Do not emit already consolidated warnings during mix xref trace, closes

#11899

lib/elixir/lib/code.ex

@@ -189,6 +189,7 @@ defmodule Code do
   @boolean_compiler_options [
     :docs,
     :debug_info,
+    :ignore_already_consolidated,
     :ignore_module_conflict,
     :relative_paths,
     :warnings_as_errors
@@ -1350,11 +1351,15 @@ defmodule Code do
       module. This allows a developer to reconstruct the original source
       code. Defaults to `true`.
 
-    * `:ignore_module_conflict` - when `true`, override modules that were
-      already defined without raising errors. Defaults to `false`.
+    * `:ignore_already_consolidated` - when `true`, does not warn when a protocol
+      has already been consolidated and a new implementation is added. Defaults
+      to `false`.
+
+    * `:ignore_module_conflict` - when `true`, does not warn when a module has
+      already been defined. Defaults to `false`.
 
     * `:relative_paths` - when `true`, use relative paths in quoted nodes,
-      warnings and errors generated by the compiler. Note disabling this option
+      warnings, and errors generated by the compiler. Note disabling this option
       won't affect runtime warnings and errors. Defaults to `true`.
 
     * `:warnings_as_errors` - causes compilation to fail when warnings are

lib/elixir/lib/protocol.ex

@@ -1021,7 +1021,8 @@ defmodule Protocol do
 
   @doc false
   def __ensure_defimpl__(protocol, for, env) do
-    if Protocol.consolidated?(protocol) do
+    if not Code.get_compiler_option(:ignore_already_consolidated) and
+         Protocol.consolidated?(protocol) do
       message =
         "the #{inspect(protocol)} protocol has already been consolidated, an " <>
           "implementation for #{inspect(for)} has no effect. If you want to " <>

lib/elixir/src/elixir.erl

@@ -58,6 +58,7 @@ start(_Type, _Args) ->
 
     %% Compiler options
     {docs, true},
+    {ignore_already_consolidated, false},
     {ignore_module_conflict, false},
     {parser_options, []},
     {debug_info, true},

lib/elixir/test/elixir/protocol/consolidation_test.exs

@@ -60,7 +60,7 @@ defmodule Protocol.ConsolidationTest do
     refute Protocol.consolidated?(Enumerable)
   end
 
-  test "consolidation prevents new implementations" do
+  test "consolidation warns on new implementations" do
     output =
       ExUnit.CaptureIO.capture_io(:stderr, fn ->
         defimpl WithAny, for: Integer do
@@ -74,6 +74,18 @@ defmodule Protocol.ConsolidationTest do
     :code.delete(WithAny.Integer)
   end
 
+  test "consolidation warns on new implementations unless disabled" do
+    Code.put_compiler_option(:ignore_already_consolidated, true)
+
+    defimpl WithAny, for: Integer do
+      def ok(_any), do: :ok
+    end
+  after
+    Code.put_compiler_option(:ignore_already_consolidated, false)
+    :code.purge(WithAny.Integer)
+    :code.delete(WithAny.Integer)
+  end
+
   test "consolidated implementations without any" do
     assert is_nil(Sample.impl_for(:foo))
     assert is_nil(Sample.impl_for(fn x -> x end))

lib/mix/lib/mix/tasks/xref.ex

@@ -462,7 +462,8 @@ defmodule Mix.Tasks.Xref do
           into: MapSet.new(),
           do: module
 
-    old = Code.compiler_options(ignore_module_conflict: true, tracers: [__MODULE__])
+    new = [ignore_already_consolidated: true, ignore_module_conflict: true, tracers: [__MODULE__]]
+    old = Code.compiler_options(new)
     ets = :ets.new(__MODULE__, [:named_table, :duplicate_bag, :public])
     :ets.insert(ets, [{:config, set, trace_label(opts[:label])}])