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Tag Archives: perl 5

In the source repository, there are a number of changes to Perl::Critic that include deprecation of existing functions/methods. One Policy author has asked us to not do the deprecation because it will result in warnings being emitted whenever his Policy is being used.

There have been a lot of discussion recently in the Perl community about what deprecation means. For me, deprecation means that the interface or functionality will be removed and not sit around in a limbo state for years.

So how do I decide whether to deprecate something? If something is merely suboptimal, I’m not going to deprecate it; I’ll merely change the documentation to discourage its use. In Perl::Critic, there was the issue of Policy constructors. For a long time, there was no requirements for the new() method for a given Policy other than it returning a blessed hash. There are some Policys [sic] outside of the core distribution with new() methods that don’t call up to the new() method in Perl::Critic::Policy. There was a point when we really wanted to add a lot of functionality to the constructor, but we couldn’t because there were Policys that didn’t call it. We worked around this by doing what we wanted after the Policy object was constructed. If you look at the developer documentation for Perl::Critic, you’ll note that it discourages creation of a new() method.

On the other hand, if something is incorrectly designed or is holding up future changes, I’m going to change it or remove it. I’m not going to just work around the issue forever. I won’t change it without notifying anyone, however.

I made a mistake with the design of Perl::Critic::Utils::PPI::get_constant_name_element_from_declaring_statement(). I didn’t realize that you can actually create multiple values using the constant pragma; Tom Wyant corrected my misconception. The function returns a single value, so it can’t correctly handle single statements that declare multiple constants. Its interface is wrong. It will be removed in the future. A suggestion was made to immediately remove it, but we’ll go through a deprecation cycle first. We won’t change things without giving notice.

I think the Policy author’s question about the warnings comes from the practice of a number of projects of “deprecating” something, but never actually removing it. Sun is a particularly egregious example of this with Java functionality that has been deprecated for more than a decade but still hangs around, allowing people to write new code against an interface that is broken. If I deprecate something, it will be removed. The warnings that are emitted allow others to deal with the change before it happens. If, in the interim, this annoys some users, too bad. It would be worse if the code just stopped working.

If you have a look at my code page, among the epigrams that you find there is “If it’s broken, fix it.”. While there has long been the saying of not fixing something that isn’t broken, I think people don’t do the opposite enough. Don’t suffer breakage. Don’t put up with things that are wrong. Change things that need changing, even if it causes some short-term pain.