allow the subs argument of apply_subs to be nil

- allow subs argument to be nil
- fix API doc
- split check for nil and empty subs

2 files changed, 12 insertions, 4 deletions

diff --git a/lib/asciidoctor/substitutors.rb b/lib/asciidoctor/substitutors.rb
index 367b9cbc..39776305 100644
--- a/lib/asciidoctor/substitutors.rb
+++ b/lib/asciidoctor/substitutors.rb
@@ -77,12 +77,12 @@ module Substitutors
   # Public: Apply the specified substitutions to the source.
   #
   # source  - The String or String Array of text to process; must not be nil.
-  # subs    - The substitutions to perform; can be a Symbol or Symbol Array; must not be nil (default: :normal).
-  # expand  - A Boolean to control whether substitution aliases are expanded (default: false).
+  # subs    - The substitutions to perform; can be a Symbol, Symbol Array or nil (default: NORMAL_SUBS).
+  # expand  - A Boolean (or nil) to control whether substitution aliases are expanded (default: nil).
   #
   # Returns a String or String Array with substitutions applied, matching the type of source argument.
-  def apply_subs source, subs = NORMAL_SUBS, expand = false
-    if source.empty? || subs.empty?
+  def apply_subs source, subs = NORMAL_SUBS, expand = nil
+    if source.empty? || !subs
       return source
     elsif expand
       if ::Symbol === subs
@@ -101,6 +101,8 @@ module Substitutors
           return source
         end
       end
+    elsif subs.empty?
+      return source
     end
 
     text = (multiline = ::Array === source) ? source * LF : source
diff --git a/test/substitutions_test.rb b/test/substitutions_test.rb
index 3f5e6a75..d10d52fd 100644
--- a/test/substitutions_test.rb
+++ b/test/substitutions_test.rb
@@ -38,6 +38,12 @@ context 'Substitutions' do
       result = para.apply_subs para.lines, [:normal], true
       assert_equal ['Asciidoctor', '<strong>bold</strong>', '2 &gt; 1'], result
     end
+
+    test 'apply_subs should allow the subs argument to be nil' do
+      block = block_from_string %([pass]\n*raw*)
+      result = block.apply_subs block.source, nil
+      assert_equal '*raw*', result
+    end
   end
 
   context 'Quotes' do