Yanick's Friends' Journals

Finally, some Test::Builder2 examples!

schwern — 2010-09-09T08:33:42+00:00

For my PDX.pm presentation tonight on Test::Builder2 I threw together some quick examples of some of its killer features, in particular demonstrating changing how Test::Builder2 behaves using method modifiers and applying object roles.

First, demonstrating end-of-assert actions, there's die on fail but even cooler is DEBUG on fail! That's right, run your test in the debugger and have it automatically set a breakpoint on a failure. How cool is that?

I'm sure somebody with better debugger foo than I can make it even cooler and stop at the top of the assert stack rather than inside DebugOnFail.

The second is reimplementing Test::NoWarnings safely. TB2::NoWarnings demonstrates hooking into the start and end of the test as well as safely altering the number of tests planned by trapping the call to set_plan.

You can safely use them all together, though its a crap shoot if DebugOnFail or DieOnFail will trigger first.

While roles and method modifiers are relatively new to the Perl community, using them in lieu of designing my own event system for TB2 has two great advantages. First, I didn't have to design and debug my own event system. :) Second, rather than having to learn the quirks of a one-off system, you learn the quirks of Mo[uo]se and then can apply that knowledge all over the place.

There's a pile of stuff to be done in TB2, a lot of them are fairly small and self contained. Have a look. Patches welcome.

Test::Builder2 at 10k Feet

schwern — 2010-09-09T08:15:22+00:00

Here's a diagram of the "flow" of assert results through Test::Builder version 1.

.-------. | foo.t | '-------' | | .-------------. | .----------------. | Test::More |<--------->| Test::Whatever | '-------------' '----------------' | | | | | | | .---------------. | '---->| Test::Builder |<----' '---------------' | v .-----. | TAP | '-----' | v .---------------. | Test::Harness | '---------------'

You write foo.t using Test::More and Test::Whatever. These both
use the same Test::Builder object. It spits out TAP which
Test::Harness converts into something human readable.

The big problem there is Test::Builder is monolithic. There's no
further breakdown of responsibilities. It only spits out TAP, and
only one version of TAP.

Here's what Test::Builder2 looks like:

.-------. .----------------| foo.t |-------------------. | '-------' | | | | | | | v v v .------------. .----------------. .------------------. | Test::More | | Test::Whatever | | Test::NotUpdated | '------------' '----------------' '------------------' | | | | v v | .----------------. .---------------. '---------->| Test::Builder2 |<------| Test::Builder | '----------------' '---------------' | v .--------------. .-------------. | TB2::History |<---| TB2::Result | '--------------' '-------------' | | .--------------------------. | .---------------------. | TB2::Formatter::TAP::v13 |<-----'------>| TB2::Formatter::GUI | '--------------------------' '---------------------' | | v | .-------------------------------. | | TB2::Formatter::Streamer::TAP | | '-------------------------------' | | | v | .-----. | | TAP | | '-----' | | | v v .---------------. .-----------------. | Test::Harness | | Pretty Pictures | '---------------' '-----------------'

It starts out the same, foo.t uses a bunch of test modules
including Test::More and Test::Whatever using the same Test::Builder2
object, but it also uses Test::NotUpdated which is still using
Test::Builder. That's ok because Test::Builder has been rewritten in
terms of Test::Builder2 (more on that below).

Test::Builder2, rather than being a monolith, produces a
Test::Builder2::Result object for each assert run. This gets stored
in a Test::Builder2::History object for possible later use. It also
gets handed to a Test::Builder2::Formatter object, the default is
Test::Builder2::TAP::v13 which produces TAP version 13. This is fed
to a Streamer that prints it to STDOUT and STDERR which is read by
Test::Harness and made human readable.

Because Test::Builder2 is not monolithic, you can swap out parts. For
example, instead of outputting TAP it could instead hand results to a
formatter that produced a simple GUI representation, maybe a green
bar, or something that hooks into a larger GUI. Or maybe one that
produces JUnit XML.

