[geary] Don't remove folders when listing throws errors

[Charles Lindsay <clindsay src gnome org>]

commit 09dc342ed776dd5c0ed85c0828e68c1cf64df035
Author: Charles Lindsay <chaz yorba org>
Date:   Tue Mar 11 12:12:37 2014 -0700

    Don't remove folders when listing throws errors
    
    We're seeing a bug where under certain conditions like a flaky internet
    connection, Geary will decide you don't have any remote folders and
    simply remove them all locally.  What's probably happening is we're
    getting an error and ignoring it.  Since we don't know what the true
    error is, this patch simply adds some logging for that case and sets a
    flag so we don't run the delete folders logic if there was an error.
    Once we get a handle on what's really going on, we can implement a more
    surgical fix.
    
    Closes: bgo #726049

 .../imap-engine/imap-engine-generic-account.vala   |   48 ++++++++++++-------
 1 files changed, 30 insertions(+), 18 deletions(-)
---
diff --git a/src/engine/imap-engine/imap-engine-generic-account.vala 
b/src/engine/imap-engine/imap-engine-generic-account.vala
index ad7d475..baec78f 100644
--- a/src/engine/imap-engine/imap-engine-generic-account.vala
+++ b/src/engine/imap-engine/imap-engine-generic-account.vala
@@ -394,11 +394,12 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.AbstractAccount {
         
         // now that all local have been enumerated and reported (this is important to assist
         // startup of the UI), enumerate the remote folders
+        bool remote_folders_suspect;
         Gee.HashMap<FolderPath, Imap.Folder>? remote_folders = yield enumerate_remote_folders_async(
-            null, cancellable);
+            null, out remote_folders_suspect, cancellable);
         
         // pair the local and remote folders and make sure everything is up-to-date
-        yield update_folders_async(existing_folders, remote_folders, cancellable);
+        yield update_folders_async(existing_folders, remote_folders, remote_folders_suspect, cancellable);
     }
     
     private async Gee.HashMap<FolderPath, ImapDB.Folder> enumerate_local_folders_async(
@@ -427,7 +428,8 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.AbstractAccount {
     }
     
     private async Gee.HashMap<FolderPath, Imap.Folder> enumerate_remote_folders_async(
-        Geary.FolderPath? parent, Cancellable? cancellable) throws Error {
+        Geary.FolderPath? parent, out bool results_suspect, Cancellable? cancellable) throws Error {
+        results_suspect = false;
         check_open();
         
         Gee.List<Imap.Folder>? remote_children = null;
@@ -437,6 +439,9 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.AbstractAccount {
             // ignore everything but I/O and IMAP errors (cancellation is an IOError)
             if (err is IOError || err is ImapError)
                 throw err;
+            debug("Ignoring error listing child folders of %s: %s",
+                (parent != null ? parent.to_string() : "root"), err.message);
+            results_suspect = true;
         }
         
         Gee.HashMap<FolderPath, Imap.Folder> result = new Gee.HashMap<FolderPath, Imap.Folder>();
@@ -444,8 +449,12 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.AbstractAccount {
             foreach (Imap.Folder remote_child in remote_children) {
                 result.set(remote_child.path, remote_child);
                 if (remote_child.properties.has_children.is_possible()) {
+                    bool recursive_results_suspect;
                     Collection.map_set_all<FolderPath, Imap.Folder>(result,
-                        yield enumerate_remote_folders_async(remote_child.path, cancellable));
+                        yield enumerate_remote_folders_async(
+                        remote_child.path, out recursive_results_suspect, cancellable));
+                    if (recursive_results_suspect)
+                        results_suspect = true;
                 }
             }
         }
@@ -633,7 +642,7 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.AbstractAccount {
     }
     
     private async void update_folders_async(Gee.Map<FolderPath, Geary.Folder> existing_folders,
-        Gee.Map<FolderPath, Imap.Folder> remote_folders, Cancellable? cancellable) {
+        Gee.Map<FolderPath, Imap.Folder> remote_folders, bool remote_folders_suspect, Cancellable? 
cancellable) {
         // update all remote folders properties in the local store and active in the system
         Gee.HashSet<Geary.FolderPath> altered_paths = new Gee.HashSet<Geary.FolderPath>();
         foreach (Imap.Folder remote_folder in remote_folders.values) {
@@ -706,20 +715,23 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.AbstractAccount {
         Gee.Collection<MinimalFolder> engine_added = new Gee.ArrayList<Geary.Folder>();
         engine_added.add_all(build_folders(folders_to_build));
         
-        notify_folders_available_unavailable(null, to_remove);
-        
         Gee.ArrayList<Geary.Folder> engine_removed = new Gee.ArrayList<Geary.Folder>();
-        
-        // Sort by path length descending, so we always remove children first.
-        to_remove.sort((a, b) => b.path.get_path_length() - a.path.get_path_length());
-        foreach (Geary.Folder folder in to_remove) {
-            try {
-                debug("Locally deleting removed folder %s", folder.to_string());
-                
-                yield local.delete_folder_async(folder, cancellable);
-                engine_removed.add(folder);
-            } catch (Error e) {
-                debug("Unable to locally delete removed folder %s: %s", folder.to_string(), e.message);
+        if (remote_folders_suspect) {
+            debug("Skipping removing folders due to prior errors");
+        } else {
+            notify_folders_available_unavailable(null, to_remove);
+            
+            // Sort by path length descending, so we always remove children first.
+            to_remove.sort((a, b) => b.path.get_path_length() - a.path.get_path_length());
+            foreach (Geary.Folder folder in to_remove) {
+                try {
+                    debug("Locally deleting removed folder %s", folder.to_string());
+                    
+                    yield local.delete_folder_async(folder, cancellable);
+                    engine_removed.add(folder);
+                } catch (Error e) {
+                    debug("Unable to locally delete removed folder %s: %s", folder.to_string(), e.message);
+                }
             }
         }