Fix race between stopped thread retrieval and continued event

If the debug adapter sends continued right after stopped, before the
client retrieved the threads the continued change was lost.

Should fix #1365

Author: mfussenegger

lua/dap/session.lua

@@ -657,7 +657,8 @@ function Session:update_threads(cb)
       threads[thread.id] = thread
       local old_thread = self.threads[thread.id]
       if old_thread then
-        thread.stopped = old_thread.stopped
+        local stopped = old_thread.stopped == nil and false or old_thread.stopped
+        thread.stopped = stopped
         thread.frames = old_thread.frames
       end
     end
@@ -689,12 +690,22 @@ function Session:event_stopped(stopped)
     local co = coroutine.running()
 
     if self.dirty.threads or (stopped.threadId and self.threads[stopped.threadId] == nil) then
+      local thread = {
+        id = stopped.threadId,
+        name = "Unknown",
+        stopped = true
+      }
+      self.threads[thread.id] = thread
       self:update_threads(coresume(co))
       local err = coroutine.yield()
       if err then
         utils.notify('Error retrieving threads: ' .. utils.fmt_error(err), vim.log.levels.ERROR)
         return
       end
+      if thread.stopped == false then
+        log.debug("Thread resumed during stopped event handling", stopped, thread)
+        return
+      end
     end
 
     local should_jump = stopped.reason ~= 'pause' or stopped.allThreadsStopped

spec/integration_spec.lua

@@ -322,6 +322,32 @@ describe('dap with fake server', function()
     })
   end)
 
+  it("Doesn't jump on stopped if continue is received before threads response", function()
+    run_and_wait_until_initialized(config, server)
+    server.client.threads = function(self, request)
+      self:send_event("continued", {
+        threadId = 1,
+      })
+      self:send_response(request, {
+        threads = { { id = 1, name = 'thread1' }, }
+      })
+    end
+    local log = require('dap.log').create_logger('dap.log')
+    local debug = log.debug
+    local messages = {}
+    log.debug = function(...)
+      table.insert(messages, {...})
+      debug(...)
+    end
+    server.client:send_event('stopped', {
+      threadId = 1,
+      reason = 'unknown',
+    })
+    wait_for_response(server, "threads")
+    wait(function() return #messages >= 5 end)
+    assert.are.same("Thread resumed during stopped event handling", messages[6][1])
+  end)
+
   it("Clears stopped state on continued event", function()
     local buf = api.nvim_create_buf(true, false)
     local win = api.nvim_get_current_win()