Add support for validation on resource classess (#56)

```ruby
class Content::Article < Perron::Resource
  validates :title, presence: true
  # or
  # validates :description, length: { in: 1..158 }

  delegate :title, :description, to: :metadata
```

Then validate using `bin/rails perron:validate`. This task can be run in
pre-commit hook or as part of your `bin/ci` script.

Output looks like this:
```bash
 rails perron:validate
FFFFFFFFFF....................
Resource: /Users/e/Tresorit/Code/OSS/perron/site/app/content/resources/faq-component-tailwind.md
  - Name is too short (minimum is 50 characters)
Resource: /Users/e/Tresorit/Code/OSS/perron/site/app/content/resources/indexnow.md
  - Name is too short (minimum is 50 characters)
Resource: /Users/e/Tresorit/Code/OSS/perron/site/app/content/resources/netlify.md
  - Name is too short (minimum is 50 characters)
Resource: /Users/e/Tresorit/Code/OSS/perron/site/app/content/resources/new.md
  - Name is too short (minimum is 50 characters)
```

Author: eelcoj

lib/perron/collection.rb

@@ -16,7 +16,7 @@ def configuration(resource_class = "Content::#{name.classify}".safe_constantize)
     end
 
     def all(resource_class = "Content::#{name.classify}".safe_constantize)
-      @all ||= Dir.glob("#{@collection_path}/**/*.*").map do |file_path|
+      Dir.glob("#{@collection_path}/**/*.*").map do |file_path|
         resource_class.new(file_path)
       end.select(&:published?)
     end
@@ -35,5 +35,7 @@ def find_by_file_name(file_name, resource_class = Resource)
         Perron.configuration.allowed_extensions.lazy.map { File.join(@collection_path, [file_name, it].join(".")) }.find { File.exist?(it) }
       )
     end
+
+    def validate = Perron::Site::Validate.new(collections: [self]).validate
   end
 end

lib/perron/engine.rb

@@ -7,7 +7,8 @@ class Engine < Rails::Engine
     end
 
     rake_tasks do
-      load File.expand_path("../tasks/perron.rake", __FILE__)
+      load File.expand_path("../tasks/build.rake", __FILE__)
+      load File.expand_path("../tasks/validate.rake", __FILE__)
     end
   end
 end

lib/perron/resource.rb

@@ -15,6 +15,8 @@ module Perron
   class Resource
     ID_LENGTH = 8
 
+    include ActiveModel::Validations
+
     include Perron::Resource::Configuration
     include Perron::Resource::Core
     include Perron::Resource::ClassMethods
@@ -24,6 +26,7 @@ class Resource
     attr_reader :file_path, :id
 
     def initialize(file_path)
+      @errors = ActiveModel::Errors.new(self)
       @file_path = file_path
       @id = generate_id
 

lib/perron/site.rb

@@ -1,20 +1,24 @@
 # frozen_string_literal: true
 
-require "perron/site/builder"
 require "perron/collection"
 require "perron/data"
 require "perron/data/proxy"
+require "perron/site/builder"
+require "perron/site/validate"
 
 module Perron
   module Site
     module_function
 
     def build = Perron::Site::Builder.new.build
 
+    def validate = Perron::Site::Validate.new.validate
+
     def collections
-      @collections ||= Dir.children(Perron.configuration.input)
+      Dir.children(Perron.configuration.input)
         .select { File.directory?(File.join(Perron.configuration.input, it)) }
         .reject { it == "data" }
+        .reject { it == "themes" } # TODO: remove me
         .map { Collection.new(it) }
     end
 

lib/perron/site/validate.rb

@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+module Perron
+  module Site
+    class Validate
+      def initialize(collections: Perron::Site.collections)
+        @collections = collections
+        @failures = []
+      end
+
+      def validate
+        @collections.each { validate_collection it }
+
+        [
+          puts,
+          failures_report,
+          puts
+        ].compact_blank.join
+
+        puts [
+          "Validation finished",
+          (" with #{@failures.count} failures" if @failures.any?),
+          "."
+        ].join
+      end
+
+      private
+
+      Failure = ::Data.define(:identifier, :errors)
+
+      GREEN = "\e[32m"
+      RED = "\e[31m"
+      RESET = "\e[0m"
+
+      def validate_collection(collection)
+        collection.resources.each do |resource|
+          resource.validate ? success : failed(resource)
+        end
+      end
+
+      def success = print "#{GREEN}.#{RESET}"
+
+      def failed(resource)
+        print "#{RED}F#{RESET}"
+
+        errors = []
+
+        if resource.respond_to?(:errors) && resource.errors.respond_to?(:full_messages) && resource.errors.any?
+          errors = resource.errors.full_messages
+        end
+
+        @failures << Failure.new(identifier: resource.file_path, errors: errors)
+      end
+
+      def failures_report
+        @failures.each do |failure|
+          puts "Resource: #{failure.identifier}"
+
+          failure.errors.each do |error_message|
+            puts "  - #{error_message}"
+          end
+        end
+      end
+    end
+  end
+end

lib/perron/tasks/perron.rake lib/perron/tasks/build.rakelib/perron/tasks/perron.rake renamed to lib/perron/tasks/build.rake

@@ -0,0 +1,6 @@
+namespace :perron do
+  desc "Validate all site resources"
+  task validate: :environment do
+    Perron::Site.validate
+  end
+end

lib/perron/tasks/validate.rake

@@ -0,0 +1,5 @@
+---
+title: Invalid
+---
+
+This page is missing a description and this should not validate.

test/dummy/app/content/pages/invalid.md

@@ -1,2 +1,5 @@
 class Content::Page < Perron::Resource
+  delegate :title, :description, to: :metadata
+
+  validates :description, presence: true
 end

test/dummy/app/models/content/page.rb

@@ -3,11 +3,13 @@
 class Perron::Site::ResourceTest < ActiveSupport::TestCase
   setup do
     @page_path = "test/dummy/app/content/pages/about.md"
+    @invalid_page = "test/dummy/app/content/pages/invalid.md"
     @post_path = "test/dummy/app/content/posts/2023-05-15-sample-post.md"
     @inline_erb_post_path = "test/dummy/app/content/posts/2025-10-01-inline-erb-post.md"
     @page = Content::Page.new(@page_path)
+    @invalid_page = Content::Page.new(@invalid_page)
     @post = Content::Post.new(@post_path)
-    @inline_erb_post = Content::Post.new(@inline_erb_post_path) # <-- Addition
+    @inline_erb_post = Content::Post.new(@inline_erb_post_path)
   end
 
   test "initialization sets file_path" do
@@ -70,4 +72,30 @@ class Perron::Site::ResourceTest < ActiveSupport::TestCase
   test "#to_partial_path returns the conventional path from a nested logical name" do
     assert_equal "content/posts/post", @post.to_partial_path
   end
+
+  test "#valid? returns true for valid page" do
+    assert_equal @page.valid?, true
+  end
+
+  test "#valid? returns false for invalid page" do
+    assert_equal @invalid_page.valid?, false
+  end
+
+  test "#validate returns true for valid page" do
+    assert_equal @page.validate, true
+  end
+
+  test "#validate returns false for invalid page" do
+    assert_equal @invalid_page.validate, false
+  end
+
+  test "#validate! returns true for valid page" do
+    assert_equal @page.validate!, true
+  end
+
+  test "#validate! returns false for invalid page" do
+    assert_raises(ActiveModel::ValidationError) { @invalid_page.validate! }
+    assert @invalid_page.errors.any?
+    assert_includes @invalid_page.errors.full_messages, "Description can't be blank"
+  end
 end