Fix get_dynamic_class_hook does not work in some scenarios

[linw1995]

Description

The get_dynamic_class_hook method of the plugin never called if the statement is a chained assignment like Bad1 = Bad2 = declarative_base(); Or if the statement is a chain of call expressions like Base = declarative_base().with_optionalA().

Test Plan

1. Update existed unit test "mypy/test/testcheck.py::TypeCheckSuite::testDynamicClassPluginNegatives"

[case testDynamicClassPluginNegatives]
# flags: --config-file tmp/mypy.ini
from mod import non_declarative_base

Bad1 = non_declarative_base()

class C1(Bad1): ...  # E: Variable "__main__.Bad1" is not valid as a type \
                     # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases \
                     # E: Invalid base class "Bad1"
[file mod.py]
def non_declarative_base(): ...
[file mypy.ini]
\[mypy]
plugins=<ROOT>/test-data/unit/plugins/dyn_class.py

2. Add two new unit tests

[case testDynamicClassPluginChainCall]
# flags: --config-file tmp/mypy.ini
from mod import declarative_base, Column, Instr

Base = declarative_base().with_optional_xxx()

class Model(Base):
    x: Column[int]

reveal_type(Model().x)  # N: Revealed type is "mod.Instr[builtins.int]"
[file mod.py]
from typing import Generic, TypeVar

class Base:
    def with_optional_xxx(self) -> Base: ...

def declarative_base() -> Base: ...

T = TypeVar('T')

class Column(Generic[T]): ...
class Instr(Generic[T]): ...

[file mypy.ini]
\[mypy]
plugins=<ROOT>/test-data/unit/plugins/dyn_class.py

[case testDynamicClassPluginChainedAssignment]
# flags: --config-file tmp/mypy.ini
from mod import declarative_base

Base1 = Base2 = declarative_base()

class C1(Base1): ...  
class C2(Base2): ...
[file mod.py]
def declarative_base(): ...
[file mypy.ini]
\[mypy]
plugins=<ROOT>/test-data/unit/plugins/dyn_class.py

[linw1995]

https://app.travis-ci.com/github/python/mypy/jobs/528284498

CI job "run test suite with python nightly" failed and produced a lot of error outputs like below

________________________ testDivReverseOperatorPython2 _________________________
[gw1] linux -- Python 3.10.0 /home/travis/build/python/mypy/.tox/py/bin/python
data: /home/travis/build/python/mypy/test-data/unit/check-classes.test:2170:
SystemExit: 1
----------------------------- Captured stderr call -----------------------------
The typed_ast package is not installed.
For Python 2 support, install mypy using `python3 -m pip install "mypy[python2]"`Alternatively, you can install typed_ast with `python3 -m pip install typed-ast`.

______________________________ testNotAsBinaryOp _______________________________
[gw0] linux -- Python 3.10.0 /home/travis/build/python/mypy/.tox/py/bin/python
data: /home/travis/build/python/mypy/test-data/unit/parse.test:934:
/home/travis/build/python/mypy/mypy/test/testparse.py:22: in run_case
    test_parser(testcase)
/home/travis/build/python/mypy/mypy/test/testparse.py:46: in test_parser
    assert_string_arrays_equal(testcase.output, a,
E   AssertionError: Invalid parser output (/home/travis/build/python/mypy/test-data/unit/parse.test, line 934)
----------------------------- Captured stderr call -----------------------------
Expected:
  main:1: error: invalid syntax. Perhaps you forgot a comma? (diff)
Actual:
  main:1: error: invalid syntax                 (diff)
Alignment of first line difference:
  E: main:1: error: invalid syntax. Perhaps you forgot a comma?
  A: main:1: error: invalid syntax

and more

[pranavrajpal]

The python nightly CI has been broken for a while (which is why it's marked as allowed to fail).

The mypyc errors seem to be related to mypyc/mypyc#864. Moving the class definition for CallExprVisitor to module level should fix those CI errors.

[linw1995]

The mypyc errors seem to be related to mypyc/mypyc#864. Moving the class definition for CallExprVisitor to module level should fix those CI errors.

The latest commit resolves this kind of errors. @pranavrajpal And thanks to you.

[linw1995]

Friendly ping, can I get a review? : )

[linw1995]

Gently ping @pranavrajpal. Can I get a review?

[pranavrajpal]

Sorry for taking so long to review this.

This mostly looks good to me (see my one comment), but you'll probably have to wait for a review from a maintainer.

[JukkaL]

Thanks, and sorry for the slow response! Looks good.