Add code actions for unknown modules and structs

apps/language_server/lib/language_server/experimental/code_mod/add_alias.ex

@@ -0,0 +1,96 @@
+defmodule ElixirLS.LanguageServer.Experimental.CodeMod.AddAlias do
+  alias ElixirLS.LanguageServer.Experimental.CodeMod.Ast
+  alias ElixirLS.LanguageServer.Experimental.CodeMod.Diff
+  alias ElixirLS.LanguageServer.Experimental.SourceFile
+  alias ElixirSense.Core.Metadata
+  alias ElixirSense.Core.Parser
+  alias LSP.Types.TextEdit
+
+  @spec text_edits(SourceFile.t(), non_neg_integer(), [atom()]) ::
+          {:ok, [TextEdit.t()], non_neg_integer()} | :error
+  def text_edits(source_file, one_based_line, suggestion) do
+    maybe_blank_line_before(source_file, one_based_line)
+
+    with {:ok, {alias_line, alias_column}} <- find_place(source_file, one_based_line),
+         {:ok, line_text} <- SourceFile.fetch_text_at(source_file, alias_line),
+         {:ok, transformed} <-
+           apply_transforms(source_file, alias_line, alias_column, suggestion) do
+      {:ok, Diff.diff(line_text, transformed), alias_line}
+    end
+  end
+
+  defp find_place(source_file, one_based_line) do
+    metadata =
+      source_file
+      |> SourceFile.to_string()
+      |> Parser.parse_string(true, true, one_based_line)
+
+    case Metadata.get_position_to_insert_alias(metadata, one_based_line) do
+      nil -> :error
+      alias_position -> {:ok, alias_position}
+    end
+  end
+
+  defp apply_transforms(source_file, line, column, suggestion) do
+    case SourceFile.fetch_text_at(source_file, line) do
+      {:ok, line_text} ->
+        leading_indent = String.duplicate(" ", column - 1)
+
+        new_alias_text = Ast.to_string({:alias, [], [{:__aliases__, [], suggestion}]}) <> "\n"
+
+        maybe_blank_line_before = maybe_blank_line_before(source_file, line)
+        maybe_blank_line_after = maybe_blank_line_after(line_text)
+
+        {:ok,
+         "#{maybe_blank_line_before}#{leading_indent}#{new_alias_text}#{maybe_blank_line_after}#{line_text}"}
+
+      _ ->
+        :error
+    end
+  end
+
+  defp maybe_blank_line_before(source_file, line) do
+    if line >= 2 do
+      case SourceFile.fetch_text_at(source_file, line - 1) do
+        {:ok, previous_line_text} ->
+          cond do
+            blank?(previous_line_text) -> ""
+            contains_alias?(previous_line_text) -> ""
+            module_definition?(previous_line_text) -> ""
+            true -> "\n"
+          end
+
+        _ ->
+          "\n"
+      end
+    else
+      ""
+    end
+  end
+
+  defp maybe_blank_line_after(line_text) do
+    cond do
+      blank?(line_text) -> ""
+      contains_alias?(line_text) -> ""
+      true -> "\n"
+    end
+  end
+
+  defp blank?(line_text) do
+    line_text |> String.trim() |> byte_size() == 0
+  end
+
+  defp contains_alias?(line_text) do
+    case Ast.from(line_text) do
+      {:ok, {:alias, _meta, _alias}} -> true
+      _ -> false
+    end
+  end
+
+  defp module_definition?(line_text) do
+    case Ast.from(line_text) do
+      {:ok, {:defmodule, _meta, _contents}} -> true
+      _ -> false
+    end
+  end
+end

