Fix event decoders with unnamed params (#180)

codegenerator/cli/src/config_parsing/system_config.rs

@@ -888,7 +888,7 @@ impl Event {
         let mut events_abi = ethers::abi::Abi::default();
 
         for event_config in events_config.iter() {
-            let event = Event::get_abi_event(&event_config.event, &abi_from_file)?;
+            let mut event = Event::get_abi_event(&event_config.event, &abi_from_file)?;
             let sighash = ethers::core::utils::hex::encode_prefixed(ethers::utils::keccak256(
                 event.abi_signature().as_bytes(),
             ));
@@ -911,6 +911,11 @@ impl Event {
                 })
                 .collect();
 
+            // All unnamed params in the ABI should be named,
+            // otherwise decoders will output parsed data as an array,
+            // instead of an object with named fields.
+            event.inputs = normalized_unnamed_params.clone();
+
             events_abi.events.entry(abi_name).or_default().push(event);
             events.push(Event {
                 name,

scenarios/test_codegen/test/Viem_test.res

@@ -0,0 +1,68 @@
+open RescriptMocha
+
+@module("viem") external parseAbi: array<string> => Ethers.abi = "parseAbi"
+
+describe("decodeEventLogOrThrow", () => {
+  it("decodes event with args as an object", () => {
+    let eventLog: Viem.eventLog = {
+      {
+        abi: parseAbi([
+          "event PoolCreated(address indexed token0, address indexed token1, uint24 indexed fee, int24 tickSpacing, address pool)",
+        ]),
+        data: "0x000000000000000000000000000000000000000000000000000000000000003c000000000000000000000000e13514aacc27a3dfd2ae0db6ada4ef7658c1e435",
+        topics: [
+          "0x783cca1c0412dd0d695e784568c96da2e9c22ff989357a2e8b1d9b2b4e6b7118",
+          "0x00000000000000000000000027d2decb4bfc9c76f0309b8e88dec3a601fe25a8",
+          "0x0000000000000000000000004200000000000000000000000000000000000006",
+          "0x0000000000000000000000000000000000000000000000000000000000000bb8",
+        ],
+      }
+    }
+    let decodedEvent = eventLog->Viem.decodeEventLogOrThrow
+
+    Assert.deepEqual(
+      decodedEvent,
+      {
+        args: {
+          "fee": 3000,
+          "pool": "0xe13514AaCc27a3dFd2ae0db6aDA4eF7658c1E435",
+          "tickSpacing": 60,
+          "token0": "0x27D2DECb4bFC9C76F0309b8E88dec3a601Fe25a8",
+          "token1": "0x4200000000000000000000000000000000000006",
+        },
+        eventName: "PoolCreated",
+      },
+    )
+  })
+
+  it("if there's a param without name, it decodes as an array, which we don't want", () => {
+    let eventLog: Viem.eventLog = {
+      {
+        abi: parseAbi([
+          "event PairCreated(address indexed token0, address indexed token1, address pair, uint256)",
+        ]),
+        data: "0x0000000000000000000000001cc744d0891457e16e94426ea4357662a9a9ba5000000000000000000000000000000000000000000000000000000000000001c1",
+        topics: [
+          "0x0d3648bd0f6ba80134a33ba9275ac585d9d315f0ad8355cddefde31afa28d0e9",
+          "0x0000000000000000000000004200000000000000000000000000000000000006",
+          "0x0000000000000000000000006d521550fc0e937cd3f4db0b17bbc256f5bfd140",
+        ],
+      }
+    }
+    let decodedEvent = eventLog->Viem.decodeEventLogOrThrow
+
+    Assert.deepEqual(
+      decodedEvent,
+      {
+        args: [
+          "0x4200000000000000000000000000000000000006",
+          "0x6D521550fc0E937CD3f4dB0B17Bbc256F5bFd140",
+          "0x1CC744d0891457E16e94426EA4357662A9A9bA50",
+          "449",
+        ],
+        eventName: "PairCreated",
+      },
+    )
+    // We don't want that /|\ to be an array, so we need to output abi with the param names
+  })
+})