Fix rewrite of single-clause case statement with assignment parent. Closes #247

Author: novaugust

CHANGELOG.md

@@ -5,6 +5,12 @@ they can and will change without that change being reflected in Styler's semanti
 
 ## main
 
+## 1.9.1
+
+### Fix
+
+- fixes rewrites of single-clause case statement with assignment parent (Closes #247, h/t @vasspilka)
+
 ## 1.9.0
 
 This was a weird one, but I found myself often writing `to_timeout` with plural units and then having to go back and fix

lib/style/blocks.ex

@@ -57,18 +57,25 @@ defmodule Styler.Style.Blocks do
 
     zipper =
       case Zipper.up(zipper) do
-        {{:=, am, [parent_lhs, _single_clause_case]}, _} = zipper ->
-          # this was a `x = case head, do: (lhs -> rhs)`. make it `x = lhs = head; rhs`
+        {{:=, am, [parent_lhs, _case_statement_rhs]}, _} = zipper ->
+          # this was a `x = case head, do: (lhs -> rhs)`. make it `x = lhs = head; x = rhs`
           meta = [line: am[:line]]
-          Zipper.replace(zipper, {:=, meta, [parent_lhs, {:=, meta, [lhs, head]}]})
+          # change the if there are multiple clauses in the case, have the final one be the new rhs of parent_lhs
+          # the meta for the final equality has an incorrect line, but it shouldn't mess with comments so leaving it be
+          siblings = List.update_at(rhs, -1, &{:=, meta, [parent_lhs, &1]})
+
+          zipper
+          |> Zipper.replace({:=, meta, [lhs, head]})
+          |> Zipper.insert_siblings(siblings)
 
         _ ->
           zipper
           |> Style.find_nearest_block()
           |> Zipper.replace({:=, [line: m[:line]], [lhs, head]})
+          |> Zipper.insert_siblings(rhs)
       end
 
-    {:cont, Zipper.insert_siblings(zipper, rhs), ctx}
+    {:cont, zipper, ctx}
   end
 
   def run({{:cond, _, [[{do_, clauses}]]}, _} = zipper, ctx) do

test/style/blocks_test.exs

@@ -100,18 +100,54 @@ defmodule Styler.Style.BlocksTest do
     test "when already an assignment" do
       assert_style(
         """
-        m
+        preroll
 
-        x =
-          case a do
-            b -> c
+        assignment =
+          case head do
+            lhs -> body
           end
         """,
         """
-        m
+        preroll
 
-        x = b = a
-        c
+        lhs = head
+        assignment = body
+        """
+      )
+
+      assert_style(
+        """
+        # assignmet
+        assignment =
+          # case head
+          case head do
+            # lhs
+            lhs ->
+              # body
+              body
+              # clauses
+              fn ->
+                look
+                im(a)
+                # big function
+                big function
+              end
+          end
+        """,
+        """
+        # assignmet
+        # case head
+        # lhs
+        lhs = head
+        # body
+        body
+        # clauses
+        assignment = fn ->
+          look
+          im(a)
+          # big function
+          big(function)
+        end
         """
       )
     end

test/style/pipes_test.exs

@@ -283,13 +283,13 @@ defmodule Styler.Style.PipesTest do
       assert_style(
         """
         case x do
-          x -> x
+          y -> z
         end
         |> foo()
         """,
         """
-        case_result = x = x
-        x
+        y = x
+        case_result = z
         foo(case_result)
         """
       )