From 72c92f95e721917b17a07b508ef3aa1a6e7881e5 Mon Sep 17 00:00:00 2001
From: Mathias Fussenegger <f.mathias@zignar.net>
Date: Thu, 30 May 2024 11:08:41 +0200
Subject: [PATCH] Provide feedback if item in variable tree has no children to
 expand

---
 lua/dap/entity.lua   | 15 +++++++++------
 lua/dap/protocol.lua |  2 +-
 lua/dap/ui.lua       |  2 ++
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/lua/dap/entity.lua b/lua/dap/entity.lua
index 5799d8cc..fe55dce8 100644
--- a/lua/dap/entity.lua
+++ b/lua/dap/entity.lua
@@ -56,6 +56,8 @@ function variable.has_children(var)
   return (var.variables and #var.variables > 0) or var.variablesReference ~= 0
 end
 
+---@param var dap.Variable
+---@result dap.Variable[]
 function variable.get_children(var)
   if islist(var.variables) then
     return var.variables
@@ -78,11 +80,12 @@ local function cmp_vars(a, b)
 end
 
 
+---@param var dap.Variable
 function variable.fetch_children(var, cb)
   local session = require('dap').session()
   if var.variables then
     cb(variable.get_children(var))
-  elseif session and var.variablesReference then
+  elseif session and var.variablesReference > 0 then
 
     ---@param err? dap.ErrorResponse
     ---@param resp? dap.VariableResponse
@@ -93,11 +96,11 @@ function variable.fetch_children(var, cb)
         local variables = resp.variables
         local unloaded = #variables
         local function countdown()
-            unloaded = unloaded - 1
-            if unloaded == 0 then
-              var.variables = variables
-              cb(variables)
-            end
+          unloaded = unloaded - 1
+          if unloaded == 0 then
+            var.variables = variables
+            cb(variables)
+          end
         end
 
         table.sort(variables, cmp_vars)
diff --git a/lua/dap/protocol.lua b/lua/dap/protocol.lua
index b778ebe5..88b792f8 100644
--- a/lua/dap/protocol.lua
+++ b/lua/dap/protocol.lua
@@ -98,7 +98,7 @@
 ---@field type? string
 ---@field presentationHint? dap.VariablePresentationHint
 ---@field evaluateName? string
----@field variablesReference number
+---@field variablesReference number if > 0 the variable is structured
 ---@field namedVariables? number
 ---@field indexedVariables? number
 ---@field memoryReference? string
diff --git a/lua/dap/ui.lua b/lua/dap/ui.lua
index b9a700e8..8c074c3d 100644
--- a/lua/dap/ui.lua
+++ b/lua/dap/ui.lua
@@ -257,6 +257,8 @@ function M.new_tree(opts)
         collapse(layer, value, lnum, context)
       elseif opts.has_children(value) then
         expand(layer, value, lnum, context)
+      else
+        utils.notify("No children on line " .. tostring(lnum) .. ". Can't expand", vim.log.levels.INFO)
       end
     end,