This fixes #34 for me. When taking a look at the zope logs I noticed that IProtocol was getting added multiple times to the MRO, which seems wrong.

Implementation-wise, this attempts to only add a single instance of an interface into the MRO. In order for the comparison check to work (to see if the interface is already in the MRO) this adds a cache to only generate a single TypeInfo for each interface.

I don't know the internals of mypy so maybe this is incorrect and we should be checking a different way?

I suspect that this will work for most cases, but some odd diamond-inheritance patterns might break as the MRO might end up in the wrong order. I.e. this ensure that only a single instance of IFoo exists in the MRO, but I'm not confident it ends up in the proper place. 😄

I attempted to make a reduced test-case of this again but was unable to. 😢 I think it has something to do with:

• Having an interface (or two).
• Having a base class that implements part of that interface, but isn't marked as an implementer.
• Having a class that is an implementer.
• Having a sub-class of the implementer.

Additionally the result needs to be cached so I think this needs to be imported from another package / module and isn't part of what is being "inspected", but I'm not 100% sure about this.

Hi,

We just ran into this stacktrace:

https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.800
Traceback (most recent call last):
  File "mypy/semanal.py", line 4835, in accept
  File "mypy/nodes.py", line 950, in accept
  File "mypy/semanal.py", line 1048, in visit_class_def
  File "mypy/semanal.py", line 1125, in analyze_class
  File "mypy/semanal.py", line 1134, in analyze_class_body_common
  File "mypy/semanal.py", line 1187, in apply_class_plugin_hooks
  File "/home/travis/virtualenv/python3.8.1/lib/python3.8/site-packages/mypy_zope/plugin.py", line 266, in analyze_metaclass
    if info and any(node.fullname == expected for node in info.mro):
AttributeError: 'Var' object has no attribute 'mro'

I haven't had time find exactly which piece of code is causing this, but will do so as soon as I can.

EDIT: this was tested on mypy 0.800. The line which hit this was something like this:

@attr.s(slots=True, frozen=True)
class Leg(metaclass=CustomMetaclass):
	a: str = attr.ib()
	b: str = attr.ib()
	c: str = attr.ib()

For your consideration: a patch which I believe fixes #76. This tackles the same kind of problem that #41 addresses. Seems to be a regression introduced in #75 as part of supporting mypy 0.970.

This turned out to be a bit of a rabbit hole. I've tried to thoroughly reproduce my working here because I really am not confident in my understanding of mypy and mypy-zope. Apologies for the verbosity! (I was very keen to nail this one down.)

Reproduction

I reproduced the problem as reported in #76:

# Setup: in a blank venv
pip install -e path/to/mypy/zope mypy==0.981 twisted[tls]==22.4.0

cat >good.py <<EOF
from twisted.web.client import HTTPClientFactory
from twisted.web.client import HTTPPageGetter

class Y(HTTPPageGetter):
    pass
EOF

cat >bad.py <<EOF
from twisted.web.client import HTTPClientFactory
from twisted.web.client import HTTPPageGetter

class Y(HTTPPageGetter, object):
    pass
EOF

# Test:
rm -r .mypy_cache/3.10/twisted/

mypy good.py
# Success: no issues found in 1 source file

mypy bad.py
# bad.py:4: error: Cannot determine consistent method resolution order (MRO) for "Y"
# Found 1 error in 1 file (checked 1 source file)

Investigation

To attempt to understand what was going on, I added a bunch of debug print statements to mypy and mypy-zope until I reached enlightenment. I don't fully grok mypy's machinery, but from what I can tell:

• During semantic analysis, when mypy encounters a class with multiple base classes, it computes the child class's MRO. 1, 2
• In order to do so, it calls a function named linearize_hierarchy.
  • If we have already computed the MRO for this type, return early.
  • There is a "dummy" error handling branch which we don't seem to hit in this example.
  • We then recurisvely compute linearize_heirarchy of each of our base classes.
  • The result are fed into the algorithm which decides what the final MRO is. We return its output (or raise if there is no consistent MRO).

