feat: alias-refactor workspace command (#386)

Adds an alias refactor workspace command to Next LS.

Your cursor should be at the target module that you wish to alias.
It will insert the alias at the of the nearest defmodule definition
scoping the refactor only to the current module instead of the whole
file.

Author: NJichev

lib/next_ls.ex

@@ -154,7 +154,8 @@ defmodule NextLS do
          execute_command_provider: %GenLSP.Structures.ExecuteCommandOptions{
            commands: [
              "to-pipe",
-             "from-pipe"
+             "from-pipe",
+             "alias-refactor"
            ]
          },
          hover_provider: true,
@@ -769,6 +770,19 @@ defmodule NextLS do
             position: position
           })
 
+        "alias-refactor" ->
+          [arguments] = params.arguments
+
+          uri = arguments["uri"]
+          position = arguments["position"]
+          text = lsp.assigns.documents[uri]
+
+          NextLS.Commands.Alias.run(%{
+            uri: uri,
+            text: text,
+            position: position
+          })
+
         _ ->
           NextLS.Logger.show_message(
             lsp.logger,
@@ -783,7 +797,7 @@ defmodule NextLS do
       %WorkspaceEdit{} = edit ->
         GenLSP.request(lsp, %WorkspaceApplyEdit{
           id: System.unique_integer([:positive]),
-          params: %ApplyWorkspaceEditParams{label: "Pipe", edit: edit}
+          params: %ApplyWorkspaceEditParams{label: NextLS.Commands.label(command), edit: edit}
         })
 
       _reply ->

lib/next_ls/commands.ex

@@ -0,0 +1,15 @@
+defmodule NextLS.Commands do
+  @moduledoc false
+
+  @labels %{
+    "from-pipe" => "Inlined pipe",
+    "to-pipe" => "Extracted to a pipe",
+    "alias-refactor" => "Refactored with an alias"
+  }
+  @doc "Creates a label for the workspace apply struct from the command name"
+  def label(command) when is_map_key(@labels, command), do: @labels[command]
+
+  def label(command) do
+    raise ArgumentError, "command #{inspect(command)} not supported"
+  end
+end

