API-34439 add breakpoint dev tool

.github/CODEOWNERS

@@ -696,6 +696,7 @@ config/initializers/backtrace_silencers.rb @department-of-veterans-affairs/va-ap
 config/initializers/betamocks.rb @department-of-veterans-affairs/va-api-engineers @department-of-veterans-affairs/backend-review-group
 config/initializers/bgs.rb @department-of-veterans-affairs/Benefits-Team-1 @department-of-veterans-affairs/va-api-engineers @department-of-veterans-affairs/backend-review-group
 config/initializers/breakers.rb @department-of-veterans-affairs/va-api-engineers @department-of-veterans-affairs/backend-review-group
+config/initializers/breakpoint.rb @department-of-veterans-affairs/va-api-engineers @department-of-veterans-affairs/backend-review-group
 config/initializers/clamscan.rb @department-of-veterans-affairs/va-api-engineers @department-of-veterans-affairs/backend-review-group
 config/initializers/config.rb @department-of-veterans-affairs/va-api-engineers @department-of-veterans-affairs/backend-review-group
 config/initializers/cookie_rotation.rb @department-of-veterans-affairs/va-api-engineers @department-of-veterans-affairs/backend-review-group

.rubocop.yml

@@ -342,6 +342,12 @@ RSpec/SubjectStub:
 Rails/FilePath:
   EnforcedStyle: arguments
 
+Lint/Debugger:
+  DebuggerMethods:
+    Breakpoint:
+      - Breakpoint.at_receiver
+      - Breakpoint.at_owner
+
 # This one doesn’t always make sense, it’s mostly the swagger,
 # factories and pact provider states — which need a tear_down block regardless
 Lint/EmptyBlock:

config/initializers/breakpoint.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+# Only load `Breakpoint` when its only dependency, `Pry`, is loaded. If
+# `Breakpoint` is ever deemed to have been loaded inappropriately, then the
+# claim ought to instead be that `Pry` was loaded inappropriately. That's what
+# we're expressing here.
+return unless defined?(Pry)
+
+module Breakpoint
+  class << self
+    # Add a breakpoint at the top of an instance's method:
+    #   `Breakpoint.at_receiver(some_instance, :some_instance_method)`
+    #
+    # Add a breakpoint at the top of a class's method:
+    #   `Breakpoint.at_receiver(SomeClass, :some_class_method)`
+    def at_receiver(receiver, name)
+      at_owner(receiver.singleton_class, name)
+    end
+
+    # Add a breakpoint at the top of a method for all of a class's instances:
+    #   `Breakpoint.at_owner(SomeClass, :some_instance_method)`
+    def at_owner(owner, name)
+      owner.is_a?(Module) or
+        raise ArgumentError, 'not an owner'
+
+      mod =
+        Module.new do
+          define_method(name) do |*args, **kwargs, &block|
+            # Now you have access to all the above arguments, plus whatever else
+            # is available in the current environment.
+            binding.pry # rubocop:disable Lint/Debugger
+            super(*args, **kwargs, &block)
+          end
+        end
+
+      owner.prepend(mod)
+    end
+  end
+end
+
+# Install breakpoints wherever you want if you need to investigate a particular
+# instance during the execution of something, or even right here if you already
+# have a handle on the thing you care about, like a class, e.g.:
+# Breakpoint.at_receiver(Blueprinter::Base, :prepare_data)