to_xml() adds linefeeds between tags, how to stop it?

[Jani Patokallio]

Greetings,

So I've got an XML document where whitespace is meaningful, but
roundtripping it through Nokogiri seems to add in linefeeds (\n)
between tag levels, even when indenting is turned off. Is there a way
to switch this off?

(rdb:1) doc = Nokogiri::XML('<p><b>Foo</b></p>')
#<Nokogiri::XML::Document:0x3bccee4 name="document"
children=[#<Nokogiri::XML::Element:0x3bccca0 name="p"
children=[#<Nokogiri::XML::Element:0x3bcca20 name="b"
children=[#<Nokogiri::XML::Text:0x3bcc7a0 "Foo">]>]>]>
(rdb:1) doc.to_xml
"<?xml version=\"1.0\"?>\n<p>\n <b>Foo</b>\n</p>\n"
(rdb:1) doc.to_xml(:indent => 0)
"<?xml version=\"1.0\"?>\n<p>\n<b>Foo</b>\n</p>\n"

Of course I can always gsub("\n", "") the output, but that seems
unnecessarily ugly.

Cheers,
-jani

[Mike Dalessio]

On Mon, Dec 6, 2010 at 10:08 PM, Jani Patokallio <jpat...@iki.fi> wrote:

Greetings,

So I've got an XML document where whitespace is meaningful

How so? Can you provide an explanation, and some details? How about a real example?

 

, but
roundtripping it through Nokogiri seems to add in linefeeds (\n)
between tag levels, even when indenting is turned off.  Is there a way
to switch this off?

(rdb:1) doc = Nokogiri::XML('<p><b>Foo</b></p>')
#<Nokogiri::XML::Document:0x3bccee4 name="document"
children=[#<Nokogiri::XML::Element:0x3bccca0 name="p"
children=[#<Nokogiri::XML::Element:0x3bcca20 name="b"
children=[#<Nokogiri::XML::Text:0x3bcc7a0 "Foo">]>]>]>
(rdb:1) doc.to_xml
"<?xml version=\"1.0\"?>\n<p>\n  <b>Foo</b>\n</p>\n"
(rdb:1) doc.to_xml(:indent => 0)
"<?xml version=\"1.0\"?>\n<p>\n<b>Foo</b>\n</p>\n"

Well, if you provide a document with some whitespace between tags, like this:

Nokogiri::XML('<p>  <b>Foo</b></p>').to_xml

# <?xml version="1.0"?>

# <p>  <b>Foo</b></p>

you see that Nokogiri (actually, libxml2 v2.7.7) respects the inter-tag whitespace and doesn't insert newlines.

I think a real example might help me understand your issue better, and will result in a more useful and targetted answer.

---

mike dalessio / @flavorjones

[Jani Patokallio]

Long story short, I'm manipulating OpenOffice ODT, which in its
autogenerated form does not contain any inter-tag whitespace.
Example:

<office:text xmlns:office="foo" xmlns:text="bar"><text:p>Plain</
text:p><text:p><text:span text:style-name="T2">Bold</text:span></
text:p></office:text>

If I load that in Nokogiri and save with to_xml, I get this:

irb(main):001:0> @doc.to_xml
"<?xml version=\"1.0\"?>\n<office:text xmlns:office=\"foo\" xmlns:text=
\"bar\">\n <text:p>Plain</text:p>\n <text:p>\n <text:span
text:style-name=\"T2\">Bold</text:span>\n </text:p>\n</office:text>
\n"=> "<?xml version=\"1.0\"?>\n<text>\n

Or in human-readable form with namespaces put back in:

<office:text>
<text:p>Plain</text:p>
<text:p>
<text:span text:style-name="T2">Bold</text:span>
</text:p>
</office:text>

And now, if I load that in OO, it inserts a spurious single space
after "Bold" that wasn't there before. If you resave the file, it
changes into this:

<office:text ...><text:p>Plain</text:p><text:p><text:span text:style-
name="T2">Bold</text:span> </text:p></office:text>

In other words, other whitespace is stripped out, but the whitespace
after the bold span is apparently considered meaningful and kept,
albeit collapsed to a single space. Whether OO *should* interpret the
input this way is certainly debatable, but unfortunately that's the
way it is now.

