fix infinite loop rewriting negated if with empty do body. closes #196

CHANGELOG.md

@@ -12,6 +12,7 @@ they can and will change without that change being reflected in Styler's semanti
 ### Fixes
 
 * `pipes`: optimizations reducing 2 pipes to 1 no longer squeeze all pipes onto one line (#180)
+* `if`: fix infinite loop rewriting negated if with empty do body `if x != y, do: (), else: :ok` (#196, h/t @itamm15)
 
 ## 1.0.0
 

lib/style/blocks.ex

@@ -201,6 +201,10 @@ defmodule Styler.Style.Blocks do
       [negator, [do_block]] when is_negator(negator) ->
         zipper |> Zipper.replace({:unless, m, [invert(negator), [do_block]]}) |> run(ctx)
 
+      # drop `else end`
+      [head, [do_block, {_, {:__block__, _, []}}]] ->
+        {:cont, Zipper.replace(zipper, {:if, m, [head, [do_block]]}), ctx}
+
       # drop `else: nil`
       [head, [do_block, {_, {:__block__, _, [nil]}}]] ->
         {:cont, Zipper.replace(zipper, {:if, m, [head, [do_block]]}), ctx}

test/style/blocks_test.exs

@@ -839,6 +839,24 @@ defmodule Styler.Style.BlocksTest do
       assert_style("if !!x, do: y", "if x, do: y")
     end
 
+    test "regression: negation with empty do body" do
+      assert_style(
+        """
+        if a != b do
+          # comment
+        else
+          :ok
+        end
+        """,
+        """
+        if a == b do
+          # comment
+          :ok
+        end
+        """
+      )
+    end
+
     test "Credo.Check.Refactor.UnlessWithElse" do
       for negator <- ["!", "not "] do
         assert_style(