When I run mypy bad.py I see that linear_hierarchy is called for HTTPPageGetter with the following TypeInfo:

TypeInfo(
  Name(twisted.web.client.HTTPPageGetter)
  Bases(twisted.web.http.HTTPClient)
  Mro(twisted.web.client.HTTPPageGetter, twisted.web.http.HTTPClient, twisted.protocols.basic.LineReceiver, twisted.internet.protocol.Protocol, twisted.internet.protocol.BaseProtocol, twisted.protocols.basic._PauseableMixin, builtins.object, twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.ILoggingContext, twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.ILoggingContext)
  Names(
    _completelyDone (builtins.bool)
    _specialHeaders (builtins.set[builtins.bytes])
    connectionLost
    connectionMade
    failed (builtins.int)
    followRedirect (builtins.bool)
    handleEndHeaders
    handleHeader
    handleResponse
    handleStatus
    handleStatusDefault
    handleStatus_200
    handleStatus_201 (def (self: Any) -> Any)
    handleStatus_202 (def (self: Any) -> Any)
    handleStatus_301
    handleStatus_302
    handleStatus_303
    headers (Any)
    message (Any)
    quietLoss (builtins.int)
    status (Any)
    timeout
    version (Any)))

In particular the MRO contains two copies of IProtocol and ILoggingContext, which doesn't seem right (c.f. #41). As I understand it, mypy bad.py is loading the TypeInfo for HttpPageGetter that we persisted at the end of mypy good.py. So what was going on when we ran mypy the first time?

I will try to summarise a shedload of debug information. At some point mypy computes the MRO for twisted.internet.protocol.Protocol. The argument to linearize_hierarchy is

TypeInfo(
    Name(twisted.internet.protocol.Protocol)
    Bases(twisted.internet.protocol.BaseProtocol)
    Mro()
    Names())

Later, mypy computes the MRO for a subclass twisted.protocols.policies.ProtocolWrapper. Linearize hierarchy receives

TypeInfo(
    Name(twisted.protocols.policies.ProtocolWrapper)
    Bases(twisted.internet.protocol.Protocol)
    Mro()
    Names())

and recursively calls itself with the twisted.internet.protocol.Protocol TypeInfo. This time the MRO and Names have already been computed!

TypeInfo(
    Name(twisted.internet.protocol.Protocol)
    Bases(twisted.internet.protocol.BaseProtocol)
    Mro(twisted.internet.protocol.Protocol, twisted.internet.protocol.BaseProtocol, builtins.object, twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.ILoggingContext)
    Names(
      connectionLost
      dataReceived
      factory (Union[twisted.internet.protocol.Factory, None])
      logPrefix))

The MRO looks sensible there.

By the time mypy comes to compute the MRO for twisted.spread.banana.Banana (yeah, no idea there) we again lookup the MRO for twisted.internet.protocol.Protocol. But the MRO now has duplicate interfaces.

TypeInfo(
    Name(twisted.spread.banana.Banana)
    Bases(twisted.internet.protocol.Protocol, twisted.persisted.styles.Ephemeral)
    Mro()
    Names())
TypeInfo(
   Name(twisted.internet.protocol.Protocol)
    Bases(twisted.internet.protocol.BaseProtocol)
    Mro(twisted.internet.protocol.Protocol, twisted.internet.protocol.BaseProtocol, builtins.object, twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.ILoggingContext, twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.ILoggingContext)

Explanation

The following dirty patch adds useful logging.

diff --git a/src/mypy_zope/plugin.py b/src/mypy_zope/plugin.py
index 312c0b5..17fa127 100644
--- a/src/mypy_zope/plugin.py
+++ b/src/mypy_zope/plugin.py
@@ -364,7 +364,7 @@ def analyze_subinterface(classdef_ctx: ClassDefContext) -> None:
     def get_customize_class_mro_hook(
         self, fullname: str
     ) -> Optional[Callable[[ClassDefContext], None]]:
-        # print(f"get_customize_class_mro_hook: {fullname}")
+        print(f"get_customize_class_mro_hook: {fullname}")
 
         def analyze_interface_base(classdef_ctx: ClassDefContext) -> None:
             # Create fake constructor to mimic adaptation signature
@@ -406,6 +406,9 @@ def analyze(classdef_ctx: ClassDefContext) -> None:
             if directiface or subinterface:
                 self._analyze_zope_interface(classdef_ctx.api, classdef_ctx.cls)
 
+            self.log(f"get_customize_class_mro_hook ending for {fullname}")
+            self.log(info.mro)
+
         if fullname == "zope.interface.interface.Interface":
             return analyze_interface_base
 
