feat: add stacktrace to SSZ

lib/ssz_ex/decode.ex

@@ -337,14 +337,17 @@ defmodule SszEx.Decode do
           :ok ->
             size = next_offset - offset
             <<chunk::binary-size(size), rest::bitstring>> = rest_bytes
-            {:cont, {rest, [{key, decode(chunk, schema)} | acc_variable_parts]}}
+
+            {:cont,
+             {rest, [{key, decode(chunk, schema) |> Error.add_trace(key)} | acc_variable_parts]}}
 
           error ->
             {:halt, {<<>>, [{key, error} | acc_variable_parts]}}
         end
 
       [{_offset, {key, schema}}], {rest_bytes, acc_variable_parts} ->
-        {:cont, {<<>>, [{key, decode(rest_bytes, schema)} | acc_variable_parts]}}
+        {:cont,
+         {<<>>, [{key, decode(rest_bytes, schema) |> Error.add_trace(key)} | acc_variable_parts]}}
     end)
     |> then(fn {<<>>, variable_parts} ->
       flatten_container_results(variable_parts)
@@ -363,7 +366,9 @@ defmodule SszEx.Decode do
       else
         ssz_fixed_len = Utils.get_fixed_size(schema)
         <<chunk::binary-size(ssz_fixed_len), rest::bitstring>> = binary
-        {rest, [{key, decode(chunk, schema)} | fixed_parts], offsets, items_index + ssz_fixed_len}
+
+        {rest, [{key, decode(chunk, schema) |> Error.add_trace(key)} | fixed_parts], offsets,
+         items_index + ssz_fixed_len}
       end
     end)
     |> then(fn {_rest_bytes, fixed_parts, offsets, items_index} ->
@@ -455,7 +460,7 @@ defmodule SszEx.Decode do
     case Enum.group_by(results, fn {_, {type, _}} -> type end, fn {key, {_, result}} ->
            {key, result}
          end) do
-      %{error: errors} -> {:error, errors}
+      %{error: [first_error | _rest]} -> {:error, first_error}
       summary -> {:ok, Map.get(summary, :ok, [])}
     end
   end

lib/ssz_ex/encode.ex

@@ -83,7 +83,7 @@ defmodule SszEx.Encode do
       {:error,
        %Error{
          message:
-           "Invalid binary length while encoding BitVector. \nExpected: #{size}.\nFound: #{bit_vector_size(bit_vector)}."
+           "Invalid binary length while encoding BitVector. \nExpected: #{size}.\nFound: #{bit_vector_size(bit_vector)}.\n"
        }}
 
   defp encode_bitvector(bit_vector, _size),
@@ -147,8 +147,7 @@ defmodule SszEx.Encode do
            Enum.reduce(variable_parts, 0, fn part, acc -> byte_size(part) + acc end),
          :ok <- check_length(fixed_length, variable_length),
          {:ok, fixed_parts} <-
-           replace_offsets(fixed_size_values, offsets)
-           |> encode_schemas() do
+           replace_offsets(fixed_size_values, offsets) |> encode_schemas() do
       (fixed_parts ++ variable_parts)
       |> Enum.join()
       |> then(&{:ok, &1})
@@ -163,23 +162,25 @@ defmodule SszEx.Encode do
 
       if Utils.variable_size?(schema) do
         {[:offset | acc_fixed_size_values], @bytes_per_length_offset + acc_fixed_length,
-         [{value, schema} | acc_variable_values]}
+         [{value, key, schema} | acc_variable_values]}
       else
-        {[{value, schema} | acc_fixed_size_values],
+        {[{value, key, schema} | acc_fixed_size_values],
          acc_fixed_length + Utils.get_fixed_size(schema), acc_variable_values}
       end
     end)
   end
 
   defp encode_schemas(tuple_values) do
-    Enum.map(tuple_values, fn {value, schema} -> encode(value, schema) end)
+    Enum.map(tuple_values, fn {value, key, schema} ->
+      encode(value, schema) |> Error.add_trace(key)
+    end)
     |> Utils.flatten_results()
   end
 
   defp calculate_offsets(variable_parts, fixed_length) do
     {offsets, _} =
       Enum.reduce(variable_parts, {[], fixed_length}, fn element, {res, acc} ->
-        {[{acc, {:int, 32}} | res], byte_size(element) + acc}
+        {[{acc, :offset, {:int, 32}} | res], byte_size(element) + acc}
       end)
 
     offsets

lib/ssz_ex/error.ex

@@ -3,13 +3,37 @@ defmodule SszEx.Error do
   Error messages for SszEx domain.
   """
   alias SszEx.Error
-  defstruct [:message]
-  @type t :: %__MODULE__{message: String.t()}
+  defstruct [:message, :stacktrace]
+  @type t :: %__MODULE__{message: String.t(), stacktrace: list()}
 
