Optimize attribute checking for :element selector

lib/capybara/selector.rb

@@ -97,7 +97,9 @@ Capybara.add_selector(:link) do
               when true
                 XPath.attr(:href)
               when Regexp
-                nil # needs to be handled in filter
+                regexp_to_substrings(href).map do |str|
+                  XPath.attr(:href).contains(str)
+                end.reduce(&:&)
               else
                 XPath.attr(:href) == href.to_s
               end
@@ -135,13 +137,19 @@ Capybara.add_selector(:link) do
 
   describe_expression_filters do |**options|
     desc = +''
-    desc << " with href #{options[:href].inspect}" if options[:href] && !options[:href].is_a?(Regexp)
+    if (href = options[:href])
+      if !href.is_a?(Regexp)
+        desc << " with href #{href.inspect}"
+      elsif regexp_to_substrings(href).any?
+        desc << " with href matching #{href.inspect}"
+      end
+    end
     desc << ' with no href attribute' if options.fetch(:href, true).nil?
     desc
   end
 
   describe_node_filters do |href: nil, **|
-    " with href matching #{href.inspect}" if href.is_a? Regexp
+    " with href matching #{href.inspect}" if href.is_a?(Regexp) && regexp_to_substrings(href).empty?
   end
 end
 
@@ -477,7 +485,9 @@ Capybara.add_selector(:element) do
   expression_filter(:attributes, matcher: /.+/) do |xpath, name, val|
     case val
     when Regexp
-      xpath
+      regexp_to_substrings(val).inject(xpath) do |xp, str|
+        xp[XPath.attr(name).contains(str)]
+      end
     when true
       xpath[XPath.attr(name)]
     when false

lib/capybara/selector/selector.rb

@@ -444,6 +444,25 @@ module Capybara
     def find_by_class_attr(classes)
       Array(classes).map { |klass| XPath.attr(:class).contains_word(klass) }.reduce(:&)
     end
+
+    def regexp_to_substrings(regexp)
+      return [] unless regexp.options.zero?
+
+      regexp.source.match(CONVERTIBLE_REGEXP) do |match|
+        match.captures.reject(&:empty?)
+      end || []
+    end
+
+    CONVERTIBLE_REGEXP = /
+      \A
+        \^?                   # start
+        ([^\[\]\\^$.|?*+()]*) # leading literal characters
+        [^|]*?                # do not try to convert expressions with alternates
+        (?<!\\)               # skip metacharacters - ie has preceding slash
+        ([^\[\]\\^$.|?*+()]*) # trailing literal characters
+        \$?                   # end
+      \z
+    /x
   end
 end
 

lib/capybara/spec/session/node_wrapper_spec.rb

@@ -34,6 +34,6 @@ Capybara::SpecHelper.spec '#to_capybara_node' do
     end.to raise_error(/^expected to find css "#second" within #<Capybara::Node::Element/)
     expect do
       expect(para).to have_link(href: %r{/without_simple_html})
-    end.to raise_error(%r{^expected to find visible link nil with href matching /\\/without_simple_html/ within #<Capybara::Node::Element})
+    end.to raise_error(%r{^expected to find link nil with href matching /\\/without_simple_html/ within #<Capybara::Node::Element})
   end
 end

spec/selector_spec.rb

@@ -257,6 +257,16 @@ RSpec.describe Capybara do
           expect(string.find(:element, 'input', type: 'submit').value).to eq 'click me'
         end
 
+        it 'supports regexp matching' do
+          expect(string.find(:element, 'input', type: /sub/).value).to eq 'click me'
+          expect(string.find(:element, 'input', title: /sub\w.*button/).value).to eq 'click me'
+          expect(string.find(:element, 'input', title: /sub.* b.*ton/).value).to eq 'click me'
+          expect(string.find(:element, 'input', title: /sub.*mit.*/).value).to eq 'click me'
+          expect(string.find(:element, 'input', title: /^submit button$/).value).to eq 'click me'
+          expect(string.find(:element, 'input', title: /^(?:submit|other) button$/).value).to eq 'click me'
+          expect(string.find(:element, 'input', title: /SuBmIt/i).value).to eq 'click me'
+        end
+
         it 'still works with system keys' do
           expect { string.all(:element, 'input', type: 'submit', count: 1) }.not_to raise_error
         end