Here's how Test::Builder and Test::Builder2 Relate.

.-----. .-----. | TB2 | | TB1 | '-----' '-----' | | | | | | | | v v .-------------. .--------------. .-------------. | TB2::Result |------->| TB2::History |<--------| TB2::Result | '-------------' '--------------' '-------------' | | | | | | | .----------------. | '------------->| TB2::Formatter |<--------------' '----------------' | v .--------. | Output | '--------'

Test::Builder and Test::Builder2 coordinate their actions by sharing
the same History and Formatter objects. If you call TB1->ok() it
produces a Result object which it hands to the History singleton and
the Formatter singleton. If you call TB2->ok() it produces a Result
object which it hands to the same History and Formatter objects.

This allows most of the Test::Builder code to remain the same while
still coordinating with Test::Builder2. It also allows radically
different builders to be made without Test::Builder2 dictating how
they're to work.

The downside is that roles applied to Test::Builder2 will not effect
Test::Builder. Because of this, Test::Builder may become more closely
coupled with Test::Builder2 in the future.

Diagrams by App::Asciio.

A month of Test::Builder2

schwern — 2010-08-28T04:08:39+00:00

I've had a grant open for Test::Builder2 for, oh god over two years now. Since I started it, Perl 6 has had a release! I think its the second oldest running dev grant.

I've cleared the decks of other responsibilities and can dedicate September to, if not finishing, then at least releasing something people can poke at. First alpha release was supposed to be "two weeks after the start" ha ha ha! oh god. The design has evolved and simplified greatly in the intervening two years, but its time to get something the hell out the door. At least a Test::Builder2 Star if you will.

There's critical components missing. There's no diagnostics, YAML or otherwise. The issues with nested asserts are still congealing. Plans are not enforced. Result objects are in the middle of being remodeled... again. But Test::Builder is using what parts of Test::Builder2 are usable. Multiple output formats and streams work. Asserts can be nested in the common, simple cases without having to fiddle with $Level. And you can hook into various events.

Step one is I'm going to seal up what's there, write docs where they're missing, and release something.

A release before October or the grant dies.

Alien::SVN - new release, new management

schwern — 2010-08-18T22:33:29+00:00

Those of you still stuck using Subversion will be happy to find a new release of Alien::SVN. It drags it forward to 1.6.12, doesn't do much else.

Also, Alien::SVN has finally found a new manager! From out of the blue comes Matthew Lanier with a patch and the will and a PAUSE ID. He'll be taking care of things from now on. Its his first CPAN module, be gentle. Godspeed, Matthew.

Test::Builder2::Design

schwern — 2010-08-10T02:31:05+00:00

In an effort to shed some light on what Test::Builder2 is about, I took a few hours and performed a brain dump about its goals and design. You can see the result in the new Test::Builder2::Design document.

The key design goals are 1) that it has to work, 2) that it has to work everywhere and 3) that it has to test everything. This throws out a lot of 98% solutions.

Method::Signatures returns! 5.12, func() and fast!

schwern — 2010-07-31T00:49:55+00:00

Chip submitted a minor performance patch to Method::Signatures today. That drove me to push out a new release making it friendly to 5.12 and adding func() for non methods!

func hello(:$greeting = "Hello", :$place = "World") {
print "$greeting, $place!\n";
}

hello( place => "Earth" );

For those who don't know, one of the neato features of Method::Signatures is that it can alias references to make working with references less of a trial:

func popn(\@array, $howmany) {
return splice @array, -$howmany;
}

my @stuff = (1,2,3,4,5);
my @last_three = popn(\@stuff, 3); # 3,4,5
print @last_three;

It does this with the amazing Data::Alias module. Unfortunately, 5.12 broke its black magic and its non-trivial to fix. Method::Signatures now makes Devel::Alias an optional dependency. If its available, it'll use it. Otherwise, no aliasing for you.

