Automatic f-string transformation for Neovim

fstring.lua

-- Treesitter automatic Python format strings
vim.api.nvim_create_augroup("py-fstring", { clear = true })
vim.api.nvim_create_autocmd("InsertCharPre", {
    pattern = { "*.py" },
    group = "py-fstring",
    --- @param opts AutoCmdCallbackOpts
    --- @return nil
    callback = function(opts)
        -- Only run if f-string escape character is typed
        if vim.v.char ~= "{" then return end

        -- Get node and return early if not in a string
        local node = vim.treesitter.get_node()

        if not node then return end
        if node:type() ~= "string" then node = node:parent() end
        if not node or node:type() ~= "string" then return end

        vim.print(node:type())
        local row, col, _, _ = vim.treesitter.get_node_range(node)

        -- Return early if string is already a format string
        local first_char = vim.api.nvim_buf_get_text(opts.buf, row, col, row, col + 1, {})[1]
        vim.print("row " .. row .. " col " .. col)
        vim.print("char: '" .. first_char .. "'")
        if first_char == "f" then return end

        -- Otherwise, make the string a format string
        vim.api.nvim_input("<Esc>m'" .. row + 1 .. "gg" .. col + 1 .. "|if<Esc>`'la")
    end,
})