@@ -695,10 +698,19 @@ def _apply_interface(self, impl: TypeInfo, iface: TypeInfo) -> None:
         # there is a decorator for the class that will create a "type promotion",
         # but ensure this only gets applied a single time per interface.
         promote = Instance(iface, [])
+        if impl.fullname == "twisted.internet.protocol.Protocol":
+            for ti in impl.mro:
+                self.log(f"DMR HMM: {ti._promote}, {promote}, {ti.fullname}")
+                self.log(f"DMR HMM: {type(ti._promote)}, {type(promote)}, {ti.fullname}")
         if not any(ti._promote == promote for ti in impl.mro):
             faketi = TypeInfo(SymbolTable(), iface.defn, iface.module_name)
             faketi._promote = [promote]
+            if impl.fullname=="twisted.internet.protocol.Protocol":
+                self.log(f"============== APPENDING {iface.defn.fullname} =====")
             impl.mro.append(faketi)
+        self.log(f"mro of {impl.fullname}@{hex(id(impl))} ({hex(id(impl.mro))}) is now:")
+        self.log(impl.mro)
+
 
 
 def plugin(version: str) -> PyType[Plugin]:

We can then see where mypy-zope is adding the duplicate interfaces.

  ZOPE: get_customize_class_mro_hook ending for twisted.internet.protocol.BaseProtocol
  ZOPE: [<TypeInfo twisted.internet.protocol.BaseProtocol>, <TypeInfo builtins.object>]
  ZOPE: get_customize_class_mro_hook ending for twisted.internet.protocol.Protocol
  ZOPE: [<TypeInfo twisted.internet.protocol.Protocol>, <TypeInfo twisted.internet.protocol.BaseProtocol>, <TypeInfo builtins.object>, <TypeInfo twisted.internet.interfaces.IProtocol>, <TypeInfo twisted.internet.interfaces.ILoggingContext>]
  ZOPE: Found implementation of twisted.internet.interfaces.IProtocol: twisted.internet.protocol.Protocol
* ZOPE: DMR HMM: [], twisted.internet.interfaces.IProtocol, twisted.internet.protocol.Protocol
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.protocol.Protocol
* ZOPE: DMR HMM: [], twisted.internet.interfaces.IProtocol, twisted.internet.protocol.BaseProtocol
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.protocol.BaseProtocol
* ZOPE: DMR HMM: [], twisted.internet.interfaces.IProtocol, builtins.object
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, builtins.object
* ZOPE: DMR HMM: [twisted.internet.interfaces.IProtocol], twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.IProtocol
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.interfaces.IProtocol
* ZOPE: DMR HMM: [twisted.internet.interfaces.ILoggingContext], twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.ILoggingContext
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.interfaces.ILoggingContext
  ZOPE: ============== APPENDING twisted.internet.interfaces.IProtocol =====
  ZOPE: mro of twisted.internet.protocol.Protocol@0x7f7a62f0a6c0 (0x7f7a66731640) is now:
  ZOPE: [<TypeInfo twisted.internet.protocol.Protocol>, <TypeInfo twisted.internet.protocol.BaseProtocol>, <TypeInfo builtins.object>, <TypeInfo twisted.internet.interfaces.IProtocol>, <TypeInfo twisted.internet.interfaces.ILoggingContext>, <TypeInfo twisted.internet.interfaces.IProt  ocol>]
  ZOPE: Found implementation of twisted.internet.interfaces.ILoggingContext: twisted.internet.protocol.Protocol
* ZOPE: DMR HMM: [], twisted.internet.interfaces.ILoggingContext, twisted.internet.protocol.Protocol
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.protocol.Protocol
* ZOPE: DMR HMM: [], twisted.internet.interfaces.ILoggingContext, twisted.internet.protocol.BaseProtocol
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.protocol.BaseProtocol
* ZOPE: DMR HMM: [], twisted.internet.interfaces.ILoggingContext, builtins.object
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, builtins.object
* ZOPE: DMR HMM: [twisted.internet.interfaces.IProtocol], twisted.internet.interfaces.ILoggingContext, twisted.internet.interfaces.IProtocol
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.interfaces.IProtocol
* ZOPE: DMR HMM: [twisted.internet.interfaces.ILoggingContext], twisted.internet.interfaces.ILoggingContext, twisted.internet.interfaces.ILoggingContext
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.interfaces.ILoggingContext
* ZOPE: DMR HMM: [twisted.internet.interfaces.IProtocol], twisted.internet.interfaces.ILoggingContext, twisted.internet.interfaces.IProtocol
* ZOPE: DMR HMM: <class 'list'>, <class 'mypy.types.Instance'>, twisted.internet.interfaces.IProtocol
  ZOPE: ============== APPENDING twisted.internet.interfaces.ILoggingContext =====