Cheers,
-jani

On Dec 7, 3:39 pm, Mike Dalessio <mike.dales...@gmail.com> wrote:

[Mike Dalessio]

On Tue, Dec 7, 2010 at 9:36 PM, Jani Patokallio <jpat...@iki.fi> wrote:

Long story short, I'm manipulating OpenOffice ODT, which in its
autogenerated form does not contain any inter-tag whitespace.
Example:

<office:text xmlns:office="foo" xmlns:text="bar"><text:p>Plain</
text:p><text:p><text:span text:style-name="T2">Bold</text:span></
text:p></office:text>

Ah, interesting. Most people who ask about whitespace preservation are doing something hacky in their tests.

 

If I load that in Nokogiri and save with to_xml, I get this:

irb(main):001:0> @doc.to_xml
"<?xml version=\"1.0\"?>\n<office:text xmlns:office=\"foo\" xmlns:text=
\"bar\">\n  <text:p>Plain</text:p>\n  <text:p>\n    <text:span
text:style-name=\"T2\">Bold</text:span>\n  </text:p>\n</office:text>
\n"=> "<?xml version=\"1.0\"?>\n<text>\n

Or in human-readable form with namespaces put back in:

<office:text>
 <text:p>Plain</text:p>
 <text:p>
   <text:span text:style-name="T2">Bold</text:span>
 </text:p>
</office:text>

And now, if I load that in OO, it inserts a spurious single space
after "Bold" that wasn't there before.  If you resave the file, it
changes into this:

<office:text ...><text:p>Plain</text:p><text:p><text:span text:style-
name="T2">Bold</text:span> </text:p></office:text>

In other words, other whitespace is stripped out, but the whitespace
after the bold span is apparently considered meaningful and kept,
albeit collapsed to a single space.  Whether OO *should* interpret the
input this way is certainly debatable, but unfortunately that's the
way it is now.

OK, if you check out the documentation for Node#serialize, you'll see that you have the option of passing in some "save options":

  - Node#serialize: http://nokogiri.org/Nokogiri/XML/Node.html#method-i-serialize

  - Node::SaveOptions: http://nokogiri.org/Nokogiri/XML/Node/SaveOptions.html

By default, what Node#to_s, #to_xml, #to_html, etc. all do is to use the save option FORMAT, which prints nicely. Usually, that's a win.

If you want to turn it off, do this:

  doc.serialize :save_with => 0

More semantically, you should be able to also do:

  doc.serialize :save_with => Nokogiri::XML::Node::SaveOptions.new

but I just found a bug with that syntax while I was writing this response, so don't use it. :-\

Thanks for using Nokogiri!

-m

[Jani Patokallio]

On Dec 9, 1:29 am, Mike Dalessio <mike.dales...@gmail.com> wrote:
> By default, what Node#to_s, #to_xml, #to_html, etc. all do is to use the
> save option FORMAT, which prints nicely. Usually, that's a win.
>
> If you want to turn it off, do this:
>
>   doc.serialize :save_with => 0

Thanks, that looks *almost* perfect. Unfortunately my actual code is
running #to_xml on a NodeSet, not a Node, so I have to add in a map
loop:

nodeset.map {|e| e.serialize(:save_with => 0)}

Works fine, but to the casual reader that doesn't exactly yell out
"output as XML without prettyprinting". I don't suppose it would be
possible to add in eg. a ":format => false" option for #to_xml & co?

Cheers,
-jani

[Mike Dalessio]

Well, in two years, you're the first person I've talked to who had a real use case for ignoring whitespace (read: not trying to make unsemantic tests pass). :)

Though perhaps we could give this idiom some attention in the nokogiri.org tutorials ... see https://github.com/flavorjones/nokogiri.org-tutorials/issues/issue/12