Correctly shift all meta line values when shrinking function heads. C…

…loses #67

lib/style.ex

@@ -42,6 +42,19 @@ defmodule Styler.Style do
     end)
   end
 
+  def shift_line(ast_node, delta) do
+    shift_line = &Keyword.replace_lazy(&1, :line, fn line -> line + delta end)
+
+    update_all_meta(ast_node, fn meta ->
+      meta
+      |> shift_line.()
+      |> Keyword.replace_lazy(:closing, shift_line)
+      |> Keyword.replace_lazy(:end_of_expression, shift_line)
+      |> Keyword.replace_lazy(:last, shift_line)
+      |> Keyword.replace_lazy(:end, shift_line)
+    end)
+  end
+
   @doc "Traverses an ast node, updating all nodes' meta with `meta_fun`"
   def update_all_meta(node, meta_fun) do
     node

lib/style/defs.ex

@@ -76,15 +76,14 @@ defmodule Styler.Style.Defs do
       else
         do_line = do_meta[:line]
         delta = def_line - do_line
-        move_up = &(&1 + delta)
 
         def_meta =
           def_meta
           |> put_in([:do, :line], def_line)
-          |> update_in([:end, :line], move_up)
+          |> update_in([:end, :line], &(&1 + delta))
 
         head = Style.set_line(head, def_line)
-        body = Style.update_all_meta(body, shift_lines(move_up))
+        body = Style.shift_line(body, delta)
         node = {def, def_meta, [head, body]}
 
         comments =
@@ -110,12 +109,4 @@ defmodule Styler.Style.Defs do
   end
 
   def run(zipper, ctx), do: {:cont, zipper, ctx}
-
-  defp shift_lines(line_mover) do
-    fn meta ->
-      meta
-      |> Keyword.replace_lazy(:line, line_mover)
-      |> Keyword.replace_lazy(:closing, &Keyword.replace_lazy(&1, :line, line_mover))
-    end
-  end
 end

test/style/defs_test.exs

@@ -12,6 +12,24 @@ defmodule Styler.Style.DefsTest do
   use Styler.StyleCase, async: true
 
   describe "run" do
+    test "comments stay put when we can't shrink the head, even with blocks" do
+      assert_style("""
+        def my_function(
+            so_long_that_this_head_will_not_fit_on_one_lineso_long_that_this_head_will_not_fit_on_one_line,
+            so_long_that_this_head_will_not_fit_on_one_line
+          ) do
+        result =
+          case foo do
+            :bar -> :baz
+            :baz -> :bong
+          end
+
+        # My comment
+        Context.process(result)
+      end
+      """)
+    end
+
     test "function with do keyword" do
       assert_style(
         """