-  def format(%Error{message: message}) do
+  def format(%Error{message: message, stacktrace: nil}), do: "#{message}"
+
+  def format(%Error{message: message, stacktrace: stacktrace}) do
     "#{message}"
+    formatted_stacktrace = stacktrace |> Enum.join(".")
+    "#{message}Stacktrace: #{formatted_stacktrace}"
+  end
+
+  def add_trace(%Error{message: message, stacktrace: nil}, new_trace) do
+    %Error{message: message, stacktrace: [new_trace]}
+  end
+
+  def add_trace(%Error{message: message, stacktrace: stacktrace}, value) when is_struct(value) do
+    new_trace =
+      value.__struct__ |> Module.split() |> List.last()
+
+    %Error{message: message, stacktrace: [new_trace | stacktrace]}
+  end
+
+  def add_trace(%Error{message: message, stacktrace: stacktrace}, new_trace) do
+    %Error{message: message, stacktrace: [new_trace | stacktrace]}
   end
 
+  def add_trace({:error, %Error{} = error}, new_trace),
+    do: {:error, Error.add_trace(error, new_trace)}
+
+  def add_trace(value, _module), do: value
+
   defimpl String.Chars, for: __MODULE__ do
     def to_string(error), do: Error.format(error)
   end

lib/ssz_ex/merkleization.ex

@@ -39,6 +39,14 @@ defmodule SszEx.Merkleization do
 
   @spec hash_tree_root(binary, {:byte_vector, non_neg_integer}) ::
           {:ok, Types.root()}
+  def hash_tree_root(value, {:byte_vector, size}) when byte_size(value) != size,
+    do:
+      {:error,
+       %Error{
+         message:
+           "Invalid binary length while merkleizing byte_vector.\nExpected size: #{size}.\nFound: #{byte_size(value)}\n"
+       }}
+
   def hash_tree_root(value, {:byte_vector, _size}) do
     packed_chunks = pack_bytes(value)
     leaf_count = packed_chunks |> get_chunks_len() |> next_pow_of_two()
@@ -118,7 +126,7 @@ defmodule SszEx.Merkleization do
 
         case hash_tree_root(value, schema) do
           {:ok, root} -> {:cont, {:ok, acc_root <> root}}
-          {:error, %Error{}} = error -> {:halt, error}
+          {:error, %Error{} = error} -> {:halt, {:error, Error.add_trace(error, key)}}
         end
       end)
 

lib/ssz_ex/ssz_ex.ex

@@ -62,12 +62,17 @@ defmodule SszEx do
 
   @spec encode(struct()) ::
           {:ok, binary()} | {:error, Error.t()}
-  def encode(%name{} = value), do: encode(value, name)
+  def encode(%name{} = value), do: encode(value, name) |> Error.add_trace(value)
 
   @spec encode(any(), schema()) ::
           {:ok, binary()} | {:error, Error.t()}
   def encode(value, schema), do: Encode.encode(value, schema)
 
+  @spec decode(binary(), schema()) ::
+          {:ok, any()} | {:error, Error.t()}
+  def decode(value, module) when is_atom(module),
+    do: Decode.decode(value, module) |> Error.add_trace(module)
+
   @spec decode(binary(), schema()) ::
           {:ok, any()} | {:error, Error.t()}
   def decode(value, schema), do: Decode.decode(value, schema)
@@ -78,6 +83,10 @@ defmodule SszEx do
   @spec hash_tree_root!(any, any) :: Types.root()
   def hash_tree_root!(value, schema), do: Merkleization.hash_tree_root!(value, schema)
 
+  @spec hash_tree_root(struct()) :: {:ok, Types.root()} | {:error, Error.t()}
+  def hash_tree_root(%name{} = value),
+    do: hash_tree_root(value, name) |> Error.add_trace(value)
+
   @spec hash_tree_root(any, any) :: {:ok, Types.root()} | {:error, Error.t()}
   def hash_tree_root(value, schema), do: Merkleization.hash_tree_root(value, schema)
 

lib/ssz_ex/utils.ex

@@ -67,7 +67,7 @@ defmodule SszEx.Utils do
 
   def flatten_results_by(results, fun) do
     case Enum.group_by(results, fn {type, _} -> type end, fn {_, result} -> result end) do
-      %{error: errors} -> {:error, errors}
+      %{error: [first_error | _rest]} -> {:error, first_error}
       summary -> {:ok, fun.(Map.get(summary, :ok, []))}
     end
   end

test/unit/ssz_ex_test.exs

@@ -1,4 +1,5 @@
 defmodule Unit.SSZExTest do
+  alias LambdaEthereumConsensus.Utils.BitVector
   alias LambdaEthereumConsensus.Utils.Diff
   alias SszEx.Error
   alias SszEx.Merkleization
@@ -17,6 +18,59 @@ defmodule Unit.SSZExTest do
     assert {:ok, deserialized} === SszEx.decode(serialized, schema)
   end
 
