fix(api): crash on invalid buffer to nvim_buf_del_user_command (#31908)

2 files changed, 12 insertions, 0 deletions

diff --git a/src/nvim/api/command.c b/src/nvim/api/command.c
index 7e79133ed4..23e08bd3fe 100644
--- a/src/nvim/api/command.c
+++ b/src/nvim/api/command.c
@@ -931,6 +931,9 @@ void nvim_buf_del_user_command(Buffer buffer, String name, Error *err)
     gap = &ucmds;
   } else {
     buf_T *buf = find_buffer_by_handle(buffer, err);
+    if (ERROR_SET(err)) {
+      return;
+    }
     gap = &buf->b_ucmds;
   }
 
diff --git a/test/functional/api/command_spec.lua b/test/functional/api/command_spec.lua
index a16c6a88e3..fabd9be6d6 100644
--- a/test/functional/api/command_spec.lua
+++ b/test/functional/api/command_spec.lua
@@ -651,6 +651,11 @@ describe('nvim_create_user_command', function()
     api.nvim_set_current_buf(bufnr)
     command('Hello')
     assert_alive()
+    eq(
+      'Invalid buffer id: 1234',
+      pcall_err(api.nvim_buf_create_user_command, 1234, 'Hello', '', {})
+    )
+    assert_alive()
   end)
 
   it('can use a Lua complete function', function()
@@ -771,5 +776,9 @@ describe('nvim_del_user_command', function()
     command('Hello')
     api.nvim_buf_del_user_command(0, 'Hello')
     matches('Not an editor command: Hello', pcall_err(command, 'Hello'))
+    eq('Invalid command (not found): Hello', pcall_err(api.nvim_buf_del_user_command, 0, 'Hello'))
+    eq('Invalid command (not found): Bye', pcall_err(api.nvim_buf_del_user_command, 0, 'Bye'))
+    eq('Invalid buffer id: 1234', pcall_err(api.nvim_buf_del_user_command, 1234, 'Hello'))
+    assert_alive()
   end)
 end)