INTERNAL ERROR when enabling mypy-zope for Twisted Klein

[wsanchez]

In commit twisted/klein@04a536c, 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

[wsanchez]

It appears that the cause of the problem here is that we have this nested class that defines the interface. The INTERNAL ERROR message goes away if I move the interface definition up to the module scope.

[kedder]

As I understand, it fails on this file: https://github.com/twisted/klein/blob/master/src/klein/test/test_trial.py.

Can you try moving IFrobbable, Frobbable and NotFrobbable out of TestCaseTests to the top level of test_trial module?

[kedder]

I see, this makes sense. I'm not exactly sure how to support this case, but I'll try to at least avoid this catastrophic failure.

[wsanchez]

Thanks. I don't know if it's hard to detect this case, but an error suggestion that perhaps you defined an interface in a non-module scope might help others from having to chase this down.

[kedder]

@wsanchez, released 0.2.12 with the fix.

[wsanchez]

Verified fixed, thanks!