lib/pleroma/akkoma/translators/libre_translate.ex

@@ -40,7 +40,7 @@ def translate(string, from_language, to_language) do
         if Map.has_key?(body, "detectedLanguage") do
           get_in(body, ["detectedLanguage", "language"])
 	else
-          from_language
+          from_language || ""
 	end
 
       {:ok, detected, translated}

test/pleroma/translators/libre_translate_test.exs

@@ -133,5 +133,21 @@ test "should gracefully handle an unsupported language" do
       assert {:error, "libre_translate: request failed (code 400)"} =
                LibreTranslate.translate("ギュギュ握りつぶしちゃうぞ", nil, "zoop")
     end
+
+    test "should work when no detected language is received" do
+      Tesla.Mock.mock(fn
+        %{method: :post, url: "http://libre.translate/translate"} ->
+          %Tesla.Env{
+            status: 200,
+            body:
+              Jason.encode!(%{
+                translatedText: "I will crush you"
+              })
+          }
+      end)
+
+      assert {:ok, "", "I will crush you"} =
+               LibreTranslate.translate("ギュギュ握りつぶしちゃうぞ", nil, "en")
+    end
   end
 end