Add auto indentation correction on slurp/barf

This adds support for automatic indentation correction when slurping and
barfing.

The goal of this implementation is to:

1) Provide a visual aid to the user that allows them to confirm they are
   operating on the correct node, and to know when to stop when
   performing recursive slurp/barf operations.
2) Be simple to maintain and understand while being as correct as
   possible
3) Be replaceable with other implementations.
4) Be as performant as possible. There should be no lag or visual jitter

The goal is _not_ to be 100% correct. If a more correct implementation
is needed then one can be provided through `indent_fn`. For example, an
implementation using `vim.lsp.buf.format` could be built if the user
doesn't mind sacrificing performance for correctness.

README.md

@@ -51,7 +51,25 @@ 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
+
+  -- 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.
+  auto_indent = true,
+  -- A function that will be called after a slurp/barf if you want to provide a custom indentation
+  -- implementation.
+  indent_fn = nil,
+
   -- list of default keybindings
   keys = {
     [">)"] = { paredit.api.slurp_forwards, "Slurp forwards" },

lua/nvim-paredit/api/barfing.lua

@@ -1,4 +1,5 @@
 local traversal = require("nvim-paredit.utils.traversal")
+local indentation = require("nvim-paredit.indentation")
 local common = require("nvim-paredit.utils.common")
 local ts = require("nvim-treesitter.ts_utils")
 local config = require("nvim-paredit.config")
@@ -28,11 +29,11 @@ function M.barf_forwards(opts)
   local child
   if opts.reversed then
     child = traversal.get_first_child_ignoring_comments(form, {
-      lang = lang
+      lang = lang,
     })
   else
     child = traversal.get_last_child_ignoring_comments(form, {
-      lang = lang
+      lang = lang,
     })
   end
   if not child then
@@ -42,7 +43,7 @@ function M.barf_forwards(opts)
   local edges = lang.get_form_edges(form)
 
   local sibling = traversal.get_prev_sibling_ignoring_comments(child, {
-    lang = lang
+    lang = lang,
   })
 
   local end_pos
@@ -55,6 +56,7 @@ function M.barf_forwards(opts)
   local buf = vim.api.nvim_get_current_buf()
 
   local range = edges.right.range
+  -- stylua: ignore
   vim.api.nvim_buf_set_text(
     buf,
     range[1], range[2],
@@ -63,6 +65,7 @@ function M.barf_forwards(opts)
   )
 
   local text = edges.right.text
+  -- stylua: ignore
   vim.api.nvim_buf_set_text(buf,
     end_pos[1], end_pos[2],
     end_pos[1], end_pos[2],
@@ -77,6 +80,19 @@ function M.barf_forwards(opts)
       vim.api.nvim_win_set_cursor(0, { end_pos[1] + 1, end_pos[2] })
     end
   end
+
+  local event = {
+    type = "barf-forwards",
+    -- stylua: ignore
+    parent_range = {
+      edges.left.range[1], edges.left.range[2],
+      end_pos[1], end_pos[2],
+    },
+    reversed = false,
+    indent_behaviour = opts.indent_behaviour or config.config.indent_behaviour,
+    lang = lang,
+  }
+  indentation.handle_indentation(event, opts)
 end
 
 function M.barf_backwards(opts)
@@ -99,7 +115,7 @@ function M.barf_backwards(opts)
   end
 
   local child = traversal.get_first_child_ignoring_comments(form, {
-    lang = lang
+    lang = lang,
   })
   if not child then
     return
@@ -108,7 +124,7 @@ function M.barf_backwards(opts)
   local edges = lang.get_form_edges(lang.get_node_root(form))
 
   local sibling = traversal.get_next_sibling_ignoring_comments(child, {
-    lang = lang
+    lang = lang,
   })
 
   local end_pos
@@ -121,13 +137,15 @@ function M.barf_backwards(opts)
   local buf = vim.api.nvim_get_current_buf()
 
   local text = edges.left.text
+  -- stylua: ignore
   vim.api.nvim_buf_set_text(buf,
     end_pos[1], end_pos[2],
     end_pos[1], end_pos[2],
     { text }
   )
 