In particular, notice the line:

 ZOPE: DMR HMM: [twisted.internet.interfaces.IProtocol], twisted.internet.interfaces.IProtocol, twisted.internet.interfaces.IProtocol

(which comes from self.log(f"DMR HMM: {ti._promote}, {promote}, {ti.fullname}") in the patch). The log lines shows we're comparing ti._promote = [Instance(IProtocol)] with promote Instance(IProtocol). These two things are not equal[^1] therefore the any(...) expression here

https://github.com/Shoobx/mypy-zope/blob/5139181a07febfde688af3035d00319942df4dcf/src/mypy_zope/plugin.py#L698

is always False.[^2] So we add a duplicate IProtocol to the end of the MRO.

A similar pattern proceeds for ILoggingContext.

Fix

Check if promote in ti._promote for any ti in impl.mro, now that ti._promote is a list.

I didn't notice a huge performance cost (rm -r .mypy_cache/3.10/twisted/; mypy good.py; mypy bad.py takes 2 seconds on my machine with the patch). I haven' tried this on a bigger project like matrix-org/synapse yet. (I'm happy to, but I doubt that anyone is implementing that many interfaces for this to be a problem.)

Regression

I think this was introduced in #75. Presumably mypy made _promote a list of types rather than just a single type?

[^1]: I even checked that Instance doesn't define a weird __req__. [^2]: I'm slightly surprised that mypy --strict-equality doesn't catch this!

Tests

Works For Me :tm: after applying the change:

 $ rm -r .mypy_cache/3.10/twisted/; mypy good.py; mypy bad.py
Success: no issues found in 1 source file
Success: no issues found in 1 source file

make tests also passes on my machine.

I wasn't sure how to add a test for this (apologies). I was uncertain about the following:

• We need to run mypy on two files in a certain order. The current tests look to run each sample file in isolation(?)
• I struggled to reproduce an example without pulling in Twisted as a dependency
• We can't directly get at the MRO from mypy's output AFAIK. (No reveal_mro like there is reveal_type?)

The project foolscap relies on zope.interface and creates a RemoteInterface as an instance of a subclass of zope.interface.interface.InterfaceClass. When tested against mypy with this plugin, the interface isn't recognized as such an results in "Method must have at least one argument" failed validations.

As an example:

draft $ cat > mypy.ini
[mypy]
ignore_missing_imports = True
plugins=mypy_zope:plugin
draft $ cat > example.py
from foolscap.api import RemoteInterface

      
class Api(RemoteInterface):
    def open():
        "open something"
draft $ pip-run -q mypy foolscap mypy-zope -- -m mypy example.py
example.py:5: error: Method must have at least one argument
Found 1 error in 1 file (checked 1 source file)

I've attempted to create an even more minimal example that doesn't involve foolscap, but I've been unsuccessful:

draft $ cat > example.py
from zope.interface import interface


RemoteInterface = interface.InterfaceClass("RemoteInterface")


class Api(RemoteInterface):
    def open():
        "open something"
draft $ pip-run -q mypy mypy-zope -- -m mypy example.py
example.py:7: error: Variable "example.RemoteInterface" is not valid as a type
example.py:7: note: See https://mypy.readthedocs.io/en/latest/common_issues.html#variables-vs-type-aliases
example.py:7: error: Invalid base class "RemoteInterface"
example.py:8: error: Method must have at least one argument
Found 3 errors in 1 file (checked 1 source file)

I don't understand why

Variable "example.RemoteInterface" is not valid as a type

The note there isn't particularly helpful, as I'm creating neither an alias nor a variable. I'm creating a proper type and in the same way that foolscap does, so why does this example error where foolscap doesn't?

And surely the example error isn't valid until mypy recogognizes RemoteInterface correctly.

Can you help to determine a solution here to support foolscap.api.RemoteInterface subclasses within mypy?

Thanks for making mypy-zope! We've been using it for Synapse (which uses Twisted) and ran into a hiccup.

The following will cause mypy-zope to emit an error:

error: Cannot determine consistent method resolution order (MRO) for "Foo" [misc]

from twisted.internet import protocol

class Foo(protocol.Protocol):
    pass

reveal_type(Foo)

The class hierarchy looks like Foo -> Protocol (which implements IProtocol and ILoggingContext) -> BaseProtocol.

