From 8e71949b785ca2b2bc61d0f95c5ac88fa87621fe Mon Sep 17 00:00:00 2001
From: Anatoly Galiulin <galiulin.anatoly@gmail.com>
Date: Thu, 29 Dec 2016 11:22:50 +0700
Subject: [PATCH] Add pending operations presence check function, fixes #5155

---
 lib/pure/asyncdispatch.nim     | 15 ++++++++++++++-
 lib/upcoming/asyncdispatch.nim | 12 +++++++++++-
 tests/async/tpendingcheck.nim  | 21 +++++++++++++++++++++
 3 files changed, 46 insertions(+), 2 deletions(-)
 create mode 100644 tests/async/tpendingcheck.nim

diff --git a/lib/pure/asyncdispatch.nim b/lib/pure/asyncdispatch.nim
index 1367bc411f..b72596060d 100644
--- a/lib/pure/asyncdispatch.nim
+++ b/lib/pure/asyncdispatch.nim
@@ -254,8 +254,14 @@ when defined(windows) or defined(nimdoc):
         "Operation performed on a socket which has not been registered with" &
         " the dispatcher yet.")
 
+  proc hasPendingOperations*(): bool =
+    ## Returns `true` if the global dispatcher has pending operations.
+    let p = getGlobalDispatcher()
+    p.handles.len != 0 or p.timers.len != 0 or p.callbacks.len != 0
+
   proc poll*(timeout = 500) =
-    ## Waits for completion events and processes them.
+    ## Waits for completion events and processes them. Raises ``ValueError``
+    ## if there are no pending operations.
     let p = getGlobalDispatcher()
     if p.handles.len == 0 and p.timers.len == 0 and p.callbacks.len == 0:
       raise newException(ValueError,
@@ -1056,8 +1062,15 @@ else:
           newCBs.add(cb)
     callbacks = newCBs & callbacks
 
+  proc hasPendingOperations*(): bool =
+    let p = getGlobalDispatcher()
+    p.selector.len != 0 or p.timers.len != 0 or p.callbacks.len != 0
+
   proc poll*(timeout = 500) =
     let p = getGlobalDispatcher()
+    if p.selector.len == 0 and p.timers.len == 0 and p.callbacks.len == 0:
+      raise newException(ValueError,
+        "No handles or timers registered in dispatcher.")
 
     if p.selector.len > 0:
       for info in p.selector.select(p.adjustedTimeout(timeout)):
diff --git a/lib/upcoming/asyncdispatch.nim b/lib/upcoming/asyncdispatch.nim
index ca5c1f64c3..78c7afffcd 100644
--- a/lib/upcoming/asyncdispatch.nim
+++ b/lib/upcoming/asyncdispatch.nim
@@ -231,8 +231,14 @@ when defined(windows) or defined(nimdoc):
         "Operation performed on a socket which has not been registered with" &
         " the dispatcher yet.")
 
+  proc hasPendingOperations*(): bool =
+    ## Returns `true` if the global dispatcher has pending operations.
+    let p = getGlobalDispatcher()
+    p.handles.len != 0 or p.timers.len != 0 or p.callbacks.len != 0
+
   proc poll*(timeout = 500) =
-    ## Waits for completion events and processes them.
+    ## Waits for completion events and processes them. Raises ``ValueError``
+    ## if there are no pending operations.
     let p = getGlobalDispatcher()
     if p.handles.len == 0 and p.timers.len == 0 and p.callbacks.len == 0:
       raise newException(ValueError,
@@ -1182,6 +1188,10 @@ else:
       raise newException(ValueError, "File descriptor not registered.")
     p.selector.updateHandle(fd.SocketHandle, newEvents)
 
+  proc hasPendingOperations*(): bool =
+    let p = getGlobalDispatcher()
+    not p.selector.isEmpty() or p.timers.len != 0 or p.callbacks.len != 0
+
   proc poll*(timeout = 500) =
     var keys: array[64, ReadyKey[AsyncData]]
 
diff --git a/tests/async/tpendingcheck.nim b/tests/async/tpendingcheck.nim
new file mode 100644
index 0000000000..825acb6135
--- /dev/null
+++ b/tests/async/tpendingcheck.nim
@@ -0,0 +1,21 @@
+discard """
+  file: "tpendingcheck.nim"
+  exitcode: 0
+  output: ""
+"""
+
+import asyncdispatch
+
+doAssert(not hasPendingOperations())
+
+proc test() {.async.} =
+  await sleepAsync(100)
+
+var f = test()
+while not f.finished:
+  doAssert(hasPendingOperations())
+  poll(10)
+f.read
+
+doAssert(not hasPendingOperations())
+