apps/language_server/lib/language_server/experimental/code_mod/replace_module.ex

@@ -0,0 +1,42 @@
+defmodule ElixirLS.LanguageServer.Experimental.CodeMod.ReplaceModule do
+  alias ElixirLS.LanguageServer.Experimental.CodeMod.Ast
+  alias ElixirLS.LanguageServer.Experimental.CodeMod.Diff
+  alias ElixirLS.LanguageServer.Experimental.CodeMod.Text
+  alias LSP.Types.TextEdit
+
+  @spec text_edits(String.t(), Ast.t(), [atom()], [atom()]) :: {:ok, [TextEdit.t()]} | :error
+  def text_edits(original_text, ast, module, suggestion) do
+    with {:ok, transformed} <- apply_transforms(original_text, ast, module, suggestion) do
+      {:ok, Diff.diff(original_text, transformed)}
+    end
+  end
+
+  defp apply_transforms(line_text, quoted_ast, module, suggestion) do
+    leading_indent = Text.leading_indent(line_text)
+
+    updated_ast =
+      Macro.postwalk(quoted_ast, fn
+        {:__aliases__, meta, ^module} -> {:__aliases__, meta, suggestion}
+        other -> other
+      end)
+
+    if updated_ast != quoted_ast do
+      updated_ast
+      |> Ast.to_string()
+      # We're dealing with a single error on a single line.
+      # If the line doesn't compile (like it has a do with no end), ElixirSense
+      # adds additional lines do documents with errors, so take the first line, as it's
+      # the properly transformed source
+      |> Text.fetch_line(0)
+      |> case do
+        {:ok, text} ->
+          {:ok, "#{leading_indent}#{text}"}
+
+        error ->
+          error
+      end
+    else
+      :error
+    end
+  end
+end

apps/language_server/lib/language_server/experimental/provider/code_action/add_alias.ex