I tried to create a reduced test-case for this, but was not able to, so it might be specific to something Twisted has done. Any help would be appreciated!

I'm trying to use the new types coming out of Twisted in particular the IReactorTCP and IReactorTime but having a bit of an issue with how they are declared. Here's a distilled example:

from zope.interface import implementer
from zope.interface import Interface
from zope.interface import classImplements

class IFoo(Interface):
    x: int

class IBar(Interface):
    y: int

def foo_it(obj: IFoo) -> int:
    return obj.x

def bar_it(obj: IBar) -> int:
    return obj.y

# An attempt at combining IFoo and IBar into one type.
class IFooBar(IFoo, IBar):
    ...

def both_it(obj: IFooBar) -> int:
    assert IFooBar.providedBy(obj)
    return foo_it(obj) + bar_it(obj)

@implementer(IFoo, IBar)
class FooBar:
    def __init__(self, x: int, y: int) -> None:
        self.x = x
        self.y = y

# This would make IFooBar.providedBy(obj) but doesn't help mypy
classImplements(FooBar, IFooBar)

obj = FooBar(6, 7)
foo_it(obj)
bar_it(obj)
both_it(obj)   # ERROR: Argument 1 to "both_it" has incompatible type "FooBar"; expected "IFooBar"

So I thought, ah this is what Protocols in mypy were made for:

from typing import Protocol
class IFooBarProtoco(IFoo, IBar, Protocol):
    ...

Which sadly gives error: All bases of a protocol must be protocols

Is there another way to possibly declare the intersection? Or maybe the plugin can do something special with the Protocol declaration? (But is that even possible)

There's a mypy issue about it too: https://github.com/python/typing/issues/21 but it doesn't provide any solutions.

In commit https://github.com/twisted/klein/pull/471/commits/04a536c8b228d687fadd0d3e325753914d3e3b85, I enabled mypy-zope for Twisted Klein and I'm getting an INTERNAL ERROR in the build.

Here is the error with --show-traceback added:

wsanchez$ tox -e mypy -- --show-traceback src
GLOB sdist-make: /Users/wsanchez/Dropbox/Developer/Twisted/klein/setup.py
mypy inst-nodeps: /Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/.tmp/package/1/klein-20.6.0.zip
mypy installed: attrs==20.3.0,Automat==20.2.0,characteristic==14.3.0,constantly==15.1.0,hyperlink==21.0.0,idna==3.1,incremental==17.5.0,klein @ file:///Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/.tmp/package/1/klein-20.6.0.zip,mypy==0.812,mypy-extensions==0.4.3,mypy-zope==0.2.11,PyHamcrest==2.0.2,six==1.15.0,Tubes==0.2.0,Twisted==20.3.0,typed-ast==1.4.2,typing-extensions==3.7.4.3,Werkzeug==1.0.1,zope.event==4.5.0,zope.interface==5.2.0,zope.schema==6.1.0
mypy run-test-pre: PYTHONHASHSEED='3790822665'
mypy run-test: commands[0] | mypy --cache-dir=/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy_cache --pretty --show-traceback src
src/klein/test/test_trial.py:33: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.812
Traceback (most recent call last):
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/__main__.py", line 11, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/main.py", line 90, in main
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/build.py", line 179, in build
    result = _build(
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/build.py", line 253, in _build
    graph = dispatch(sources, manager, stdout)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/build.py", line 2638, in dispatch
    process_graph(graph, manager)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/build.py", line 2962, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/build.py", line 3060, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/build.py", line 2130, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checker.py", line 294, in check_first_pass
    self.accept(d)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checker.py", line 401, in accept
    stmt.accept(self)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/nodes.py", line 950, in accept
    return visitor.visit_class_def(self)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checker.py", line 1723, in visit_class_def
    self.accept(defn.defs)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checker.py", line 401, in accept
    stmt.accept(self)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/nodes.py", line 1015, in accept
    return visitor.visit_block(self)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checker.py", line 1972, in visit_block
    self.accept(s)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checker.py", line 401, in accept
    stmt.accept(self)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/nodes.py", line 950, in accept
    return visitor.visit_class_def(self)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checker.py", line 1749, in visit_class_def
    sig, _ = self.expr_checker.check_call(dec, [temp],
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checkexpr.py", line 930, in check_call
    result = self.check_call(call_function, args, arg_kinds, context, arg_names,
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checkexpr.py", line 911, in check_call
    return self.check_callable_call(callee, args, arg_kinds, context, arg_names,
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checkexpr.py", line 1023, in check_callable_call
    new_ret_type = self.apply_function_plugin(
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy/checkexpr.py", line 732, in apply_function_plugin
    return method_callback(
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy_zope/plugin.py", line 171, in analyze_implementation
    iface_type = self._lookup_type(ifacename, method_ctx.api)
  File "/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/lib/python3.9/site-packages/mypy_zope/plugin.py", line 583, in _lookup_type
    module = api.modules[module_name]
KeyError: 'klein.test.test_trial.TestCaseTests'
src/klein/test/test_trial.py:33: : note: use --pdb to drop into pdb
ERROR: InvocationError for command /Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy/bin/mypy --cache-dir=/Users/wsanchez/Dropbox/Developer/Twisted/klein/.tox/mypy_cache --pretty --show-traceback src (exited with code 2)
__________________________________________ summary __________________________________________
ERROR:   mypy: commands failed

