let String#strip_heredoc handle blank lines even if they are not indented

activesupport/lib/active_support/core_ext/string/strip.rb

+require 'active_support/core_ext/object/try'
+
 class String
   # Strips indentation in heredocs.
   #
@@ -18,7 +20,7 @@ class String
   # Technically, it looks for the least indented line in the whole string, and removes
   # that amount of leading whitespace.
   def strip_heredoc
-    indent = chomp.scan(/^\s*/).min.size
-    gsub(/^\s{#{indent}}/, '')
+    indent = scan(/^[ \t]*(?=\S)/).min.try(:size) || 0
+    gsub(/^[ \t]{#{indent}}/, '')
   end
-end
\ No newline at end of file
+end

activesupport/test/core_ext/string_ext_test.rb

@@ -33,6 +33,15 @@ def test_strip_heredoc_on_a_regular_indented_heredoc
     EOS
   end
 
+  def test_strip_heredoc_on_a_regular_indented_heredoc_with_blank_lines
+    assert_equal "foo\n  bar\n\nbaz\n", <<-EOS.strip_heredoc
+      foo
+        bar
+
+      baz
+    EOS
+  end
+
   def test_pluralize
     SingularToPlural.each do |singular, plural|
       assert_equal(plural, singular.pluralize)