[geary/wip/778276-better-flag-updates: 4/19] Add a Cancellable for terminating internal folder operations.

[Michael Gratton <mjog src gnome org>]

commit 6bf0ccc47d312103816eb7c751a045f67c58a5a8
Author: Michael James Gratton <mike vee net>
Date:   Mon Nov 20 19:34:16 2017 +1100

    Add a Cancellable for terminating internal folder operations.
    
    * src/engine/imap-engine/imap-engine-minimal-folder.vala (Folder): Add
      open_cancellable member, construct new instance when opening and
      cancell then null out when closing the folder.

 .../imap-engine/imap-engine-minimal-folder.vala    |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)
---
diff --git a/src/engine/imap-engine/imap-engine-minimal-folder.vala 
b/src/engine/imap-engine/imap-engine-minimal-folder.vala
index 5afd866..a7423f3 100644
--- a/src/engine/imap-engine/imap-engine-minimal-folder.vala
+++ b/src/engine/imap-engine/imap-engine-minimal-folder.vala
@@ -69,8 +69,9 @@ private class Geary.ImapEngine.MinimalFolder : Geary.Folder, Geary.FolderSupport
     private int remote_count = -1;
     private Nonblocking.Mutex open_mutex = new Nonblocking.Mutex();
     private Nonblocking.Mutex close_mutex = new Nonblocking.Mutex();
+    private Cancellable? open_cancellable = null;
+
 
-    
     /**
      * Called when the folder is closing (and not reestablishing a connection) and will be flushing
      * the replay queue.  Subscribers may add ReplayOperations to the list, which will be enqueued
@@ -579,6 +580,8 @@ private class Geary.ImapEngine.MinimalFolder : Geary.Folder, Geary.FolderSupport
         
         // reset to force waiting in wait_for_close_async()
         closed_semaphore.reset();
+
+        this.open_cancellable = new Cancellable();
         
         // Unless NO_DELAY is set, do NOT open the remote side here; wait for the ReplayQueue to
         // require a remote connection or wait_for_open_async() to be called ... this allows for
@@ -964,6 +967,10 @@ private class Geary.ImapEngine.MinimalFolder : Geary.Folder, Geary.FolderSupport
 
     // Returns the remote_folder, if it was set
     private Imap.Folder? clear_remote_folder() {
+        // Cancel any internal pending operations before unhooking
+        this.open_cancellable.cancel();
+        this.open_cancellable = null;
+
         if (remote_folder != null) {
             // disconnect signals before ripping out reference
             remote_folder.appended.disconnect(on_remote_appended);