Fix event selector matching (#157)

* fix: event selector matching

* fix: update method_id type

Author: k1rill-fedoseev

lib/abi.ex

@@ -212,7 +212,7 @@ defmodule ABI do
       ...> |> Jason.decode!
       ...> |> ABI.parse_specification(include_events?: true)
       ...> |> Enum.filter(&(&1.type == :event))
-      [%ABI.FunctionSelector{type: :event, function: "WantsPets", input_names: ["_from_human", "_number", "_belly"], inputs_indexed: [true, false, true], method_id: <<235, 155, 60, 76>>, types: [:string, {:uint, 256}, :bool]}]
+      [%ABI.FunctionSelector{type: :event, function: "WantsPets", input_names: ["_from_human", "_number", "_belly"], inputs_indexed: [true, false, true], method_id: <<235, 155, 60, 76, 236, 41, 90, 133, 158, 131, 71, 199, 88, 206, 85, 83, 36, 105, 140, 112, 231, 125, 249, 63, 87, 99, 121, 242, 184, 82, 161, 19>>, types: [:string, {:uint, 256}, :bool]}]
 
       iex> File.read!("priv/example1.abi.json")
       ...> |> Jason.decode!

lib/abi/event.ex

@@ -54,7 +54,7 @@ defmodule ABI.Event do
           function: "WantsPets",
           input_names: ["_from_human", "_number", "_belly"],
           inputs_indexed: [true, false, true],
-          method_id: <<235, 155, 60, 76>>,
+          method_id: <<235, 155, 60, 76, 236, 41, 90, 133, 158, 131, 71, 199, 88, 206, 85, 83, 36, 105, 140, 112, 231, 125, 249, 63, 87, 99, 121, 242, 184, 82, 161, 19>>,
           types: [:string, {:uint, 256}, :bool]
         },
         [
@@ -69,9 +69,8 @@ defmodule ABI.Event do
   def find_and_decode(function_selectors, topic1, topic2, topic3, topic4, data) do
     input_topics = [topic2, topic3, topic4]
 
-    with {:ok, method_id, _rest} <- Util.split_method_id(topic1),
-         {:ok, selector} when not is_nil(selector) <-
-           Util.find_selector_by_event_id(function_selectors, method_id, input_topics) do
+    with {:ok, selector} when not is_nil(selector) <-
+           Util.find_selector_by_event_id(function_selectors, topic1, input_topics) do
       args = Enum.zip([selector.input_names, selector.types, selector.inputs_indexed])
 
       {indexed_args, unindexed_args} =

lib/abi/function_selector.ex

@@ -29,14 +29,14 @@ defmodule ABI.FunctionSelector do
   * `:types` - Function's input types
   * `:returns` - Function's return types
   * `:return_names` - Names of the return values (output names)
-  * `:method_id` - First four bits of the hashed function signature
+  * `:method_id` - First four bytes of the hashed function signature or full 32 byte hash for events
   * `:input_names` - Names of the input values (argument names)
   * `:type` - The type of the selector. Events are part of the ABI, but are not considered functions
   * `:inputs_index` - A list of true/false values denoting if each input is indexed. Only populated for events.
   """
   @type t :: %__MODULE__{
           function: String.t() | nil,
-          method_id: String.t() | nil,
+          method_id: binary | nil,
           input_names: [String.t()],
           types: [type],
           returns: [type],
@@ -260,7 +260,7 @@ defmodule ABI.FunctionSelector do
         type: :event
       }
 
-      add_method_id(selector)
+      add_event_id(selector)
     else
       _ -> nil
     end
@@ -415,6 +415,12 @@ defmodule ABI.FunctionSelector do
     end
   end
 
