mypy strict: error: Module "streamlit" does not explicitly export attribute "experimental_dialog" [attr-defined] (among others)

[wyattscarpenter]

Checklist

• I have searched the existing issues for similar issues.
• I added a very descriptive title to this issue.
• I have provided sufficient information below to help reproduce this issue.

Summary

Trying to use the experimental_dialog decorator at all gives an error in typechecking in mypy strict mode. (strict mode turns on no_implicit_reexport). Also in pyright as well.

The mypy error is error: Module "streamlit" does not explicitly export attribute "experimental_dialog" [attr-defined]. The pyright error is error: "experimental_dialog" is not exported from module "streamlit" (reportPrivateImportUsage)

After much staring at https://github.com/streamlit/streamlit/blob/1.34.0/lib/streamlit/__init__.py#L77 , I realized the answer is actually simple: a reexport is not explicit unless you as the variable to the same name. As mypy documentation says https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-no-implicit-reexport:

# This won't re-export the value
from foo import bar

# Neither will this
from foo import bar as bang

# This will re-export it as bar and allow other modules to import it
from foo import bar as bar

Therefore, exports like dialog_decorator as experimental_dialog are a problem, and do not serve their intended purpose.

So, you cannot rename the variable in the reexport and have it still work. But I'm pretty sure you can still put experimental_dialog = dialog_decorator in the source file, though, and then have your reexport line be

from streamlit.elements.dialog_decorator import (
  experimental_dialog as experimental_dialog
)

if you want.

P.S.: The Modules that the user should have access to. These are imported with "as" syntax pass mypy checking with implicit_reexport disabled." comment block, seems to have a typo, by the way, and also doesn't seem very useful as currently written, and also possibly is misplaced.

Reproducible Code Example

#example.py

import streamlit as st

@st.experimental_dialog("Fun example")
def f() -> None:
  st.write("This works fine, but doesn't typecheck under strict.")
f()

Steps To Reproduce

$ mypy --strict example.py
example.py:3: error: Module "streamlit" does not explicitly export attribute "experimental_dialog" [attr-defined]
$ mypy example.py
Success: no issues found in 1 source file

Expected Behavior

No response

Current Behavior

No response

Is this a regression?

• Yes, this used to work in a previous version.

Debug info

• Streamlit version: Streamlit, version 1.34.0
• Python version: Python 3.11.0
• Operating System: Windows 10
• Browser: Firefox
• mypy: mypy 1.10.0 (compiled: yes)

Additional Information

No response

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[raethlein]

Thanks @wyattscarpenter for the detailed issue! I have created a PR here #8728 to fix the explicit-export issue and update the comment.