But that's ok, because perl5i makes working with references enjoyable. And while perl5i is adding its own simple signatures, they're forward compatible with Method::Signatures! They play together, so if you want perl5i and the full power of Method::Signatures you can have them.

use perl5i::2;
use Method::Signatures;

func echo($message is ro) {
say $message;
}

Just make sure you load MS after perl5i. The last one loaded wins.

Finally, I was comparing Method::Signatures with MooseX::Method::Signatures and made a disturbing discovery. I always new MooseX::Method::Signatures would have a performance penalty, it does more checks than Method::Signatures, I just didn't realize how bad it was.

Here's comparing an empty signature: method foo() {}.

Rate MMS MS Std MMS 3207/s -- -100% -100% MS 1498875/s 46644% -- -1% Std 1508351/s 46940% 1% --

That's showing MooseX::Method::Signatures is 450x slower than either Method::Signatures or a normal method call creaking out a mere 3500 method calls per second as compared to the 1.5 million it should be doing. And that's for a method with an empty signature!

To be clear, that's the speed of calling a method, not compiling them.

Here's one comparing a simple signature that requires a check, so MS can't optimize it away: method foo($arg!) { return $arg + 1 } That's a required positional argument.

Rate MMS MS Std MMS 2928/s -- -100% -100% MS 983127/s 33481% -- -2% Std 1005357/s 34240% 2% --

3000 method calls instead of a million.

Now I'm the first to counter arguments bemoaning method call overhead. Usually it doesn't matter. Usually the extra cost of calling a method and checking arguments is insignificant compared to what that method actually does. And MooseX::Method::Signatures has features Method::Signatures does not, most significantly type checking. But my god! Three orders of magnitude of performance lost! And its not even using the extra MMS features. That's just too much.

Perl 6 Is The Language Your Language Could Smell Like

schwern — 2010-07-29T19:24:09+00:00

Hello programmers. Look at your code, now at Perl 6, now back at your code, now back at Perl 6! Sadly, your code is not written in Perl 6. But if you use Rakudo Star then Perl 6 is the language your code could be written in!

Now Microsoft scented!

"def" or "func"?

schwern — 2010-07-13T00:06:57+00:00

perl5i 2.3.0_01 now has basic methods and subroutine signatures with code basically lifted straight from Method::Signatures::Simple. MooseX::Declare got me addicted, now I want them everywhere.

use perl5i::2; def add($this, $that) { return $this + $that; } method new($class: %args) { return bless \%args, $class; } my $echo = def($arg) { return $arg };

Its alpha for two reasons. First, I don't have time right now to really thoroughly test it, but I really want it.

Second, overriding "sub" is hard. Its been done but its a bit twitchy. Defining a new keyword is easy(er). So what should that keyword be? I've come up with two that have good arguments. "def" and "func". Both are short. "def" has the benefit of being used by other programming languages a Perl programmer is likely to encounter and not hate (Python, Ruby, Scala, Groovy). "func" is nice because it pretty clearly means "function" whereas "define" is a bit ambiguous.

perl5i currently does both. Only one will survive in version 3 (the other will be deprecated). Before you comment on which is your favorite, try it for a little bit. I found a difference between what I thought I like and what I actually use.

Where The Hell Is Test::Builder2?

schwern — 2010-06-27T19:16:09+00:00

My progress and communication about the Test::Builder2 grant has been nothing short of appalling. There is a sort of herky-jerky progress where I figure out a design problem, push the code forward, then remember a use-case that throws a wrench in the whole design and the whole thing comes to a screeching halt again.

At the QA hackathon we elegantly solved the problem of things like die-on-fail and Test::NoWarnings but then ran afoul of things like Test::Warn and Test::Exception which runs tests inside of tests but those aren't actually part of the test stack.