I think I may have stumbled onto another defect in mypy.zope. Consider this code:

from zope.interface import implementer
from twisted.cred.credentials import ICredentials


class IToken(ICredentials):
    pass


@implementer(IToken)
class Token:
    pass

Run that through mypy with this mypy.ini:

[mypy]
ignore_missing_imports = True
plugins=mypy_zope:plugin

With twisted and zope interface installed, and this error occurs:

$ .tox/typechecks/bin/python -m mypy --no-incremental creds.py
creds.py:9: error: zope.interface.implementer accepts interface, not creds.IToken.
creds.py:9: error: Make sure you have stubs for all packages that provide interfaces for creds.IToken class hierarchy.
Found 2 errors in 1 file (checked 1 source file)

But make either of these tweaks and the errors go away:

1. Save the implementer in a separate variable.

from zope.interface import implementer
from twisted.cred.credentials import ICredentials


class IToken(ICredentials):
    pass


_impl = implementer(IToken)

@_impl
class Token:
    pass

2. Inline the definition of ICredentials.

from zope.interface import implementer, Interface


class ICredentials(Interface):
    pass


class IToken(ICredentials):
    pass


@implementer(IToken)
class Token:
    pass

Not sure if this is a mypy-zope or mypy issue.

It looks like variable vs type aliases is not supported by mypy-zope

I am looking at the folloing mypy documentation https://mypy.readthedocs.io/en/latest/common_issues.html#variables-vs-type-aliases

I have the following code:

class _IWaker(Interface):
    """
    Interface to wake up the event loop based on the self-pipe trick.

    The U{I{self-pipe trick}<http://cr.yp.to/docs/selfpipe.html>}, used to wake
    up the main loop from another thread or a signal handler.
    This is why we have wakeUp together with doRead

    This is used by threads or signals to wake up the event loop.
    """
    disconnected = Attribute('')

    def wakeUp():
        """
        Called when the event should be wake up.
        """

    def doRead():
        """
        Read some data from my connection and discard it.
        """

    def connectionLost(reason: failure.Failure):
        """
        Called when connection was closed and the pipes.
        """


@implementer(_IWaker)
class _SocketWaker(log.Logger):
    disconnected = 0

    def __init__(self, reactor):
        """Initialize.
        """

    def wakeUp(self):
        """Send a byte to my connection.
        """


    def doRead(self):
        """
        Read some data from my connection.
        """


    def connectionLost(self, reason):


class _FDWaker(log.Logger, object):
    disconnected = 0

    def __init__(self, reactor):
        """Initialize.
        """


    def doRead(self):
        """
        Read some bytes from the pipe and discard them.
        """


    def connectionLost(self, reason):
        """Close both ends of my pipe.
        """


@implementer(_IWaker)
class _UnixWaker(_FDWaker):
    def wakeUp(self):
        """Write one byte to the pipe, and flush it.
        """


_Waker: _IWaker
if platformType == 'posix':
    _Waker = _UnixWaker
else:
    # Primarily Windows and Jython.
    _Waker = _SocketWaker

with mypy I got the following error:

src/twisted/internet/posixbase.py:228:14: error: Incompatible types in assignment (expression has type "Type[_UnixWaker]", variable has type "_IWaker")  [assignment]
src/twisted/internet/posixbase.py:231:14: error: Incompatible types in assignment (expression has type "Type[_SocketWaker]", variable has type "_IWaker")  [assignment]

I am expecting this not to raise any issue.

