1 files changed, 43 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/string/indent.rb b/activesupport/lib/active_support/core_ext/string/indent.rb
new file mode 100644
index 0000000000..afc3032272
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/string/indent.rb
@@ -0,0 +1,43 @@
+class String
+  # Same as +indent+, except it indents the receiver in-place.
+  #
+  # Returns the indented string, or +nil+ if there was nothing to indent.
+  def indent!(amount, indent_string=nil, indent_empty_lines=false)
+    indent_string = indent_string || self[/^[ \t]/] || ' '
+    re = indent_empty_lines ? /^/ : /^(?!$)/
+    gsub!(re, indent_string * amount)
+  end
+
+  # Indents the lines in the receiver:
+  #
+  #   <<EOS.indent(2)
+  #   def some_method
+  #     some_code
+  #   end
+  #   EOS
+  #   # =>
+  #     def some_method
+  #       some_code
+  #     end
+  #
+  # The second argument, +indent_string+, specifies which indent string to
+  # use. The default is +nil+, which tells the method to make a guess by
+  # peeking at the first indented line, and fallback to a space if there is
+  # none.
+  #
+  #   "  foo".indent(2)        # => "    foo"
+  #   "foo\n\t\tbar".indent(2) # => "\t\tfoo\n\t\t\t\tbar"
+  #   "foo".indent(2, "\t")    # => "\t\tfoo"
+  #
+  # While +indent_string+ is tipically one space or tab, it may be any string.
+  #
+  # The third argument, +indent_empty_lines+, is a flag that says whether
+  # empty lines should be indented. Default is false.
+  #
+  #   "foo\n\nbar".indent(2)            # => "  foo\n\n  bar"
+  #   "foo\n\nbar".indent(2, nil, true) # => "  foo\n  \n  bar"
+  #
+  def indent(amount, indent_string=nil, indent_empty_lines=false)
+    dup.tap {|_| _.indent!(amount, indent_string, indent_empty_lines)}
+  end
+end