resolves #420 don't raise error if Asciidoctor::Extensions.unregister is called before groups are initialized (PR #4271)

3 files changed, 15 insertions, 1 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 0743514a..aa4f590b 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -54,6 +54,7 @@ Improvements::
 
 Bug Fixes::
 
+  * Don't raise error if `Asciidoctor::Extensions.unregister` is called before groups are initialized
   * If path is included both partially and fully, store it with true value (included fully) in includes table of document catalog
   * Reset registry if activate is called on it again (#4256)
   * Format source location in exception message when extension code is malformed
diff --git a/lib/asciidoctor/extensions.rb b/lib/asciidoctor/extensions.rb
index 194b3ea9..3ed02088 100644
--- a/lib/asciidoctor/extensions.rb
+++ b/lib/asciidoctor/extensions.rb
@@ -1531,7 +1531,7 @@ module Extensions
     #
     # Returns nothing
     def unregister *names
-      names.each {|group| @groups.delete group.to_sym }
+      names.each_with_object(groups) {|group, catalog| catalog.delete group.to_sym }
       nil
     end
   end
diff --git a/test/extensions_test.rb b/test/extensions_test.rb
index 8a2632c1..f37ad635 100644
--- a/test/extensions_test.rb
+++ b/test/extensions_test.rb
@@ -345,6 +345,19 @@ context 'Extensions' do
       end
     end
 
+    test 'should not fail to unregister extension group if not registered' do
+      refute_nil Asciidoctor::Extensions.groups
+      assert_equal 0, Asciidoctor::Extensions.groups.size
+      Asciidoctor::Extensions.unregister :sample
+      assert_equal 0, Asciidoctor::Extensions.groups.size
+    end
+
+    test 'should not fail to unregister extension group if extension groups are not initialized' do
+      Asciidoctor::Extensions.remove_instance_variable :@groups
+      Asciidoctor::Extensions.unregister :sample
+      assert_equal 0, Asciidoctor::Extensions.groups.size
+    end
+
     test 'should raise NameError if extension class cannot be resolved from string' do
       begin
         Asciidoctor::Extensions.register do