0x02000000 Being Returned in Extrinsic Receipt and Failing Error Module Indexing

Question

When submitting a stake request through the Python substrate-interface library, the extrinsic receipt comes back with the following parameters:

({'Module': {'index': 6, 'error': '0x02000000'}}, {'weight': 558355000, 'class': 'Normal', 'pays_fee': 'Yes'})

Also seen it return from the unbond endpoint with a similar response:

({'Module': {'index': 6, 'error': '0x07000000'}}, {'weight': 1163003000, 'class': 'Normal', 'pays_fee': 'Yes'})

When this map gets passed down through the error handling, it fails with a TypeError because '0x02000000' is not a valid int index on the map.

Stack trace:

File "/Users/kristian/Documents/v0MMVP/venv/lib/python3.9/site-packages/eulith_staking_manager/staking/dot/fxn_implementations/substrateCallImplementation.py", line 54, in call
    if receipt.is_success:
  File "/Users/kristian/Documents/v0MMVP/venv/lib/python3.9/site-packages/substrateinterface/base.py", line 3305, in is_success
    self.process_events()
  File "/Users/kristian/Documents/v0MMVP/venv/lib/python3.9/site-packages/substrateinterface/base.py", line 3204, in process_events
    module_error = self.substrate.metadata_decoder.get_module_error(
  File "/Users/kristian/Documents/v0MMVP/venv/lib/python3.9/site-packages/scalecodec/types.py", line 1907, in get_module_error
    return module.errors[error_index]
  File "/Users/kristian/Documents/v0MMVP/venv/lib/python3.9/site-packages/scalecodec/base.py", line 790, in __getitem__
    return self.value_object[item]
TypeError: list indices must be integers or slices, not str

What does this error code mean, and what is the correct fix to interpret the returned error?

Thank you!

Answer 1

The error encoding has changed slightly in Substrate master, specifically after this PR

In this case your results seems to match up with the recent encoding where error is 4 bytes -

• the first byte still refers to the actual error index
• the additional bytes are additional (encoded) error details

Answer 2

I am assuming this is for the Kusama runtime?

There is a good resource for interpreting error messages here.

Index 6 in the Kusama runtime is the Staking pallet.

Staking: pallet_staking::{Pallet, Call, Storage, Config<T>, Event<T>} = 6,

0x02 in decimal is 2 and error 2 in the Staking pallet is AlreadyBonded with the message: Stash is already bonded.

0x07 in decimal is 7 and error 7 in the Staking pallet is InsufficientValue with the message Can not bond with value less than minimum balance.

You could also try something like this:

receipt = substrate.submit_extrinsic(extrinsic, wait_for_inclusion=True)
print(receipt.error_message['name'])

As to why you're getting the leading zeros, I am not sure. Typically when I am working with Substrate I get error messages like this: {'Module': {'index': 6, 'error': '7'}. You could start to debug it here. Also, there was a new release of FRAME metadata recently where the scale-info was updated to v2.0.0 and the parity-scale-codec was also updated to v3.0.0. Maybe consider opening an issue in the py-substrate-interface repo.

Answer 3

This is indeed caused by recently released PR https://github.com/paritytech/substrate/pull/10242, updated DispatchError processing released in https://github.com/polkascan/py-substrate-interface/releases/tag/v1.2.4