Confused? I'll post more about it another time. Point is, TB2 continues to move forward, its just that there's long periods of rumination between sprints of development. And I get distracted by other projects. At this rate I'll be collecting Social Security before I collect the second half of the grant. I really want TB2 to happen, but something decisive has to be done. I work best with hard deadlines, so the plan is to clear a month for working mostly on TB2. A lot of the wibbling is trying to come up with the most elegant solution, but I usually have a less than elegant way to solve it and move forward. If its between an elegant TB2 that doesn't exist and a less elegant TB2 that does, well, go with the one that exists. With the way my schedule is looking, that will probably be mid-August to mid-September. If that doesn't produce an alpha, then I'll kill the grant.

That doesn't mean TPF gets nothing for your money. Chunks of TB2 can be harvested to improve TB1. Specifically, the TB2 formatting and history objects. The TB2 formatter makes the guts of TB1 cleaner, and it also allows it to produce something other than TAP. Used together, history and formatter allows non-Test::Builder based test frameworks to work together with Test::Builder providing even more flexibility. This is already done in the TB2 branch.

Looking at the grant deliverables, most of it is done:

* Split up global shared Test resources into individual objects * The test counter * The output filehandles * The plan * Allow hooks for global beginning and end of test functions. * Ensure multiple hooks "stack" * die on fail * debug on fail * Hooks for global beginning and end of test actions * Example: A safer Test::NoWarnings * Example: Don't cleanup temp files on failure so they can be debugged * Allow for test output other than TAP * Allow another Test::Builder-like module to work in the same process as Test::Builder (for example, sharing the counter). * Rewrite Test::Builder in terms of Test::Builder2.

Here's what's not complete:

* Split up localizable behaviors into objects * Allow individual test modules to locally override Test::Builder2 behaviors * Allow test modules to globally override Test::Builder2 behaviors * How the plan works

Since I'm not writing to the letter of the law, there's more than that to be done before release, but the project does move.

The Post-YAPC Plan

schwern — 2010-06-27T18:34:30+00:00

I spent most of YAPC::NA mildly sick, sleep deprived and writing talks. Each of those things alone isn't so bad, but put all together meant I had time and energy enough to do my talks, discuss with people after, and that's about it. As a result, I was kind of dead in the head most of the time and didn't do a whole lot of interaction with people. I didn't feel like I got the most out of the one opportunity a year I get to hang out with huge gobs of Perl folk.

One of the things which I wanted to do at YAPC was get gitpan restarted. It can run right now, but the code is a mess and needs to be babied. It needs a rewrite. That rewrite was supposed to happen at YAPC but see above. I'm doing that now, using MooseX::Declare, perl5i and Path::Class just to mess around with them seriously. Also log4perl, which I'm finally learning a decade late. Its fun, far more pleasant than knocking it together without, once you learn to cope with Moose's idiosyncrasies. Better to learn the quirks of one complete system than nine incomplete ones.

That's what's absorbing my time right now. After that I want to add subroutine signatures to perl5i and the über file and directory objects. They were supposed to be in, at least as a prototype, by YAPC but that didn't work out. Using MooseX::Declare, Path::Class and perl5i together has me drooling for them.

Will Coleda, representing the TPF, found me at YAPC and mercifully did not break my legs. We hashed out a plan to make a last stab at Test::Builder2 before calling the grant done. That's not going to happen until August, I'll post about that later.

Oh, and I have a talk to do at OSCON about how the world is going to end in 2038 assuming 2012 doesn't claim the prize first. And a two part Git tutorial for Drupal programmers that I'm developing into a commercial class. And two paid clients to keep happy.

One thing I *don't* have to worry about is MakeMaker. Gird your loins, MakeMaker has provisionally been handed off to Matt Trout. Maybe I need to worry about it more...

Object::ID - A unique object identifier for any object

schwern — 2010-05-02T17:17:01+00:00

Something Perl's OO has been missing has been a reliable way to identify an object. Is $this the same as $that? Not asking if it contains the same information, but is it a referent to the same object? Have we seen it before? When I alter $this will I also be changing $that?

package Foo; use Object::ID; ...write the class however you want...