lib/next_ls/commands/alias.ex

@@ -0,0 +1,140 @@
+defmodule NextLS.Commands.Alias do
+  @moduledoc """
+  Refactors a module with fully qualified calls to an alias.
+  The cursor position should be under the module name that you wish to alias.
+  """
+  import Schematic
+
+  alias GenLSP.Enumerations.ErrorCodes
+  alias GenLSP.Structures.Position
+  alias GenLSP.Structures.Range
+  alias GenLSP.Structures.TextEdit
+  alias GenLSP.Structures.WorkspaceEdit
+  alias NextLS.ASTHelpers
+  alias NextLS.EditHelpers
+  alias Sourceror.Zipper, as: Z
+
+  @line_length 121
+
+  defp opts do
+    map(%{
+      position: Position.schematic(),
+      uri: str(),
+      text: list(str())
+    })
+  end
+
+  def run(opts) do
+    with {:ok, %{text: text, uri: uri, position: position}} <- unify(opts(), Map.new(opts)),
+         {:ok, ast, comments} = parse(text),
+         {:ok, defm} <- ASTHelpers.get_surrounding_module(ast, position),
+         {:ok, {:__aliases__, _, modules}} <- get_node(ast, position) do
+      range = make_range(defm)
+      indent = EditHelpers.get_indent(text, range.start.line)
+      aliased = get_aliased(defm, modules)
+
+      comments =
+        Enum.filter(comments, fn comment ->
+          comment.line > range.start.line && comment.line <= range.end.line
+        end)
+
+      to_algebra_opts = [comments: comments]
+      doc = Code.quoted_to_algebra(aliased, to_algebra_opts)
+      formatted = doc |> Inspect.Algebra.format(@line_length) |> IO.iodata_to_binary()
+
+      %WorkspaceEdit{
+        changes: %{
+          uri => [
+            %TextEdit{
+              new_text:
+                EditHelpers.add_indent_to_edit(
+                  formatted,
+                  indent
+                ),
+              range: range
+            }
+          ]
+        }
+      }
+    else
+      {:error, message} ->
+        %GenLSP.ErrorResponse{code: ErrorCodes.parse_error(), message: inspect(message)}
+    end
+  end
+
+  defp parse(lines) do
+    lines
+    |> Enum.join("\n")
+    |> Spitfire.parse_with_comments(literal_encoder: &{:ok, {:__block__, &2, [&1]}})
+    |> case do
+      {:error, ast, comments, _errors} ->
+        {:ok, ast, comments}
+
+      other ->
+        other
+    end
+  end
+
+  defp make_range(original_ast) do
+    range = Sourceror.get_range(original_ast)
+
+    %Range{
+      start: %Position{line: range.start[:line] - 1, character: range.start[:column] - 1},
+      end: %Position{line: range.end[:line] - 1, character: range.end[:column] - 1}
+    }
+  end
+
+  def get_node(ast, pos) do
+    pos = [line: pos.line + 1, column: pos.character + 1]
+
+    result =
+      ast
+      |> Z.zip()
+      |> Z.traverse(nil, fn tree, acc ->
+        node = Z.node(tree)
+        range = Sourceror.get_range(node)
+
+        if not is_nil(range) and
+             match?({:__aliases__, _context, _modules}, node) &&
+             Sourceror.compare_positions(range.start, pos) in [:lt, :eq] &&
+             Sourceror.compare_positions(range.end, pos) in [:gt, :eq] do
+          {tree, node}
+        else
+          {tree, acc}
+        end
+      end)
+
+    case result do
+      {_, nil} ->
+        {:error, "could not find a module to alias at the cursor position"}
+
+      {_, {_t, _m, []}} ->
+        {:error, "could not find a module to alias at the cursor position"}
+
+      {_, {_t, _m, [_argument | _rest]} = node} ->
+        {:ok, node}
+    end
+  end
+
+  defp get_aliased(defm, modules) do
+    last = List.last(modules)
+
+    replaced =
+      Macro.prewalk(defm, fn
+        {:__aliases__, context, ^modules} -> {:__aliases__, context, [last]}
+        ast -> ast
+      end)
+
+    alias_to_add = {:alias, [alias: false], [{:__aliases__, [], modules}]}
+
+    {:defmodule, context, [module, [{do_block, block}]]} = replaced
+
+    case block do
+      {:__block__, block_context, defs} ->
+        {:defmodule, context, [module, [{do_block, {:__block__, block_context, [alias_to_add | defs]}}]]}
+
+      {_, _, _} = original ->
+        {:defmodule, context, [module, [{do_block, {:__block__, [], [alias_to_add, original]}}]]}
+    end
+  end
+end

lib/next_ls/extensions/elixir_extension/code_action/require.ex

@@ -7,6 +7,7 @@ defmodule NextLS.ElixirExtension.CodeAction.Require do
   alias GenLSP.Structures.Range
   alias GenLSP.Structures.TextEdit
   alias GenLSP.Structures.WorkspaceEdit
+  alias NextLS.ASTHelpers
 
   @one_indentation_level "  "
   @spec new(diagnostic :: Diagnostic.t(), [text :: String.t()], uri :: String.t()) :: [CodeAction.t()]
@@ -15,7 +16,7 @@ defmodule NextLS.ElixirExtension.CodeAction.Require do
 
     with {:ok, require_module} <- get_edit(diagnostic.message),
          {:ok, ast} <- parse_ast(text),
-         {:ok, defm} <- nearest_defmodule(ast, range),
+         {:ok, defm} <- ASTHelpers.get_surrounding_module(ast, range.start),
          indentation <- get_indent(text, defm),
          nearest <- find_nearest_node_for_require(defm),
          range <- get_edit_range(nearest) do
@@ -47,27 +48,6 @@ defmodule NextLS.ElixirExtension.CodeAction.Require do
     |> Spitfire.parse()
   end
 
