[aptos-vm] enable automatic creation of sponsored accounts

This is the implementation of AIP-52:
https://github.com/aptos-foundation/AIPs/blob/main/aips/aip-52.md

This AIP proposes to allow sponsored transactions, one in which the gas
payer is not the primary signer of the transaction, to create accounts
for the primary signer if it does not exist. Currently when submitting a
sponsored transaction an account must first exist. This is an
unnecessary friction for using gas fee payer accounts for new accounts.
As it means that the gas fee payer solution must first submit an
independent transaction to the blockchain.

I also cleaned up the tests for fee payer since there were a lot, and they
were excessively complex.

aptos-move/aptos-release-builder/src/components/feature_flags.rs

@@ -84,6 +84,7 @@ pub enum FeatureFlag {
     SaferResourceGroups,
     SaferMetadata,
     Secp256k1ECDSAAuthenticator,
+    SponsoredAutomaticAccountCreation,
 }
 
 fn generate_features_blob(writer: &CodeWriter, data: &[u64]) {
@@ -220,6 +221,9 @@ impl From<FeatureFlag> for AptosFeatureFlag {
             FeatureFlag::Secp256k1ECDSAAuthenticator => {
                 AptosFeatureFlag::SECP256K1_ECDSA_AUTHENTICATOR
             },
+            FeatureFlag::SponsoredAutomaticAccountCreation => {
+                AptosFeatureFlag::SPONSORED_AUTOMATIC_ACCOUNT_CREATION
+            },
         }
     }
 }
@@ -279,6 +283,9 @@ impl From<AptosFeatureFlag> for FeatureFlag {
             AptosFeatureFlag::SECP256K1_ECDSA_AUTHENTICATOR => {
                 FeatureFlag::Secp256k1ECDSAAuthenticator
             },
+            AptosFeatureFlag::SPONSORED_AUTOMATIC_ACCOUNT_CREATION => {
+                FeatureFlag::SponsoredAutomaticAccountCreation
+            },
         }
     }
 }

aptos-move/aptos-vm/src/aptos_vm.rs

@@ -1103,6 +1103,27 @@ impl AptosVM {
             session = self.0.new_session(resolver, SessionId::txn(txn));
         }
 
+        if let aptos_types::transaction::authenticator::TransactionAuthenticator::FeePayer {
+            ..
+        } = &txn.authenticator_ref()
+        {
+            if self
+                .0
+                .get_features()
+                .is_enabled(FeatureFlag::SPONSORED_AUTOMATIC_ACCOUNT_CREATION)
+            {
+                if let Err(err) = session.execute_function_bypass_visibility(
+                    &ACCOUNT_MODULE,
+                    CREATE_ACCOUNT_IF_DOES_NOT_EXIST,
+                    vec![],
+                    serialize_values(&vec![MoveValue::Address(txn.sender())]),
+                    gas_meter,
+                ) {
+                    return discard_error_vm_status(err.into());
+                };
+            }
+        }
+
         let storage_gas_params = unwrap_or_discard!(self.0.get_storage_gas_parameters(log_context));
         let txn_data = TransactionMetadata::new(txn);
 

aptos-move/aptos-vm/src/aptos_vm_impl.rs

@@ -378,6 +378,7 @@ impl AptosVMImpl {
             .iter()
             .map(|auth_key| MoveValue::vector_u8(auth_key.to_vec()))
             .collect();
+
         let (prologue_function_name, args) = if let (Some(fee_payer), Some(fee_payer_auth_key)) = (
             txn_data.fee_payer(),
             txn_data.fee_payer_authentication_key.as_ref(),
@@ -429,7 +430,6 @@ impl AptosVMImpl {
             .execute_function_bypass_visibility(
                 &APTOS_TRANSACTION_VALIDATION.module_id(),
                 prologue_function_name,
-                // TODO: Deprecate this once we remove gas currency on the Move side.
                 vec![],
                 serialize_values(&args),
                 &mut gas_meter,
@@ -458,7 +458,6 @@ impl AptosVMImpl {
             .execute_function_bypass_visibility(
                 &APTOS_TRANSACTION_VALIDATION.module_id(),
                 &APTOS_TRANSACTION_VALIDATION.module_prologue_name,
-                // TODO: Deprecate this once we remove gas currency on the Move side.
                 vec![],
                 serialize_values(&vec![
                     MoveValue::Signer(txn_data.sender),

aptos-move/aptos-vm/src/system_module_names.rs

@@ -8,6 +8,16 @@ use aptos_types::account_config;
 use move_core_types::{ident_str, identifier::IdentStr, language_storage::ModuleId};
 use once_cell::sync::Lazy;
 
+pub static ACCOUNT_MODULE: Lazy<ModuleId> = Lazy::new(|| {
+    ModuleId::new(
+        account_config::CORE_CODE_ADDRESS,
+        ident_str!("account").to_owned(),
+    )
+});
+
+pub const CREATE_ACCOUNT_IF_DOES_NOT_EXIST: &IdentStr =
+    ident_str!("create_account_if_does_not_exist");
+
 // Data to resolve basic account and transaction flow functions and structs
 /// The ModuleId for the aptos block module
 pub static BLOCK_MODULE: Lazy<ModuleId> = Lazy::new(|| {