handle w:fldSimple with extra runs.

Closes senny#32.

It's possible that a simple field contains more than a single `w:r`
tag. Previously sablon would replace the text of the first `w:r` to
reuse it's formatting and keep all additional `w:r` as is. The result
was half-replaced fields that still contained leftovers from the merge
fields display.

This patch removes all extra `w:r` tags.

lib/sablon/parser/mail_merge.rb

@@ -73,6 +73,7 @@ def initialize(node)
         end
 
         def replace(content)
+          remove_extra_runs!
           replace_field_display(@node, content)
           @node.replace(@node.children)
         end
@@ -89,6 +90,11 @@ def start_node
           @node
         end
         alias_method :end_node, :start_node
+
+        private
+        def remove_extra_runs!
+          @node.search(".//w:r")[1..-1].each(&:remove)
+        end
       end
 
       def parse_fields(xml)

test/fixtures/xml/simple_field_with_styling.xml

@@ -0,0 +1,20 @@
+<w:p>
+  <w:r><w:t xml:space="preserve">Generated by </w:t></w:r>
+  <w:fldSimple w:instr=" MERGEFIELD  =system_name  \* MERGEFORMAT ">
+    <w:r w:rsidR="002D39A9">
+      <w:rPr>
+        <w:rFonts w:hint="eastAsia"/>
+        <w:noProof/>
+      </w:rPr>
+      <w:t>«</w:t>
+    </w:r>
+    <w:r w:rsidR="002D39A9">
+      <w:rPr><w:noProof/></w:rPr>
+      <w:t>=system_name</w:t>
+    </w:r>
+    <w:r w:rsidR="002D39A9">
+      <w:rPr><w:rFonts w:hint="eastAsia"/><w:noProof/></w:rPr>
+      <w:t>»</w:t>
+    </w:r>
+  </w:fldSimple>
+</w:p>

test/processor/document_test.rb

@@ -40,6 +40,24 @@ def test_simple_field_replacement_with_nil
     document
   end
 
+  def test_simple_field_with_styling_replacement
+    result = process(snippet("simple_field_with_styling"), {"system_name" => "Sablon 1 million"})
+
+    assert_equal "Generated by Sablon 1 million", text(result)
+    assert_xml_equal <<-document, result
+    <w:p>
+      <w:r><w:t xml:space="preserve">Generated by </w:t></w:r>
+        <w:r w:rsidR="002D39A9">
+          <w:rPr>
+            <w:rFonts w:hint="eastAsia"/>
+            <w:noProof/>
+          </w:rPr>
+          <w:t>Sablon 1 million</w:t>
+        </w:r>
+    </w:p>
+    document
+  end
+
   def test_context_can_contain_string_and_symbol_keys
     result = process(snippet("simple_fields"), {"first_name" => "Jack", last_name: "Davis"})
     assert_equal "Jack Davis", text(result)