refactor: simplify zipper usage (#45)

* build: add otp version to elixir in .tool-versions

* refactor: don't make subtree zippers unless needed in `Igniter.Code.Common`

* refactor: internal function in `Igniter.Code.Common`

* docs: add docstring for `Igniter.Code.Common.use_aliases/2`

* refactor: simplify zipper usage

Refactored using these two general rules:

1. Don't make subtrees unnecessarily

    zipper
    |> Zipper.subtree()
    |> Zipper.root()

    # is equivalent to
    zipper
    |> Zipper.node()

2. Access `zipper.node` when appropriate

    zipper
    |> Zipper.node()
    |> case do
      ...
    end

    # is equivalent to
    case zipper.node do
      ...
    end

* fix: remove redundant case clause in `Igniter.Code.Common`

.tool-versions

@@ -1,2 +1,2 @@
 erlang 26.0.2
-elixir 1.17.1
+elixir 1.17.1-otp-26

lib/igniter/code/common.ex

@@ -61,8 +61,7 @@ defmodule Igniter.Code.Common do
       ast =
         unquote(zipper)
         |> Igniter.Code.Common.maybe_move_to_single_child_block()
-        |> Zipper.subtree()
-        |> Zipper.root()
+        |> Zipper.node()
 
       match?(unquote(pattern), ast)
     end
@@ -133,20 +132,14 @@ defmodule Igniter.Code.Common do
   end
 
   defp do_add_code(zipper, new_code, placement, expand_env? \\ true) do
-    current_code =
-      zipper
-      |> Zipper.subtree()
-
     new_code =
       if expand_env? do
-        use_aliases(new_code, current_code)
+        use_aliases(new_code, zipper)
       else
         new_code
       end
 
-    current_code = Zipper.root(current_code)
-
-    case current_code do
+    case zipper.node do
       {:__block__, meta, stuff} when length(stuff) > 1 or stuff == [] ->
         new_stuff =
           if placement == :after do
@@ -161,19 +154,7 @@ defmodule Igniter.Code.Common do
         zipper
         |> highest_adjacent_block()
         |> case do
-          nil ->
-            if placement == :after do
-              Zipper.replace(zipper, {:__block__, [], [code, new_code]})
-            else
-              Zipper.replace(zipper, {:__block__, [], [new_code, code]})
-            end
-
-          upwards ->
-            upwards
-            |> Zipper.subtree()
-            |> Zipper.root()
-            |> case do
-              {:__block__, meta, stuff} ->
+          %Zipper{node: {:__block__, meta, stuff}} = upwards ->
             new_stuff =
               if placement == :after do
                 List.wrap(stuff) ++ [new_code]
@@ -198,43 +179,30 @@ defmodule Igniter.Code.Common do
         end
     end
   end
-  end
 
   def replace_code(zipper, code) when is_binary(code) do
     add_code(zipper, Sourceror.parse_string!(code))
   end
 
   def replace_code(zipper, code) do
-    current_code =
-      zipper
-      |> Zipper.subtree()
-
-    code = use_aliases(code, current_code)
-
+    code = use_aliases(code, zipper)
     Zipper.replace(zipper, code)
   end
 
   defp highest_adjacent_block(zipper) do
     case Zipper.up(zipper) do
-      nil ->
-        nil
-
-      upwards ->
-        upwards
-        |> Zipper.node()
-        |> case do
-          {:__block__, _, _} ->
-            case highest_adjacent_block(upwards) do
-              nil -> upwards
-              zipper -> zipper
-            end
+      %Zipper{node: {:__block__, _, _}} = upwards ->
+        highest_adjacent_block(upwards) || upwards
 
       _ ->
         nil
     end
   end
-  end
 
+  @doc """
+  Replaces full module names in `new_code` with any aliases for that
+  module found in the `current_code` environment.
+  """
   def use_aliases(new_code, current_code) do
     case current_env(current_code) do
       {:ok, env} ->
@@ -333,10 +301,7 @@ defmodule Igniter.Code.Common do
   def maybe_move_to_single_child_block(nil), do: nil
 
   def maybe_move_to_single_child_block(zipper) do
-    zipper
-    |> Zipper.subtree()
-    |> Zipper.root()
-    |> case do
+    case zipper.node do
       {:__block__, _, [_]} ->
         zipper
         |> Zipper.down()
@@ -360,10 +325,7 @@ defmodule Igniter.Code.Common do
   def maybe_move_to_block(nil), do: nil
 
