Treat a whitespace-only header line as obs-fold

lib/net/http/response.rb

@@ -188,11 +188,14 @@ def each_response_header(sock)
         line = read_line(sock, MAX_RESPONSE_HEADER_LENGTH, true)
         remaining -= line.bytesize
         raise Net::HTTPBadResponse, 'response header too large' if remaining < 0
-        line = line.sub(/\s+\z/, '')
+        line = line.chomp
         break if line.empty?
         if line[0] == ?\s or line[0] == ?\t and value
-          value << ' ' unless value.empty?
-          value << line.strip
+          folded = line.strip
+          unless folded.empty?
+            value << ' ' unless value.empty?
+            value << folded
+          end
         else
           yield key, value if key
           key, value = line.strip.split(/\s*:\s*/, 2)

test/net/http/test_httpresponse.rb

@@ -93,6 +93,40 @@ def test_multiline_header
     assert_equal('XXX YYY', res['x-bar'])
   end
 
+  def test_multiline_header_whitespace_only
+    io = dummy_io(<<EOS)
+HTTP/1.1 200 OK
+Content-Length: 5
+
+X-After: value
+
+hello
+EOS
+    res = Net::HTTPResponse.read_new(io)
+    # Whitespace only line is ignored
+    assert_equal('5', res['content-length'])
+    assert_equal('value', res['x-after'])
+    body = nil
+    res.reading_body io, true do
+      body = res.read_body
+    end
+    assert_equal('hello', body)
+  end
+
+  def test_multiline_header_no_preceding_header
+    io = dummy_io(<<EOS)
+HTTP/1.1 200 OK
+
+Content-Length: 5
+
+hello
+EOS
+    e = assert_raise(Net::HTTPBadResponse) do
+      Net::HTTPResponse.read_new(io)
+    end
+    assert_equal 'wrong header line format', e.message
+  end
+
   def test_read_body
     io = dummy_io(<<EOS)
 HTTP/1.1 200 OK