Incremental LSP rename command based on Neovim's command-preview feature

inc_rename.lua

-- Usage: type :IncrementalRename <new_name> while your cursor is placed above an identifier (LSP must be enabled)
-- Update: this gist will no longer be updated since this command has been turned into a plugin! 
-- You can find the plugin here: https://github.com/smjonas/inc-rename.nvim

local state = {
    added_lines = false,
    orig_lines = {},
    lsp_positions = {},
}

local function incremental_rename(opts, preview_ns, preview_buf)
    -- Store the lines of the buffer at the first invocation
    if not state.added_lines then
        -- Get positions of LSP reference symbols
        local params = vim.lsp.util.make_position_params()
        vim.lsp.buf_request(0, "textDocument/references", params, function(err, result, _, _)
            if err then
                vim.notify("Error while finding references: " .. err.message, vim.lsp.log_levels.ERROR)
                return
            end
            if not result or vim.tbl_isempty(result) then
                vim.notify("No results from textDocument/references", vim.lsp.log_levels.WARN)
                return
            end
            state.lsp_positions = vim.tbl_map(function(x)
                return x.range
            end, result)

            local buf = vim.api.nvim_get_current_buf()
            state.orig_lines = {}
            for _, position in ipairs(state.lsp_positions) do
                local line_nr = position.start.line
                local line = vim.api.nvim_buf_get_lines(buf, line_nr, line_nr + 1, 0)[1]
                local start_col, end_col = position.start.character, position["end"].character
                local line_item = { text = line, start_col = start_col, end_col = end_col }
                -- Same line was already seen, this case needs to be handled separately
                if state.orig_lines[line_nr] then
                    table.insert(state.orig_lines[line_nr], line_item)
                else
                    state.orig_lines[line_nr] = { line_item }
                end
            end
            state.added_lines = true
        end)
        return
    end

    for line_nr, line_items in pairs(state.orig_lines) do
        local offset = 0
        local updated_line = line_items[1].text
        local highlight_positions = {}
        for _, item in ipairs(line_items) do
            updated_line = updated_line:sub(1, item.start_col + offset)
                .. opts.args
                .. updated_line:sub(item.end_col + 1 + offset)
            table.insert(highlight_positions, {
                start_col = item.start_col + offset,
                end_col = item.start_col + #opts.args + offset,
            })
            -- Offset by the length difference between the old and new names
            offset = offset + #opts.args - (item.end_col - item.start_col)
        end
        if preview_ns then
            vim.api.nvim_buf_set_lines(0, line_nr, line_nr + 1, false, { updated_line })
            if preview_buf then
                vim.api.nvim_buf_set_lines(preview_buf, line_nr, line_nr + 1, false, { updated_line })
            end
            for _, hl_pos in ipairs(highlight_positions) do
                vim.api.nvim_buf_add_highlight(
                    0,
                    preview_ns,
                    "Substitute",
                    line_nr,
                    hl_pos.start_col,
                    hl_pos.end_col
                )
                if preview_buf then
                    vim.api.nvim_buf_add_highlight(
                        preview_buf,
                        preview_ns,
                        "Substitute",
                        line_nr,
                        hl_pos.start_col,
                        hl_pos.end_col
                    )
                end
            end
        end
    end
    if not preview_ns then
        -- Now execute the actual LSP rename command
        vim.lsp.buf.rename(opts.args)
        state.added_lines = false
    end

    if preview_ns then
        return 2
    end
end

-- Create the user command
vim.api.nvim_create_user_command(
    "IncrementalRename",
    incremental_rename,
    { nargs = 1, range = "%", addr = "lines", preview = incremental_rename }
)