[config] Refactoring of configurables, allowing partially configured objects.

Configurables did not allow more than one "method" option, and mixed
scenarios (options+methods+...) were sometimes flaky, forcing the user
to know what order was the right one. Now, all options work the same,
sharing the same "order" namespace.

Backward incompatible change: Options are now required by default,
unless a default is provided.

Also adds a few candies for debugging/testing, found in the
bonobo.util.inspect module.

tests/config/test_configurables.py

@@ -2,12 +2,17 @@ import pytest
 
 from bonobo.config.configurables import Configurable
 from bonobo.config.options import Option
+from bonobo.util.inspect import inspect_node
+
+
+class NoOptConfigurable(Configurable):
+    pass
 
 
 class MyConfigurable(Configurable):
-    required_str = Option(str, required=True)
+    required_str = Option(str)
     default_str = Option(str, default='foo')
-    integer = Option(int)
+    integer = Option(int, required=False)
 
 
 class MyHarderConfigurable(MyConfigurable):
@@ -25,14 +30,20 @@ class MyConfigurableUsingPositionalOptions(MyConfigurable):
 
 
 def test_missing_required_option_error():
+    with inspect_node(MyConfigurable()) as ni:
+        assert ni.partial
+
     with pytest.raises(TypeError) as exc:
-        MyConfigurable()
+        MyConfigurable(_final=True)
     assert exc.match('missing 1 required option:')
 
 
 def test_missing_required_options_error():
+    with inspect_node(MyHarderConfigurable()) as ni:
+        assert ni.partial
+
     with pytest.raises(TypeError) as exc:
-        MyHarderConfigurable()
+        MyHarderConfigurable(_final=True)
     assert exc.match('missing 2 required options:')
 
 
@@ -50,6 +61,10 @@ def test_extraneous_options_error():
 
 def test_defaults():
     o = MyConfigurable(required_str='hello')
+
+    with inspect_node(o) as ni:
+        assert not ni.partial
+
     assert o.required_str == 'hello'
     assert o.default_str == 'foo'
     assert o.integer == None
@@ -57,6 +72,10 @@ def test_defaults():
 
 def test_str_type_factory():
     o = MyConfigurable(required_str=42)
+
+    with inspect_node(o) as ni:
+        assert not ni.partial
+
     assert o.required_str == '42'
     assert o.default_str == 'foo'
     assert o.integer == None
@@ -64,6 +83,10 @@ def test_str_type_factory():
 
 def test_int_type_factory():
     o = MyConfigurable(required_str='yo', default_str='bar', integer='42')
+
+    with inspect_node(o) as ni:
+        assert not ni.partial
+
     assert o.required_str == 'yo'
     assert o.default_str == 'bar'
     assert o.integer == 42
@@ -71,6 +94,10 @@ def test_int_type_factory():
 
 def test_bool_type_factory():
     o = MyHarderConfigurable(required_str='yes', also_required='True')
+
+    with inspect_node(o) as ni:
+        assert not ni.partial
+
     assert o.required_str == 'yes'
     assert o.default_str == 'foo'
     assert o.integer == None
@@ -79,6 +106,10 @@ def test_bool_type_factory():
 
 def test_option_resolution_order():
     o = MyBetterConfigurable()
+
+    with inspect_node(o) as ni:
+        assert not ni.partial
+
     assert o.required_str == 'kaboom'
     assert o.default_str == 'foo'
     assert o.integer == None
@@ -86,3 +117,21 @@ def test_option_resolution_order():
 
 def test_option_positional():
     o = MyConfigurableUsingPositionalOptions('1', '2', '3', required_str='hello')
+
+    with inspect_node(o) as ni:
+        assert not ni.partial
+
+    assert o.first == '1'
+    assert o.second == '2'
+    assert o.third == '3'
+    assert o.required_str == 'hello'
+    assert o.default_str == 'foo'
+    assert o.integer is None
+
+
+def test_no_opt_configurable():
+    o = NoOptConfigurable()
+
+    with inspect_node(o) as ni:
+        assert not ni.partial
+