refs https://github.com/nim-lang/Nim/pull/25353 make tasyncclosestall… (#25366)

….nim less flaky

(cherry picked from commit 334ac3f588)

tests/async/tasyncclosestall.nim

@@ -8,7 +8,7 @@ import asyncdispatch, asyncnet
 when defined(windows):
   from winlean import ERROR_NETNAME_DELETED
 else:
-  from posix import EBADF
+  from posix import EBADF, ECONNRESET, EPIPE
 
 # This reproduces a case where a socket remains stuck waiting for writes
 # even when the socket is closed.
@@ -18,12 +18,37 @@ var port = Port(0)
 
 var sent = 0
 
+proc isExpectedDisconnectionError(errCode: int32): bool =
+  ## Check if an error code indicates an expected disconnection.
+  ## On POSIX systems, the error code depends on timing:
+  ## - EBADF: Socket was closed locally before kernel detected remote state
+  ## - ECONNRESET: Remote peer sent RST packet (detected first)
+  ## - EPIPE: Socket is no longer connected (broken pipe)
+  ## All three are valid disconnection errors for this test scenario.
+  when defined(windows):
+    errCode == ERROR_NETNAME_DELETED
+  else:
+    errCode == EBADF or errCode == ECONNRESET or errCode == EPIPE
+
 proc keepSendingTo(c: AsyncSocket) {.async.} =
   while true:
     # This write will eventually get stuck because the client is not reading
     # its messages.
     let sendFut = c.send("Foobar" & $sent & "\n", flags = {})
-    if not await withTimeout(sendFut, timeout):
+    var sendTimedOut = false
+    try:
+      # On some platforms (notably macOS ARM64), the kernel may return
+      # ECONNRESET immediately when detecting a non-responsive connection,
+      # rather than letting the send stall. We catch this case here.
+      sendTimedOut = not await withTimeout(sendFut, timeout)
+    except OSError as e:
+      if isExpectedDisconnectionError(e.errorCode):
+        echo("send has errored. As expected. All good!")
+        quit(QuitSuccess)
+      else:
+        raise
+
+    if sendTimedOut:
       # The write is stuck. Let's simulate a scenario where the socket
       # does not respond to PING messages, and we close it. The above future
       # should complete after the socket is closed, not continue stalling.
@@ -38,26 +63,16 @@ proc keepSendingTo(c: AsyncSocket) {.async.} =
         # is raised which we classif as a "diconnection error", hence we overwrite
         # the flags above in the `send` call so that this error is raised.
         #
-        # On Linux the EBADF error code is raised, this is because the socket
-        # is closed.
-        #
         # This means that by default the behaviours will differ between Windows
-        # and Linux. I think this is fine though, it makes sense mainly because
+        # and POSIX. I think this is fine though, it makes sense mainly because
         # Windows doesn't use a IO readiness model. We can fix this later if
         # necessary to reclassify ERROR_NETNAME_DELETED as not a "disconnection
         # error" (TODO)
-        when defined(windows):
-          if errCode == ERROR_NETNAME_DELETED:
-            echo("send has errored. As expected. All good!")
-            quit(QuitSuccess)
-          else:
-            raise newException(ValueError, "Test failed. Send failed with code " & $errCode)
+        if isExpectedDisconnectionError(errCode):
+          echo("send has errored. As expected. All good!")
+          quit(QuitSuccess)
         else:
-          if errCode == EBADF:
-            echo("send has errored. As expected. All good!")
-            quit(QuitSuccess)
-          else:
-            raise newException(ValueError, "Test failed. Send failed with code " & $errCode)
+          raise newException(ValueError, "Test failed. Send failed with code " & $errCode)
 
       # The write shouldn't succeed and also shouldn't be stalled.
       if timeoutFut.read():