Support default values at construction time

CHANGELOG.rst

@@ -2,6 +2,13 @@
 CHANGELOG
 =========
 
+
+0.23.0
+===============
+
+* Support for default values at construction time.
+
+
 0.22.0
 ===============
 

docs/conf.py

@@ -51,9 +51,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = '0.22'
+version = '0.23'
 # The full version, including alpha/beta/rc tags.
-release = '0.22.0'
+release = '0.23.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.

setup.py

@@ -38,7 +38,7 @@ def requirements(at_path: Path):
 # ----------------------------
 
 setup(name='typeit',
-      version='0.22.0',
+      version='0.23.0',
       description='typeit brings typed data into your project',
       long_description=README,
       classifiers=[

tests/parser/test_dataclasses.py

@@ -11,7 +11,7 @@ def test_dataclasses():
         class InventoryItem:
             name: str
             unit_price: float
-            quantity_on_hand: int = 0
+            quantity_on_hand: int
 
         overrides = {
             (InventoryItem, 'quantity_on_hand'): 'quantity'
@@ -27,3 +27,17 @@ class InventoryItem:
         x = mk_inv(serialized)
         assert isinstance(x, InventoryItem)
         assert serialize_inv(x) == serialized
+
+    def test_with_default_values():
+
+        @dataclass
+        class X:
+            one: int
+            two: int = 2
+            three: int = 3
+
+        data = {'one': 1}
+
+        mk_x, serialize_x = typeit.TypeConstructor ^ X
+        x = mk_x(data)
+        assert serialize_x(x) == {'one': 1, 'two': 2, 'three': 3}

tests/parser/test_parser.py

@@ -435,3 +435,33 @@ class X(NamedTuple):
 ])
 def test_parse_builtins_and_sequences(typ):
     mk_x, serialize_x = typeit.TypeConstructor ^ typ
+
+
+def test_default_namedtuple_values():
+    class X(NamedTuple):
+        x: int = 1
+
+    data = {}
+
+    mk_x, serialize_x = typeit.TypeConstructor ^ X
+
+    x = mk_x(data)
+    assert isinstance(x, X)
+    assert x.x == 1
+    assert serialize_x(x) == {'x': 1}
+
+
+def test_default_init_based_value():
+    class X:
+        def __init__(self, x: int, y: int = 1):
+            self.x = x
+            self.y = y
+
+    data = {'x': 0}
+
+    mk_x, serialize_x = typeit.TypeConstructor ^ X
+
+    x = mk_x(data)
+    assert isinstance(x, X)
+    assert x.x == 0 and x.y == 1
+    assert serialize_x(x) == {'x': 0, 'y': 1}

typeit/parser.py

@@ -4,6 +4,7 @@
     MutableSet, TypeVar, FrozenSet, Mapping, Callable,
 )
 
+import inspect
 import collections
 
 import colander as col
@@ -376,6 +377,7 @@ def _maybe_node_for_user_type(
         hints_source = typ
         attribute_hints = _type_hints_getter(hints_source)
         get_override_identifier = lambda x: getattr(typ, x)
+        defaults = typ._field_defaults
 
         deserialize_overrides = pmap({
             # try to get a specific override for a field, if it doesn't exist, use the global modifier
@@ -396,6 +398,11 @@ def _maybe_node_for_user_type(
         hints_source = typ.__init__
         attribute_hints = _type_hints_getter(hints_source)
         get_override_identifier = lambda x: (typ, x)
+        defaults = {
+            k: v.default
+            for k, v in inspect.signature(typ.__init__).parameters.items()
+            if k != 'self' and v.default != inspect.Parameter.empty
+        }
 
         deserialize_overrides = pmap({
             # try to get a specific override for a field, if it doesn't exist, use the global modifier
@@ -438,6 +445,7 @@ def _maybe_node_for_user_type(
         # might be from the cache already
         node = clone_schema_node(node)
         node.name = serialized_field_name
+        node.missing = defaults.get(field_name, node.missing)
         type_schema.add(node)
     return type_schema, memo
 

typeit/utils.py

@@ -1,12 +1,19 @@
 import re
 import keyword
 import string
-from typing import Any, Type
+from typing import Any, Type, TypeVar
+
+from colander import TupleSchema, SequenceSchema
+
+from typeit.schema.nodes import SchemaNode
 
 NORMALIZATION_PREFIX = 'overridden__'
 SUPPORTED_CHARS = string.ascii_letters + string.digits
 
 
+T = TypeVar('T', SchemaNode, TupleSchema, SequenceSchema)
+
+
 def normalize_name(name: str,
                    pattern=re.compile('^([_0-9]+).*$')) -> str:
     """ Some field name patterns are not allowed in NamedTuples
@@ -28,7 +35,7 @@ def is_named_tuple(typ: Type[Any]) -> bool:
     return hasattr(typ, '_fields')
 
 
-def clone_schema_node(node):
+def clone_schema_node(node: T) -> T:
     """ Clonning the node and reassigning the same children,
     because clonning is recursive, but we are only interested
     in a new version of the outermost schema node, the children nodes