fix: invalid metadata requests (#11210)

* fix: prevent empty requests to metadata service

* fix: remove empty hashes from request parameters

* Small fix

* Add docs

---------

Co-authored-by: Leonid Tyurin <lenyatyurin162586@gmail.com>

apps/explorer/lib/explorer/chain/address/metadata_preloader.ex

@@ -86,9 +86,8 @@ defmodule Explorer.Chain.Address.MetadataPreloader do
   def preload_metadata_to_list(items) do
     address_hash_strings =
       items
-      |> Enum.reduce([], fn item, acc ->
+      |> Enum.flat_map(&item_to_address_hash_strings/1)
-        item_to_address_hash_strings(item) ++ acc
+      |> Enum.filter(&(&1 != ""))
-      end)
       |> Enum.uniq()
 
     case Metadata.get_addresses_tags(address_hash_strings) do

apps/explorer/lib/explorer/microservice_interfaces/metadata.ex

@@ -18,16 +18,34 @@ defmodule Explorer.MicroserviceInterfaces.Metadata do
   @page_size 50
   @request_error_msg "Error while sending request to Metadata microservice"
 
-  @spec get_addresses_tags([String.t()]) :: {:error, :disabled | <<_::416>> | Jason.DecodeError.t()} | {:ok, any()}
+  @doc """
+  Retrieves tags for a list of addresses.
+
+  ## Parameters
+  - `addresses`: A list of addresses for which tags need to be fetched.
+
+  ## Returns
+    - A map with metadata tags from microservice. Returns `:ignore` when the input list is empty.
+
+  ## Examples
+
+      iex> get_addresses_tags([])
+      :ignore
+
+  """
+  @spec get_addresses_tags([String.t()]) ::
+          {:error, :disabled | <<_::416>> | Jason.DecodeError.t()} | {:ok, any()} | :ignore
+  def get_addresses_tags([]), do: :ignore
+
   def get_addresses_tags(addresses) do
     with :ok <- Microservice.check_enabled(__MODULE__) do
-      body = %{
+      params = %{
         addresses: Enum.join(addresses, ","),
         tags_limit: @tags_per_address_limit,
         chain_id: Application.get_env(:block_scout_web, :chain_id)
       }
 
-      http_get_request(addresses_metadata_url(), body)
+      http_get_request(addresses_metadata_url(), params)
     end
   end