resolves #2622 raise clearer exception when extension class cannot be resolved (PR #2623)

- split impl of class_for_name by Ruby version
- add tests to verify correct error message is thrown when passed an illegal constant name
- add tests to verify top-level class is not resolved when namespaced class is requested

2 files changed, 68 insertions, 9 deletions

diff --git a/lib/asciidoctor/extensions.rb b/lib/asciidoctor/extensions.rb
index 4e9b34d8..acb8988e 100644
--- a/lib/asciidoctor/extensions.rb
+++ b/lib/asciidoctor/extensions.rb
@@ -1481,17 +1481,36 @@ module Extensions
     # Public: Resolves the Class object for the qualified name.
     #
     # Returns Class
-    def class_for_name qualified_name
-      resolved = ::Object
-      (qualified_name.split '::').each do |name|
-        unless name.empty? || ((resolved.const_defined? name) && ::Module === (resolved = resolved.const_get name))
-          raise ::NameError, %(Could not resolve class for name: #{qualified_name})
+    if RUBY_MIN_VERSION_2
+      def class_for_name qualified_name
+        resolved = ::Object.const_get qualified_name, false
+        raise unless ::Class === resolved
+        resolved
+      rescue
+        raise ::NameError, %(Could not resolve class for name: #{qualified_name})
+      end
+    elsif RUBY_MIN_VERSION_1_9
+      def class_for_name qualified_name
+        resolved = (qualified_name.split '::').reduce ::Object do |current, name|
+          name.empty? ? current : (current.const_get name, false)
+        end
+        raise unless ::Class === resolved
+        resolved
+      rescue
+        raise ::NameError, %(Could not resolve class for name: #{qualified_name})
+      end
+    else
+      def class_for_name qualified_name
+        resolved = (qualified_name.split '::').reduce ::Object do |current, name|
+          # NOTE on Ruby 1.8, const_defined? only checks for constant in current scope
+          name.empty? ? current : ((current.const_defined? name) ? (current.const_get name) : raise)
         end
+        raise unless ::Class === resolved
+        resolved
+      rescue
+        raise ::NameError, %(Could not resolve class for name: #{qualified_name})
       end
-      raise ::NameError, %(Could not resolve class for name: #{qualified_name}) unless ::Class === resolved
-      resolved
     end
   end
-
 end
 end
diff --git a/test/extensions_test.rb b/test/extensions_test.rb
index b4f3d51e..c2d3ea6a 100644
--- a/test/extensions_test.rb
+++ b/test/extensions_test.rb
@@ -340,6 +340,24 @@ context 'Extensions' do
       end
     end
 
+    test 'should raise exception if constant name is invalid' do
+      begin
+        Asciidoctor::Extensions.class_for_name 'foobar'
+        flunk 'Expecting RuntimeError to be raised'
+      rescue NameError => e
+        assert_equal 'Could not resolve class for name: foobar', e.message
+      end
+    end
+
+    test 'should raise exception if class not found in scope' do
+      begin
+        Asciidoctor::Extensions.class_for_name 'Asciidoctor::Extensions::String'
+        flunk 'Expecting RuntimeError to be raised'
+      rescue NameError => e
+        assert_equal 'Could not resolve class for name: Asciidoctor::Extensions::String', e.message
+      end
+    end
+
     test 'should raise exception if name resolves to module' do
       begin
         Asciidoctor::Extensions.class_for_name 'Asciidoctor::Extensions'
@@ -361,6 +379,29 @@ context 'Extensions' do
       assert_equal Asciidoctor::Document, clazz
     end
 
+    test 'should not resolve class if not in scope' do
+      begin
+        Asciidoctor::Extensions.resolve_class 'Asciidoctor::Extensions::String'
+        flunk 'Expecting RuntimeError to be raised'
+      rescue NameError => e
+        assert_equal 'Could not resolve class for name: Asciidoctor::Extensions::String', e.message
+      end
+    end
+
+    test 'should raise NameError if extension class cannot be resolved from string' do
+      begin
+        Asciidoctor::Extensions.register do
+          block 'foobar'
+        end
+        doc = empty_document
+        flunk 'Expecting RuntimeError to be raised'
+      rescue NameError => e
+        assert_equal 'Could not resolve class for name: foobar', e.message
+      ensure
+        Asciidoctor::Extensions.unregister_all
+      end
+    end
+
     test 'should allow standalone registry to be created but not registered' do
       registry = Asciidoctor::Extensions.create 'sample' do
         block do
@@ -1197,7 +1238,6 @@ sample content
       end
     end
 
-
     test 'should add multiple docinfo to document' do
       input = <<-EOS
 = Document Title