Fix Body#extract_parts leaving boundary's CRLF at head of raw_source

CHANGELOG.rdoc

@@ -24,6 +24,7 @@ Bug Fixes:
 
 * Regression: Preserve message-level charset when adding parts (related to Rails ActionMailer) @shields
 * Regression: Adding a part should not reset the mail's charset to nil @railsbob
+* Multipart::Body#extract_parts left the boundary delimiter's own trailing CRLF at the head of each subsequent part's raw_source instead of the part's actual content (RFC 2046 "dash-boundary transport-padding CRLF")
 
 Performance:
 

lib/mail/body.rb

@@ -287,7 +287,13 @@ def extract_parts
         final_separator = parts[-2][1]
         parts << [""] if final_separator != "--#{boundary}--"
       end
-      parts.map(&:first)
+
+      # The CRLF that terminates a boundary delimiter line (RFC 2046: "dash-boundary
+      # transport-padding CRLF") is left dangling at the head of the content that
+      # follows, since the regex above only looks ahead at it without consuming it.
+      # Strip that one delimiter-owned line break so raw_source for each part after
+      # the first starts at its actual content, not the boundary's own line ending.
+      parts.map(&:first).each_with_index.map { |part, index| index > 0 ? part.sub(/\A\r?\n/, '') : part }
     end
 
     def crlf_boundary

spec/mail/body_spec.rb

@@ -160,6 +160,15 @@ def assert_split_into(body, pre, epi, parts)
       assert_split_into(multipart_body, "this is some text", "", 1)
     end
 
+    it "should not leave the boundary's own line break at the head of each part's raw_source" do
+      multipart_body = "this is some text\r\n\r\n------=_Part_2192_32400445\r\nContent-Type: text/plain; charset=ISO-8859-1\r\n\r\nThis is a plain text\r\n\r\n------=_Part_2192_32400445\r\nContent-Type: text/html\r\n\r\n<p>This is HTML</p>\r\n------=_Part_2192_32400445--\r\n"
+      body = Mail::Body.new(multipart_body)
+      body.split!('----=_Part_2192_32400445')
+
+      expect(body.parts[0].raw_source).to eq "Content-Type: text/plain; charset=ISO-8859-1\r\n\r\nThis is a plain text\r\n"
+      expect(body.parts[1].raw_source).to eq "Content-Type: text/html\r\n\r\n<p>This is HTML</p>"
+    end
+
     it "should keep the preamble text as its own preamble" do
       multipart_body = "this is some text\r\n\r\n------=_Part_2192_32400445\r\nContent-Type: text/plain; charset=ISO-8859-1\r\n\r\nThis is a plain text\r\n\r\n------=_Part_2192_32400445\r\nContent-Type: text/html\r\n\r\n<p>This is HTML</p>\r\n------=_Part_2192_32400445--\r\n"
       body = Mail::Body.new(multipart_body)