Thanks!

Hi,

I ran across an interesting issue. The signature of open() unexpectedly became typing.IO[Any] instead of typing.TextIO when the plugin is enabled.

example.py:

reveal_type(open('str'))

plugin.ini:

[mypy]
plugins = mypy_zope:plugin

Here is small test:

$ more example.py 
reveal_type(open('str'))
$ more plugin.ini 
[mypy]
plugins = mypy_zope:plugin
$ mypy --config plugin.ini example.py 
example.py:1: note: Revealed type is 'typing.IO[Any]'
$ mypy example.py 
example.py:1: note: Revealed type is 'typing.TextIO'

I created a test-case here:

https://github.com/Shoobx/mypy-zope/compare/master...arnimarj:bug/open-signature-changes

Hi,

First of all, thank you for this amazing library. I'm using this library on some projects with extensive use of getUtility and getAdapter, and I was expecting that these functions would have as a return type the interface of provides argument. Right now we need to do add the interface explicitly u: IMyUtility = getUtility(IMyUtility) to get type validation.

from zope.interface import Interface
from zope.interface import implementer
from zope.component import getUtility


class IMyUtility(Interface):
    def foo(x: int):
        pass


@implementer(IMyUtility)
class MyUtility():
    def foo(self, x):
        return 2 * x


u = getUtility(IMyUtility)
# Mypy doesn't produce any error
u.foo("2")


u2: IMyUtility = getUtility(IMyUtility)
# Mypy validation works and provides this error:
#   error: Argument 1 to "foo" of "IMyUtility" has incompatible type "str"; expected "int"
u2.foo("2")

I tried adding def getUtility(self, provided: T, name: str = ...) -> T: ... (https://github.com/Shoobx/mypy-zope/blob/master/src/zope-stubs/interface/registry.pyi#L27) but I'm getting Type[IMyUtility] instead of IMyUtility.

Any idea on how to fix it? Does it make sense to add this to mypy-zope?

Thank you!

Hi. With the latest version of mypy (0.991) and mypy-zope (0.3.11) we're getting mypy errors that I think are cache related. The error goes away after rm -rf .mypy_cache

Here's the easiest repro I could make:

iface.py

from zope.interface import Interface
from zope.interface import implementer

class ISomething(Interface):
    pass

class ISomething2(Interface):
    pass

@implementer(ISomething)
class OneInterface:
    pass

@implementer(ISomething, ISomething2)
class TwoInterfaces:
    pass

foo.py

from iface import OneInterface, TwoInterfaces

class Good(OneInterface):
    pass

class Bad(TwoInterfaces):
    pass

I am able to reliably hit the problem by running the following commands:

$ rm -rf .mypy_cache
$ mypy iface.py 
Success: no issues found in 1 source file
$ mypy foo.py 
foo.py:6: error: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases  [misc]
Found 1 error in 1 file (checked 1 source file)

As you can tell this only happens when there are multiple interfaces.

Bumps mypy from 0.981 to 0.991.

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

Hi. I was testing the upcoming mypy release and it seems to be emitting new warning for interface definitions:

import zope.interface


class IZomething(zope.interface.Interface):
	def Query(a: str, b: str) -> list[int]:
		pass

gives:

$ mypy --config=mypy.ini int.py 
int.py:5: error: Missing return statement  [empty-body]
Found 1 error in 1 file (checked 1 source file)

Replacing the function body with ellipses silences the warning. Perhaps that should be the preferred way to define interfaces moving forward?

i.e.

from zope.interface import Interface

class IFoo(Interface):
    def foo() -> int:
        ...

reveal_type(IFoo(object(), None))

Revealed type is "IFoo"

This ought to be IFoo | None.

Tried to update to mypy 0.942, but I started seeing this:

mypy.ini:4: error: Error importing plugin "mypy_zope": cannot import name 'SemanticAnalyzerPass2' from 'mypy.semanal' (/home/runner/.cache/pre-commit/repo_fawoait/py_env-python3.8/lib/python3.8/site-packages/mypy/semanal.cpython-38-x86_64-linux-gnu.so)  [misc]

I do see a green build on https://github.com/Shoobx/mypy-zope/pull/68, which is a bit curious.

Is there any more info I can provide to help debug this? My current workaround it to keep mypy at 0.941.