chore: return nil for invalid amount of aex9 holders (#1409)

Author: jyeshe

docs/swagger_v2/aexn.spec.yaml

@@ -162,7 +162,7 @@ schemas:
         items:
           type: string
       holders:
-        description: Count of accounts having balance
+        description: Count of accounts having balance (nil when contract is not complaint)
         type: integer
       name:
         description: The name of AEX9 token

lib/ae_mdw_web/views/aexn_view.ex

@@ -133,6 +133,11 @@ defmodule AeMdwWeb.AexnView do
         :not_found -> 0
       end
 
+    num_holders =
+      with num when num < 0 <- Stats.fetch_aex9_holders_count(state, contract_pk) do
+        nil
+      end
+
     %{
       name: name,
       symbol: symbol,
@@ -142,7 +147,7 @@ defmodule AeMdwWeb.AexnView do
       extensions: extensions,
       initial_supply: initial_supply,
       event_supply: event_supply,
-      holders: Stats.fetch_aex9_holders_count(state, contract_pk)
+      holders: num_holders
     }
   end
 

test/ae_mdw/db/contract_call_mutation_test.exs

@@ -1511,6 +1511,70 @@ defmodule AeMdw.Db.ContractCallMutationTest do
     end
   end
 
+  describe "aex9 non-compliant" do
+    test "call without a transfer event leads to negative aex9 holder count", %{store: store} do
+      unknown_event_hash = :crypto.strong_rand_bytes(32)
+      contract_pk = :crypto.strong_rand_bytes(32)
+      account_pk = :crypto.strong_rand_bytes(32)
+      amount = Enum.random(100_000_000..999_999_999)
+      height = Enum.random(100_000..999_999)
+      call_txi = Enum.random(100_000_000..999_999_999)
+
+      fun_arg_res = %{
+        arguments: [
+          %{
+            type: :address,
+            value: encode_account(account_pk)
+          },
+          %{
+            type: :int,
+            value: amount
+          }
+        ],
+        function: "deposit",
+        result: %{type: :unit, value: ""}
+      }
+
+      call_rec =
+        call_rec("logs", contract_pk, height, nil, [
+          {
+            contract_pk,
+            [unknown_event_hash, account_pk, <<amount::256>>],
+            ""
+          }
+        ])
+
+      mutation =
+        ContractCallMutation.new(
+          contract_pk,
+          call_txi,
+          fun_arg_res,
+          call_rec
+        )
+
+      functions =
+        AeMdw.Node.aex9_signatures()
+        |> Enum.into(%{}, fn {hash, type} -> {hash, {nil, type, nil}} end)
+
+      type_info = {:fcode, functions, nil, nil}
+      AeMdw.EtsCache.put(AeMdw.Contract, contract_pk, {type_info, nil, nil})
+
+      store =
+        store
+        |> Store.put(
+          Model.Stat,
+          Model.stat(index: Stats.aex9_holder_count_key(contract_pk), payload: -1)
+        )
+        |> Store.put(
+          Model.Field,
+          Model.field(index: {:contract_create_tx, nil, contract_pk, call_txi - 1})
+        )
+        |> change_store([mutation])
+
+      assert -1 = Stats.fetch_aex9_holders_count(State.new(store), contract_pk)
+    end
+  end
+
   defp contract_call_mutation(fname, call_txi, contract_pk) do
     %{arguments: args} = fun_arg_res = fun_args_res(fname)
     call_rec = call_rec(fname)

test/ae_mdw_web/views/aexn_view_test.exs

@@ -0,0 +1,48 @@
+defmodule AeMdwWeb.AexnViewTest do
+  use ExUnit.Case
+
+  alias AeMdw.Db.Model
+  alias AeMdw.Db.MemStore
+  alias AeMdw.Db.NullStore
+  alias AeMdw.Db.State
+  alias AeMdw.Db.Sync.Stats
+  alias AeMdwWeb.AexnView
+
+  import AeMdw.Util.Encoding
+
+  require Model
+
+  describe "render_contract/3" do
+    test "returns NA for invalid amount of holders" do
+      contract_pk = :crypto.strong_rand_bytes(32)
+      contract_id = encode_contract(contract_pk)
+      aex9_meta_info = {name, symbol, decimals} = {"Token1", "TK1", 18}
+      txi = 1_123_456_789
+      extensions = ["ext1", "ext2"]
+
+      state =
+        NullStore.new()
+        |> MemStore.new()
+        |> State.new()
+        |> Stats.decrement_aex9_holders(contract_pk)
+
+      m_aex9 =
+        Model.aexn_contract(
+          index: {:aex9, contract_pk},
+          txi: txi,
+          meta_info: aex9_meta_info,
+          extensions: extensions
+        )
+
+      assert %{
+               name: ^name,
+               symbol: ^symbol,
+               decimals: ^decimals,
+               contract_txi: ^txi,
+               contract_id: ^contract_id,
+               extensions: ^extensions,
+               holders: nil
+             } = AexnView.render_contract(state, m_aex9)
+    end
+  end
+end