From fe1de82a44c10436aa208b2843e2d4cdea750b7c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Janosch=20Mu=CC=88ller?= <janosch84@gmail.com>
Date: Thu, 7 Nov 2024 12:46:24 +0100
Subject: [PATCH] Add RouteFinder

---
 lib/taro/export/open_api_v3.rb            |  2 +-
 lib/taro/rails.rb                         |  5 +++
 lib/taro/rails/active_definitions.rb      |  6 +--
 lib/taro/rails/definition.rb              |  8 +++-
 lib/taro/rails/definition_buffer.rb       | 16 ++++++-
 lib/taro/rails/param_parsing.rb           |  8 ++--
 lib/taro/rails/railtie.rb                 |  6 ++-
 lib/taro/rails/route_finder.rb            | 54 +++++++++++++++++++++++
 lib/taro/types/field.rb                   |  1 -
 spec/spec_helper.rb                       |  5 +++
 spec/support/stub_rails.rb                | 24 ++++++++++
 spec/taro/rails/definition_buffer_spec.rb | 12 +++++
 spec/taro/rails/definition_spec.rb        |  8 ++++
 spec/taro/rails/integration_spec.rb       |  4 +-
 spec/taro/rails/param_parsing_spec.rb     |  4 +-
 spec/taro/rails/route_finder_spec.rb      | 35 +++++++++++++++
 16 files changed, 182 insertions(+), 16 deletions(-)
 create mode 100644 lib/taro/rails/route_finder.rb
 create mode 100644 spec/support/stub_rails.rb
 create mode 100644 spec/taro/rails/definition_buffer_spec.rb
 create mode 100644 spec/taro/rails/route_finder_spec.rb

diff --git a/lib/taro/export/open_api_v3.rb b/lib/taro/export/open_api_v3.rb
index 6679b3f..14b8743 100644
--- a/lib/taro/export/open_api_v3.rb
+++ b/lib/taro/export/open_api_v3.rb
@@ -3,7 +3,7 @@ class Taro::Export::OpenAPIv3
 
   # TODO:
   # - accept Taro::Rails.definitions as an argument
-  # - get routes, params, status codes, responses etc. from each Definition
+  # - get routes (#openapi_paths), params, status codes, responses etc. from each Definition
   # - use methods below to render their details
   # - support list/array type
   # - use json-schema gem to validate overall result against OpenAPIv3 schema
diff --git a/lib/taro/rails.rb b/lib/taro/rails.rb
index 0082b43..43b8fa3 100644
--- a/lib/taro/rails.rb
+++ b/lib/taro/rails.rb
@@ -7,4 +7,9 @@ module Taro::Rails
 
   extend ActiveDefinitions
   extend DefinitionBuffer
+
+  def self.reset
+    definitions.clear
+    RouteFinder.clear_cache
+  end
 end
diff --git a/lib/taro/rails/active_definitions.rb b/lib/taro/rails/active_definitions.rb
index 1810bb4..2154b84 100644
--- a/lib/taro/rails/active_definitions.rb
+++ b/lib/taro/rails/active_definitions.rb
@@ -1,7 +1,7 @@
 module Taro::Rails::ActiveDefinitions
-  def apply(definition:, controller_class:, method_name:)
-    (definitions[controller_class] ||= {})[method_name] = definition
-    Taro::Rails::ParamParsing.install(controller_class:, method_name:)
+  def apply(definition:, controller_class:, action_name:)
+    (definitions[controller_class] ||= {})[action_name] = definition
+    Taro::Rails::ParamParsing.install(controller_class:, action_name:)
   end
 
   def definitions
diff --git a/lib/taro/rails/definition.rb b/lib/taro/rails/definition.rb
index 9a9f6ba..535f855 100644
--- a/lib/taro/rails/definition.rb
+++ b/lib/taro/rails/definition.rb
@@ -1,4 +1,4 @@
-Taro::Rails::Definition = Struct.new(:api, :accepts, :returns) do
+Taro::Rails::Definition = Struct.new(:api, :accepts, :returns, :routes) do
   def accepts=(type)
     validated_type = Taro::Types::CoerceToType.call(type)
     self[:accepts] = validated_type
@@ -17,6 +17,12 @@ def parse_params(params)
     accepts.new(hash).coerce_input
   end
 
