Lesson6: AttributeError: 'NoneType' object has no attribute '_with_attr'

[jamsubzero]

Hi, I am getting this error while executing test_fund_me.py when running brownie test .
I first encountered this error while following the tutorial.

Since I couldn't solve it, I decided to clone the lesson's repo to get the exact same source code, and to my surprise, I still got the same error.

Maybe there is something wrong with my setup, please help.

[cromewar]

Hello @jamsubzero I just cloned the repo and ran the test, which went fine as you can see bellow, this is estrange as is the exact same code but anyways I have some hints that could be handy.

1. Please execute the test like this: brownie test -s -k test_only_owner_can_withdraw and paste here the result.
2. NoneType means that instead of an instance of a Class, Object or whatever else you might got, you actually got None, for example like fund_me returns None or bad_actor is None. So I wonder if you cloned the entire repo and executed the test on it, or you cloned the repo and just replaced the test script into your code? If is the second one, you may have something else missing elsewhere.
3. May be your python is getting fussy, would you try to execute the project on a different python instance? you can manage virtual python versions using virtualenv, here you have a guide.

Attached Image (test running fine)

[jamsubzero]

A bit of update on this @cromewar
I have tried using virtualenv and freshly install Brownie but I got the same error. I even use the same version of Python and Brownie as what you have in your screenshot above.

Additional details on the issue:
Brownie only throws this error when calling a function that didn't pass the modifier's require condition (i.e. onlyOwner). Any other function call on the contract works fine.

My hunch is that when a revert error is thrown, for some reason, Brownie cannot make sense of what is thrown by the EVM.

Sadly, only I encountered this issue so there must be something wrong with my setup. For now, I will just continue with the rest of the tutorial.

[cromewar]

So it seems when the require condition is not fulfilled it throws an error but brownie don't show as it should, I highly recommend you to post this issue on official brownie repo https://github.com/eth-brownie/brownie on issues section.

I hope you will be able to continue the rest of the course without this problems

[jamsubzero]

Update on this. I finally got it to work.

I first examined the internals of brownie how it is throwing the null reference. It happens in transaction.py#_raise_if_reverted line 421 and it seems it uses the exception thrown in contract.py#__call__. But for some reason that exc object is a None thus causing the issue on my end.

I have tried a lot of things like reinstalling brownie and using a venv for python since for me those are the obvious culprit/s.
And lastly, I reinstalled ganache-cli but this time to a directory I owned (not by root). I'm not sure if this is the real issue since I am able to change a state variable in the contract.

To anyone who encounters the same, try the combination I did:

• use virtual env,
• install brownie to the venv,
• reinstall your ganache-cli to the directory you own (or simply chown your node_modules dir)

[andreitoma8]

How can I reinstall ganache-cli to a dir I own? I ve got the same issue and there is no other option left for me.

[cromewar]

hello @andreitoma8 it depends on which OS you are using, for linux you can use EVM to install node and For MAC you can use Brew, this will allow you to install ganache on a non-root directory.

[gnoparus]

I've got the same problem.

AttributeError: 'NoneType' object has no attribute '_with_attr'

After I did some research in this discussion forum, I tried reinstall ganache-cli as follows.

uninstall ganache-cli

npm uninstall ganache-cli
sudo npm uninstall ganache-cli --global

reinstall ganache-cli

sudo npm install ganache-cli --global
npm install ganache-cli

test again
brownie test -k test_only_owner_can_withdraw

And it worked.

FAILED tests/test_fund_me.py::test_only_owner_can_withdraw - brownie.exceptions.VirtualMachineError: revert

There are node_modules/ and package-lock.json appear on brownie_fund_me project path.

[cromewar]

Nice catch @gnoparus !!