feat: add getGasPerPubdataByte endpoint (#1778)

## What ❔

Add a `getGasPerPubdataByte` endpoint in `zks` namespace, that returns
the amount of L2 gas required to pay for 1 byte of pubdata.

## Why ❔

One of our partners requires this endpoint, they want to have a better
insight into the pricing model.

## Checklist

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<!-- For draft PRs check the boxes as you complete them. -->

- [ ] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [ ] Tests for the changes have been added / updated.
- [ ] Documentation comments have been added / updated.
- [ ] Code has been formatted via `zk fmt` and `zk lint`.
- [ ] Spellcheck has been run via `zk spellcheck`.
- [ ] Linkcheck has been run via `zk linkcheck`.

core/lib/types/src/fee_model.rs

@@ -146,7 +146,7 @@ pub struct L1PeggedBatchFeeModelInput {
 }
 
 /// Pubdata price may be independent from L1 gas price.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub struct PubdataIndependentBatchFeeModelInput {
     /// Fair L2 gas price to provide
     pub fair_l2_gas_price: u64,

core/lib/web3_decl/src/namespaces/zks.rs

@@ -7,7 +7,7 @@ use zksync_types::{
         TransactionDetailedResult, TransactionDetails,
     },
     fee::Fee,
-    fee_model::FeeParams,
+    fee_model::{FeeParams, PubdataIndependentBatchFeeModelInput},
     transaction_request::CallRequest,
     Address, L1BatchNumber, L2BlockNumber, H256, U256, U64,
 };
@@ -122,6 +122,9 @@ pub trait ZksNamespace {
         l1_batch_number: L1BatchNumber,
     ) -> RpcResult<Option<Proof>>;
 
+    #[method(name = "getBatchFeeInput")]
+    async fn get_batch_fee_input(&self) -> RpcResult<PubdataIndependentBatchFeeModelInput>;
+
     #[method(name = "sendRawTransactionWithDetailedOutput")]
     async fn send_raw_transaction_with_detailed_output(
         &self,

core/lib/zksync_core/src/api_server/web3/backend_jsonrpsee/namespaces/zks.rs

@@ -7,7 +7,7 @@ use zksync_types::{
         ProtocolVersion, TransactionDetailedResult, TransactionDetails,
     },
     fee::Fee,
-    fee_model::FeeParams,
+    fee_model::{FeeParams, PubdataIndependentBatchFeeModelInput},
     transaction_request::CallRequest,
     Address, Bytes, L1BatchNumber, L2BlockNumber, StorageLogQueryType, H256, U256, U64,
 };
@@ -141,16 +141,24 @@ impl ZksNamespaceServer for ZksNamespace {
             .map_err(|err| self.current_method().map_err(err))
     }
 
+    // to be removed in favor of `get_batch_fee_input`
     async fn get_l1_gas_price(&self) -> RpcResult<U64> {
-        self.get_l1_gas_price_impl()
-            .await
-            .map_err(|err| self.current_method().map_err(err))
+        match self.get_batch_fee_input_impl().await {
+            Ok(fee_input) => Ok(fee_input.l1_gas_price.into()),
+            Err(err) => Err(self.current_method().map_err(err)),
+        }
     }
 
     async fn get_fee_params(&self) -> RpcResult<FeeParams> {
         Ok(self.get_fee_params_impl())
     }
 
+    async fn get_batch_fee_input(&self) -> RpcResult<PubdataIndependentBatchFeeModelInput> {
+        self.get_batch_fee_input_impl()
+            .await
+            .map_err(|err| self.current_method().map_err(err))
+    }
+
     async fn get_protocol_version(
         &self,
         version_id: Option<u16>,

core/lib/zksync_core/src/api_server/web3/namespaces/zks.rs

@@ -11,7 +11,7 @@ use zksync_types::{
         ProtocolVersion, StorageProof, TransactionDetails,
     },
     fee::Fee,
-    fee_model::FeeParams,
+    fee_model::{FeeParams, PubdataIndependentBatchFeeModelInput},
     l1::L1Tx,
     l2::L2Tx,
     l2_to_l1_log::{l2_to_l1_logs_tree_size, L2ToL1Log},
@@ -442,12 +442,7 @@ impl ZksNamespace {
             .map_err(DalError::generalize)?)
     }
 
-    pub async fn get_l1_gas_price_impl(&self) -> Result<U64, Web3Error> {
-        let fee_input_provider = &self.state.tx_sender.0.batch_fee_input_provider;
-        let fee_input = fee_input_provider.get_batch_fee_input().await?;
-        Ok(fee_input.l1_gas_price().into())
-    }
-
+    #[tracing::instrument(skip(self))]
     pub fn get_fee_params_impl(&self) -> FeeParams {
         self.state
             .tx_sender
@@ -539,6 +534,20 @@ impl ZksNamespace {
             .ok_or(Web3Error::NotImplemented)
     }
 
+    #[tracing::instrument(skip(self))]
+    pub async fn get_batch_fee_input_impl(
+        &self,
+    ) -> Result<PubdataIndependentBatchFeeModelInput, Web3Error> {
+        Ok(self
+            .state
+            .tx_sender
+            .0
+            .batch_fee_input_provider
+            .get_batch_fee_input()
+            .await?
+            .into_pubdata_independent())
+    }
+
     #[tracing::instrument(skip(self, tx_bytes))]
     pub async fn send_raw_transaction_with_detailed_output_impl(
         &self,