`VM.validate_header()` is called twice during `Chain.import_block()`?

What is wrong?

The current calling route:

class Chain(BaseChain):
    def import_block(self,
                     block: BaseBlock,
                     perform_validation: bool=True
                     ) -> Tuple[BaseBlock, Tuple[BaseBlock, ...], Tuple[BaseBlock, ...]]:
        ....
        base_header_for_import = self.create_header_from_parent(parent_header)
        imported_block = self.get_vm(base_header_for_import).import_block(block)
        # ^^^^^^ dive into VM.import_block()

        # Validate the imported block.
        if perform_validation:
        # ^^^^^^ perform_validation is True by default.
            validate_imported_block_unchanged(imported_block, block)
            self.validate_block(imported_block)
        ....

    def validate_block(self, block: BaseBlock) -> None:
        if block.is_genesis:
            raise ValidationError("Cannot validate genesis block this way")
        VM = self.get_vm_class_for_block_number(BlockNumber(block.number))
        parent_block = self.get_block_by_hash(block.header.parent_hash)
        VM.validate_header(block.header, parent_block.header, check_seal=True)
        # ^^^^^^ second time call VM.validate_header!
        ....

class VM(BaseVM):
    def import_block(self, block):
        ....
        return self.mine_block()

    def mine_block(self, *args, **kwargs):
        ....
        # Perform validation
        self.validate_block(final_block)

        return final_block

    def validate_block(self, block):
        ....
        if block.is_genesis:
            validate_length_lte(block.header.extra_data, 32, title="BlockHeader.extra_data")
        else:
            parent_header = get_parent_header(block.header, self.chaindb)
            self.validate_header(block.header, parent_header)
            # ^^^^^^ first time calling VM.validate_header! check_seal is True by default.
        ....

How can it be fixed

Is Chain.import_block the main API for syncing? I guess perform_validation is for testing. Can we remove the second call and set the first call check_seal=True?

[hwwhww]

@pipermerriam whoops sorry, my question was do I have to extract the block validation from BeaconStateMachine.import_block and BeaconStateMachine.process_block, and make BeaconChain trigger the block validation. Your second response answered my question. 👍

[pipermerriam]

@hwwhww 1) I’m not sure I understand your question and 2) BeaconChain should not try to be shaped like Chain in any case where it doesn’t fit well. It’s better for BeaconChain to be properly architected than for it to have API parity with Chain.