resolves asciidoctor#4244 extract the require logic of the OpenURI li…

…brary

lib/asciidoctor/abstract_node.rb

@@ -400,15 +400,7 @@ def generate_data_uri target_image, asset_dir_key = nil
   # Returns A data URI string built from Base64 encoded data read from the URI
   # and the mime type specified in the Content Type header.
   def generate_data_uri_from_uri image_uri, cache_uri = false
-    if cache_uri
-      # caching requires the open-uri-cached gem to be installed
-      # processing will be automatically aborted if these libraries can't be opened
-      Helpers.require_library 'open-uri/cached', 'open-uri-cached'
-    elsif !RUBY_ENGINE_OPAL
-      # autoload open-uri
-      ::OpenURI
-    end
-
+    Helpers.require_open_uri cache_uri
     begin
       mimetype, bindata = ::OpenURI.open_uri(image_uri, URI_READ_MODE) {|f| [f.content_type, f.read] }
       # NOTE base64 is autoloaded by reference to ::Base64

lib/asciidoctor/helpers.rb

@@ -300,5 +300,21 @@ def class_for_name qualified_name
   rescue
     raise ::NameError, %(Could not resolve class for name: #{qualified_name})
   end
+
+  # Internal: Require the OpenURI library.
+  #
+  # Attempts to load `open-uri-cached` if the cache argument is true otherwise autoload `open-uri`.
+  #
+  # cache - A Boolean flag indicating whether to activate content cache URI
+  def require_open_uri cache = false
+    if cache
+      # caching requires the open-uri-cached gem to be installed
+      # processing will be automatically aborted if these libraries can't be opened
+      require_library 'open-uri/cached', 'open-uri-cached' unless defined? ::OpenURI::Cache
+    elsif !RUBY_ENGINE_OPAL
+      # autoload open-uri
+      ::OpenURI
+    end
+  end
 end
 end

lib/asciidoctor/reader.rb

@@ -1221,14 +1221,7 @@ def resolve_include_path target, attrlist, attributes
     doc = @document
     if (Helpers.uriish? target) || (::String === @dir ? nil : (target = %(#{@dir}/#{target})))
       return replace_next_line %(link:#{target}[#{attrlist}]) unless doc.attr? 'allow-uri-read'
-      if doc.attr? 'cache-uri'
-        # caching requires the open-uri-cached gem to be installed
-        # processing will be automatically aborted if these libraries can't be opened
-        Helpers.require_library 'open-uri/cached', 'open-uri-cached' unless defined? ::OpenURI::Cache
-      elsif !RUBY_ENGINE_OPAL
-        # autoload open-uri
-        ::OpenURI
-      end
+      Helpers.require_open_uri doc.attr?('cache-uri')
       [(::URI.parse target), :uri, target]
     else
       # include file is resolved relative to dir of current include, or base_dir if within original docfile