Deprecate p shorthand in favor of partial

lib/nice_partials/monkey_patch.rb

@@ -24,11 +24,19 @@ def with_nice_partials_t_prefix(lookup_context, block)
   end
 end
 
+require "active_support/deprecation"
+NicePartials::DEPRECATOR = ActiveSupport::Deprecation.new("1.0", "nice_partials")
+
 module NicePartials::RenderingWithAutoContext
   attr_reader :partial
 
   def p(*args)
-    args.empty? ? partial : super
+    if args.empty?
+      NicePartials::DEPRECATOR.deprecation_warning :p, :partial # In-branch printing so we don't warn on legit `Kernel.p` calls.
+      partial
+    else
+      super # …we're really Kernel.p
+    end
   end
 
   def render(options = {}, locals = {}, &block)

test/fixtures/_clobberer.html.erb

@@ -1,2 +1,3 @@
 <% p "it's clobbering time" %>
+<%# TODO: Remove this file once `p` has been removed post deprecation, but don't change it yet. %>
 <%= p.yield :message %>

test/renderer_test.rb

@@ -34,4 +34,12 @@ class RendererTest < NicePartials::Test
 
     assert_rendered "hello from nice partials"
   end
+
+  test "deprecates top-level access through p method" do
+    assert_deprecated /p is deprecated and will be removed from nice_partials \d/, NicePartials::DEPRECATOR do
+      assert_output "\"it's clobbering time\"\n" do
+        render("clobberer") { |p| p.content_for :message, "hello from nice partials" }
+      end
+    end
+  end
 end