   def maybe_move_to_block(zipper) do
-    zipper
-    |> Zipper.subtree()
-    |> Zipper.root()
-    |> case do
+    case zipper.node do
       {:__block__, _, _} ->
         zipper
         |> Zipper.down()
@@ -550,7 +512,6 @@ defmodule Igniter.Code.Common do
 
   zipper
   |> Igniter.Code.Common.move_to_cursor(pattern)
-  |> Zipper.subtree()
   |> Zipper.node()
   # => 10
   ```
@@ -569,7 +530,7 @@ defmodule Igniter.Code.Common do
 
   defp do_move_to_cursor(%Zipper{} = zipper, %Zipper{} = pattern_zipper) do
     cond do
-      cursor?(pattern_zipper |> Zipper.subtree() |> Zipper.node()) ->
+      pattern_zipper |> Zipper.node() |> cursor?() ->
         {:ok, zipper}
 
       match_type = zippers_match(zipper, pattern_zipper) ->
@@ -593,17 +554,7 @@ defmodule Igniter.Code.Common do
   defp cursor?(_other), do: false
 
   defp zippers_match(zipper, pattern_zipper) do
-    zipper_node =
-      zipper
-      |> Zipper.subtree()
-      |> Zipper.node()
-
-    pattern_node =
-      pattern_zipper
-      |> Zipper.subtree()
-      |> Zipper.node()
-
-    case {zipper_node, pattern_node} do
+    case {zipper.node, pattern_zipper.node} do
       {_, {:__, _, _}} ->
         :skip
 
@@ -673,8 +624,7 @@ defmodule Igniter.Code.Common do
   @spec nodes_equal?(Zipper.t() | Macro.t(), Macro.t()) :: boolean
   def nodes_equal?(%Zipper{} = left, right) do
     with zipper when not is_nil(zipper) <- Zipper.up(left),
-         {:defmodule, _, [{:__aliases__, _, parts}, _]} <-
-           zipper |> Zipper.subtree() |> Zipper.node(),
+         {:defmodule, _, [{:__aliases__, _, parts}, _]} <- Zipper.node(zipper),
          {:ok, env} <- current_env(zipper),
          true <- nodes_equal?({:__aliases__, [], [Module.concat([env.module | parts])]}, right) do
       true
@@ -682,7 +632,6 @@ defmodule Igniter.Code.Common do
       _ ->
         left
         |> expand_aliases()
-        |> Zipper.subtree()
         |> Zipper.node()
         |> nodes_equal?(right)
     end
@@ -700,10 +649,7 @@ defmodule Igniter.Code.Common do
 
   @spec expand_alias(Zipper.t()) :: Zipper.t()
   def expand_alias(zipper) do
-    zipper
-    |> Zipper.subtree()
-    |> Zipper.node()
-    |> case do
+    case zipper.node do
       {:__aliases__, _, parts} ->
         case current_env(zipper) do
           {:ok, env} ->

lib/igniter/code/function.ex

@@ -13,12 +13,7 @@ defmodule Igniter.Code.Function do
         unquote(zipper),
         unquote(index),
         fn zipper ->
-          code_at_node =
-            zipper
-            |> Sourceror.Zipper.subtree()
-            |> Sourceror.Zipper.root()
-
-          match?(unquote(pattern), code_at_node)
+          match?(unquote(pattern), zipper.node)
         end
       )
     end
@@ -87,8 +82,7 @@ defmodule Igniter.Code.Function do
   def function_call?(%Zipper{} = zipper, name, arity) do
     zipper
     |> Common.maybe_move_to_single_child_block()
-    |> Zipper.subtree()
-    |> Zipper.root()
+    |> Zipper.node()
     |> case do
       {^name, _, args} ->
         Enum.count(args) == arity
@@ -112,8 +106,7 @@ defmodule Igniter.Code.Function do
   def function_call?(%Zipper{} = zipper, name) do
     zipper
     |> Common.maybe_move_to_single_child_block()
-    |> Zipper.subtree()
-    |> Zipper.root()
+    |> Zipper.node()
     |> case do
       {^name, _, _} ->
         true
@@ -137,8 +130,7 @@ defmodule Igniter.Code.Function do
   def function_call?(%Zipper{} = zipper) do
     zipper
     |> Common.maybe_move_to_single_child_block()
-    |> Zipper.subtree()
-    |> Zipper.root()
+    |> Zipper.node()
     |> case do
       {:|>, _, [{name, _, context} | _rest]} when is_atom(context) and is_atom(name) ->
         true
@@ -391,10 +383,7 @@ defmodule Igniter.Code.Function do
   end
 
   defp pipeline?(zipper) do
-    zipper
-    |> Zipper.subtree()
-    |> Zipper.root()
