Merge pull request #1326 from tahoe-lafs/4056.provides

attrs "provides()"

integration/grid.py

@@ -31,9 +31,15 @@ from twisted.internet.defer import (
 from twisted.internet.task import (
     deferLater,
 )
-from twisted.internet.protocol import ProcessProtocol  # see ticket 4056
+from twisted.internet.interfaces import (
+    IProcessTransport,
+    IProcessProtocol,
+)
 from twisted.internet.error import ProcessTerminated
 
+from allmydata.util.attrs_provides import (
+    provides,
+)
 from allmydata.node import read_config
 from .util import (
     _CollectOutputProtocol,
@@ -67,16 +73,11 @@ class FlogGatherer(object):
     """
     Flog Gatherer process.
     """
-
+    process = attr.ib(
-    # it would be best to use attr.validators.provides() here with the
+        validator=provides(IProcessTransport)
-    # corresponding Twisted interface (IProcessTransport,
+    )
-    # IProcessProtocol) but that is deprecated; please replace with
-    # our own "provides" as part of
-    # https://tahoe-lafs.org/trac/tahoe-lafs/ticket/4056#ticket
-    # insisting on a subclass is narrower than necessary
-    process = attr.ib()
     protocol = attr.ib(
-        validator=attr.validators.instance_of(ProcessProtocol)
+        validator=provides(IProcessProtocol)
     )
     furl = attr.ib()
 
@@ -156,7 +157,7 @@ class StorageServer(object):
         validator=attr.validators.instance_of(TahoeProcess)
     )
     protocol = attr.ib(
-        validator=attr.validators.instance_of(ProcessProtocol)
+        validator=provides(IProcessProtocol)
     )
 
     @inlineCallbacks
@@ -208,7 +209,7 @@ class Client(object):
         validator=attr.validators.instance_of(TahoeProcess)
     )
     protocol = attr.ib(
-        validator=attr.validators.instance_of(ProcessProtocol)
+        validator=provides(IProcessProtocol)
     )
     request = attr.ib()  # original request, for addfinalizer()
 
@@ -336,7 +337,7 @@ class Introducer(object):
         validator=attr.validators.instance_of(TahoeProcess)
     )
     protocol = attr.ib(
-        validator=attr.validators.instance_of(ProcessProtocol)
+        validator=provides(IProcessProtocol)
     )
     furl = attr.ib()
 

newsfragments/4056.bugfix

@@ -0,0 +1,3 @@
+Provide our own copy of attrs' "provides()" validator
+
+This validator is deprecated and slated for removal; that project's suggestion is to copy the code to our project.

src/allmydata/storage_client.py

@@ -88,6 +88,7 @@ from allmydata.util.rrefutil import add_version_to_remote_reference
 from allmydata.util.hashutil import permute_server_hash
 from allmydata.util.dictutil import BytesKeyDict, UnicodeKeyDict
 from allmydata.util.deferredutil import async_to_deferred, race
+from allmydata.util.attrs_provides import provides
 from allmydata.storage.http_client import (
     StorageClient, StorageClientImmutables, StorageClientGeneral,
     ClientException as HTTPClientException, StorageClientMutables,
@@ -659,7 +660,7 @@ class _FoolscapStorage(object):
     permutation_seed = attr.ib()
     tubid = attr.ib()
 
-    storage_server = attr.ib(validator=attr.validators.provides(IStorageServer))
+    storage_server = attr.ib(validator=provides(IStorageServer))
 
     _furl = attr.ib()
     _short_description = attr.ib()

src/allmydata/util/attrs_provides.py

@@ -0,0 +1,50 @@
+"""
+Utilities related to attrs
+
+Handling for zope.interface is deprecated in attrs so we copy the
+relevant support method here since we depend on zope.interface anyway
+"""
+
+from attr._make import attrs, attrib
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _ProvidesValidator:
+    interface = attrib()
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if not self.interface.providedBy(value):
+            raise TypeError(
+                "'{name}' must provide {interface!r} which {value!r} "
+                "doesn't.".format(
+                    name=attr.name, interface=self.interface, value=value
+                ),
+                attr,
+                self.interface,
+                value,
+            )
+
+    def __repr__(self):
+        return "<provides validator for interface {interface!r}>".format(
+            interface=self.interface
+        )
+
+
+def provides(interface):
+    """
+    A validator that raises a `TypeError` if the initializer is called
+    with an object that does not provide the requested *interface* (checks are
+    performed using ``interface.providedBy(value)`` (see `zope.interface
+    <https://zopeinterface.readthedocs.io/en/latest/>`_).
+
+    :param interface: The interface to check for.
+    :type interface: ``zope.interface.Interface``
+
+    :raises TypeError: With a human readable error message, the attribute
+        (of type `attrs.Attribute`), the expected interface, and the
+        value it got.
+    """
+    return _ProvidesValidator(interface)