+  def build_broken_attester_slashing() do
+    checkpoint_source = %Types.Checkpoint{
+      epoch: 3_776_037_760_046_644_755,
+      root:
+        <<29, 22, 191, 147, 188, 238, 162, 89, 147, 162, 202, 111, 169, 162, 84, 95, 194, 85, 54,
+          172, 44, 74, 37, 128, 248, 21, 86, 246, 151, 54, 24, 54>>
+    }
+
+    checkpoint_target = %Types.Checkpoint{
+      epoch: 2_840_053_453_521_072_037,
+      root:
+        <<15, 174, 23, 120, 4, 9, 2, 116, 67, 73, 254, 53, 197, 3, 191, 166, 104, 34, 121, 2, 57,
+          69, 75, 69, 254, 237, 132, 68, 254, 49, 127, 175>>
+    }
+
+    attestation_data = %Types.AttestationData{
+      slot: 5_057_010_135_270_197_978,
+      index: 6_920_931_864_607_509_210,
+      beacon_block_root:
+        <<31, 38, 101, 174, 248, 168, 116, 226, 15, 39, 218, 148, 42, 8, 80, 80, 241, 149, 162,
+          32, 176, 208, 120, 120, 89, 123, 136, 115, 154, 28, 21, 174>>,
+      source: checkpoint_source,
+      target: checkpoint_target
+    }
+
+    indexed_attestation_1 = %Types.IndexedAttestation{
+      attesting_indices: [15_833_676_831_095_072_535, 7_978_643_446_947_046_229],
+      data: attestation_data,
+      signature:
+        <<46, 244, 83, 164, 182, 222, 218, 247, 8, 186, 138, 100, 5, 96, 34, 117, 134, 123, 219,
+          188, 181, 11, 209, 57, 207, 24, 249, 42, 74, 27, 228, 97, 73, 46, 219, 202, 122, 149,
+          135, 30, 91, 126, 180, 69, 129, 170, 147, 142, 242, 27, 233, 63, 242, 7, 144, 8, 192,
+          165, 194, 220, 77, 247, 128, 107, 41, 199, 166, 59, 34, 160, 222, 114, 250, 250, 3, 130,
+          145, 8, 45, 65, 13, 82, 44, 80, 30, 181, 239, 54, 152, 237, 244, 72, 231, 179, 239, 22>>
+    }
+
+    broken_attestation = %Types.IndexedAttestation{
+      attesting_indices: List.duplicate(0, 3000),
+      data: attestation_data,
+      signature:
+        <<46, 244, 83, 164, 182, 222, 218, 247, 8, 186, 138, 100, 5, 96, 34, 117, 134, 123, 219,
+          188, 181, 11, 209, 57, 207, 24, 249, 42, 74, 27, 228, 97, 73, 46, 219, 202, 122, 149,
+          135, 30, 91, 126, 180, 69, 129, 170, 147, 142, 242, 27, 233, 63, 242, 7, 144, 8, 192,
+          165, 194, 220, 77, 247, 128, 107, 41, 199, 166, 59, 34, 160, 222, 114, 250, 250, 3, 130,
+          145, 8, 45, 65, 13, 82, 44, 80, 30, 181, 239, 54, 152, 237, 244, 72, 231, 179, 239, 22>>
+    }
+
+    %Types.AttesterSlashing{
+      attestation_1: indexed_attestation_1,
+      attestation_2: broken_attestation
+    }
+  end
+
   test "packing a list of uints" do
     list_1 = [1, 2, 3, 4, 5]
 
@@ -737,24 +791,20 @@ defmodule Unit.SSZExTest do
     encoded_checkpoint =
       <<0, 0, 0>>
 
-    assert SszEx.decode(encoded_checkpoint, Checkpoint) ==
-             {:error,
-              %Error{
-                message:
-                  "Invalid binary length while decoding Elixir.Types.Checkpoint. \nExpected 40. \nFound 3.\n"
-              }}
+    {:error, error} = SszEx.decode(encoded_checkpoint, Checkpoint)
+
+    assert "#{error}" ==
+             "Invalid binary length while decoding Elixir.Types.Checkpoint. \nExpected 40. \nFound 3.\nStacktrace: Elixir.Types.Checkpoint"
   end
 
   test "decode longer checkpoint" do
     encoded_checkpoint =
       <<0::size(41 * 8)>>
 
