4 files changed, 58 insertions, 28 deletions
diff --git a/lib/asciidoctor/interdoc_reftext.rb b/lib/asciidoctor/interdoc_reftext.rb
index e1f3389..dc884cb 100644
--- a/lib/asciidoctor/interdoc_reftext.rb
+++ b/lib/asciidoctor/interdoc_reftext.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
-require 'asciidoctor'
-require 'asciidoctor/extensions'
+require 'asciidoctor' unless RUBY_PLATFORM == 'opal'
+require 'asciidoctor/extensions' unless RUBY_PLATFORM == 'opal'
 require 'asciidoctor/interdoc_reftext/version'
 require 'asciidoctor/interdoc_reftext/processor'
 
diff --git a/lib/asciidoctor/interdoc_reftext/inline_node_mixin.rb b/lib/asciidoctor/interdoc_reftext/inline_node_mixin.rb
index f82b7a3..17370b0 100644
--- a/lib/asciidoctor/interdoc_reftext/inline_node_mixin.rb
+++ b/lib/asciidoctor/interdoc_reftext/inline_node_mixin.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
+require 'asciidoctor' unless RUBY_PLATFORM == 'opal'
 require 'asciidoctor/interdoc_reftext/version'
-require 'asciidoctor'
 
 module Asciidoctor::InterdocReftext
   # Mixin intended to be prepended into `Asciidoctor::Inline`.
@@ -10,29 +10,39 @@ module Asciidoctor::InterdocReftext
   # represents an inter-document cross reference).
   module InlineNodeMixin
 
-    # Returns text of this inline element.
-    #
-    # @note This method will override the same name attribute reader in
-    #   class `Asciidoctor::Inline`.
-    #
-    # @return [String, nil]
-    def text
-      if (value = super)
-        value
-      # If this node is an inter-document cross reference...
-      elsif @node_name == 'inline_anchor' && @attributes['path']
-        resolver = interdoc_reftext_resolver
-        @text = resolver.call(@attributes['refid']) if resolver
+    if RUBY_PLATFORM == 'opal'
+      # Opal does not support `Module#prepend`, so we have to fallback to
+      # `include` with poor alias method chain approach.
+      def self.included(base_klass)
+        base_klass.send(:alias_method, :text_without_reftext, :text)
+        base_klass.send(:define_method, :text) do
+          text_without_reftext || interdoc_reftext
+        end
+      end
+    else
+      # Returns text of this inline element.
+      #
+      # @note This method will override the same name attribute reader in
+      #   class `Asciidoctor::Inline`.
+      def text
+        super || interdoc_reftext
       end
     end
 
     private
 
-    # @return [#call, nil] an inter-document reftext resolver, or nil if not
-    #   set for the document.
-    def interdoc_reftext_resolver
+    # Returns resolved reftext of this inline node if it is a valid
+    # inter-document cross-reference, otherwise returns nil.
+    #
+    # @return [String, nil]
+    def interdoc_reftext
+      # If this node is not an inter-document cross reference...
+      return if @node_name != 'inline_anchor' || @attributes['path'].nil?
+
       # This variable is injected into the document by {Processor}.
-      @document.instance_variable_get(Processor::RESOLVER_VAR_NAME)
+      if (resolver = @document.instance_variable_get(Processor::RESOLVER_VAR_NAME))
+        @text = resolver.call(@attributes['refid'])
+      end
     end
   end
 end
diff --git a/lib/asciidoctor/interdoc_reftext/processor.rb b/lib/asciidoctor/interdoc_reftext/processor.rb
index 0fa69fb..724a154 100644
--- a/lib/asciidoctor/interdoc_reftext/processor.rb
+++ b/lib/asciidoctor/interdoc_reftext/processor.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
-require 'asciidoctor'
-require 'asciidoctor/extensions'
+require 'asciidoctor' unless RUBY_PLATFORM == 'opal'
+require 'asciidoctor/extensions' unless RUBY_PLATFORM == 'opal'
 require 'asciidoctor/interdoc_reftext/inline_node_mixin'
 require 'asciidoctor/interdoc_reftext/resolver'
 require 'asciidoctor/interdoc_reftext/version'
@@ -34,7 +34,7 @@ module Asciidoctor::InterdocReftext
   #
   # Eh, this is really nasty... The least evil way how to achieve the goal
   # seems to be monkey-patching of the `Asciidoctor::Inline` class. This is
-  # done via {InlineNodeMixin} which is prepended into the `Inline` class on
+  # done via {InlineNodeMixin} which is prepended* into the `Inline` class on
   # initialization of this processor.
   #
   # The actual logic that resolves reflabel for the given *refid* is
@@ -43,11 +43,16 @@ module Asciidoctor::InterdocReftext
   # it into instance variable {RESOLVER_VAR_NAME} in the document, so
   # {InlineNodeMixin} can access it.
   #
-  # Prepending {InlineNodeMixin} into the `Asciidoctor::Inline` class has
+  # Prepending* {InlineNodeMixin} into the `Asciidoctor::Inline` class has
   # (obviously) a global effect. However, if {RESOLVER_VAR_NAME} is not
   # injected in the document object (e.g. extension is not active), `Inline`
   # behaves the same as without {InlineNodeMixin}.
   #
+  # _\* If running under Opal (JavaScript), {InlineNodeMixin} is not prepended
+  # into the `Asciidoctor::Inline`, because Opal does not support that. Thus
+  # it's included and the `#text` method is overriden using poor alias method
+  # chain approach.
+  #
   # NOTE: We use _reftext_ and _reflabel_ as interchangeable terms in this gem.
   class Processor < ::Asciidoctor::Extensions::TreeProcessor
 
@@ -65,7 +70,13 @@ module Asciidoctor::InterdocReftext
 
       # Monkey-patch Asciidoctor::Inline unless already patched.
       unless ::Asciidoctor::Inline.include? InlineNodeMixin
-        ::Asciidoctor::Inline.send(:prepend, InlineNodeMixin)
+        if RUBY_PLATFORM == 'opal'
+          # Opal does not support `Module#prepend`, so we have to fallback to
+          # `include` with poor alias method chain approach.
+          ::Asciidoctor::Inline.send(:include, InlineNodeMixin)
+        else
+          ::Asciidoctor::Inline.send(:prepend, InlineNodeMixin)
+        end
       end
     end
 
diff --git a/lib/asciidoctor/interdoc_reftext/resolver.rb b/lib/asciidoctor/interdoc_reftext/resolver.rb
index e4a8eef..0f9a7c1 100644
--- a/lib/asciidoctor/interdoc_reftext/resolver.rb
+++ b/lib/asciidoctor/interdoc_reftext/resolver.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
+require 'asciidoctor' unless RUBY_PLATFORM == 'opal'
+require 'logger' unless RUBY_PLATFORM == 'opal'
 require 'asciidoctor/interdoc_reftext/version'
-require 'asciidoctor'
-require 'logger'
 
 module Asciidoctor::InterdocReftext
   # Resolver of inter-document cross reference texts.
@@ -20,8 +20,17 @@ module Asciidoctor::InterdocReftext
 
       logger ||= if defined? ::Asciidoctor::LoggerManager
         ::Asciidoctor::LoggerManager.logger
-      else
+      elsif defined? ::Logger
         ::Logger.new(STDERR)
+      else
+        # Fake logger for Opal.
+        # TODO: Remove after update to Asciidoctor 1.5.7 or Opal with Logger.
+        Object.new.tap do |o|
+          # rubocop: disable MethodMissing
+          def o.method_missing(_, *args)
+            STDERR.puts(*args)
+          end
+        end
       end
 
       @document = document