fix: do not clamp character recvd from client (#123)

Author: heywhy

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

@@ -148,15 +148,15 @@ defmodule Expert.Protocol.Conversions do
     {:ok, character}
   end
 
-  defp extract_elixir_character(%LSPosition{} = position, line(ascii?: true, text: text)) do
-    character = min(position.character + 1, byte_size(text) + 1)
-    {:ok, character}
+  defp extract_elixir_character(%LSPosition{} = position, line(ascii?: true)) do
+    {:ok, position.character + 1}
   end
 
   defp extract_elixir_character(%LSPosition{} = position, line(text: utf8_text)) do
-    with {:ok, code_unit} <- CodeUnit.utf16_offset_to_utf8_offset(utf8_text, position.character) do
-      character = min(code_unit, byte_size(utf8_text) + 1)
-      {:ok, character}
+    case CodeUnit.utf16_offset_to_utf8_offset(utf8_text, position.character) do
+      {:ok, _code_unit} = result -> result
+      {:error, :out_of_bounds} -> {:ok, position.character + 1}
+      {:error, _reason} = result -> result
     end
   end
 end

apps/expert/test/conversions_test.exs

@@ -54,7 +54,7 @@ defmodule Expert.Protocol.ConversionsTest do
 
     test "position > line length of a document with characters" do
       assert {:ok, pos} = Conversions.to_elixir(lsp_position(0, 15), doc("abcde"))
-      assert %ExPosition{line: 1, character: 6} = pos
+      assert %ExPosition{line: 1, character: 16} = pos
     end
 
     #  This is not specified in LSP but some clients fail to synchronize text properly

apps/expert/test/forge/document_test.exs

@@ -96,6 +96,44 @@ defmodule Forge.DocumentTest do
       {:ok, doc} = run_changes("hello there", [range_change])
       assert "hello people" == text(doc)
     end
+
+    test "applying batched incremental changes" do
+      content = """
+      defmodule Proxy do
+        String.dow
+      end
+      """
+
+      expected = """
+      defmodule Proxy do
+        String.downcase(string)
+      end
+      """
+
+      changes = [
+        %{text: "", range: new_range(1, 11, 1, 12), range_length: 1},
+        %{text: "", range: new_range(1, 10, 1, 11), range_length: 1},
+        %{text: "", range: new_range(1, 9, 1, 10), range_length: 1},
+        %{text: "d", range: new_range(1, 9, 1, 9), range_length: 0},
+        %{text: "o", range: new_range(1, 10, 1, 10), range_length: 0},
+        %{text: "w", range: new_range(1, 11, 1, 11), range_length: 0},
+        %{text: "n", range: new_range(1, 12, 1, 12), range_length: 0},
+        %{text: "c", range: new_range(1, 13, 1, 13), range_length: 0},
+        %{text: "a", range: new_range(1, 14, 1, 14), range_length: 0},
+        %{text: "s", range: new_range(1, 15, 1, 15), range_length: 0},
+        %{text: "e", range: new_range(1, 16, 1, 17), range_length: 0},
+        %{text: "", range: new_range(1, 9, 1, 17), range_length: 8},
+        %{text: "", range: new_range(1, 9, 1, 9), range_length: 0},
+        %{text: "downcase(", range: new_range(1, 9, 1, 9), range_length: 0},
+        %{text: "string", range: new_range(1, 18, 1, 18), range_length: 0},
+        %{text: ")", range: new_range(1, 24, 1, 24), range_length: 0},
+        %{text: "", range: new_range(1, 25, 1, 25), range_length: 0}
+      ]
+
+      {:ok, doc} = run_changes(content, changes)
+
+      assert text(doc) == expected
+    end
   end
 
   describe "apply_content_changes" do