Indentation doesn't get applied on yS

Checklist

[X] Have you tried updating the plugin to the latest version?
[X] Have you checked the Breaking Changes issue?
[X] Have you read through :h nvim-surround to see if there might be any relevant information there?

Neovim Version

NVIM v0.8.

Plugin Version

Tagged (Stable)

Minimal Configuration

My config is in nix and I don't want to rewrite it. Please let me know if you need it. The relevant points in my config are:

lspconfig with sumneko_lua
tree-sitter

this config for plugin:

require('nvim-surround').setup({
          indent_lines = function(start, stop)
            local b = vim.bo
            -- Only re-indent the selection if a formatter is set up already
            if start <= stop and (b.equalprg ~= "" or b.indentexpr ~= "" or b.cindent or b.smartindent or b.lisp) then
                vim.cmd(string.format("silent normal! %dG=%dG", start, stop))
                vim.cmd("echo 'did it'")
            end
            vim.cmd("echo 'did it again'")
          end,
        })

Indentation is set by filetype.lua

Sample Buffer

any file with a recognized filetype

Keystroke Sequence

ySS -- [on any line] ySa({ -- [on any (...) block] etc ...

Expected behavior

'='-indentation should apply

Actual behavior

no indentation is applied at all

Additional context

I added the upper config for some debugging and noticed that my debug messages do not print. The if statement however should be entered because vim.ob.indentexpr is definitely set. I can confirm that ds for example works as intended. My conclusion is that the function specified in indent_line probably doesn't run.

If this has already been fixed in a newer version I shall make a pull request to upgrade the nixpkg.

kylechui / nvim-surround