From 1cc52976df8fe2665e8e6caa311fbbb8df08f8d9 Mon Sep 17 00:00:00 2001
From: Zahary Karadjov <zahary@gmail.com>
Date: Thu, 28 Mar 2019 12:52:31 +0200
Subject: [PATCH] Add a new asyncDiscard replacement that traces recoverable
 errors and aborts on defects

---
 eth/async_utils.nim        | 12 ++++++++++++
 tests/test_async_utils.nim | 26 ++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 eth/async_utils.nim
 create mode 100644 tests/test_async_utils.nim

diff --git a/eth/async_utils.nim b/eth/async_utils.nim
new file mode 100644
index 0000000..f456038
--- /dev/null
+++ b/eth/async_utils.nim
@@ -0,0 +1,12 @@
+import
+  chronos/asyncfutures2, chronicles
+
+proc traceAsyncErrors*(fut: FutureBase) =
+  fut.addCallback do (arg: pointer):
+    if not fut.error.isNil:
+      if fut.error[] of CatchableError:
+        trace "Async operation ended with a recoverable error", err = fut.error.msg
+      else:
+        fatal "Fatal exception reached", err = fut.error.msg
+        quit 1
+
diff --git a/tests/test_async_utils.nim b/tests/test_async_utils.nim
new file mode 100644
index 0000000..610678e
--- /dev/null
+++ b/tests/test_async_utils.nim
@@ -0,0 +1,26 @@
+# TODO: Make this part of the test suite.
+# We need to be able to test that a program fails in certain way.
+# The testing framework from Chronicles can be extracted in a separate package.
+
+import
+  chronos, ../eth/async_utils
+
+type
+  SomeRecoverableError = object of CatchableError
+  SomeDefect = object of Defect
+
+proc failingAsyncProc(err: ref Exception = nil) {.async.} =
+  await sleepAsync(0)
+  if err != nil:
+    raise err
+
+proc main {.async.} =
+  type Error =
+    # Exception
+    SomeDefect
+    # SomeRecoverableError
+  traceAsyncErrors failingAsyncProc(newException(Error, "some exception"))
+
+waitFor main()
+waitFor sleepAsync(2000)
+