add KeyValueMap

Author: asottile

README.md

@@ -116,6 +116,15 @@ Used to nest maps inside of arrays.  For arrays of scalars, see `check_array`.
 
 When validated, this will check that each element adheres to the sub-schema.
 
+### `KeyValueMap(object_name, key_check_fn, value_schema)`
+
+Used to make a schema representing a homogenous mapping where the keys are
+of a specific type and the values match a schema
+
+- `object_name`: will be displayed in error messages
+- `key_check_fn`: a [check function](#check-functions) for the key
+- `value_schema`: a `Map` / `Array` or other sub-schema.
+
 ## Validator objects
 
 Validator objects are used to validate key-value-pairs of a `Map`.

cfgv.py

@@ -258,6 +258,40 @@ def remove_defaults(self, v):
         return ret
 
 
+class KeyValueMap(
+        collections.namedtuple(
+            'KeyValueMap',
+            ('object_name', 'check_key_fn', 'value_schema'),
+        ),
+):
+    __slots__ = ()
+
+    def check(self, v):
+        if not isinstance(v, dict):
+            raise ValidationError(
+                f'Expected a {self.object_name} map but got a '
+                f'{type(v).__name__}',
+            )
+        with validate_context(f'At {self.object_name}()'):
+            for k, val in v.items():
+                with validate_context(f'For key: {k}'):
+                    self.check_key_fn(k)
+                with validate_context(f'At key: {k}'):
+                    validate(val, self.value_schema)
+
+    def apply_defaults(self, v):
+        return {
+            k: apply_defaults(val, self.value_schema)
+            for k, val in v.items()
+        }
+
+    def remove_defaults(self, v):
+        return {
+            k: remove_defaults(val, self.value_schema)
+            for k, val in v.items()
+        }
+
+
 class Array(collections.namedtuple('Array', ('of', 'allow_empty'))):
     __slots__ = ()
 

tests/cfgv_test.py

@@ -11,13 +11,16 @@
 from cfgv import check_any
 from cfgv import check_array
 from cfgv import check_bool
+from cfgv import check_int
 from cfgv import check_one_of
 from cfgv import check_regex
+from cfgv import check_string
 from cfgv import check_type
 from cfgv import Conditional
 from cfgv import ConditionalOptional
 from cfgv import ConditionalRecurse
 from cfgv import In
+from cfgv import KeyValueMap
 from cfgv import load_from_filename
 from cfgv import Map
 from cfgv import MISSING
@@ -728,3 +731,79 @@ def test_warn_additional_keys_when_has_extra_keys(warn_additional_keys):
 def test_warn_additional_keys_when_no_extra_keys(warn_additional_keys):
     validate({True: True}, warn_additional_keys.schema)
     assert not warn_additional_keys.record.called
+
+
+key_value_map_schema = KeyValueMap(
+    'Container',
+    check_string,
+    Map(
+        'Object', 'name',
+        Required('name', check_string),
+        Optional('setting', check_bool, False),
+    ),
+)
+key_value_map_ints_schema = KeyValueMap(
+    'Container',
+    check_int,
+    Array(Map('Object', 'nane', Required('name', check_string))),
+)
+
+
+def test_key_value_map_schema_ok():
+    validate(
+        {'hello': {'name': 'hello'}, 'world': {'name': 'world'}},
+        key_value_map_schema,
+    )
+    validate(
+        {1: [{'name': 'hello'}], 2: [{'name': 'world'}]},
+        key_value_map_ints_schema,
+    )
+
+
+def test_key_value_map_apply_defaults():
+    orig = {'hello': {'name': 'hello'}}
+    ret = apply_defaults(orig, key_value_map_schema)
+    assert orig == {'hello': {'name': 'hello'}}
+    assert ret == {'hello': {'name': 'hello', 'setting': False}}
+
+
+def test_key_value_map_remove_defaults():
+    orig = {'hello': {'name': 'hello', 'setting': False}}
+    ret = remove_defaults(orig, key_value_map_schema)
+    assert orig == {'hello': {'name': 'hello', 'setting': False}}
+    assert ret == {'hello': {'name': 'hello'}}
+
+
+def test_key_value_map_not_a_map():
+    with pytest.raises(ValidationError) as excinfo:
+        validate([], key_value_map_schema)
+    expected = (
+        'Expected a Container map but got a list',
+    )
+    _assert_exception_trace(excinfo.value, expected)
+
+
+def test_key_value_map_wrong_key_type():
+    with pytest.raises(ValidationError) as excinfo:
+        val = {1: {'name': 'hello'}}
+        validate(val, key_value_map_schema)
+    expected = (
+        'At Container()',
+        'For key: 1',
+        'Expected string got int',
+    )
+    _assert_exception_trace(excinfo.value, expected)
+
+
+def test_key_value_map_error_in_child_schema():
+    with pytest.raises(ValidationError) as excinfo:
+        val = {'hello': {'name': 1}}
+        validate(val, key_value_map_schema)
+    expected = (
+        'At Container()',
+        'At key: hello',
+        'At Object(name=1)',
+        'At key: name',
+        'Expected string got int',
+    )
+    _assert_exception_trace(excinfo.value, expected)