+  def openapi_paths
+    routes.to_a.map do |route|
+      route.path.spec.to_s.gsub(/:(\w+)/, '{\1}').gsub('(.:format)', '')
+    end
+  end
+
   require 'rack'
   def self.coerce_status_to_int(status)
     # support using http status numbers directly
diff --git a/lib/taro/rails/definition_buffer.rb b/lib/taro/rails/definition_buffer.rb
index 928eb42..3da9c49 100644
--- a/lib/taro/rails/definition_buffer.rb
+++ b/lib/taro/rails/definition_buffer.rb
@@ -9,14 +9,26 @@ def buffered_definitions
     @buffered_definitions ||= {}
   end
 
-  def apply_buffered_definition(controller_class, method_name)
+  def apply_buffered_definition(controller_class, action_name)
     definition = pop_buffered_definition(controller_class)
     return unless definition
 
-    Taro::Rails.apply(definition:, controller_class:, method_name:)
+    routes = Taro::Rails::RouteFinder.call(controller_class:, action_name:)
+    routes.any? || raise_missing_route(controller_class, action_name)
+
+    definition.routes = routes
+    Taro::Rails.apply(definition:, controller_class:, action_name:)
   end
 
   def pop_buffered_definition(controller_class)
     buffered_definitions.delete(controller_class)
   end
+
+  def raise_missing_route(controller_class, action_name)
+    raise Taro::Error, <<~MSG
+      Found no route that points to #{controller_class}##{action_name}.
+      This might be a bug in Taro. If you really don't have a route
+      for this action, we recommend you comment out the api declaration.
+    MSG
+  end
 end
diff --git a/lib/taro/rails/param_parsing.rb b/lib/taro/rails/param_parsing.rb
index 323a6e2..c129115 100644
--- a/lib/taro/rails/param_parsing.rb
+++ b/lib/taro/rails/param_parsing.rb
@@ -1,14 +1,14 @@
 module Taro::Rails::ParamParsing
-  def self.install(controller_class:, method_name:)
+  def self.install(controller_class:, action_name:)
     return unless Taro.config.parse_params
 
-    key = [controller_class, method_name]
+    key = [controller_class, action_name]
     return if installed[key]
 
