fix: handle FDWatcher exception on closed sockets

src/Curl/Multi.jl

@@ -43,14 +43,18 @@
 
 function add_handle(multi::Multi, easy::Easy)
     connect_semaphore_acquire(easy)
-    lock(multi.lock) do
+    added = lock(multi.lock) do
         if isempty(multi.easies)
             preserve_handle(multi)
         end
         push!(multi.easies, easy)
         init!(multi)
         @check curl_multi_add_handle(multi.handle, easy.handle)
     end
+    if added != 0
+        connect_semaphore_release(easy)
+    end
+    return added
 end
 
 const MULTIS_LOCK = Base.ReentrantLock()
@@ -170,7 +174,25 @@
         if action in (CURL_POLL_IN, CURL_POLL_OUT, CURL_POLL_INOUT)
             readable = action in (CURL_POLL_IN,  CURL_POLL_INOUT)
             writable = action in (CURL_POLL_OUT, CURL_POLL_INOUT)
-            watcher = FDWatcher(OS_HANDLE(sock), readable, writable)
+            watcher = try
+                FDWatcher(OS_HANDLE(sock), readable, writable)
+            catch watcher_ex
+                if watcher_ex isa Base.IOError
+                    task = @async begin
+                        lock(multi.lock) do
+                            @check curl_multi_socket_action(multi.handle, sock, CURL_CSELECT_ERR)
+                            check_multi_info(multi)
+                        end
+                    end
+                    @isdefined(errormonitor) && errormonitor(task)
+                    nothing
+                else
+                    rethrow()
+                end
+            end
+            if watcher === nothing
+                return -1
+            end
             preserve_handle(watcher)
             watcher_p = pointer_from_objref(watcher)
             @check curl_multi_assign(multi.handle, sock, watcher_p)

src/Downloads.jl

@@ -395,7 +395,16 @@
                 easy_hook(downloader, easy, info)
 
                 # do the request
-                add_handle(downloader.multi, easy)
+                add_handle_error = add_handle(downloader.multi, easy)
+                if add_handle_error != 0
+                    no_response = Response(nothing, "", 0, "", [])
+                    request_error = RequestError(url, add_handle_error, "", no_response)
+                    if throw
+                        Base.throw(request_error)
+                    else
+                        return request_error
+                    end
+                end
                 interrupted = Threads.Atomic{Bool}(false)
                 if interrupt !== nothing
                     interrupt_task = @async begin