check for nil ctx and set iter.finished correctly

datastore/threads/threadproxyds.nim

@@ -115,6 +115,10 @@ proc signalMonitor[T](ctx: ptr TaskCtx, fut: Future[T]) {.async.} =
   ## the cancellation flag is set
   ##
 
+  if ctx.isNil:
+    trace "ctx is nil"
+    return
+
   try:
     await ctx[].signal.wait()
     trace "Received signal"
@@ -134,7 +138,12 @@ proc asyncHasTask(
   ctx: ptr TaskCtx[bool],
   key: ptr Key) {.async.} =
   defer:
-    discard ctx[].signal.fireSync()
+    if not ctx.isNil:
+      discard ctx[].signal.fireSync()
+
+  if ctx.isNil:
+    trace "ctx is nil"
+    return
 
   let
     fut = ctx[].ds.has(key[])
@@ -167,7 +176,12 @@ method has*(self: ThreadDatastore, key: Key): Future[?!bool] {.async.} =
 
 proc asyncDelTask(ctx: ptr TaskCtx[void], key: ptr Key) {.async.} =
   defer:
-    discard ctx[].signal.fireSync()
+    if not ctx.isNil:
+      discard ctx[].signal.fireSync()
+
+  if ctx.isNil:
+    trace "ctx is nil"
+    return
 
   let
     fut = ctx[].ds.delete(key[])
@@ -218,7 +232,12 @@ proc asyncPutTask(
   data: ptr UncheckedArray[byte],
   len: int) {.async.} =
   defer:
-    discard ctx[].signal.fireSync()
+    if not ctx.isNil:
+      discard ctx[].signal.fireSync()
+
+  if ctx.isNil:
+    trace "ctx is nil"
+    return
 
   let
     fut = ctx[].ds.put(key[], @(data.toOpenArray(0, len - 1)))
@@ -278,7 +297,12 @@ proc asyncGetTask(
   ctx: ptr TaskCtx[DataBuffer],
   key: ptr Key) {.async.} =
   defer:
-    discard ctx[].signal.fireSync()
+    if not ctx.isNil:
+      discard ctx[].signal.fireSync()
+
+  if ctx.isNil:
+    trace "ctx is nil"
+    return
 
   let
     fut = ctx[].ds.get(key[])
@@ -328,7 +352,12 @@ proc asyncQueryTask(
   ctx: ptr TaskCtx,
   iter: ptr QueryIter) {.async.} =
   defer:
-    discard ctx[].signal.fireSync()
+    if not ctx.isNil:
+      discard ctx[].signal.fireSync()
+
+  if ctx.isNil or iter.isNil:
+    trace "ctx is nil"
+    return
 
   let
     fut = iter[].next()
@@ -368,24 +397,23 @@ method query*(
 
   var
     iter = QueryIter.new()
-    locked = false
+    lock = newAsyncLock() # serialize querying under threads
 
   proc next(): Future[?!QueryResponse] {.async.} =
     defer:
-      locked = false
+      if lock.locked:
+        lock.release()
 
     trace "About to query"
-    if locked:
+    if lock.locked:
       return failure (ref DatastoreError)(msg: "Should always await query features")
 
-    locked = true
+    await lock.acquire()
 
     if iter.finished == true:
       return failure (ref QueryEndedError)(msg: "Calling next on a finished query!")
 
-    if iter.finished == true:
-      return success (Key.none, EmptyBytes)
-
+    iter.finished = childIter.finished
     var
       res = ThreadResult[ThreadQueryRes]()
       ctx = TaskCtx[ThreadQueryRes](