Clear children from parent if child session closes

Otherwise the session remains in memory longer than necessary and the
sessions widget continues showing the child session until the parent
session ends.

Author: mfussenegger

lua/dap/session.lua

@@ -1018,9 +1018,16 @@ local function start_debugging(self, request)
       return
     end
 
+    ---@param session Session
     local function on_child_session(session)
       session.parent = self
       self.children[session.id] = session
+      session.on_close['dap.session.child'] = function(s)
+        if s.parent then
+          s.parent.children[s.id] = nil
+          s.parent = nil
+        end
+      end
       session:initialize(config)
       self:response(request, {success = true})
     end

tests/sessions_spec.lua

@@ -16,7 +16,7 @@ local function run_and_wait_until_initialized(conf, server)
     -- wait for initialize and launch requests
     return (session and session.initialized and #server.spy.requests == 2)
   end)
-  return dap.session()
+  return assert(dap.session(), "Must have session after dap.run")
 end
 
 
@@ -83,5 +83,9 @@ describe('sessions', function()
     )
     local _, child = next(dap.session().children)
     assert.are.same("Subprocess", child.config.name)
+
+    srv2.stop()
+    wait(function() return vim.tbl_count(dap.session().children) == 0 end)
+    assert.are.same({}, dap.session().children)
   end)
 end)