+  defp add_event_id(selector) do
+    signature = encode(selector)
+
+    %{selector | method_id: ExKeccak.hash_256(signature)}
+  end
+
   defp get_types(function_selector) do
     for type <- function_selector.types do
       get_type(type)

test/abi/util_test.exs

@@ -4,7 +4,9 @@ defmodule ABI.UtilTest do
   @selectors [
     %ABI.FunctionSelector{
       function: "Transfer",
-      method_id: <<221, 242, 82, 173>>,
+      method_id:
+        <<221, 242, 82, 173, 27, 226, 200, 155, 105, 194, 176, 104, 252, 55, 141, 170, 149, 43,
+          167, 241, 99, 196, 161, 22, 40, 245, 90, 77, 245, 35, 179, 239>>,
       type: :event,
       inputs_indexed: [false, false, false],
       state_mutability: nil,
@@ -14,7 +16,9 @@ defmodule ABI.UtilTest do
     },
     %ABI.FunctionSelector{
       function: "Transfer",
-      method_id: <<221, 242, 82, 173>>,
+      method_id:
+        <<221, 242, 82, 173, 27, 226, 200, 155, 105, 194, 176, 104, 252, 55, 141, 170, 149, 43,
+          167, 241, 99, 196, 161, 22, 40, 245, 90, 77, 245, 35, 179, 239>>,
       type: :event,
       inputs_indexed: [true, true, true],
       state_mutability: nil,
@@ -24,7 +28,9 @@ defmodule ABI.UtilTest do
     },
     %ABI.FunctionSelector{
       function: "OwnershipTransferred",
-      method_id: <<139, 224, 7, 156>>,
+      method_id:
+        <<139, 224, 7, 156, 83, 22, 89, 20, 19, 68, 205, 31, 208, 164, 242, 132, 25, 73, 127, 151,
+          34, 163, 218, 175, 227, 180, 24, 111, 107, 100, 87, 224>>,
       type: :event,
       inputs_indexed: [true, true],
       state_mutability: nil,
@@ -37,28 +43,38 @@ defmodule ABI.UtilTest do
   describe "decode events" do
     test "successfully decodes ERC721 transfer event" do
       {:ok, selector} =
-        ABI.Util.find_selector_by_event_id(@selectors, <<221, 242, 82, 173>>, [
-          <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 230, 218, 29, 25, 253, 206, 193, 121, 186, 151,
-            85, 242, 198, 19, 159, 143, 254, 203, 254, 176>>,
-          <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 168, 47, 182, 247, 249, 220, 207, 188, 171, 157,
-            153, 173, 222, 184, 132, 3, 58, 241, 27, 134>>,
-          <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 12, 12>>
-        ])
+        ABI.Util.find_selector_by_event_id(
+          @selectors,
+          <<221, 242, 82, 173, 27, 226, 200, 155, 105, 194, 176, 104, 252, 55, 141, 170, 149, 43,
+            167, 241, 99, 196, 161, 22, 40, 245, 90, 77, 245, 35, 179, 239>>,
+          [
+            <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 230, 218, 29, 25, 253, 206, 193, 121, 186, 151,
+              85, 242, 198, 19, 159, 143, 254, 203, 254, 176>>,
+            <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 168, 47, 182, 247, 249, 220, 207, 188, 171, 157,
+              153, 173, 222, 184, 132, 3, 58, 241, 27, 134>>,
+            <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+              0, 0, 12, 12>>
+          ]
+        )
 
       assert selector.function == "Transfer"
       assert selector.inputs_indexed == [true, true, true]
     end
 
     test "decode OwnershipTransferred event" do
       {:ok, selector} =
-        ABI.Util.find_selector_by_event_id(@selectors, <<139, 224, 7, 156>>, [
-          <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0>>,
-          <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 79, 181, 74, 58, 157, 2, 63, 219, 87, 69, 216,
-            158, 228, 106, 170, 82, 18, 171, 87, 125>>,
-          nil
-        ])
+        ABI.Util.find_selector_by_event_id(
+          @selectors,
+          <<139, 224, 7, 156, 83, 22, 89, 20, 19, 68, 205, 31, 208, 164, 242, 132, 25, 73, 127,
+            151, 34, 163, 218, 175, 227, 180, 24, 111, 107, 100, 87, 224>>,
+          [
+            <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+              0, 0, 0, 0>>,
+            <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 79, 181, 74, 58, 157, 2, 63, 219, 87, 69, 216,
+              158, 228, 106, 170, 82, 18, 171, 87, 125>>,
+            nil
+          ]
+        )
 
       assert selector.function == "OwnershipTransferred"
       assert selector.inputs_indexed == [true, true]