@@ -0,0 +1,181 @@
+defmodule ElixirLS.LanguageServer.Experimental.Provider.CodeAction.AddAlias do
+  alias ElixirLS.LanguageServer.Experimental.CodeMod
+  alias ElixirLS.LanguageServer.Experimental.CodeMod.Ast
+  alias ElixirLS.LanguageServer.Experimental.SourceFile
+  alias ElixirSense.Core.Metadata
+  alias ElixirSense.Core.Parser
+  alias ElixirSense.Core.State.Env
+  alias LSP.Requests.CodeAction
+  alias LSP.Types.CodeAction, as: CodeActionResult
+  alias LSP.Types.Diagnostic
+  alias LSP.Types.TextEdit
+  alias LSP.Types.Workspace
+
+  @undefined_module_re ~r/(.*) is undefined \(module (.*) is not available or is yet to be defined\)/s
+  @unknown_struct_re ~r/\(CompileError\) (.*).__struct__\/1 is undefined, cannot expand struct (.*). Make sure the struct name is correct./s
+
+  @spec apply(CodeAction.t()) :: [CodeActionResult.t()]
+  def apply(%CodeAction{} = code_action) do
+    source_file = code_action.source_file
+    diagnostics = get_in(code_action, [:context, :diagnostics]) || []
+
+    Enum.flat_map(diagnostics, fn %Diagnostic{} = diagnostic ->
+      one_based_line = extract_start_line(diagnostic)
+
+      with {:ok, module_string} <- parse_message(diagnostic.message),
+           true <- module_present?(source_file, one_based_line, module_string),
+           {:ok, suggestions} <- create_suggestions(module_string, source_file, one_based_line),
+           {:ok, replies} <- build_code_actions(source_file, one_based_line, suggestions) do
+        replies
+      else
+        _ -> []
+      end
+    end)
+  end
+
+  defp extract_start_line(%Diagnostic{} = diagnostic) do
+    diagnostic.range.start.line
+  end
+
+  defp parse_message(message) do
+    case Regex.scan(@undefined_module_re, message) do
+      [[_message, _function, module]] ->
+        {:ok, module}
+
+      _ ->
+        case Regex.scan(@unknown_struct_re, message) do
+          [[_message, module, module]] -> {:ok, module}
+          _ -> :error
+        end
+    end
+  end
+
+  defp module_present?(source_file, one_based_line, module_string) do
+    module = module_to_alias_list(module_string)
+
+    with {:ok, line_text} <- SourceFile.fetch_text_at(source_file, one_based_line),
+         {:ok, line_ast} <- Ast.from(line_text) do
+      line_ast
+      |> Macro.postwalk(false, fn
+        {:., _fun_meta, [{:__aliases__, _aliases_meta, ^module} | _fun]} = ast, _acc ->
+          {ast, true}
+
+        {:%, _struct_meta, [{:__aliases__, _aliases_meta, ^module} | _fields]} = ast, _acc ->
+          {ast, true}
+
+        other_ast, acc ->
+          {other_ast, acc}
+      end)
+      |> elem(1)
+    end
+  end
+
+  @max_suggestions 3
+  defp create_suggestions(module_string, source_file, one_based_line) do
+    with {:ok, current_namespace} <- current_module_namespace(source_file, one_based_line) do
+      suggestions =
+        ElixirSense.all_modules()
+        |> Enum.filter(&String.ends_with?(&1, "." <> module_string))
+        |> Enum.sort_by(&same_namespace?(&1, current_namespace))
+        |> Enum.take(@max_suggestions)
+        |> Enum.map(&module_to_alias_list/1)
+
+      {:ok, suggestions}
+    end
+  end
+
+  defp same_namespace?(suggested_module_string, current_namespace) do
+    suggested_module_namespace =
+      suggested_module_string
+      |> module_to_alias_list()
+      |> List.first()
+      |> Atom.to_string()
+
+    current_namespace == suggested_module_namespace
+  end
+
+  defp current_module_namespace(source_file, one_based_line) do
+    %Metadata{lines_to_env: lines_to_env} =
+      source_file
+      |> SourceFile.to_string()
+      |> Parser.parse_string(true, true, one_based_line)
+
+    case Map.get(lines_to_env, one_based_line) do
+      nil ->
+        :error
+
+      %Env{module: module} ->
+        namespace =
+          module
+          |> module_to_alias_list()
+          |> List.first()
+          |> Atom.to_string()
+
+        {:ok, namespace}
+    end
+  end
+
+  defp module_to_alias_list(module) when is_atom(module) do
+    case Atom.to_string(module) do
+      "Elixir." <> module_string -> module_to_alias_list(module_string)
+      module_string -> module_to_alias_list(module_string)
+    end
+  end
+
+  defp module_to_alias_list(module) when is_binary(module) do
+    module
+    |> String.split(".")
+    |> Enum.map(&String.to_atom/1)
+  end
+
+  defp build_code_actions(source_file, one_based_line, suggestions) do
+    with {:ok, edits_per_suggestion} <-
+           text_edits_per_suggestion(source_file, one_based_line, suggestions) do
+      case edits_per_suggestion do
+        [] ->
+          :error
+
+        [_ | _] ->
+          replies =
+            Enum.map(edits_per_suggestion, fn {text_edits, alias_line, suggestion} ->
+              text_edits = Enum.map(text_edits, &update_line(&1, alias_line))
+
+              CodeActionResult.new(
+                title: construct_title(suggestion),
+                kind: :quick_fix,
+                edit: Workspace.Edit.new(changes: %{source_file.uri => text_edits})
+              )
+            end)
+
+          {:ok, replies}
+      end
+    end
+  end
+
+  defp text_edits_per_suggestion(source_file, one_based_line, suggestions) do
+    suggestions
+    |> Enum.reduce_while([], fn suggestion, acc ->
+      case CodeMod.AddAlias.text_edits(source_file, one_based_line, suggestion) do
+        {:ok, [], _alias_line} -> {:cont, acc}
+        {:ok, edits, alias_line} -> {:cont, [{edits, alias_line, suggestion} | acc]}
+        :error -> {:halt, :error}
+      end
+    end)
+    |> case do
+      :error -> :error
+      edits -> {:ok, edits}
+    end
+  end
+
+  defp update_line(%TextEdit{} = text_edit, line_number) do
+    text_edit
+    |> put_in([:range, :start, :line], line_number - 1)
+    |> put_in([:range, :end, :line], line_number - 1)
+  end
+
+  defp construct_title(suggestion) do
+    module_string = Enum.map_join(suggestion, ".", &Atom.to_string/1)
+
+    "Add alias #{module_string}"
+  end
+end