From 19015ab29d0648f26f9e2b492db05797658790c1 Mon Sep 17 00:00:00 2001
From: Matt Enlow <enlow@adobe.com>
Date: Sun, 12 Nov 2023 08:11:11 -0700
Subject: [PATCH] with statement: drop singleton identity else. closes #84

---
 lib/style/blocks.ex        | 12 ++++++++++--
 test/style/blocks_test.exs | 21 +++++++++++++++++----
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/lib/style/blocks.ex b/lib/style/blocks.ex
index 8387c818..4f3a0fc3 100644
--- a/lib/style/blocks.ex
+++ b/lib/style/blocks.ex
@@ -88,15 +88,23 @@ defmodule Styler.Style.Blocks do
           do: {rest, [rhs]},
           else: {reversed_clauses, Enum.reverse(postroll, [do_body])}
 
-      do_else = [{do_block, {:__block__, do_body_meta, do_body}} | elses]
+      # drop singleton identity else clauses like `else foo -> foo end`
+      new_elses =
+        case elses do
+          [{{_, _, [:else]}, [{:->, _, [[left], right]}]}] -> if nodes_equivalent?(left, right), do: [], else: elses
+          _ -> elses
+        end
+
+      do_else = [{do_block, {:__block__, do_body_meta, do_body}} | new_elses]
       children = Enum.reverse(reversed_clauses, [do_else])
 
       # only rewrite if it needs rewriting!
+      # can probably stop optimizing like this once we handle comments nicely
       cond do
         Enum.any?(preroll) ->
           {:__block__, m, preroll ++ [{:with, m, children}]}
 
-        rewrite_body? or Enum.any?(postroll) ->
+        rewrite_body? or Enum.any?(postroll) or new_elses != elses ->
           {:with, m, children}
 
         true ->
diff --git a/test/style/blocks_test.exs b/test/style/blocks_test.exs
index cd9fc29e..355812c8 100644
--- a/test/style/blocks_test.exs
+++ b/test/style/blocks_test.exs
@@ -117,6 +117,23 @@ defmodule Styler.Style.BlocksTest do
       """)
     end
 
+    test "removes identity else clauses" do
+      assert_style(
+        """
+        with :ok <- b(), :ok <- b() do
+          :ok
+        else
+          :what -> :what
+        end
+        """,
+        """
+        with :ok <- b(), :ok <- b() do
+          :ok
+        end
+        """
+      )
+    end
+
     test "Credo.Check.Readability.WithSingleClause" do
       assert_style(
         """
@@ -164,8 +181,6 @@ defmodule Styler.Style.BlocksTest do
           a = bop
           boop
           :horay!
-        else
-          :error -> :error
         end
         """
       )
@@ -183,8 +198,6 @@ defmodule Styler.Style.BlocksTest do
           a = bop
           boop
           :horay!
-        else
-          :error -> :error
         end
         """
       )