Properly get beam file for preloaded modules (#218)

Author: lukaszsamson

apps/language_server/lib/language_server/dialyzer.ex

@@ -359,7 +359,7 @@ defmodule ElixirLS.LanguageServer.Dialyzer do
 
         files_to_analyze =
           for module <- modules_to_analyze do
-            temp_modules[module] || :code.which(module)
+            temp_modules[module] || Utils.get_beam_file(module)
           end
 
         # Clear warnings for files that changed or need to be re-analyzed

apps/language_server/lib/language_server/dialyzer/manifest.ex

@@ -1,5 +1,5 @@
 defmodule ElixirLS.LanguageServer.Dialyzer.Manifest do
-  alias ElixirLS.LanguageServer.{Dialyzer, JsonRpc}
+  alias ElixirLS.LanguageServer.{Dialyzer, Dialyzer.Utils, JsonRpc}
   import Record
   import Dialyzer.Utils
 
@@ -125,7 +125,7 @@ defmodule ElixirLS.LanguageServer.Dialyzer.Manifest do
       |> Path.wildcard()
       |> Enum.map(&pathname_to_module/1)
       |> expand_references()
-      |> Enum.map(&:code.which/1)
+      |> Enum.map(&Utils.get_beam_file/1)
       |> Enum.filter(&is_list/1)
 
     File.mkdir_p!(Path.dirname(elixir_plt_path()))

apps/language_server/lib/language_server/dialyzer/utils.ex

@@ -1,11 +1,26 @@
 defmodule ElixirLS.LanguageServer.Dialyzer.Utils do
   @epoch_gregorian_seconds 62_167_219_200
 
+  @spec dialyzable?(module()) :: boolean()
   def dialyzable?(module) do
-    file = :code.which(module)
+    file = get_beam_file(module)
     is_list(file) and match?({:ok, _}, :dialyzer_utils.get_core_from_beam(file))
   end
 
+  @spec get_beam_file(module()) :: charlist() | :preloaded | :non_existing | :cover_compiled
+  def get_beam_file(module) do
+    case :code.which(module) do
+      file when is_list(file) ->
+        file
+
+      other ->
+        case :code.get_object_code(module) do
+          {_module, _binary, beam_filename} -> beam_filename
+          :error -> other
+        end
+    end
+  end
+
   def pathname_to_module(path) do
     String.to_atom(Path.basename(path, ".beam"))
   end