From c63e19c8a0ccca1ad30b90bc262f11919f5397c1 Mon Sep 17 00:00:00 2001
From: Xavier Noria <fxn@hashref.com>
Date: Sat, 26 Sep 2009 03:48:49 +0200
Subject: [PATCH] AS guide: documents Regexp#multiline?

---
 .../source/active_support_overview.textile    | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/railties/guides/source/active_support_overview.textile b/railties/guides/source/active_support_overview.textile
index 89c959c49f31f..9c3610dc2cef8 100644
--- a/railties/guides/source/active_support_overview.textile
+++ b/railties/guides/source/active_support_overview.textile
@@ -1573,6 +1573,31 @@ def recognition_extraction
 end
 </ruby>
 
+h4. +multiline?+
+
+The method +multiline?+ says whether a regexp has the +/m+ flag set, that is, whether the dot matches newlines.
+
+<ruby>
+%r{.}.multiline?  # => false
+%r{.}m.multiline? # => true
+
+Regexp.new('.').multiline?                    # => false
+Regexp.new('.', Regexp::MULTILINE).multiline? # => true
+</ruby>
+
+Rails uses this method in a single place, also in the routing code. Multiline regexps are disallowed for route requirements and this flag eases enforcing that constraint.
+
+<ruby>
+def assign_route_options(segments, defaults, requirements)
+  ...
+  if requirement.multiline?
+    raise ArgumentError, "Regexp multiline option not allowed in routing requirements: #{requirement.inspect}"
+  end
+  ...
+end
+</ruby>
+
+
 h3. Extensions to +Range+
 
 ...