Raise an error if the umbrella app's dir name and mix.exs app name doesn't match (#9072)

Closes #9038.

Author: leandrocp

lib/mix/lib/mix/dep/loader.ex

@@ -287,7 +287,7 @@ defmodule Mix.Dep.Loader do
     end
   end
 
-  defp mix_dep(%Mix.Dep{opts: opts} = dep, nil) do
+  defp mix_dep(%Mix.Dep{app: app, opts: opts} = dep, nil) do
     Mix.Dep.in_dependency(dep, fn _ ->
       opts =
         if Mix.Project.umbrella?() do
@@ -298,6 +298,17 @@ defmodule Mix.Dep.Loader do
 
       child_opts =
         if opts[:from_umbrella] do
+          config = Mix.Project.config()
+
+          if config[:app] != app do
+            Mix.raise(
+              "Umbrella app #{inspect(config[:app])} is located at " <>
+                "directory #{Atom.to_string(app)}, and different names cause " <>
+                "a name mismatch that's not allowed. Please rename either " <>
+                "app's directory name or app's name in mix.exs to be equal."
+            )
+          end
+
           []
         else
           [env: Keyword.fetch!(opts, :env)]

lib/mix/test/mix/umbrella_test.exs

@@ -30,6 +30,28 @@ defmodule Mix.UmbrellaTest do
     end)
   end
 
+  test "umbrella app dir and the app name defined in mix.exs should be equal" do
+    in_fixture("umbrella_dep/deps/umbrella", fn ->
+      Mix.Project.in_project(:umbrella, ".", fn _ ->
+        File.write!("apps/bar/mix.exs", """
+        defmodule Bar.MixProject do
+          use Mix.Project
+
+          def project do
+            [app: :baz,
+             version: "0.1.0",
+             deps: []]
+          end
+        end
+        """)
+
+        assert_raise Mix.Error, ~r/^Umbrella app :baz is located at directory bar/, fn ->
+          Mix.Task.run("deps")
+        end
+      end)
+    end)
+  end
+
   test "compiles umbrella" do
     in_fixture("umbrella_dep/deps/umbrella", fn ->
       Mix.Project.in_project(:umbrella, ".", fn _ ->