '__slots__')
+    assert len(nested_slot_types_dict) == len(nested_slots)
+    expected_nested_slot_types_dict = {
+        'primitives': 'rosidl_generator_py/Primitives',
+        'two_primitives': 'rosidl_generator_py/Primitives[2]',
+        'up_to_three_primitives': 'rosidl_generator_py/Primitives[<=3]',
+        'unbounded_primitives': 'rosidl_generator_py/Primitives[]',
+    }
+    assert len(nested_slot_types_dict) == len(expected_nested_slot_types_dict)
+
+    for expected_field, expected_slot_type in expected_nested_slot_types_dict.items():
+        assert expected_field in nested_slot_types_dict.keys()
+        assert expected_slot_type == nested_slot_types_dict[expected_field]
+
+
+def test_primative_slot_attributes():
+    b = StringArrays()
+    assert hasattr(b, 'get_fields_and_field_types')
+    assert hasattr(b, '__slots__')
+    string_slot_types_dict = getattr(b, 'get_fields_and_field_types')()
+    string_slots = getattr(b, '__slots__')
+    assert len(string_slot_types_dict) == len(string_slots)
+    expected_string_slot_types_dict = {
+        'ub_string_static_array_value': 'string<=5[3]',
+        'ub_string_ub_array_value': 'string<=5[<=10]',
+        'ub_string_dynamic_array_value': 'string<=5[]',
+        'string_dynamic_array_value': 'string[]',
+        'string_static_array_value': 'string[3]',
+        'string_bounded_array_value': 'string[<=10]',
+        'def_string_dynamic_array_value': 'string[]',
+        'def_string_static_array_value': 'string[3]',
+        'def_string_bounded_array_value': 'string[<=10]',
+        'def_various_quotes': 'string[]',
+        'def_various_commas': 'string[]',
+    }
+
+    assert len(string_slot_types_dict) == len(expected_string_slot_types_dict)
+
+    for expected_field, expected_slot_type in expected_string_slot_types_dict.items():
+        assert expected_field in string_slot_types_dict.keys()
+        assert expected_slot_type == string_slot_types_dict[expected_field]
+
+
+def test_modifying_slot_fields_and_types():
+    b = StringArrays()
+    assert hasattr(b, 'get_fields_and_field_types')
+    string_slot_types_dict = getattr(b, 'get_fields_and_field_types')()
+    string_slot_types_dict_len = len(string_slot_types_dict)
+    string_slot_types_dict[1] = 2
+    assert len(getattr(b, 'get_fields_and_field_types')()) == string_slot_types_dict_len