Bug #62204 for XML-Twig: XML::Twig::Elt att() accessor behavior change (lvalue issue)

Sun Oct 17 10:09:47 2010 jmgdoc [...] cpan.org - Ticket created

Subject:

XML::Twig::Elt att() accessor behavior change (lvalue issue)

Since the XML::Twig::Elt att() accessor is :lvalue, its behavior as a read accessor is changed. Assuming that foo() is an arbitrary user-defined function, the first instruction below should produce the same result as the 2-line following sequence: $result = foo($elt->att('any_attribute')); $value = $elf->att('any_attribute'); $result = foo($value); It was true up to XML::Twig 3.35, but it no longer works in 3.36 and 3.37. Due to some lvalue-related side effect, the first form (i.e. when the att() call is directly used as an argument for another function call), it *creates* the attribute (with an empty string as value) if it was not defined.

Sun Oct 17 10:19:41 2010 jmgdoc [...] cpan.org - Correspondence added

The issue comes with various Perl versions including 5.10.1, 5.12.0, 5.12.1, 5.12.2RC1

Sun Oct 17 10:19:42 2010 jmgdoc [...] cpan.org - Status changed from 'new' to 'open'

Sun Oct 17 14:37:41 2010 xmltwig [...] gmail.com - Correspondence added

Subject:	Re: [rt.cpan.org #62204] XML::Twig::Elt att() accessor behavior change (lvalue issue)
Date:	Sun, 17 Oct 2010 20:37:31 +0200
To:	bug-XML-Twig [...] rt.cpan.org
From:	Michel Rodriguez <xmltwig [...] gmail.com>

On Sun, Oct 17, 2010 at 4:09 PM, Jean-Marie Gouarné via RT <bug-XML-Twig@rt.cpan.org> wrote: Show quoted text

> Sun Oct 17 10:09:47 2010: Request 62204 was acted upon. > Transaction: Ticket created by JMGDOC > Queue: XML-Twig > Subject: XML::Twig::Elt att() accessor behavior change (lvalue issue) > Broken in: 3.36 > Severity: Important > Owner: Nobody > Requestors: jmgdoc@cpan.org > Status: new > Ticket <URL: https://rt.cpan.org/Ticket/Display.html?id=62204 > > > > Since the XML::Twig::Elt att() accessor is :lvalue, its behavior as a > read accessor is changed. Assuming that foo() is an arbitrary > user-defined function, the first instruction below should produce the > same result as the 2-line following sequence: > > $result = foo($elt->att('any_attribute')); > > $value = $elf->att('any_attribute'); > $result = foo($value); > > It was true up to XML::Twig 3.35, but it no longer works in 3.36 and > 3.37. Due to some lvalue-related side effect, the first form (i.e. when > the att() call is directly used as an argument for another function > call), it *creates* the attribute (with an empty string as value) if it > was not defined.

Oops! I'll look at this tomorrow Thanks -- mirod

Mon Feb 28 12:57:22 2011 MIROD [...] cpan.org - Correspondence added

On Sun Oct 17 14:37:41 2010, xmltwig@gmail.com wrote: Show quoted text

> On Sun, Oct 17, 2010 at 4:09 PM, Jean-Marie Gouarné via RT > <bug-XML-Twig@rt.cpan.org> wrote:

Show quoted text

> > Since the XML::Twig::Elt att() accessor is :lvalue, its behavior as a > > read accessor is changed. Assuming that foo() is an arbitrary > > user-defined function, the first instruction below should produce the > > same result as the 2-line following sequence: > > > > $result = foo($elt->att('any_attribute')); > > > > $value = $elf->att('any_attribute'); > > $result = foo($value); > > > > It was true up to XML::Twig 3.35, but it no longer works in 3.36 and > > 3.37. Due to some lvalue-related side effect, the first form (i.e. when > > the att() call is directly used as an argument for another function > > call), it *creates* the attribute (with an empty string as value) if it > > was not defined.

OK, there are ways to fix this, but the only clean one I found was to use Want, which is a dependency I don't want to have, as it is an XS module. Plus it implies quite a bit of processing for something as simple as getting an attribute value So I ditched att and class as lvalues latt and lclass are now lvalues. __ mirod

Mon Feb 28 12:57:39 2011 MIROD [...] cpan.org - Status changed from 'open' to 'resolved'

Mon Feb 28 12:57:39 2011 MIROD [...] cpan.org - Fixed in 3.38 added