Empty document test

Hi,

I am in the process of porting a Perl module Data::YAML to Python (using 
PyYAML in background) and working through the Data::YAML tests. I have 
stumbled on this test

     {
       out   => undef,
       in    => [ '---', '...' ],
       name  => 'Regression: only_header',
       error => qr{Premature\s+end}i,
     },

which could be hopefully translated into this Perl script

	#!/usr/bin/perl -Wall
	
	use strict;
	use warnings;
	use Data::YAML::Reader;
	
	my %test = (
		name  => 'Hello World 5',
		in    => [ '---', '...', ],
		error => qr{Missing\s+'[.][.][.]'},
	);
	
	sub iter {
		my $ar = shift;
		return sub {
			return shift @$ar;
		};
	}
	
	my $yaml = Data::YAML::Reader->new;
	my $source = join( "\n", @{ $test{in} } ) . "\n";
	print "\$source = $source\n";
	
	my $iter = iter( $test{in} );
	my $got = $yaml->read($iter) ;
	print "\$got = $got\n";

This happily crashes as expected:

mitmanek:yamlish (master) $ perl test-perl.pl
$source = ---
...


Premature end of YAML at test-perl.pl line 25
mitmanek:yamlish (master) $

However, when I attempt to generate the similar exception with this script

	#!/usr/bin/python
	import yaml
	
	IN = {
	    "name": 'Hello World 6',
	    "in": """---
	...
	    """
	  }
	
	print IN['in']
	res = yaml.load(IN['in'], Loader=yaml.SafeLoader)
	print "'%s'" % res

PyYAML doesn't crash and returns None (or empty string with 
yaml.BaseLoader, which I otherwise use).

mitmanek:yamlish (master) $ python failing_test.py
---
...

'None'
mitmanek:yamlish (master) $

Whose fault this difference is? Data::YAML, PyYAML, or (most likely) 
mine, because I misunderstood something? When looking through the spec 
(http://www.yaml.org/spec/1.2/spec.html) I haven't found explicit 
treatment of empty documents, but from all the careful wordings about 
when individual objects can be empty, it seems that generally emptiness 
is a problem. So, why PyYAML doesn't raise an exception?

Do I have to explicitly check for empty documents to 100% emulate 
Data::YAML or are there some configuration options for yaml.load() (or 
something) to behave the same?

Thank you in advance for any hints,

Matěj

-- 
http://www.ceplovi.cz/matej/, Jabber: mcepl<at>ceplovi.cz
GPG Finger: 89EF 4BC6 288A BF43 1BAB  25C3 E09F EF25 D964 84AC

If trains stop at train stations, what happens at work stations?


------------------------------------------------------------------------------
Virtualization & Cloud Management Using Capacity Planning
Cloud computing makes use of virtualization - but cloud computing 
also focuses on allowing computing to be delivered as a service.
http://www.accelacomm.com/jaw/sfnl/114/51521223/
_______________________________________________
Yaml-core mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/yaml-core