Improve native indent impl under some edge cases

There are a few cases, especially when comments are involved, where the
indent would break or do the wrong thing.

This adds some more tests for edge-cases and fixes the behaviour for
those cases.

lua/nvim-paredit/indentation/native.lua

@@ -96,7 +96,11 @@ local function indent_barf(event)
   local lhs_range = { lhs:range() }
   local node_range = { node:range() }
 
-  if not utils.node_is_first_on_line(node, opts) or lhs_range[1] == node_range[1] then
+  if lhs_range[3] == node_range[1] then
+    return
+  end
+
+  if not utils.node_is_first_on_line(node, opts) then
     return
   end
 
@@ -136,13 +140,25 @@ local function indent_slurp(event)
   if event.type == "slurp-forwards" then
     child = parent:named_child(parent:named_child_count() - 1)
   else
-    child = parent:named_child(1)
+    local first = parent:named_child(0)
+    if not first then
+      return
+    end
+    child = traversal.get_next_sibling_ignoring_comments(first, opts)
+  end
+
+  if not child then
+    return
   end
 
   local parent_range = { parent:range() }
   local child_range = { child:range() }
 
-  if not utils.node_is_first_on_line(child, opts) or parent_range[1] == child_range[1] then
+  if parent_range[1] == child_range[1] then
+    return
+  end
+
+  if not utils.node_is_first_on_line(child, opts) then
     return
   end
 

lua/nvim-paredit/indentation/utils.lua

@@ -3,9 +3,19 @@ local common = require("nvim-paredit.utils.common")
 
 local M = {}
 
+local function get_corrected_line_range(range)
+  -- if the node is at the zeroth position on the last line, it's not actually
+  -- part of the line.
+  if range[4] == 0 then
+    return range[1], range[3] - 1
+  end
+  return range[1], range[3]
+end
+
 function M.get_node_line_range(range)
+  local start, _end = get_corrected_line_range(range)
   local lines = {}
-  for i = range[1], range[3], 1 do
+  for i = start, _end, 1 do
     table.insert(lines, i)
   end
   return lines
@@ -57,8 +67,8 @@ function M.node_is_first_on_line(node, opts)
     return true
   end
 
-  local sibling_range = { sibling:range() }
-  return sibling_range[3] ~= node_range[1]
+  local _, sibling_end = get_corrected_line_range({ sibling:range() })
+  return sibling_end ~= node_range[1]
 end
 
 -- This functions finds the closest sibling to a given `node` which is:

tests/nvim-paredit/indentation_spec.lua

@@ -62,6 +62,13 @@ describe("indentation ::", function()
         after_content = "( 1)",
         after_cursor = { 1, 1 },
       },
+      {
+        "should not indent when on same line [multiline]",
+        before_content = {"(", " a) b"},
+        before_cursor = { 1, 0 },
+        after_content = {"(", " a b)"},
+        after_cursor = { 1, 0 },
+      },
       {
         "should dedent when node is too far indented",
         before_content = { "()", "  a" },
@@ -78,9 +85,9 @@ describe("indentation ::", function()
       },
       {
         "should indent the correct node ignoring comments",
-        before_content = { "()", ";; comment", "a" },
+        before_content = { "()", ";; comment", "a ;; another comment", "b" },
         before_cursor = { 1, 1 },
-        after_content = { "(", ";; comment", " a)" },
+        after_content = { "(", ";; comment", " a) ;; another comment", "b" },
         after_cursor = { 1, 0 },
       },
 
@@ -107,13 +114,27 @@ describe("indentation ::", function()
         after_content = { "(a", " b)" },
         after_cursor = { 2, 2 },
       },
+      {
+        "should indent with a comment in the way",
+        before_content = { "a ;; comment", "(b)" },
+        before_cursor = { 2, 1 },
+        after_content = { "(a ;; comment", " b)" },
+        after_cursor = { 2, 2 },
+      },
       {
         "should not indent when on same line",
         before_content = { "a (b)" },
         before_cursor = { 1, 3 },
         after_content = { "(a b)" },
         after_cursor = { 1, 3 },
       },
+      {
+        "should handle empty children",
+        before_content = { "a", "()" },
+        before_cursor = { 2, 1 },
+        after_content = { "(a", ")" },
+        after_cursor = { 2, 0 },
+      },
     })
   end)
 
@@ -146,9 +167,9 @@ describe("indentation ::", function()
       },
       {
         "should not dedent if node is on the same line",
-        before_content = { "(a", "b c)" },
+        before_content = { "(a", " b c)" },
         before_cursor = { 1, 1 },
-        after_content = { "(a", "b) c" },
+        after_content = { "(a", " b) c" },
         after_cursor = { 1, 1 },
       },
       {