fix: do not crash when Expert.Protocol.Conversions.to_elixir/2 receives nil as document

apps/expert/lib/expert/protocol/conversions.ex

@@ -29,18 +29,26 @@ defmodule Expert.Protocol.Conversions do
     end
   end
 
-  def to_elixir(%LSPosition{} = position, %Document{} = document) do
-    to_elixir(position, document.lines)
+  def to_elixir(%LSRange{}, nil) do
+    {:error, {:invalid_document, nil}}
   end
 
   def to_elixir(%ElixirPosition{} = position, _) do
     {:ok, position}
   end
 
+  def to_elixir(%LSPosition{} = position, %Document{} = document) do
+    to_elixir(position, document.lines)
+  end
+
   def to_elixir(%LSPosition{line: line} = position, _) when line < 0 do
     {:error, {:invalid_position, position}}
   end
 
+  def to_elixir(%LSPosition{}, nil) do
+    {:error, {:invalid_document, nil}}
+  end
+
   def to_elixir(%LSPosition{} = position, %Lines{} = lines) do
     line_count = Lines.size(lines)
     # we need to handle out of bounds line numbers, because it's possible to build a document
@@ -68,7 +76,7 @@ defmodule Expert.Protocol.Conversions do
     end
   end
 
-  def to_elixir(%{range: %{start: start_pos, end: end_pos}}, document) do
+  def to_elixir(%{range: %{start: start_pos, end: end_pos}}, %Document{} = document) do
     # this is actually an elixir sense range... note that it's a bare map with
     # column keys rather than character keys.
     %{line: start_line, column: start_col} = start_pos
@@ -83,6 +91,10 @@ defmodule Expert.Protocol.Conversions do
     {:ok, range}
   end
 
+  def to_elixir(%{range: %{start: _start_pos, end: _end_pos}}, nil) do
+    {:error, {:invalid_document, nil}}
+  end
+
   def to_lsp(%LSRange{start: %LSPosition{}, end: %LSPosition{}} = ls_range) do
     {:ok, ls_range}
   end

apps/expert/test/conversions_test.exs

@@ -64,6 +64,18 @@ defmodule Expert.Protocol.ConversionsTest do
       assert {:ok, pos} = Conversions.to_elixir(lsp_position(8, 2), doc("abcde\n1234"))
       assert %ExPosition{line: 3, character: 1} = pos
     end
+
+    test "document is nil" do
+      assert Conversions.to_elixir(
+               %GenLSP.Structures.Range{end: lsp_position(0, 0), start: lsp_position(0, 0)},
+               nil
+             ) == {:error, {:invalid_document, nil}}
+
+      assert Conversions.to_elixir(lsp_position(0, 0), nil) == {:error, {:invalid_document, nil}}
+
+      assert Conversions.to_elixir(%{range: %{start: 0, end: 0}}, nil) ==
+               {:error, {:invalid_document, nil}}
+    end
   end
 
   describe "to_lsp/2 for positions" do