Latest release `py-evm==0.12.0b2` seems to break on `_init_vm` for excess blob gas

[s3bc40]

Hey!

We had two discussions issues on moccasin course concerning the following error:

Traceback (most recent call last):

[... mox error]

  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/boa/__init__.py", line 35, in <module>
    env = Env.get_singleton()
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/boa/environment.py", line 193, in get_singleton
    cls._singleton = cls()
                     ~~~^^
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/boa/environment.py", line 48, in __init__
    self.evm = PyEVM(self, fast_mode_enabled, fork_try_prefetch_state)
               ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/boa/vm/py_evm.py", line 391, in __init__
    self._init_vm()
    ~~~~~~~~~~~~~^^
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/boa/vm/py_evm.py", line 394, in _init_vm
    self.vm = self.chain.get_vm()
              ~~~~~~~~~~~~~~~~~^^
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/eth/chains/base.py", line 263, in get_vm
    header = self.ensure_header(at_header)
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/eth/chains/base.py", line 306, in ensure_header
    return self.create_header_from_parent(head)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/eth/chains/base.py", line 280, in create_header_from_parent
    return self.get_vm_class_for_block_number(
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        block_number=BlockNumber(parent_header.block_number + 1),
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ).create_header_from_parent(parent_header, **header_params)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "cytoolz/functoolz.pyx", line 268, in cytoolz.functoolz.curry.__call__
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/eth/vm/forks/prague/headers.py", line 59, in create_prague_header_from_parent
    all_fields["excess_blob_gas"] = calc_excess_blob_gas_prague(parent_header)
                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/eth/vm/forks/prague/headers.py", line 31, in calc_excess_blob_gas_prague
    parent_header.excess_blob_gas + parent_header.blob_gas_used
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/s3bc40/.local/share/uv/tools/moccasin/lib/python3.13/site-packages/eth/rlp/headers.py", line 202, in excess_blob_gas
    raise AttributeError("Excess blob gas not available until Cancun fork")
AttributeError: Excess blob gas not available until Cancun fork

It seems the recent release of py-evm==0.12.0b2 (Released: Apr 23, 2025) is breaking the moccasin process.

In boa (line 394, /boa/vm/py_evm.py):

_init_vm
    self.vm = self.chain.get_vm()

In py-evm (line 31, eth/vm/forks/prague/headers.py):

calc_excess_blob_gas_prague
    parent_header.excess_blob_gas + parent_header.blob_gas_used

Forcing the py-evm version fixes the issue:

➜ uv tool install --with py-evm==0.10.0b4 moccasin
Resolved 109 packages in 267ms
Prepared 1 package in 313ms
Uninstalled 1 package in 11ms
Installed 1 package in 6ms
 - py-evm==0.12.0b2
 + py-evm==0.10.0b4

Any idea what could be the best solution?

[charles-cooper]

this has been fixed on the py-evm side by ethereum/py-evm#2212. but apparently going forward the MainnetChain API is a deprecated way of doing things, and we want to update to use MiningChain, which is done in #398.