gjtorikian · gjtorikian · Jun 16, 2019 · Mar 14, 2019 · Mar 14, 2019 · Mar 14, 2019
diff --git a/README.md b/README.md
@@ -78,6 +78,19 @@ Below is mostly comprehensive list of checks that HTMLProofer can perform.
 
 You can configure HTMLProofer to run on a file, a directory, an array of directories, or an array of links.
 
+There's also a rack middleware.
+
+### Using in a rails app
+
+Add to `config/application.rb`
+
+    config.middleware.use HTMLProofer::Middleware if Rails.env.test?
+    config.middleware.use HTMLProofer::Middleware if Rails.env.development?
+
+This will raise an error at runtime if your HTML is invalid.
+
+Particularly helpful for projects which have extensive CI, since any invalid HTML will fail your build.
+
 ### Using in a script
 
 1. Require the gem.

diff --git a/lib/html-proofer/middleware.rb b/lib/html-proofer/middleware.rb
@@ -0,0 +1,80 @@
+
+
+module HTMLProofer
+  class Middleware
+
+    class InvalidHtmlError < StandardError
+      def initialize(failures)
+        @failures = failures
+      end
+
+      def message
+          "HTML Validation errors (skip by adding ?SKIP_VALIDATION to URL): \n#{@failures.join("\n")}"
+      end
+    end
+
+    def self.options
+      @options ||= {
+        type:                :file,
+        allow_missing_href:  true, # Permitted in html5
+        allow_hash_href:     true,
+        check_external_hash: true,
+        check_html:          true,
+        url_ignore:          [/.*/], # Don't try to check local files exist
+      }
+    end
+
+    def initialize(app)
+      @app = app
+    end
+
+    HTML_SIGNATURE = [
+      '<!DOCTYPE HTML',
+      '<HTML',
+      '<HEAD',
+      '<SCRIPT',
+      '<IFRAME',
+      '<H1',
+      '<DIV',
+      '<FONT',
+      '<TABLE',
+      '<A',
+      '<STYLE',
+      '<TITLE',
+      '<B',
+      '<BODY',
+      '<BR',
+      '<P',
+      '<!--'
+    ]
+
+    def call(env)
+      result = @app.call(env)
+      return result if env['REQUEST_METHOD'] != 'GET'
+      return result if env['QUERY_STRING'] =~ /SKIP_VALIDATION/
+      return result if result.first != 200
+      body = []
+      result.last.each { |e| body << e }
+
+      body = body.join('')
+      begin
+        html = body.lstrip
+      rescue
+        return result # Invalid encoding; it's not gonna be html.
+      end
+      if HTML_SIGNATURE.any? { |sig| html.upcase.starts_with? sig }
+        parsed = HTMLProofer::Runner.new(
+          'response',
+          Middleware.options
+        ).check_parsed(
+          Nokogiri::HTML(Utils.clean_content(html)), 'response'
+        )
+
+        if parsed[:failures].length > 0
+          raise InvalidHtmlError.new(parsed[:failures])
+        end
+      end
+      result
+    end
+  end
+end
diff --git a/lib/html-proofer/runner.rb b/lib/html-proofer/runner.rb
@@ -90,9 +90,8 @@ def process_files
       end
     end
 
-    def check_path(path)
+    def check_parsed(html, path)
       result = { external_urls: {}, failures: [] }
-      html = create_nokogiri(path)
 
       @src = [@src] if @type == :file
 
@@ -112,6 +111,10 @@ def check_path(path)
       result
     end
 
+    def check_path(path)
+      check_parsed create_nokogiri(path), path
+    end
+
     def validate_urls
       url_validator = HTMLProofer::UrlValidator.new(@logger, @external_urls, @options)
       @failures.concat(url_validator.run)

diff --git a/...nks/integrity_and_cors_pagination_rels_html_check_sri_true_log_level_error_type_file_.yml b/...nks/integrity_and_cors_pagination_rels_html_check_sri_true_log_level_error_type_file_.yml
diff --git a/spec/html-proofer/middleware_spec.rb b/spec/html-proofer/middleware_spec.rb
@@ -0,0 +1,33 @@
+require 'spec_helper'
+
+describe 'Middleware test' do
+  let(:request) { {'REQUEST_METHOD' => 'GET'} }
+  let(:response) { File.open(response_fixture) }
+  let(:app) { Proc.new { |*args| [200, {}, response] } }
+  let(:middleware) { HTMLProofer::Middleware.new(app) }
+  subject { middleware.call(request) }
+
+  context 'with invalid HTML' do
+    let(:response_fixture) { File.join(FIXTURES_DIR, 'html', 'missing_closing_quotes.html') }
+    it 'raises an error' do
+      expect {
+        subject
+      }.to raise_error(HTMLProofer::Middleware::InvalidHtmlError)
+    end
+  end
+
+  context 'with valid HTML' do
+    let(:response_fixture) { File.join(FIXTURES_DIR, 'html', 'html5_tags.html') }
+    it 'does not raise an error' do
+      subject
+    end
+  end
+
+  context 'with non-HTML content' do
+    let(:response_fixture) { File.join(FIXTURES_DIR, 'images', 'gpl.png') }
+    it 'does not raise an error' do
+      subject
+    end
+  end
+
+end