-  defp nearest_defmodule(ast, range) do
-    defmodules =
-      ast
-      |> Macro.prewalker()
-      |> Enum.filter(fn
-        {:defmodule, _, _} -> true
-        _ -> false
-      end)
-
-    if defmodules != [] do
-      defm =
-        Enum.min_by(defmodules, fn {_, ctx, _} ->
-          range.start.character - ctx[:line] + 1
-        end)
-
-      {:ok, defm}
-    else
-      {:error, "no defmodule definition"}
-    end
-  end
-
   @module_name ~r/require\s+([^\s]+)\s+before/
   defp get_edit(message) do
     case Regex.run(@module_name, message) do

lib/next_ls/helpers/ast_helpers.ex

@@ -1,5 +1,6 @@
 defmodule NextLS.ASTHelpers do
   @moduledoc false
+  alias GenLSP.Structures.Position
   alias Sourceror.Zipper
 
   defmodule Attributes do
@@ -154,6 +155,29 @@ defmodule NextLS.ASTHelpers do
     end)
   end
 
+  @spec get_surrounding_module(ast :: Macro.t(), position :: Position.t()) :: {:ok, Macro.t()} | {:error, String.t()}
+  def get_surrounding_module(ast, position) do
+    defm =
+      ast
+      |> Macro.prewalker()
+      |> Enum.filter(fn node -> match?({:defmodule, _, _}, node) end)
+      |> Enum.filter(fn {_, ctx, _} ->
+        position.line + 1 - ctx[:line] >= 0
+      end)
+      |> Enum.min_by(
+        fn {_, ctx, _} ->
+          abs(ctx[:line] - 1 - position.line)
+        end,
+        fn -> nil end
+      )
+
+    if defm do
+      {:ok, defm}
+    else
+      {:error, "no defmodule definition"}
+    end
+  end
+
   def find_cursor(ast) do
     with nil <-
            ast

test/next_ls/alias_test.exs

@@ -0,0 +1,91 @@
+defmodule NextLS.AliasTest do
+  use ExUnit.Case, async: true
+
+  import GenLSP.Test
+  import NextLS.Support.Utils
+
+  @moduletag :tmp_dir
+  @moduletag root_paths: ["my_proj"]
+
+  setup %{tmp_dir: tmp_dir} do
+    File.mkdir_p!(Path.join(tmp_dir, "my_proj/lib"))
+    File.write!(Path.join(tmp_dir, "my_proj/mix.exs"), mix_exs())
+
+    cwd = Path.join(tmp_dir, "my_proj")
+
+    foo_path = Path.join(cwd, "lib/foo.ex")
+
+    foo = """
+    defmodule Foo do
+      def to_list() do
+        Foo.Bar.to_list(Map.new())
+      end
+
+      def to_map() do
+        Foo.Bar.to_map(List.new())
+      end
+    end
+    """
+
+    File.write!(foo_path, foo)
+
+    [foo: foo, foo_path: foo_path]
+  end
+
+  setup :with_lsp
+
+  setup context do
+    assert :ok == notify(context.client, %{method: "initialized", jsonrpc: "2.0", params: %{}})
+    assert_is_ready(context, "my_proj")
+    assert_compiled(context, "my_proj")
+    assert_notification "$/progress", %{"value" => %{"kind" => "end", "message" => "Finished indexing!"}}
+
+    did_open(context.client, context.foo_path, context.foo)
+    context
+  end
+
+  test "refactors with alias", %{client: client, foo_path: foo} do
+    foo_uri = uri(foo)
+    id = 1
+
+    request client, %{
+      method: "workspace/executeCommand",
+      id: id,
+      jsonrpc: "2.0",
+      params: %{
+        command: "alias-refactor",
+        arguments: [%{uri: foo_uri, position: %{line: 2, character: 8}}]
+      }
+    }
+
+    expected_edit =
+      String.trim("""
+      defmodule Foo do
+        alias Foo.Bar
+
+        def to_list() do
+          Bar.to_list(Map.new())
+        end
+
+        def to_map() do
+          Bar.to_map(List.new())
+        end
+      end
+      """)
+
+    assert_request(client, "workspace/applyEdit", 500, fn params ->
+      assert %{"edit" => edit, "label" => "Refactored with an alias"} = params
+
+      assert %{
+               "changes" => %{
+                 ^foo_uri => [%{"newText" => text, "range" => range}]
+               }
+             } = edit
+
+      assert text == expected_edit
+
+      assert range["start"] == %{"character" => 0, "line" => 0}
+      assert range["end"] == %{"character" => 3, "line" => 8}
+    end)
+  end
+end