tag_helper.rb

# frozen_string_literal: true

require "active_support/core_ext/string/output_safety"
require "set"

module ActionView
  # = Action View Tag Helpers
  module Helpers #:nodoc:
    # Provides methods to generate HTML tags programmatically both as a modern
    # HTML5 compliant builder style and legacy XHTML compliant tags.
    module TagHelper
      extend ActiveSupport::Concern
      include CaptureHelper
      include OutputSafetyHelper

      BOOLEAN_ATTRIBUTES = %w(allowfullscreen async autofocus autoplay checked
                              compact controls declare default defaultchecked
                              defaultmuted defaultselected defer disabled
                              enabled formnovalidate hidden indeterminate inert
                              ismap itemscope loop multiple muted nohref
                              noresize noshade novalidate nowrap open
                              pauseonexit readonly required reversed scoped
                              seamless selected sortable truespeed typemustmatch
                              visible).to_set

      BOOLEAN_ATTRIBUTES.merge(BOOLEAN_ATTRIBUTES.map(&:to_sym))

      TAG_PREFIXES = ["aria", "data", :aria, :data].to_set

      PRE_CONTENT_STRINGS             = Hash.new { "" }
      PRE_CONTENT_STRINGS[:textarea]  = "\n"
      PRE_CONTENT_STRINGS["textarea"] = "\n"

      class TagBuilder #:nodoc:
        include CaptureHelper
        include OutputSafetyHelper

        VOID_ELEMENTS = %i(area base br col embed hr img input keygen link meta param source track wbr).to_set

        def initialize(view_context)
          @view_context = view_context
        end

        def tag_string(name, content = nil, escape_attributes: true, **options, &block)
          content = @view_context.capture(self, &block) if block_given?
          if VOID_ELEMENTS.include?(name) && content.nil?
            "<#{name.to_s.dasherize}#{tag_options(options, escape_attributes)}>".html_safe
          else
            content_tag_string(name.to_s.dasherize, content || "", options, escape_attributes)
          end
        end

        def content_tag_string(name, content, options, escape = true)
          tag_options = tag_options(options, escape) if options
          content     = ERB::Util.unwrapped_html_escape(content) if escape
          "<#{name}#{tag_options}>#{PRE_CONTENT_STRINGS[name]}#{content}</#{name}>".html_safe
        end

        def tag_options(options, escape = true)
          return if options.blank?
          output = "".dup
          sep    = " "
          options.each_pair do |key, value|
            if TAG_PREFIXES.include?(key) && value.is_a?(Hash)
              value.each_pair do |k, v|
                next if v.nil?
                output << sep
                output << prefix_tag_option(key, k, v, escape)
              end
            elsif BOOLEAN_ATTRIBUTES.include?(key)
              if value
                output << sep
                output << boolean_tag_option(key)
              end
            elsif !value.nil?
              output << sep
              output << tag_option(key, value, escape)
            end
          end
          output unless output.empty?
        end

        def boolean_tag_option(key)
          %(#{key}="#{key}")
        end

        def tag_option(key, value, escape)
          if value.is_a?(Array)
            value = escape ? safe_join(value, " ".freeze) : value.join(" ".freeze)
          else
            value = escape ? ERB::Util.unwrapped_html_escape(value) : value.to_s.dup
          end
          value.gsub!('"'.freeze, '&quot;'.freeze)
          %(#{key}="#{value}")
        end

        private
          def prefix_tag_option(prefix, key, value, escape)
            key = "#{prefix}-#{key.to_s.dasherize}"
            unless value.is_a?(String) || value.is_a?(Symbol) || value.is_a?(BigDecimal)
              value = value.to_json
            end
            tag_option(key, value, escape)
          end

          def respond_to_missing?(*args)
            true
          end

          def method_missing(called, *args, &block)
            tag_string(called, *args, &block)
          end
      end

