mypy errors starting with release 3.2.0

[danielnovotny-wf]

Summary

Starting with release version 3.2.0 we began getting mypy errors that did not used to exist when using version 3.1.1.

Details

As part of the commit that introduced the new PropsDictType variable, the troposphere/py.typed file was also added. In accordance with PEP 561, the presence of this file should be used when the underlying code has types or stubs defined. The example below demonstrates how the py.typed can cause mypy to throw errors that did not trigger before.

example.py

from troposphere import Template
import troposphere.ec2 as ec2
t = Template()
instance = ec2.Instance("myinstance")
instance.ImageId = "ami-951945d0"
instance.InstanceType = "t1.micro"
t.add_resource(instance)
print(t.to_yaml())

setup.cfg

[mypy]
disallow_any_generics = True
disallow_incomplete_defs = True
disallow_subclassing_any = True
disallow_untyped_calls = True
disallow_untyped_decorators = True
disallow_untyped_defs = True
exclude = scripts
ignore_missing_imports = True
no_implicit_optional = True
show_error_codes = True

mypy errors

$ python3 --version
Python 3.7.10

$ pip3 install mypy

$ pip3 install troposphere==3.1.1
$ mypy example.py 
Success: no issues found in 1 source file

$ pip3 install troposphere==3.2.2
$ mypy example.py 
example.py:3: error: Call to untyped function "Template" in typed context  [no-untyped-call]
example.py:4: error: Call to untyped function "Instance" in typed context  [no-untyped-call]
example.py:7: error: Call to untyped function "add_resource" in typed context  [no-untyped-call]
example.py:8: error: Call to untyped function "to_yaml" in typed context  [no-untyped-call]
Found 4 errors in 1 file (checked 1 source file)

$ rm lib/python3.7/site-packages/troposphere/py.typed 
$ mypy example.py 
Success: no issues found in 1 source file

Suggested Solution

Until troposphere fully supports typing across its codebase, I would suggest we remove the py.typed file.

[markpeek]

Thank you for the change and detailed report on why py.typed should be removed for now.