From 2306f0d35457c3b3715a86eb848e19c7c2fdd4b3 Mon Sep 17 00:00:00 2001
From: Julien Vincent <m@julienvincent.io>
Date: Sun, 10 Sep 2023 16:15:44 +0100
Subject: [PATCH] Add README section on auto-indentation

---
 README.md                     | 80 +++++++++++++++++++++++++++++++++++
 lua/nvim-paredit/defaults.lua |  2 +-
 2 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index dc1bf8a..c1c8493 100644
--- a/README.md
+++ b/README.md
@@ -51,7 +51,27 @@ require("nvim-paredit").setup({
   -- defaults to all supported file types including custom lang
   -- extensions (see next section)
   filetypes = { "clojure" },
+
+  -- This controls where the cursor is placed when performing slurp/barf operations
+  --
+  -- - "remain" - It will never change the cursor position, keeping it in the same place
+  -- - "follow" - It will always place the cursor on the form edge that was moved
+  -- - "auto"   - A combination of remain and follow, it will try keep the cursor in the original position
+  --              unless doing so would result in the cursor no longer being within the original form. In
+  --              this case it will place the cursor on the moved edge
   cursor_behaviour = "auto", -- remain, follow, auto
+
+  indent = {
+    -- This controls how nvim-paredit handles indentation when performing operations which
+    -- should change the indentation of the form (such as when slurping or barfing).
+    --
+    -- When set to true then it will attempt to fix the indentation of nodes operated on.
+    enabled = false,
+    -- A function that will be called after a slurp/barf if you want to provide a custom indentation
+    -- implementation.
+    indentor = require("nvim-paredit.indentation.native").indentor,
+  },
+
   -- list of default keybindings
   keys = {
     [">)"] = { paredit.api.slurp_forwards, "Slurp forwards" },
@@ -112,6 +132,65 @@ require("nvim-paredit").setup({
 })
 ```
 
+## Auto Indentation
+
+Nvim-paredit comes with built-in support for fixing form indentation when performing slurp and barf operations. By default this behaviour is disabled and can be enabled by setting `indent.enabled = true` in the [configuration](#configuration)
+
+The main goal of this implementation is to provide a visual aid to the user, allowing them to confirm they are operating on the correct node and to know when to stop when performing recursive slurp/barf operations. This implementation is fast and does not result in any UI lag or jitter.
+
+The goal is _not_ to be 100% correct. The implementation follows a simple set of rules which account for most scenarios but not all. If a more correct implementation is needed then the native implementation can be replaced by setting the configuration property `intent.indentor`. For example an implementation using `vim.lsp.buf.format` could be built if the user doesn't mind sacrificing performance for correctness.
+
+### Recipes
+
+<details>
+  <summary><code>vim.lsp.buf.format</code></summary>
+
+  Below is a reference implementation for using `vim.lsp.buf.format` to replace the native implementation. This implementation won't be nearly as performant but it will be more correct.
+
+  ```lua
+  local function lsp_indent(event, opts)
+    local traversal = require("nvim-paredit.utils.traversal")
+    local utils = require("nvim-paredit.indentation.utils")
+    local langs = require("nvim-paredit.lang")
+
+    local lang = langs.get_language_api()
+
+    local parent = event.parent
+
+    local child
+    if event.type == "slurp-forwards" then
+      child = parent:named_child(parent:named_child_count() - 1)
+    elseif event.type == "slurp-backwards" then
+      child = parent:named_child(1)
+    elseif event.type == "barf-forwards" then
+      child = traversal.get_next_sibling_ignoring_comments(event.parent, { lang = lang })
+    elseif event.type == "barf-backwards" then
+      child = event.parent
+    else
+      return
+    end
+
+    local child_range = { child:range() }
+    local lines = utils.find_affected_lines(child, utils.get_node_line_range(child_range))
+
+    vim.lsp.buf.format({
+      bufnr = opts.buf or 0,
+      range = {
+        ["start"] = { lines[1] + 1, 0 },
+        ["end"] = { lines[#lines] + 1, 0 },
+      },
+    })
+  end
+
+  require("nvim-paredit").setup({
+    indent = {
+      enabled = true,
+      indentor = lsp_indent
+    }
+  })
+  ```
+</details>
+
 ## Language Support
 
 As this is built using Treesitter it requires that you have the relevant Treesitter grammar installed for your language of choice. Additionally `nvim-paredit` will need explicit support for the treesitter grammar as the node names and metadata of nodes vary between languages.
@@ -270,6 +349,7 @@ The main reasons you might want to consider `nvim-paredit` instead are:
 - Easier configuration and an exposed lua API
 - Control over how the cursor is moved during slurp/barf. (For example if you don't want the cursor to always be moved)
 - Recursive slurp/barf operations. If your cursor is in a nested form you can still slurp from the forms parent(s)
+- Automatic form/element indentations on slurp/barf
 - Subjectively better out-of-the-box keybindings
 
 ### [vim-sexp-mappings-for-regular-people](https://github.com/tpope/vim-sexp-mappings-for-regular-people)
diff --git a/lua/nvim-paredit/defaults.lua b/lua/nvim-paredit/defaults.lua
index 9796505..1a5e4ae 100644
--- a/lua/nvim-paredit/defaults.lua
+++ b/lua/nvim-paredit/defaults.lua
@@ -62,7 +62,7 @@ M.defaults = {
   use_default_keys = true,
   cursor_behaviour = "auto", -- remain, follow, auto
   indent = {
-    enabled = true,
+    enabled = false,
     indentor = require("nvim-paredit.indentation.native").indentor,
   },
   keys = {},