fix: provide clear error when importing VerifiedRoutes instead of using

lib/phoenix/verified_routes.ex

@@ -925,7 +925,7 @@ defmodule Phoenix.VerifiedRoutes do
   defp to_param(data), do: Phoenix.Param.to_param(data)
 
   defp build_route(route_ast, sigil_p, env, endpoint_ctx, router) do
-    config = Module.get_attribute(env.module, :phoenix_verified_config, [])
+    config = verified_config!(env)
 
     router =
       case Macro.expand(router, env) do
@@ -1026,6 +1026,8 @@ defmodule Phoenix.VerifiedRoutes do
   end
 
   defp attr!(env, :endpoint) do
+    verified_config!(env)
+
     Module.get_attribute(env.module, :endpoint) ||
       raise """
       expected @endpoint to be set. For dynamic endpoint resolution, use path/2 instead.
@@ -1037,9 +1039,29 @@ defmodule Phoenix.VerifiedRoutes do
   end
 
   defp attr!(env, name) do
+    verified_config!(env)
+
     Module.get_attribute(env.module, name) || raise "expected @#{name} module attribute to be set"
   end
 
+  defp verified_config!(env) do
+    case Module.get_attribute(env.module, :phoenix_verified_config) do
+      nil ->
+        raise ArgumentError, """
+        attempted to use Phoenix.VerifiedRoutes without calling `use Phoenix.VerifiedRoutes` first.
+
+        You must use `use Phoenix.VerifiedRoutes` with the appropriate options instead of importing it:
+
+            use Phoenix.VerifiedRoutes, endpoint: MyAppWeb.Endpoint, router: MyAppWeb.Router
+
+        See the documentation for more details on configuration options.
+        """
+
+      config ->
+        config
+    end
+  end
+
   defp static_path?(path, statics) do
     Enum.find(statics, &String.starts_with?(path, "/" <> &1))
   end

test/phoenix/verified_routes_test.exs

@@ -302,6 +302,17 @@ defmodule Phoenix.VerifiedRoutesTest do
     :code.delete(__MODULE__.SigilPPrefix)
   end
 
+  test "~p raises when VerifiedRoutes is imported instead of used" do
+    assert_raise ArgumentError,
+                 ~r|attempted to use Phoenix.VerifiedRoutes without calling|,
+                 fn ->
+                   defmodule BadImportedVerifiedRoutes do
+                     import Phoenix.VerifiedRoutes
+                     def test, do: ~p"/posts/1"
+                   end
+                 end
+  end
+
   test "path arities" do
     assert path(Endpoint, ~p"/posts/1") == "/posts/1"
     assert path(conn_with_endpoint(), ~p"/posts/1") == "/posts/1"