-    |> case do
+    case zipper.node do
       {:|>, _, _} -> true
       _ -> false
     end

lib/igniter/code/keyword.ex

@@ -117,10 +117,7 @@ defmodule Igniter.Code.Keyword do
           value = Common.use_aliases(value, zipper)
 
           to_append =
-            zipper
-            |> Zipper.subtree()
-            |> Zipper.node()
-            |> case do
+            case zipper.node do
               [{{:__block__, meta, _}, _} | _] ->
                 if meta[:format] do
                   {{:__block__, [format: meta[:format]], [key]}, {:__block__, [], [value]}}
@@ -172,10 +169,7 @@ defmodule Igniter.Code.Keyword do
            end) do
         :error ->
           to_append =
-            zipper
-            |> Zipper.subtree()
-            |> Zipper.node()
-            |> case do
+            case zipper.node do
               [{{:__block__, meta, _}, {:__block__, _, _}} | _] ->
                 value =
                   value

lib/igniter/code/map.ex

@@ -136,10 +136,7 @@ defmodule Igniter.Code.Map do
   end
 
   defp map_keys_format(zipper) do
-    zipper
-    |> Zipper.subtree()
-    |> Zipper.node()
-    |> case do
+    case zipper.node do
       value when is_list(value) ->
         Enum.all?(value, fn
           {:__block__, meta, _} ->

lib/igniter/code/module.ex

@@ -156,17 +156,13 @@ defmodule Igniter.Code.Module do
         |> Rewrite.Source.get(:quoted)
         |> Zipper.zip()
         |> Zipper.traverse([], fn zipper, acc ->
-          zipper
-          |> Zipper.subtree()
-          |> Zipper.node()
-          |> case do
+          case zipper.node do
             {:defmodule, _, [_, _]} ->
               {:ok, mod_zipper} = Igniter.Code.Function.move_to_nth_argument(zipper, 0)
 
               module_name =
                 mod_zipper
                 |> Igniter.Code.Common.expand_alias()
-                |> Zipper.subtree()
                 |> Zipper.node()
                 |> Igniter.Code.Module.to_module_name()
 
@@ -265,7 +261,6 @@ defmodule Igniter.Code.Module do
            module <-
              zipper
              |> Igniter.Code.Common.expand_alias()
-             |> Zipper.subtree()
              |> Zipper.node(),
            module when not is_nil(module) <- to_module_name(module),
            new_path when not is_nil(new_path) <-

lib/igniter/code/tuple.ex

@@ -8,10 +8,7 @@ defmodule Igniter.Code.Tuple do
   @doc "Returns `true` if the zipper is at a literal tuple, `false` if not."
   @spec tuple?(Zipper.t()) :: boolean()
   def tuple?(item) do
-    item
-    |> Zipper.subtree()
-    |> Zipper.root()
-    |> case do
+    case item.node do
       {:{}, _, _} -> true
       {_, _} -> true
       _ -> false

lib/igniter/project/deps.ex

@@ -89,7 +89,6 @@ defmodule Igniter.Project.Deps do
              end
            end) do
       current_declaration
-      |> Zipper.subtree()
       |> Zipper.node()
       |> Sourceror.to_string()
     else

lib/igniter/util/debug.ex

@@ -5,8 +5,7 @@ defmodule Igniter.Util.Debug do
   @doc "Puts the formatted code at the node of the zipper to the console"
   def puts_code_at_node(zipper) do
     zipper
-    |> Zipper.subtree()
-    |> Zipper.root()
+    |> Zipper.node()
     |> Sourceror.to_string()
     |> then(&"==code==\n#{&1}\n==code==\n")
     |> IO.puts()
@@ -17,16 +16,14 @@ defmodule Igniter.Util.Debug do
   @doc "Returns the formatted code at the node of the zipper to the console"
   def code_at_node(zipper) do
     zipper
-    |> Zipper.subtree()
-    |> Zipper.root()
+    |> Zipper.node()
     |> Sourceror.to_string()
   end
 
   @doc "Puts the ast at the node of the zipper to the console"
   def puts_ast_at_node(zipper) do
     zipper
-    |> Zipper.subtree()
-    |> Zipper.root()
+    |> Zipper.node()
     |> then(&"==ast==\n#{inspect(&1, pretty: true)}\n==ast==\n")
     |> IO.puts()