      # Returns an HTML tag.
      #
      # === Building HTML tags
      #
      # Builds HTML5 compliant tags with a tag proxy. Every tag can be built with:
      #
      #   tag.<tag name>(optional content, options)
      #
      # where tag name can be e.g. br, div, section, article, or any tag really.
      #
      # ==== Passing content
      #
      # Tags can pass content to embed within it:
      #
      #   tag.h1 'All titles fit to print' # => <h1>All titles fit to print</h1>
      #
      #   tag.div tag.p('Hello world!')  # => <div><p>Hello world!</p></div>
      #
      # Content can also be captured with a block, which is useful in templates:
      #
      #   <%= tag.p do %>
      #     The next great American novel starts here.
      #   <% end %>
      #   # => <p>The next great American novel starts here.</p>
      #
      # ==== Options
      #
      # Use symbol keyed options to add attributes to the generated tag.
      #
      #   tag.section class: %w( kitties puppies )
      #   # => <section class="kitties puppies"></section>
      #
      #   tag.section id: dom_id(@post)
      #   # => <section id="<generated dom id>"></section>
      #
      # Pass +true+ for any attributes that can render with no values, like +disabled+ and +readonly+.
      #
      #   tag.input type: 'text', disabled: true
      #   # => <input type="text" disabled="disabled">
      #
      # HTML5 <tt>data-*</tt> attributes can be set with a single +data+ key
      # pointing to a hash of sub-attributes.
      #
      # To play nicely with JavaScript conventions, sub-attributes are dasherized.
      #
      #   tag.article data: { user_id: 123 }
      #   # => <article data-user-id="123"></article>
      #
      # Thus <tt>data-user-id</tt> can be accessed as <tt>dataset.userId</tt>.
      #
      # Data attribute values are encoded to JSON, with the exception of strings, symbols and
      # BigDecimals.
      # This may come in handy when using jQuery's HTML5-aware <tt>.data()</tt>
      # from 1.4.3.
      #
      #   tag.div data: { city_state: %w( Chicago IL ) }
      #   # => <div data-city-state="[&quot;Chicago&quot;,&quot;IL&quot;]"></div>
      #
      # The generated attributes are escaped by default. This can be disabled using
      # +escape_attributes+.
      #
      #   tag.img src: 'open & shut.png'
      #   # => <img src="open &amp; shut.png">
      #
      #   tag.img src: 'open & shut.png', escape_attributes: false
      #   # => <img src="open & shut.png">
      #
      # The tag builder respects
      # {HTML5 void elements}[https://www.w3.org/TR/html5/syntax.html#void-elements]
      # if no content is passed, and omits closing tags for those elements.
      #
      #   # A standard element:
      #   tag.div # => <div></div>
      #
      #   # A void element:
      #   tag.br  # => <br>
      #
      # === Legacy syntax
      #
      # The following format is for legacy syntax support. It will be deprecated in future versions of Rails.
      #
      #   tag(name, options = nil, open = false, escape = true)
      #
      # It returns an empty HTML tag of type +name+ which by default is XHTML
      # compliant. Set +open+ to true to create an open tag compatible
      # with HTML 4.0 and below. Add HTML attributes by passing an attributes
      # hash to +options+. Set +escape+ to false to disable attribute value
      # escaping.
      #
      # ==== Options
      #
      # You can use symbols or strings for the attribute names.
      #
      # Use +true+ with boolean attributes that can render with no value, like
      # +disabled+ and +readonly+.
      #
      # HTML5 <tt>data-*</tt> attributes can be set with a single +data+ key
      # pointing to a hash of sub-attributes.
      #
      # ==== Examples
      #
      #   tag("br")
      #   # => <br />
      #
      #   tag("br", nil, true)
      #   # => <br>
      #
      #   tag("input", type: 'text', disabled: true)
      #   # => <input type="text" disabled="disabled" />
      #
      #   tag("input", type: 'text', class: ["strong", "highlight"])
      #   # => <input class="strong highlight" type="text" />
      #
      #   tag("img", src: "open & shut.png")
      #   # => <img src="open &amp; shut.png" />
      #
      #   tag("img", { src: "open &amp; shut.png" }, false, false)
      #   # => <img src="open &amp; shut.png" />
      #
      #   tag("div", data: { name: 'Stephen', city_state: %w(Chicago IL) })
      #   # => <div data-name="Stephen" data-city-state="[&quot;Chicago&quot;,&quot;IL&quot;]" />
      def tag(name = nil, options = nil, open = false, escape = true)
        if name.nil?
          tag_builder
        else
          "<#{name}#{tag_builder.tag_options(options, escape) if options}#{open ? ">" : " />"}".html_safe
        end
      end

      # Returns an HTML block tag of type +name+ surrounding the +content+. Add
      # HTML attributes by passing an attributes hash to +options+.
      # Instead of passing the content as an argument, you can also use a block
      # in which case, you pass your +options+ as the second parameter.
      # Set escape to false to disable attribute value escaping.
      # Note: this is legacy syntax, see +tag+ method description for details.
      #
      # ==== Options
      # The +options+ hash can be used with attributes with no value like (<tt>disabled</tt> and
      # <tt>readonly</tt>), which you can give a value of true in the +options+ hash. You can use
      # symbols or strings for the attribute names.
      #
      # ==== Examples
      #   content_tag(:p, "Hello world!")
      #    # => <p>Hello world!</p>
      #   content_tag(:div, content_tag(:p, "Hello world!"), class: "strong")
      #    # => <div class="strong"><p>Hello world!</p></div>
      #   content_tag(:div, "Hello world!", class: ["strong", "highlight"])
      #    # => <div class="strong highlight">Hello world!</div>
      #   content_tag("select", options, multiple: true)
      #    # => <select multiple="multiple">...options...</select>
      #
      #   <%= content_tag :div, class: "strong" do -%>
      #     Hello world!
      #   <% end -%>
      #    # => <div class="strong">Hello world!</div>
      def content_tag(name, content_or_options_with_block = nil, options = nil, escape = true, &block)
        if block_given?
          options = content_or_options_with_block if content_or_options_with_block.is_a?(Hash)
          tag_builder.content_tag_string(name, capture(&block), options, escape)
        else
          tag_builder.content_tag_string(name, content_or_options_with_block, options, escape)
        end
      end

      # Returns a CDATA section with the given +content+. CDATA sections
      # are used to escape blocks of text containing characters which would
      # otherwise be recognized as markup. CDATA sections begin with the string
      # <tt><![CDATA[</tt> and end with (and may not contain) the string <tt>]]></tt>.
      #
      #   cdata_section("<hello world>")
      #   # => <![CDATA[<hello world>]]>
      #
      #   cdata_section(File.read("hello_world.txt"))
      #   # => <![CDATA[<hello from a text file]]>
      #
      #   cdata_section("hello]]>world")
      #   # => <![CDATA[hello]]]]><![CDATA[>world]]>
      def cdata_section(content)
        splitted = content.to_s.gsub(/\]\]\>/, "]]]]><![CDATA[>")
        "<![CDATA[#{splitted}]]>".html_safe
      end

      # Returns an escaped version of +html+ without affecting existing escaped entities.
      #
      #   escape_once("1 < 2 &amp; 3")
      #   # => "1 &lt; 2 &amp; 3"
      #
      #   escape_once("&lt;&lt; Accept & Checkout")
      #   # => "&lt;&lt; Accept &amp; Checkout"
      def escape_once(html)
        ERB::Util.html_escape_once(html)
      end

      private
        def tag_builder
          @tag_builder ||= TagBuilder.new(self)
        end
    end
  end
end