change imap idle done handling

Author: dutow

app/services/imap/gmail_client.rb

@@ -122,13 +122,17 @@ def idle_once(timeout: 1500)
       begin
         if @imap.respond_to?(:idle)
           # Break IDLE promptly on first response so the caller can FETCH.
+          # Response handlers run outside the monitor in the receiver thread,
+          # and idle's wait releases the monitor, so idle_done can be called
+          # directly without deadlock. Avoids a detached Thread that can
+          # outlive the connection and hit a torn-down monitor.
           idle_done_called = false
           @imap.idle(timeout) do |resp|
             got_activity = true
             yield resp if block_given?
             unless idle_done_called
               idle_done_called = true
-              Thread.new { @imap.idle_done }
+              @imap.idle_done
             end
           end
         else

app/services/imap_idle_runner.rb

@@ -28,7 +28,7 @@ def run(max_cycles: nil, idle_timeout: DEFAULT_IDLE_TIMEOUT)
       begin
         main_loop(max_cycles: max_cycles, idle_timeout: idle_timeout)
       rescue => e
-        @logger.error("IMAP runner fatal error: #{e.class}: #{e.message}")
+        @logger.error("IMAP runner fatal error: #{e.class}: #{e.message}\n#{e.backtrace&.first(10)&.join("\n")}")
         update_state(last_error: short_error(e))
         raise
       end

spec/services/imap/gmail_client_spec.rb

@@ -49,10 +49,6 @@
     # Simulate Net::IMAP#idle with yielding one response
     allow(imap_double).to receive(:respond_to?).with(:idle).and_return(true)
     allow(imap_double).to receive(:idle_done)
-    allow(Thread).to receive(:new).and_wrap_original do |m, *args, &blk|
-      blk.call
-      double('Thread', join: true)
-    end
     yielded = []
     expect(imap_double).to receive(:idle) do |timeout, &blk|
       blk.call(double('Resp', name: 'EXISTS', data: 1))