Really, HOWEVER YOU WANT! Inside out, outside in, code refs, regexes, globs, Moose, Mouse... Call the constructor whatever you like, add in a DESTROY method. Doesn't matter, it'll work.

my $id = $obj->object_id; my $uuid = $obj->object_uuid;

object_id() is a cheap, process-specific identifier. object_uuid() is a bit more expensive on first call (it has to generate the UUID, about 30% slower) but it should be universally unique across machines and processes.

That's great for YOUR objects, but what about everyone else? You can either inject the Object::ID role one class at a time...

package DateTime; use Object::ID; my $date = DateTime->now; say $date->object_id;

or you can load UNIVERSAL::Object::ID and every object has it. EVERY OBJECT! Even things you don't realize are objects.

use UNIVERSAL::Object::ID; # Regexes are objects say qr/foo/->object_id; # Loading IO::Handle turns all filehandles into objects use IO::Handle; open my $fh, "foo/bar"; say $fh->object_id;

But OH GOD UNIVERSAL! Well, use at your own risk. Its handy to use in your own programs and private libraries. Or you can use Method::Lexical and apply it lexically.

Why not just use the object's reference address? Well, as people implementing inside-out objects discovered, they're not unique. They're not thread safe, and worse they're not even unique for the life of the process. Perl will reuse the reference of a destroyed object. Observe:

{ package Foo; sub new { my $class = shift; return bless {}, $class; } } for(1..3) { my $obj = Foo->new; print "Object's reference is $obj\n"; }

Run that and you should get the same reference, three times, for three different objects.

And then there's the problem of string overloaded objects. You have to be careful to always use Scalar::Util::refaddr or overload::StrVal.

It turns out inside-out objects have nearly the same problem, and 5.10.0 introduced field hashes to solve that. rjbs explains the pain of all this at slide 120 in his excellent 5.10 For People Who Aren't Totally Insane. You can read the gory details of field hashes but it comes down to this: in 5.10 you can A) get a process unique, thread safe identifier for an object and B) you can store it in hash such that it gets destroyed when the object is destroyed. Perfect!

Because of this, if you look inside Object::ID you'll see there's not a lot to it. It makes a field hash to store the IDs in, a state variable to hold an ID counter, and then just accesses the field hash.

use Hash::Util::FieldHash qw(fieldhash); fieldhash(my %IDs); sub object_id { my $self = shift; state $last_id = "a"; return $IDs{$self} //= ++$last_id; }

No scary black magic (beyond what's inside fieldhash). Its so simple, which is why it works with everything.

Now, I didn't come up with this implementation. I just laid out the requirements and Vincent Pit filled in the blanks. I was only vaguely aware of field hashes, Vincent made the connection. Thank you VPIT!

Practical applications? Honestly, I'm not sure. I needed it as a shortcut for expensive object equality checks in perl5i. Maybe some of the OO theorists out there can fill this part in. Let me know what you might use it for.

Possible extensions? Well... with some tweaking Object::ID can be used as a universal object registry. Not only can you ask "does the object associated with this ID still exist" but field hashes provide the ability to get the object associated with an ID. It would only work on objects that have had their ID asked of them, and thus registered with the field hash, but how else would you have the ID? Is this useful? Is this a security hole? I dunno, but it would be easy.

Bob Jacobsen interview on FLOSS Weekly

merlyn — 2010-04-23T03:55:11+00:00

Last week, I interviewed Bob Jacobsen for FLOSS Weekly. Bob used Perl's Artistic 1.0 license on some Java code to manage model trains. The code was later patented by an Oregon-based company(!) and then Bob got sued(!!) for Bob distributing the other company's patented code(!!!). The good part of the story is that this is the first test at the US Federal Appeals Court level for an open source license to be enforceable even if no money exchanges hands, and... we won!

Bob spent a lot of time and money on the case though. Listen to the podcast and contribute to his legal defense if you care about open source.

OMG UNICORNIFY::URL!!! <3

schwern — 2010-04-01T22:51:34+00:00

OMG! A UNICORN PONY FOR MEEEE!!!

