check if to_address_hash is contract address to fetch internal transactions

apps/explorer/lib/explorer/chain.ex

@@ -17,6 +17,8 @@ defmodule Explorer.Chain do
       where: 3
     ]
 
+  import EthereumJSONRPC, only: [integer_to_quantity: 1]
+
   alias Ecto.Adapters.SQL
   alias Ecto.{Changeset, Multi}
 
@@ -1868,6 +1870,46 @@ defmodule Explorer.Chain do
     |> Data.to_string()
   end
 
+  @doc """
+  Checks if an address is a contract
+  """
+  @spec contract_address?(String.t(), non_neg_integer(), Keyword.t()) :: boolean() | :json_rpc_error
+  def contract_address?(address_hash, block_number, json_rpc_named_arguments \\ []) do
+    {:ok, binary_hash} = Explorer.Chain.Hash.Address.cast(address_hash)
+
+    query =
+      from(
+        address in Address,
+        where: address.hash == ^binary_hash
+      )
+
+    address = Repo.one(query)
+
+    cond do
+      is_nil(address) ->
+        block_quantity = integer_to_quantity(block_number)
+
+        case EthereumJSONRPC.fetch_codes(
+               [%{block_quantity: block_quantity, address: address_hash}],
+               json_rpc_named_arguments
+             ) do
+          {:ok, %EthereumJSONRPC.FetchedCodes{params_list: fetched_codes}} ->
+            result = List.first(fetched_codes)
+
+            result && !(is_nil(result[:code]) || result[:code] == "" || result[:code] == "0x")
+
+          _ ->
+            :json_rpc_error
+        end
+
+      is_nil(address.contract_code) ->
+        false
+
+      true ->
+        true
+    end
+  end
+
   @doc """
   Fetches contract creation input data.
   """

apps/explorer/test/explorer/chain_test.exs

@@ -1,10 +1,12 @@
 defmodule Explorer.ChainTest do
   use Explorer.DataCase
+  use EthereumJSONRPC.Case, async: true
 
   require Ecto.Query
 
   import Ecto.Query
   import Explorer.Factory
+  import Mox
 
   alias Explorer.{Chain, Factory, PagingOptions, Repo}
 
@@ -27,6 +29,10 @@ defmodule Explorer.ChainTest do
 
   doctest Explorer.Chain
 
+  setup :set_mox_global
+
+  setup :verify_on_exit!
+
   describe "count_addresses_with_balance_from_cache/0" do
     test "returns the number of addresses with fetched_coin_balance > 0" do
       insert(:address, fetched_coin_balance: 0)
@@ -3631,4 +3637,68 @@ defmodule Explorer.ChainTest do
       assert found_creation_data == ""
     end
   end
+
+  describe "contract_address?/2" do
+    test "returns true if address has contract code" do
+      code = %Data{
+        bytes: <<1, 2, 3, 4, 5>>
+      }
+
+      address = insert(:address, contract_code: code)
+
+      assert Chain.contract_address?(to_string(address.hash), 1)
+    end
+
+    test "returns false if address has not contract code" do
+      address = insert(:address)
+
+      refute Chain.contract_address?(to_string(address.hash), 1)
+    end
+
+    @tag :no_parity
+    @tag :no_geth
+    test "returns true if fetched code from json rpc", %{
+      json_rpc_named_arguments: json_rpc_named_arguments
+    } do
+      hash = "0x71300d93a8CdF93385Af9635388cF2D00b95a480"
+
+      if json_rpc_named_arguments[:transport] == EthereumJSONRPC.Mox do
+        EthereumJSONRPC.Mox
+        |> expect(:json_rpc, fn _arguments, _options ->
+          {:ok,
+           [
+             %{
+               id: 0,
+               result: "0x0102030405"
+             }
+           ]}
+        end)
+      end
+
+      assert Chain.contract_address?(to_string(hash), 1, json_rpc_named_arguments)
+    end
+
+    @tag :no_parity
+    @tag :no_geth
+    test "returns false if no fetched code from json rpc", %{
+      json_rpc_named_arguments: json_rpc_named_arguments
+    } do
+      hash = "0x71300d93a8CdF93385Af9635388cF2D00b95a480"
+
+      if json_rpc_named_arguments[:transport] == EthereumJSONRPC.Mox do
+        EthereumJSONRPC.Mox
+        |> expect(:json_rpc, fn _arguments, _options ->
+          {:ok,
+           [
+             %{
+               id: 0,
+               result: "0x"
+             }
+           ]}
+        end)
+      end
+
+      refute Chain.contract_address?(to_string(hash), 1, json_rpc_named_arguments)
+    end
+  end
 end

apps/indexer/lib/indexer/block/realtime/fetcher.ex

@@ -435,8 +435,13 @@ defmodule Indexer.Block.Realtime.Fetcher do
     end
   end
 
-  # Input-less transactions are value-transfers only, so their internal transactions do not need to be indexed
-  defp fetch_internal_transactions?(%{status: :ok, created_contract_address_hash: nil, input: "0x"}, _), do: false
+  defp fetch_internal_transactions?(
+         %{status: :ok, created_contract_address_hash: nil, input: "0x", to_address_hash: from_address_hash},
+         _
+       ) do
+    Chain.contract_address?(from_address_hash)
+  end
+
   # Token transfers not transferred during contract creation don't need internal transactions as the token transfers
   # derive completely from the logs.
   defp fetch_internal_transactions?(%{status: :ok, created_contract_address_hash: nil}, true), do: false