fix(message): concatenate multi-chunk nvim_echo({err}) for exception message #38131

Problem:  Exception error message only prints the first chunk of a
          multi-chunk nvim_echo() message.
Solution: Concatenate consecutive message chunks in the exception
          message list.

1 files changed, 7 insertions, 0 deletions

diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index 6029da0fc4..6447cbd0e4 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -445,6 +445,13 @@ describe('API', function()
       api.nvim_exec2('hi VisualNC', { output = true })
       eq('VisualNC       xxx cleared', api.nvim_exec2('hi VisualNC', { output = true }).output)
     end)
+
+    it('captures multi-chunk err nvim_echo() #36883', function()
+      eq(
+        'nvim_exec2(), line 1: Vim(call):abc',
+        pcall_err(request, 'nvim_exec2', 'call nvim_echo([["a"],["b"],["c"] ], 0, #{err:1})', {})
+      )
+    end)
   end)
 
   describe('nvim_command', function()