You can get 1 2 wth Unicornify::URL!! Here's a program to do it at the command line.

use Acme::Pony; bUf Fybuf FyBuFFYbU FfyBUFfYbUff YBuffybuFfyBuF fYbUffYBUfFYbUff YbUFfYBuffYBuFFYBu FFybUffYBUffYBUfFYb UffYbUFfyBUffYBuFfyB UFFybUfFYBuffYbUFF ybUfFyBuFfyBufFy BuffYBufFyBUfFYB uffY bUffybuffyBUFfyBuf FYBuFfy BuFFybUFFyBUffyBuFFYbuffybUf fYbUfFYBu fFYB uFFyBufFyBUfFYbufFYbUFFYbUFfyBufFYBufFYBu FFyBufFyBUffYBufFYbUffYBUFfYBUFFyBuFfYbUFFybUffYBU ffyBU fFYbuffYbUffybuffYbuFfYbuFFyBuFFyBUfFybufFYbUf fYbUF fybUFfYBuffybuFfyBuFFYBuffYBUFFybuffybUffYBu fFYBuf fyBuFFyBufFyBUffYBufFYbufFyBUFfybUFfYbuffyb uFfyB UffYBUfFybUfFYbuFfYBUFfYbUffYBuffybuFf yBuFFY BuffYBUFFybuffybUffYbufFYb ufFyb UFfybufFYBuffybufFyb UffYb UffybUFfY buffybuF fybUf fyBuffy BUFfYbuF FYbUF fyBuffYbuFFyBUFf ybUf Fybu ffYb UffybuF fYbu ffYB UFFy BuFFYB UfFy BuF fybU ffYB Uff Ybu fFyb uFf YBUF F yBuFFYBUfFy

<3 k thx bye!!1!11!!!

Some Facts About Schwern

schwern — 2010-03-26T03:45:05+00:00

Open Source Bridge requested that I improve my bio, so I decided to share some facts about myself...

Schwern has a copy of Perl 6, he lets Larry Wall borrow it and take notes.
Schwern once sneezed into a microphone and the text-to-speech conversion was a regex that turns crap into gold.
Damian Conway and Schwern once had an arm wrestling contest. The superposition still hasn’t collapsed.
Schwern was the keynote speaker at the first YAPC::Mars.
When Schwern runs a smoke test, the fire department is notified.
Dan Brown analyzed a JAPH Schwern wrote and discovered it contained the Bible.
Schwern writes Perl code that writes Makefiles that write shell scripts on VMS.
Schwern does not commit to master, master commits to Schwern.
SETI broadcast some of Schwern’s Perl code into space. 8 years later they got a reply thanking them for the improved hyper drive plans.
Schwern once accidentally typed “git pull —hard” and dragged Github’s server room 10 miles.
There are no free namespaces on CPAN, there are just modules Schwern has not written yet.
Perl's threads are implemented with a single strand of Schwern's hair.
"Schwern" cmp "Chuck Norris" will cause Perl to segfault rather than try to compare them.
Schwern’s tears are said to cure cancer, unfortunately his Perl code gives it right back.

The Basic Unit of Bug Report Frustration

schwern — 2010-03-22T23:57:26+00:00

I submitted a proposal to OSCON called "How To Report A Bug" about the social issues involved in reporting and accepting bug reports. Its still pending, but its caused me to do a little writing for it. I came up with this introduction which I feel sums up the problem well. I'm also tickled that one measures bug report frustration in bags of shit.

Developers often treat bug reports like someone dumping a bag of shit on your doorstep, ringing the bell and telling you to clean it up. That's not what they are. A bug report is someone pointing out that there's some shit on your doorstep, they stepped in it, and maybe it should be cleaned up.
Either way, nobody likes stepping in shit. And nobody likes cleaning up shit. So the whole interaction starts off on the wrong foot, perhaps the one covered in shit. Your job, as developer or as reporter, is to deliberately steer it back to being a positive one where the developer wants to fix shit and the reporter wants to continue to report shit.

ah, dreams...

