feat: add and handle diff_opts.on_unsaved_changes option

Author: derethil

README.md

@@ -273,6 +273,7 @@ For deep technical details, see [ARCHITECTURE.md](./ARCHITECTURE.md).
       vertical_split = true,
       open_in_current_tab = true,
       keep_terminal_focus = false, -- If true, moves focus back to terminal after diff opens
+      on_unsaved_changes = "error"
     },
   },
   keys = {

lua/claudecode/config.lua

@@ -24,6 +24,7 @@ M.defaults = {
     vertical_split = true,
     open_in_current_tab = true, -- Use current tab instead of creating new tab
     keep_terminal_focus = false, -- If true, moves focus back to terminal after diff opens
+    on_unsaved_changes = "error", -- "error", "discard" - How to handle unsaved changes when creating diffs
   },
   models = {
     { name = "Claude Opus 4.1 (Latest)", value = "opus" },
@@ -110,6 +111,16 @@ function M.validate(config)
   assert(type(config.diff_opts.open_in_current_tab) == "boolean", "diff_opts.open_in_current_tab must be a boolean")
   assert(type(config.diff_opts.keep_terminal_focus) == "boolean", "diff_opts.keep_terminal_focus must be a boolean")
 
+  local valid_behaviors = { "error", "discard" }
+  local is_valid_behavior = false
+  for _, behavior in ipairs(valid_behaviors) do
+    if config.diff_opts.on_unsaved_changes == behavior then
+      is_valid_behavior = true
+      break
+    end
+  end
+  assert(is_valid_behavior, "diff_opts.on_unsaved_changes must be one of: " .. table.concat(valid_behaviors, ", "))
+
   -- Validate env
   assert(type(config.env) == "table", "env must be a table")
   for key, value in pairs(config.env) do

lua/claudecode/diff.lua

@@ -112,6 +112,29 @@ local function is_buffer_dirty(file_path)
   return is_dirty, nil
 end
 
+---Discard unsaved changes in a buffer by reloading from disk.
+---@param file_path string The file path whose buffer changes should be discarded
+---@return boolean success True if changes were discarded successfully
+---@return string? error Error message if discard failed
+local function discard_buffer_changes(file_path)
+  local bufnr = vim.fn.bufnr(file_path)
+  if bufnr == -1 then
+    return false, "Buffer for " .. file_path .. " is not available"
+  end
+
+  local discard_success, discard_error = pcall(function()
+    vim.api.nvim_buf_call(bufnr, function()
+      vim.cmd("edit!") -- Force reload from disk, discarding changes
+    end)
+  end)
+
+  if not discard_success then
+    return false, "Discard error: " .. tostring(discard_error)
+  end
+
+  return true, nil
+end
+
 ---Setup the diff module
 ---@param user_config ClaudeCodeConfig? The configuration passed from init.lua
 function M.setup(user_config)
@@ -712,15 +735,29 @@ function M._setup_blocking_diff(params, resolution_callback)
     local old_file_exists = vim.fn.filereadable(params.old_file_path) == 1
     local is_new_file = not old_file_exists
 
-    -- Step 1.5: Check if the file buffer has unsaved changes
+    -- Step 1.5: Handle unsaved changes based on configuration
     if old_file_exists then
       local is_dirty = is_buffer_dirty(params.old_file_path)
       if is_dirty then
-        error({
-          code = -32000,
-          message = "Cannot create diff: file has unsaved changes",
-          data = "Please save (:w) or discard (:e!) changes to " .. params.old_file_path .. " before creating diff",
-        })
+        local behavior = config and config.diff_opts and config.diff_opts.on_unsaved_changes or "error"
+
+        if behavior == "error" then
+          error({
+            code = -32000,
+            message = "Cannot create diff: file has unsaved changes",
+            data = "Please save (:w) or discard (:e!) changes to " .. params.old_file_path .. " before creating diff",
+          })
+        elseif behavior == "discard" then
+          -- Discard unsaved changes using the extracted function
+          local discard_success, discard_err = discard_buffer_changes(params.old_file_path)
+          if not discard_success then
+            error({
+              code = -32000,
+              message = "Failed to discard unsaved changes before creating diff",
+              data = discard_err,
+            })
+          end
+        end
       end
     end