   local range = edges.left.range
+  -- stylua: ignore
   vim.api.nvim_buf_set_text(
     buf,
     range[1], range[2],
@@ -143,6 +161,16 @@ function M.barf_backwards(opts)
       vim.api.nvim_win_set_cursor(0, { end_pos[1] + 1, end_pos[2] })
     end
   end
+
+  local event = {
+    type = "barf-backwards",
+    -- stylua: ignore
+    parent_range = {
+      end_pos[1], end_pos[2],
+      edges.right.range[1], edges.right.range[2],
+    },
+  }
+  indentation.handle_indentation(event, opts)
 end
 
 return M

lua/nvim-paredit/api/slurping.lua

@@ -1,4 +1,5 @@
 local traversal = require("nvim-paredit.utils.traversal")
+local indentation = require("nvim-paredit.indentation")
 local common = require("nvim-paredit.utils.common")
 local ts = require("nvim-treesitter.ts_utils")
 local config = require("nvim-paredit.config")
@@ -40,11 +41,12 @@ local function slurp(opts)
   end
 
   local buf = vim.api.nvim_get_current_buf()
+  local form_edges = lang.get_form_edges(form)
   local left_or_right_edge
   if opts.reversed then
-    left_or_right_edge = lang.get_form_edges(form).left
+    left_or_right_edge = form_edges.left
   else
-    left_or_right_edge = lang.get_form_edges(form).right
+    left_or_right_edge = form_edges.right
   end
 
   local start_or_end
@@ -57,6 +59,7 @@ local function slurp(opts)
   local row = start_or_end[1]
   local col = start_or_end[2]
 
+  -- stylua: ignore
   vim.api.nvim_buf_set_text(buf,
     row, col,
     row, col,
@@ -65,9 +68,10 @@ local function slurp(opts)
 
   local offset = 0
   if opts.reversed and row == left_or_right_edge.range[1] then
-    offset = string.len(left_or_right_edge.text)
+    offset = #left_or_right_edge.text
   end
 
+  -- stylua: ignore
   vim.api.nvim_buf_set_text(
     buf,
     left_or_right_edge.range[1], left_or_right_edge.range[2] + offset,
@@ -77,7 +81,7 @@ local function slurp(opts)
 
   local cursor_behaviour = opts.cursor_behaviour or config.config.cursor_behaviour
   if cursor_behaviour == "follow" then
-    local offset = 0
+    offset = 0
     if not opts.reversed then
       offset = string.len(left_or_right_edge.text)
     end
@@ -88,6 +92,30 @@ local function slurp(opts)
       vim.api.nvim_win_set_cursor(0, cursor_pos)
     end
   end
+
+  local operation_type
+  local new_range
+  if not opts.reversed then
+    operation_type = "slurp-forwards"
+    -- stylua: ignore
+    new_range = {
+      form_edges.left.range[1], form_edges.left.range[2],
+      row, col,
+    }
+  else
+    operation_type = "slurp-backwards"
+    -- stylua: ignore
+    new_range = {
+      row, col,
+      form_edges.right.range[1], form_edges.right.range[2],
+    }
+  end
+
+  local event = {
+    type = operation_type,
+    parent_range = new_range,
+  }
+  indentation.handle_indentation(event, opts)
 end
 
 function M.slurp_forwards(opts)
@@ -96,7 +124,7 @@ end
 
 function M.slurp_backwards(opts)
   slurp(common.merge(opts or {}, {
-    reversed = true
+    reversed = true,
   }))
 end
 

lua/nvim-paredit/defaults.lua

@@ -61,6 +61,7 @@ M.default_keys = {
 M.defaults = {
   use_default_keys = true,
   cursor_behaviour = "auto", -- remain, follow, auto
+  auto_indent = true,
   keys = {},
 }
 

lua/nvim-paredit/indentation/init.lua

@@ -0,0 +1,31 @@
+local native = require("nvim-paredit.indentation.native")
+local config = require("nvim-paredit.config")
+
+local M = {}
+
+function M.handle_indentation(event, opts)
+  local auto_indent = opts.auto_indent or config.config.auto_indent
+  if not auto_indent then
+    return
+  end
+
+  local indent_fn = opts.indent_fn or config.config.indent_fn or native.indent
+  if not indent_fn then
+    return
+  end
+
+  local tree = vim.treesitter.get_parser(0)
+
+  tree:parse()
+
+  local parent = tree:named_node_for_range(event.parent_range)
+  indent_fn(
+    vim.tbl_deep_extend("force", event, {
+      tree = tree,
+      parent = parent,
+    }),
+    opts
+  )
+end
+
+return M