Validate --no-exit in "mix format" (#12530)

2 files changed, 10 insertions, 0 deletions

diff --git a/lib/mix/lib/mix/tasks/format.ex b/lib/mix/lib/mix/tasks/format.ex
index 52015db56..6d4afc874 100644
--- a/lib/mix/lib/mix/tasks/format.ex
+++ b/lib/mix/lib/mix/tasks/format.ex
@@ -225,6 +225,10 @@ defmodule Mix.Tasks.Format do
       IO.warn("--check-equivalent has been deprecated and has no effect")
     end
 
+    if opts[:no_exit] && !opts[:check_formatted] do
+      Mix.raise("--no-exit can only be used together with --check-formatted")
+    end
+
     {formatter_opts_and_subs, _sources} =
       eval_deps_and_subdirectories(dot_formatter, [], formatter_opts, [dot_formatter])
 
diff --git a/lib/mix/test/mix/tasks/format_test.exs b/lib/mix/test/mix/tasks/format_test.exs
index 6e63246e3..cf6f6b544 100644
--- a/lib/mix/test/mix/tasks/format_test.exs
+++ b/lib/mix/test/mix/tasks/format_test.exs
@@ -175,6 +175,12 @@ defmodule Mix.Tasks.FormatTest do
     assert_received {:mix_shell, :info, ["The following files are not formatted" <> _]}
   end
 
+  test "raises an error if --no-exit is passed without --check-formatted" do
+    assert_raise Mix.Error, ~r"--no-exit can only be used together", fn ->
+      Mix.Tasks.Format.run(["--no-exit", "-"])
+    end
+  end
+
   test "uses inputs and configuration from .formatter.exs", context do
     in_tmp(context.test, fn ->
       File.write!(".formatter.exs", """