Specify that "mix new" APP name only takes lowercase ASCII letters (#7872)

Author: eksperimental

lib/mix/lib/mix/tasks/new.ex

@@ -168,8 +168,8 @@ defmodule Mix.Tasks.New do
   defp check_application_name!(name, inferred?) do
     unless name =~ Regex.recompile!(~r/^[a-z][a-z0-9_]*$/) do
       Mix.raise(
-        "Application name must start with a letter and have only lowercase " <>
-          "letters, numbers and underscore, got: #{inspect(name)}" <>
+        "Application name must start with a lowercase ASCII letter, followed by " <>
+          "lowercase ASCII letters, numbers, or underscores, got: #{inspect(name)}" <>
           if inferred? do
             ". The application name is inferred from the path, if you'd like to " <>
               "explicitly name the application then use the \"--app APP\" option"

lib/mix/test/mix/tasks/new_test.exs

@@ -145,17 +145,27 @@ defmodule Mix.Tasks.NewTest do
 
   test "new with invalid args" do
     in_tmp("new with an invalid application name", fn ->
-      assert_raise Mix.Error, ~r"Application name must start with a letter and ", fn ->
-        Mix.Tasks.New.run(["007invalid"])
-      end
-
-      assert_raise Mix.Error, ~r"only lowercase letters, numbers and underscore", fn ->
-        Mix.Tasks.New.run(["invAlid"])
-      end
+      assert_raise Mix.Error,
+                   ~r"Application name must start with a lowercase ASCII letter",
+                   fn ->
+                     Mix.Tasks.New.run(["007invalid"])
+                   end
+
+      assert_raise Mix.Error,
+                   ~r"followed by lowercase ASCII letters, numbers, or underscores",
+                   fn ->
+                     Mix.Tasks.New.run(["invAlid"])
+                   end
+
+      assert_raise Mix.Error,
+                   ~r"followed by lowercase ASCII letters, numbers, or underscores",
+                   fn ->
+                     Mix.Tasks.New.run(["inválido"])
+                   end
     end)
 
     in_tmp("new with an invalid application name from the app option", fn ->
-      assert_raise Mix.Error, ~r"Application name must start with a letter and ", fn ->
+      assert_raise Mix.Error, ~r"Application name must start with a lowercase ASCII letter", fn ->
         Mix.Tasks.New.run(["valid", "--app", "007invalid"])
       end
     end)