Bug: `E976: Using a Blob as a String` when rendering Markdown

[pjgoodall]

🐞 Bug: E976: Using a Blob as a String when rendering Markdown

render-markdown.nvim throws a Lua error every time a Markdown buffer is opened.
The stack trace points to lib/str.lua:23 where vim.fn.strdisplaywidth() is
called with a blob rather than a string.

Some help from ChatGPT o3 in producing this report. The bug is very persistent. Reinstalled markdown support, about 1 hour checking.

---

Minimal reproducible config

init.lua (drop-in)

-- minimal repro (tested in an empty directory)
vim.opt.runtimepath:prepend(vim.fn.stdpath("data") .. "/render-repro")  -- isolate
vim.cmd("packadd lazy.

![Image](https://github.com/user-attachments/assets/d54e36df-2d2d-47f0-8e56-aed3956e2b4f)

nvim")                                            -- any plugin manager works
require("lazy").setup({
  { "nvim-treesitter/nvim-treesitter", build = ":TSUpdate" },
  { "MeanderingProgrammer/render-markdown.nvim" },  -- ❗ latest HEAD
})

[MeanderingProgrammer]

Can you give me the full stack trace and the file you had open when you ran into this error.

As far as I can tell no code paths should result in vim.fn.strdisplaywidth() being called with anything but a string. I know there are sometimes edge cases where APIs can return blobs so I need to find what is actually causing this.

The minimal reproducible config is unfortunately completely invalid. There's a random image link copied in the middle and I have no idea what's in your render-repro directory. If it's an empty directory than I'm unable to reproduce this issue with what has been provided.

If you want to give this another shot please create a new issue using the bug report template and here's a starting point for a minimal reproducible config:

local lazypath = vim.fn.stdpath('data') .. '/lazy/lazy.nvim'
assert(vim.uv.fs_stat(lazypath))
vim.opt.rtp:prepend(lazypath)

require('lazy').setup({
    {
        'nvim-treesitter/nvim-treesitter',
        branch = 'main',
        build = ':TSUpdate',
        config = function()
            require('nvim-treesitter').install({ 'markdown', 'markdown_inline' })

            vim.api.nvim_create_autocmd('FileType', {
                group = vim.api.nvim_create_augroup('Highlighter', {}),
                pattern = 'markdown',
                callback = function(args)
                    vim.treesitter.start(args.buf)
                end,
            })
        end,
    },
    {
        'echasnovski/mini.nvim',
        config = function()
            require('mini.icons').setup({})
        end,
    },
    {
        'MeanderingProgrammer/render-markdown.nvim',
        dependencies = {
            'nvim-treesitter/nvim-treesitter',
            'echasnovski/mini.nvim',
        },
        config = function()
            require('render-markdown').setup({})
        end,
    },
})

[softinio]

I just got the same error after updating my Neovim plugins:

Error executing vim.schedule lua callback: Vim:E976: Using a Blob as a String
stack traceback:
        [C]: in function 'strdisplaywidth'
        ...azy/render-markdown.nvim/lua/render-markdown/lib/str.lua:23: in function 'f'
        ...zy/render-markdown.nvim/lua/render-markdown/lib/iter.lua:14: in function 'widths'
        ...rkdown.nvim/lua/render-markdown/render/markdown/code.lua:33: in function 'setup'
        ...render-markdown.nvim/lua/render-markdown/render/base.lua:20: in function 'execute'
        ...r-markdown.nvim/lua/render-markdown/handler/markdown.lua:67: in function 'callback'
        ...ender-markdown.nvim/lua/render-markdown/request/view.lua:74: in function 'callback'
        ...ender-markdown.nvim/lua/render-markdown/request/view.lua:85: in function 'query'
        ...ender-markdown.nvim/lua/render-markdown/request/view.lua:70: in function 'nodes'
        ...r-markdown.nvim/lua/render-markdown/handler/markdown.lua:64: in function 'parse'
        ...nder-markdown.nvim/lua/render-markdown/core/handlers.lua:72: in function 'tree'
        ...nder-markdown.nvim/lua/render-markdown/core/handlers.lua:43: in function 'run'
        ...azy/render-markdown.nvim/lua/render-markdown/core/ui.lua:170: in function 'parse'
        ...azy/render-markdown.nvim/lua/render-markdown/core/ui.lua:143: in function 'render'
        ...azy/render-markdown.nvim/lua/render-markdown/core/ui.lua:126: in function 'run'
        ...azy/render-markdown.nvim/lua/render-markdown/core/ui.lua:92: in function <...azy/render-markdown.nvim/lua/render-markdown/core/ui.lua:91>

My config if helpful: https://github.com/softinio/nvim-config/blob/main/lua/plugins/render-markdown.lua

@MeanderingProgrammer @pjgoodall was a solution found for this? Thanks for your time and help.

[MeanderingProgrammer]

I appreciate the stack trace, it does point me to a chunk of code that gets the lines from a buffer and computes their widths using vim.fn.strdisplaywidth. What I really need is a way to replicate this behavior so I know how to handle it, if I can at all. I'm not sure how a buffer gets Blobs instead of Strings. Do you have a file that can trigger this issue consistently?

[MeanderingProgrammer]

I'm fairly certain the cause of this is going to be avante buffers somehow containing blobs. Blobs are binary garbage objects, things that can't really be interpreted as text, so the solution would be to have avante not write out binary garbage to buffers, probably by doing a type check on whatever LLM's output is causing this. If you can give me some file that can reproduce this then I can take a closer look on me end.

[MeanderingProgrammer]

I was able to reproduce the error, it's definitely caused by something writing invalid text to a buffer, which should be handled by whatever plugin is doing that.

But this plugin should avoid throwing errors and just ignore that text, which it does after: 3115ff7.

[pjgoodall]

Thanks all