event handlers should't be permitted to raise anything other than a Defect

tests/test.nim

@@ -91,14 +91,20 @@ proc test() {.async.} =
     let notifFut = newFuture[void]()
     var notificationsReceived = 0
 
-    let s = await ns.subscribe(Transfer) do(fromAddr, toAddr: Address, value: Uint256):
-      echo "onTransfer: ", fromAddr, " transferred ", value, " to ", toAddr
-      inc notificationsReceived
-      assert(fromAddr == web3.defaultAccount)
-      assert((notificationsReceived == 1 and value == 50.u256) or
-              (notificationsReceived == 2 and value == 100.u256))
-      if notificationsReceived == 2:
-        notifFut.complete()
+    let s = await ns.subscribe(Transfer) do (
+        fromAddr, toAddr: Address, value: Uint256)
+        {.raises: [Defect], gcsafe.}:
+      try:
+        echo "onTransfer: ", fromAddr, " transferred ", value, " to ", toAddr
+        inc notificationsReceived
+        assert(fromAddr == web3.defaultAccount)
+        assert((notificationsReceived == 1 and value == 50.u256) or
+                (notificationsReceived == 2 and value == 100.u256))
+        if notificationsReceived == 2:
+          notifFut.complete()
+      except Exception as err:
+        # chronos still raises exceptions which inherit directly from Exception
+        doAssert false, err.msg
 
     echo "getbalance (now): ", await ns.getBalance(web3.defaultAccount).call()
     echo "getbalance (after creation): ", await ns.getBalance(web3.defaultAccount).call(blockNumber = deployedAtBlock)

tests/test_deposit_contract.nim

@@ -32,15 +32,21 @@ proc test() {.async.} =
 
   var fut = newFuture[void]()
 
-  let s = await ns.subscribe(DepositEvent, %*{"fromBlock": "0x0"}) do(pubkey: Bytes48, withdrawalCredentials: Bytes32, amount: Bytes8, signature: Bytes96, merkleTreeIndex: Bytes8):
-    echo "onDeposit"
-    echo "pubkey: ", pubkey
-    echo "withdrawalCredentials: ", withdrawalCredentials
-    echo "amount: ", amount
-    echo "signature: ", signature
-    echo "merkleTreeIndex: ", merkleTreeIndex
-    assert(pubkey == pk)
-    fut.complete()
+  let s = await ns.subscribe(DepositEvent, %*{"fromBlock": "0x0"}) do (
+      pubkey: Bytes48, withdrawalCredentials: Bytes32, amount: Bytes8, signature: Bytes96, merkleTreeIndex: Bytes8)
+      {.raises: [Defect], gcsafe.}:
+    try:
+      echo "onDeposit"
+      echo "pubkey: ", pubkey
+      echo "withdrawalCredentials: ", withdrawalCredentials
+      echo "amount: ", amount
+      echo "signature: ", signature
+      echo "merkleTreeIndex: ", merkleTreeIndex
+      assert(pubkey == pk)
+      fut.complete()
+    except Exception as err:
+      # chronos still raises exceptions which inherit directly from Exception
+      doAssert false, err.msg
 
   discard await ns.deposit(pk, cr, sig, dataRoot).send(value = 32.u256.ethToWei)
 

tests/test_logs.nim

@@ -62,12 +62,18 @@ proc test() {.async.} =
     let notifFut = newFuture[void]()
     var notificationsReceived = 0
 
-    let s = await ns.subscribe(MyEvent, %*{"fromBlock": "0x0"}) do(sender: Address, value: Uint256):
-      echo "onEvent: ", sender, " value ", value
-      inc notificationsReceived
+    let s = await ns.subscribe(MyEvent, %*{"fromBlock": "0x0"}) do (
+        sender: Address, value: Uint256)
+        {.raises: [Defect], gcsafe.}:
+      try:
+        echo "onEvent: ", sender, " value ", value
+        inc notificationsReceived
 
-      if notificationsReceived == invocationsBefore + invocationsAfter:
-        notifFut.complete()
+        if notificationsReceived == invocationsBefore + invocationsAfter:
+          notifFut.complete()
+      except Exception as err:
+        # chronos still raises exceptions which inherit directly from Exception
+        doAssert false, err.msg
 
     for i in 1 .. invocationsAfter:
       await testInvoke()

web3.nim

@@ -648,7 +648,18 @@ macro contract*(cname: untyped, body: untyped): untyped =
           procTy = nnkProcTy.newTree(params, newEmptyNode())
           signature = getSignature(obj.eventObject)
 
-        procTy[1] = nnkPragma.newTree(ident"gcsafe") # TODO: use addPragma in nim 0.20.4 and later
+        # generated with dumpAstGen - produces "{.raises: [Defect], gcsafe.}"
+        let pragmas = nnkPragma.newTree(
+          nnkExprColonExpr.newTree(
+            newIdentNode("raises"),
+            nnkBracket.newTree(
+              newIdentNode("Defect")
+            )
+          ),
+          newIdentNode("gcsafe")
+        )
+
+        procTy[1] = pragmas
 
         callWithRawData.add jsonIdent
         paramsWithRawData.add nnkIdentDefs.newTree(
@@ -658,7 +669,7 @@ macro contract*(cname: untyped, body: untyped): untyped =
         )
 
         let procTyWithRawData = nnkProcTy.newTree(paramsWithRawData, newEmptyNode())
-        procTyWithRawData[1] = nnkPragma.newTree(ident"gcsafe") # TODO: use addPragma in nim 0.20.4 and later
+        procTyWithRawData[1] = pragmas
 
         result.add quote do:
           type `cbident` = object