TemplateSyntaxError raised by do_block do not allow using doublicate block

[netinsideout@…]

This ticket is related to changeset: https://code.djangoproject.com/changeset/12655 and ticket:
https://code.djangoproject.com/ticket/10975
I realised that django template system supports construction like this:

{% ifnotequal setting u'inverted'%}
   {% block a %}{% endblock %}
   {% block b %}{% endblock %}
{% else %}
   {% block b %}{% endblock %}
   {% block a %}{% endblock %}
{% endifnotequal %}

but function do_block raises TemplateSyntaxError when checking for duplicate block in template.

Original in django 1.3:
django/template/loader_tags.py

def do_block(parser, token):
    """
    Define a block that can be overridden by child templates.
    """
    bits = token.contents.split()
    if len(bits) != 2:
        raise TemplateSyntaxError("'%s' tag takes only one argument" % bits[0])
    block_name = bits[1]
    # Keep track of the names of BlockNodes found in this template, so we can
    # check for duplication.
    try:
        if block_name in parser.__loaded_blocks:
            raise TemplateSyntaxError("'%s' tag with name '%s' appears more than once" % (bits[0], block_name))
        parser.__loaded_blocks.append(block_name)
    except AttributeError: # parser.__loaded_blocks isn't a list yet
        parser.__loaded_blocks = [block_name]
    nodelist = parser.parse(('endblock', 'endblock %s' % block_name))
    parser.delete_first_token()
    return BlockNode(block_name, nodelist)

I just removed 2 lines and construction like above starts working as expected.

def do_block(parser, token):
    """
    Define a block that can be overridden by child templates.
    """
    bits = token.contents.split()
    if len(bits) != 2:
        raise TemplateSyntaxError("'%s' tag takes only one argument" % bits[0])
    block_name = bits[1]
    # Keep track of the names of BlockNodes found in this template, so we can
    # check for duplication.
    try:
        parser.__loaded_blocks.append(block_name)
    except AttributeError: # parser.__loaded_blocks isn't a list yet
        parser.__loaded_blocks = [block_name]
    nodelist = parser.parse(('endblock', 'endblock %s' % block_name))
    parser.delete_first_token()
    return BlockNode(block_name, nodelist)

[Michael Manfre]

Setting as DDN because this should be brought to the developers list.

Quoting ubernostrum from #10975:

"A block cannot be defined conditionally within any sort of "if" construct, and this is by design; the structure of the template is the structure of the template."

If you disagree, please take it to the django-developers list.

Didn't mark as wontfix because in same ticket SmileyChris stated that wontfix bug was fixed.

[Jacob]

Milestone 1.4 deleted

[Aymeric Augustin]

SmileyChris refers to a more specific inconsistency between if and ifequal: https://code.djangoproject.com/ticket/6510#comment:16

I believe ubernostrum's comment also applies here.

(Taking this to django-developers is also the way to go if you think my wontfix is incorrect.)