URI.append_query/2: Handle trailing ampersand (#12069)

Author: wojtekmach

lib/elixir/lib/uri.ex

@@ -966,7 +966,11 @@ defmodule URI do
   end
 
   def append_query(%URI{} = uri, query) when is_binary(query) do
-    %{uri | query: uri.query <> "&" <> query}
+    if String.ends_with?(uri.query, "&") do
+      %{uri | query: uri.query <> query}
+    else
+      %{uri | query: uri.query <> "&" <> query}
+    end
   end
 end
 

lib/elixir/test/elixir/uri_test.exs

@@ -400,6 +400,11 @@ defmodule URITest do
              "https://images.example.com/t/1600x/https://images.example.com/foo.jpg"
   end
 
+  test "append_query/2" do
+    assert URI.append_query(URI.parse("http://example.com/?x=1"), "x=2").query == "x=1&x=2"
+    assert URI.append_query(URI.parse("http://example.com/?x=1&"), "x=2").query == "x=1&x=2"
+  end
+
   ## Deprecate API
 
   describe "authority" do