-    assert SszEx.decode(encoded_checkpoint, Checkpoint) ==
-             {:error,
-              %Error{
-                message:
-                  "Invalid binary length while decoding Elixir.Types.Checkpoint. \nExpected 40. \nFound 41.\n"
-              }}
+    {:error, error} = SszEx.decode(encoded_checkpoint, Checkpoint)
+
+    assert "#{error}" ==
+             "Invalid binary length while decoding Elixir.Types.Checkpoint. \nExpected 40. \nFound 41.\nStacktrace: Elixir.Types.Checkpoint"
   end
 
   test "hash tree root of list exceeding max size" do
@@ -766,4 +816,87 @@ defmodule Unit.SSZExTest do
     {:error, result} = SszEx.hash_tree_root(initial_list, {:list, {:int, 8}, 2})
     assert error == "#{result}"
   end
+
+  test "hash_tree_root with invalid logs_bloom" do
+    execution_payload = %ExecutionPayload{
+      parent_hash: @default_hash,
+      fee_recipient: <<0::size(20 * 8)>>,
+      state_root: @default_root,
+      receipts_root: @default_root,
+      logs_bloom: <<0, 0, 0>>,
+      prev_randao: <<0::size(32 * 8)>>,
+      block_number: 0,
+      gas_limit: 0,
+      gas_used: 0,
+      timestamp: 0,
+      extra_data: <<>>,
+      base_fee_per_gas: 0,
+      block_hash: @default_hash,
+      transactions: [],
+      withdrawals: [],
+      blob_gas_used: 0,
+      excess_blob_gas: 0
+    }
+
+    {:error, error} = SszEx.hash_tree_root(execution_payload, ExecutionPayload)
+
+    assert "#{error}" ==
+             "Invalid binary length while merkleizing byte_vector.\nExpected size: 256.\nFound: 3\nStacktrace: logs_bloom"
+  end
+
+  test "stacktrace in hash_tree_root with invalid logs_bloom" do
+    execution_payload = %ExecutionPayload{
+      parent_hash: @default_hash,
+      fee_recipient: <<0::size(20 * 8)>>,
+      state_root: @default_root,
+      receipts_root: @default_root,
+      logs_bloom: <<0, 0, 0>>,
+      prev_randao: <<0::size(32 * 8)>>,
+      block_number: 0,
+      gas_limit: 0,
+      gas_used: 0,
+      timestamp: 0,
+      extra_data: <<>>,
+      base_fee_per_gas: 0,
+      block_hash: @default_hash,
+      transactions: [],
+      withdrawals: [],
+      blob_gas_used: 0,
+      excess_blob_gas: 0
+    }
+
+    {:error, error} = SszEx.hash_tree_root(execution_payload)
+
+    assert "#{error}" ==
+             "Invalid binary length while merkleizing byte_vector.\nExpected size: 256.\nFound: 3\nStacktrace: ExecutionPayload.logs_bloom"
+  end
+
+  test "stacktrace in encode with invalid sync_committee_bits" do
+    sync_aggregate = %SyncAggregate{
+      sync_committee_bits: BitVector.new(2),
+      sync_committee_signature: <<0::size(32 * 8)>>
+    }
+
+    {:error, error} = SszEx.encode(sync_aggregate)
+
+    assert "#{error}" ==
+             "Invalid binary length while encoding BitVector. \nExpected: 512.\nFound: 2.\nStacktrace: SyncAggregate.sync_committee_bits"
+  end
+
+  test "stacktrace encode nested container" do
+    attester_slashing = build_broken_attester_slashing()
+
+    {:error, error} = SszEx.encode(attester_slashing)
+
+    assert "#{error}" ==
+             "Invalid binary length while encoding list of {:int, 64}.\nExpected max_size: 2048.\nFound: 3000\nStacktrace: AttesterSlashing.attestation_2.attesting_indices"
+  end
+
+  test "stacktrace hash_tree_root nested container" do
+    attester_slashing = build_broken_attester_slashing()
+    {:error, error} = SszEx.hash_tree_root(attester_slashing)
+
+    assert "Invalid binary length while merkleizing list of {:int, 64}.\nExpected max_size: 2048.\nFound: 3000\nStacktrace: AttesterSlashing.attestation_2.attesting_indices" =
+             "#{error}"
+  end
 end