Add attr validator integration

requirements.txt

@@ -1,5 +1,7 @@
 pyparsing==2.2.2
 decorator==4.0.10
 six==1.10.0
+backports.functools-lru-cache==1.5
+qualname==0.1.0
 future
 numpy<1.16

setup.py

@@ -1,5 +1,4 @@
 import os
-
 from setuptools import setup, find_packages
 
 description = (
@@ -65,7 +64,7 @@ def get_version(filename):
 
       package_dir={'': 'src'},
       packages=find_packages('src'),
-      install_requires=['pyparsing', 'decorator', 'six', 'future'],
+      install_requires=['pyparsing', 'decorator', 'six', 'future', 'backports.functools-lru-cache', 'qualname', ],
       tests_require=['nose'],
       entry_points={},
       )

src/contracts/__init__.py

@@ -1,4 +1,4 @@
-__version__ = '1.8.12'
+__version__ = '1.8.13'
 
 import logging
 

src/contracts/integrations/AttrValidator.py

@@ -0,0 +1,58 @@
+import functools
+try:
+    # python 3.5+
+    from functools import lru_cache
+except ImportError:
+    # python 2
+    from backports.functools_lru_cache import lru_cache
+
+try:
+    # python 3.3+
+
+    object.__qualname__
+
+    import operator
+    qualname = operator.attrgetter("__qualname__")
+except AttributeError:
+    # python 2
+    from qualname import qualname
+
+import attr  # attr is only a dependency of pycontracts if this module is imported. Otherwise, it does not depend on it.
+from contracts.interface import ContractNotRespected
+from contracts.main import new_contract
+
+
+@attr.s(repr=False, slots=True, hash=True)
+class AttrValidator(object):
+    '''
+        Validator linking C{pycontracts} with C{attr}'s validators
+    '''
+
+    def __call__(self, inst, attr, value):
+        """
+            Executes the validator by checking it against the contract it was configured with.
+        """
+        try:
+            AttrValidator.__get_contract(inst.__class__, attr.name, self.contract).check(
+                                   value,
+                                   )
+        except ContractNotRespected as e:
+            # adding formatted debug information to the error
+            e.error = "{!r}.{}\n{}".format(inst, attr.name, e.error)
+            raise e
+
+    def __repr__(self):
+        return (
+            "<Validator linking attr's validators with pycontracts' contract: {contract!r}>"
+            .format(contract=self.contract)
+        )
+
+    @staticmethod
+    @lru_cache(typed=True)
+    def __get_contract(inst_class, name, contract):
+        # compiling the contract takes time, we want to cache active contracts as they come up
+        return new_contract("{}___{}".format(qualname(inst_class).replace('.', '___'), name), contract,)
+
+    contract = attr.ib()
+    """ Contract honoured by the given validator"""
+

src/contracts/integrations/__init__.py

@@ -0,0 +1 @@
+# This space for rent