     installed[key] = true
 
-    controller_class.before_action(only: method_name) do
-      definition = Taro::Rails.definitions[controller_class][method_name]
+    controller_class.before_action(only: action_name) do
+      definition = Taro::Rails.definitions[controller_class][action_name]
       @api_params = definition.parse_params(params)
     end
   end
diff --git a/lib/taro/rails/railtie.rb b/lib/taro/rails/railtie.rb
index 2a75160..568d376 100644
--- a/lib/taro/rails/railtie.rb
+++ b/lib/taro/rails/railtie.rb
@@ -1,7 +1,11 @@
 class Taro::Rails::Railtie < ::Rails::Railtie
-  initializer("taro") do |_app|
+  initializer("taro") do |app|
     ActiveSupport.on_load(:action_controller_base) do
       ActionController::Base.prepend(Taro::Rails::ControllerExtension)
     end
+
+    app.reloader.to_prepare do
+      Taro::Rails.reset
+    end
   end
 end
diff --git a/lib/taro/rails/route_finder.rb b/lib/taro/rails/route_finder.rb
new file mode 100644
index 0000000..c59cc68
--- /dev/null
+++ b/lib/taro/rails/route_finder.rb
@@ -0,0 +1,54 @@
+module Taro::Rails::RouteFinder
+  class << self
+    def call(controller_class:, action_name:)
+      cache["#{controller_class.controller_path}##{action_name}"] || []
+    end
+
+    def clear_cache
+      @cache = nil
+    end
+
+    private
+
+    def cache
+      @cache ||= build_cache
+    end
+
+    def build_cache
+      # Build a Hash like
+      # { { controller: 'users', action: 'show', verb: 'GET' } => #<Route> }
+      routes_by_attributes = map_routes_by_attributes
+
+      # Rails has both PATCH and PUT routes for updates. We only need one copy.
+      routes_by_attributes.reject! do |attrs, _route|
+        attrs[:verb] == 'PATCH' && routes_by_attributes[attrs.merge(verb: 'PUT')]
+      end
+
+      # Build a Hash like
+      # { 'users#show' } => [#<Route>, #<Route>] }
+      routes_by_attributes.each_with_object({}) do |(attrs, route), map|
+        (map["#{attrs[:controller]}##{attrs[:action]}"] ||= []) << route
+      end
+    end
+
+    def map_routes_by_attributes
+      routes.each_with_object({}) do |route, map|
+        # Route#verb is a String. Its usually something like 'POST', but manual
+        # matched routes may have e.g. 'GET|POST' (🤢). We only need one copy.
+        verb = route.verb.to_s.scan(/\w+/).sort.last
+        next unless verb
+
+        # The #requirements Hash contains :controller (an underscored
+        # controller name) and :action (the action name as String, e.g. 'show').
+        attrs = route.requirements.slice(:controller, :action).merge(verb:)
+        map[attrs] = route
+      end
+    end
+
+    def routes
+      # make sure routes are loaded
+      Rails.application.reload_routes! unless Rails.application.routes.routes.any?
+      Rails.application.routes.routes
+    end
+  end
+end
diff --git a/lib/taro/types/field.rb b/lib/taro/types/field.rb
index 21bf759..d04812d 100644
--- a/lib/taro/types/field.rb
+++ b/lib/taro/types/field.rb
@@ -88,4 +88,3 @@ def raise_coercion_error(object)
     MSG
   end
 end
-Taro::Types::Field::NOT_GIVEN = Object.new
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index e40278b..8ace091 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,4 +1,5 @@
 require_relative "support/coverage"
+require_relative "support/stub_rails"
 require "rails"
 require "taro"
 require "debug"
@@ -15,4 +16,8 @@
   config.expect_with :rspec do |c|
     c.syntax = :expect
   end
+
+  config.before(:each) do
+    Taro::Rails.reset
+  end
 end
diff --git a/spec/support/stub_rails.rb b/spec/support/stub_rails.rb
new file mode 100644
index 0000000..193965c
--- /dev/null
+++ b/spec/support/stub_rails.rb
@@ -0,0 +1,24 @@
+def stub_rails(with_routes: [])
+  rails = Module.new { def self.name = 'Rails' }
+  application = instance_double(
+    Rails::Application,
+    env_config: {},
+    reloader: ActiveSupport::Reloader,
+    reload_routes!: true,
+    routes: instance_double(ActionDispatch::Routing::RouteSet, routes: with_routes),
+  )
+  rails.define_singleton_method(:application) { application }
+  stub_const('Rails', rails)
+end
+
+def mock_user_route(verb: 'GET')
+  instance_double(
+    ActionDispatch::Journey::Route,
+    path: instance_double(
+      ActionDispatch::Journey::Path::Pattern,
+      spec: instance_double(ActionDispatch::Journey::Nodes::Cat, to_s: '/users/:id'),
+    ),
+    requirements: { controller: 'users', action: 'show' },
+    verb:,
+  )
+end
diff --git a/spec/taro/rails/definition_buffer_spec.rb b/spec/taro/rails/definition_buffer_spec.rb
new file mode 100644
index 0000000..4090352
--- /dev/null
+++ b/spec/taro/rails/definition_buffer_spec.rb
@@ -0,0 +1,12 @@
+describe Taro::Rails::DefinitionBuffer do
+  it 'raises if an endpoint has a definition but no route pointing to it' do
+    buffer = Object.extend(described_class)
+    controller_class = :dummy
+    buffer.buffered_definition(controller_class)
+    allow(Taro::Rails::RouteFinder).to receive(:call).and_return([])
+
+    expect do
+      buffer.apply_buffered_definition(controller_class, :create)
+    end.to raise_error(Taro::Error, /route.*dummy#create/i)
+  end
+end
diff --git a/spec/taro/rails/definition_spec.rb b/spec/taro/rails/definition_spec.rb
index 15dd6ca..1017977 100644
--- a/spec/taro/rails/definition_spec.rb
+++ b/spec/taro/rails/definition_spec.rb
@@ -38,6 +38,14 @@
     end
   end
 
