Use lhs sibling as indentation ref point

lua/nvim-paredit/indentation/native.lua

@@ -99,8 +99,17 @@ local function indent_barf(event)
   if parent:type() == "source" then
     delta = node_range[2]
   else
-    local form_edges = lang.get_form_edges(parent)
-    delta = node_range[2] - form_edges.left.range[2] - 1
+    local row
+    local ref_node = utils.get_first_sibling_on_upper_line(node, { lang = lang })
+    if ref_node then
+      local range = { ref_node:range() }
+      row = range[2]
+    else
+      local form_edges = lang.get_form_edges(parent)
+      row = form_edges.left.range[2] - 1
+    end
+
+    delta = node_range[2] - row
   end
 
   indent_lines(lines, delta * -1, {
@@ -127,9 +136,18 @@ local function indent_slurp(event)
   end
 
   local lines = utils.find_affected_lines(child, utils.get_node_line_range(child_range))
-  local form_edges = lang.get_form_edges(parent)
 
-  local delta = form_edges.left.range[4] - child_range[2]
+  local row
+  local ref_node = utils.get_first_sibling_on_upper_line(child, { lang = lang })
+  if ref_node then
+    local range = { ref_node:range() }
+    row = range[2]
+  else
+    local form_edges = lang.get_form_edges(parent)
+    row = form_edges.left.range[4]
+  end
+
+  local delta = row - child_range[2]
   indent_lines(lines, delta, {
     buf = event.buf,
   })

lua/nvim-paredit/indentation/utils.lua

@@ -61,4 +61,35 @@ function M.node_is_first_on_line(node, opts)
   return sibling_range[3] ~= node_range[1]
 end
 
+-- This functions finds the closest sibling to a given `node` which is:
+-- 1) Not on the same line (one line higher)
+-- 2) Is the first node on the line
+--
+-- This node can be used as an indentation reference point.
+function M.get_first_sibling_on_upper_line(node, opts)
+  local node_range = { node:range() }
+
+  local reference
+  local prev = node
+
+  while prev do
+    prev = traversal.get_prev_sibling_ignoring_comments(prev, opts)
+    if not prev then
+      return reference
+    end
+
+    local sibling_range = { prev:range() }
+
+    if reference and reference:range() ~= sibling_range[1] then
+      return reference
+    end
+
+    if sibling_range[1] ~= node_range[1] then
+      reference = prev
+    end
+  end
+
+  return reference
+end
+
 return M

tests/nvim-paredit/indentation_spec.lua

@@ -66,6 +66,14 @@ describe("forward slurping indentation", function()
       after_content = { "(", ";; comment", " a)" },
       after_cursor = { 1, 0 },
     },
+
+    {
+      "should indent to the first relevant siblings indentation",
+      before_content = { "(def a []", "  target sibling)", "child" },
+      before_cursor = { 1, 1 },
+      after_content = { "(def a []", "  target sibling", "  child)" },
+      after_cursor = { 1, 1 },
+    },
   })
 end)
 
@@ -90,6 +98,14 @@ describe("backward slurping indentation", function()
       after_content = { "(a b)" },
       after_cursor = { 1, 3 },
     },
+
+    {
+      "should indent to the first relevant siblings indentation",
+      before_content = { "(def a []", "  target sibling)", "child" },
+      before_cursor = { 1, 1 },
+      after_content = { "(def a []", "  target sibling", "  child)" },
+      after_cursor = { 1, 1 },
+    },
   })
 end)
 
@@ -142,6 +158,14 @@ describe("forward barfing indentation", function()
       after_content = { "()", ";; comment", "a" },
       after_cursor = { 1, 0 },
     },
+
+    {
+      "should indent to the first relevant siblings indentation",
+      before_content = { "(def a []", "  target (sibling", "          child))" },
+      before_cursor = { 2, 10 },
+      after_content = { "(def a []", "  target (sibling)", "  child)" },
+      after_cursor = { 2, 10 },
+    },
   })
 end)
 
@@ -166,5 +190,13 @@ describe("backward barfing indentation", function()
       after_content = { "(a", " (bc", " de))" },
       after_cursor = { 2, 3 },
     },
+
+    {
+      "should indent to the first relevant siblings indentation",
+      before_content = { "(def a []", "  target (sibling", "          child))" },
+      before_cursor = { 3, 1 },
+      after_content = { "(def a []", "  target sibling", "  (child))" },
+      after_cursor = { 3, 2 },
+    },
   })
 end)