Date filters should never raise an exception (#5722)

Merge pull request 5722

lib/jekyll/filters.rb

@@ -80,6 +80,7 @@ module Jekyll
     #
     # Returns the formatted String.
     def date_to_long_string(date)
+      return date if date.to_s.empty?
       time(date).strftime("%d %B %Y")
     end
 
@@ -94,6 +95,7 @@ module Jekyll
     #
     # Returns the formatted String.
     def date_to_xmlschema(date)
+      return date if date.to_s.empty?
       time(date).xmlschema
     end
 
@@ -108,6 +110,7 @@ module Jekyll
     #
     # Returns the formatted String.
     def date_to_rfc822(date)
+      return date if date.to_s.empty?
       time(date).rfc822
     end
 

test/test_filters.rb

@@ -284,11 +284,9 @@ class TestFilters < JekyllUnitTest
       end
 
       context "without input" do
-        should "raise an error if input is nil" do
-          err = assert_raises Jekyll::Errors::InvalidDateError do
-            @filter.date_to_xmlschema(nil)
-          end
-          assert_equal "Invalid Date: 'nil' is not a valid datetime.", err.message
+        should "return input" do
+          assert_nil(@filter.date_to_xmlschema(nil))
+          assert_equal("", @filter.date_to_xmlschema(""))
         end
       end
     end