+  describe '#openapi_paths' do
+    it 'returns the paths of the routes in an openapi compatible format' do
+      definition = described_class.new
+      definition.routes = [mock_user_route]
+      expect(definition.openapi_paths).to eq(['/users/{id}'])
+    end
+  end
+
   require 'action_controller'
 
   describe '#parse_params' do
diff --git a/spec/taro/rails/integration_spec.rb b/spec/taro/rails/integration_spec.rb
index 0312a30..6d7e145 100644
--- a/spec/taro/rails/integration_spec.rb
+++ b/spec/taro/rails/integration_spec.rb
@@ -5,8 +5,10 @@
 describe 'Rails integration' do
   it 'works' do
     # fake railtie and action controller loading
-    Taro::Rails::Railtie.initializers.each(&:run)
+    stub_rails(with_routes: [mock_user_route])
+    Taro::Rails::Railtie.initializers.each { |i| i.run(Rails.application) }
     ActiveSupport.run_load_hooks(:action_controller_base, nil)
+    Rails.application.reloader.prepare!
 
     input_type = Class.new(Taro::Types::InputType)
     input_type.define_singleton_method(:name) { 'UserInputType' }
diff --git a/spec/taro/rails/param_parsing_spec.rb b/spec/taro/rails/param_parsing_spec.rb
index 7039432..322b042 100644
--- a/spec/taro/rails/param_parsing_spec.rb
+++ b/spec/taro/rails/param_parsing_spec.rb
@@ -3,7 +3,7 @@
     controller_class = Class.new
     controller_class.define_singleton_method(:before_action) { |*| nil }
     expect(controller_class).to receive(:before_action).once
-    2.times { described_class.install(controller_class:, method_name: :index) }
+    2.times { described_class.install(controller_class:, action_name: :index) }
   end
 
   it 'does not install the before_action if param parsing is disabled' do
@@ -13,7 +13,7 @@
     controller_class = Class.new
     controller_class.define_singleton_method(:before_action) { |*| nil }
     expect(controller_class).not_to receive(:before_action)
-    described_class.install(controller_class:, method_name: :index)
+    described_class.install(controller_class:, action_name: :index)
   ensure
     Taro.config.parse_params = orig
   end
diff --git a/spec/taro/rails/route_finder_spec.rb b/spec/taro/rails/route_finder_spec.rb
new file mode 100644
index 0000000..a2cdd18
--- /dev/null
+++ b/spec/taro/rails/route_finder_spec.rb
@@ -0,0 +1,35 @@
+require 'action_controller'
+
+describe Taro::Rails::RouteFinder do
+  let(:controller_class) { instance_double(ActionController::Base, controller_path: 'users') }
+
+  it 'returns matching routes' do
+    route = mock_user_route
+    allow(described_class).to receive(:routes).and_return([route])
+    expect(described_class.call(controller_class:, action_name: 'show')).to eq([route])
+  end
+
+  it 'returns an empty Array when no routes are found' do
+    allow(described_class).to receive(:routes).and_return([])
+    expect(described_class.call(controller_class:, action_name: 'show')).to eq([])
+  end
+
+  it 'ignores routes without verb' do
+    allow(described_class).to receive(:routes).and_return([mock_user_route(verb: nil)])
+    expect(described_class.send(:build_cache)).to be_empty
+  end
+
+  describe '::routes' do
+    it 'loads the routes if needed' do
+      stub_rails
+      expect(Rails.application).to receive(:reload_routes!)
+      described_class.send(:routes)
+    end
+
+    it 'does not load the routes if they are already loaded' do
+      stub_rails(with_routes: [:some_route])
+      expect(Rails.application).not_to receive(:reload_routes!)
+      described_class.send(:routes)
+    end
+  end
+end