Matts — 2010-01-26T10:31:17+00:00

I just woke from a dream where it was rjbs' birthday and we got him an onion cake. Only the person who made the cake misunderstood, and instead of a cake shaped like an onion he cooked it WITH onions in it.

Bizarro.

Time::Piece test failures on Win32

Matts — 2010-01-25T23:23:53+00:00

Can someone with Time::Piece test failures on Win32 please contact me offlist? I have a proposed patch I'd like to test, but no Win32 perl to test it on.

The return of perl5i!

schwern — 2010-01-24T02:00:43+00:00

After an extended period in hibernation, perl5i returns to CPAN with a rack of new changes since the last CPAN release. Thanks to Bruno Vecchi, Chas Owens, Darian Patrick, Jeff Lavallee, Michael Greb, rjbs, benh and chromatic for contributing!

Why was it deleted from CPAN? Version numbers. I'd used my usual ISO date integer style versioning but realized pretty quick that I need full X.Y.Z versioning to indicate incompatible changes. Yes, perl5i is planning to be incompatible but without breaking your code!

How? By allowing you to declare what major version of perl5i you rely on. At this point its most likely going to be "use perl5i::2" which has the nice benefit of also allowing you to declare a dependency on perl5i::2. Easy peasy.

The question remains, what should "use perl5i" do? Should it A) load the currently installed version of perl5i? Or B) die with instructions on what to do? A is convenient, but means you'll get (probably unknowingly) walloped by an incompatibility later. B is a little inconvenient, but it makes the planned incompatibilities explicit and visible. The existence of a perl5i command line program (which also works on the #! line) makes A less of a concern if you want to go that route. So likely in short order "use perl5i" won't work any more. But I'd still like your thoughts on the matter.

Great Perl Code

schwern — 2010-01-11T22:59:39+00:00

I was in a bar the other day talking with somebody about Perl. He asked, "what is some great Perl code I could read?" He was looking for a non-trivial amount of production Perl 5 code that elegantly solves a problem, and is beautiful to read.

I'm couldn't answer that. The code I see is either beautiful to read but fairly boring in what it does OR is an elegant solution but is terrifying to read (for example, autodie). I'm a biased observer, I work mostly with the plumbing so I see mostly the scary stuff that implements the elegant solutions.

What code would you show a non-Perl programmer read that is both beautiful and interesting?

gitPAN now updating

schwern — 2010-01-07T03:05:02+00:00

After a month's break I've fixed up the gitPAN importer so it can update distributions in place fairly efficiently. This involved a major overhaul of Parse::BACKPAN::Packages into the new SQLite and DBIx::Class backed BackPAN::Index. Faster, leaner, far more flexible.

Its grinding through an update now, should be done before tomorrow morning. Still running off my laptop, hosting is in the works and then daily updates can happen.

UPDATE: The update is complete. Hit a few snags. 1) I wasn't always sorting releases by date, so I might have gotten some out of order in this update. Eventually there will be a full sweep and rebuild. 2) Some parts of github are case sensitive, some parts are not, and this caused some issues when distribution names subtly change case (like WebService vs Webservice). BackPAN::Index treats this as two different distributions, github treats it as one repository, hilarity ensues.

So that's the first 90% complete. Given that too about a month and the last 10% takes 90% of the time... see you in 2011.

Warning compiling perl stuff on Snow Leopard

Matts — 2010-01-04T22:13:57+00:00

I've searched but can't find any reference to this...

Compiling IO::KQueue on Snow Leopard I get the following warning:

KQueue.xs: In function 'XS_IO__KQueue_kevent': KQueue.xs:71: warning: format not a string literal and no format arguments

Yet that line is just:

Newxz(ke, max_events, struct kevent);

Which seems to me pretty standard perl, and no format strings involved (though Newxz expands quite a few macros).

CPAN's Greatest Hits - Path::Class

schwern — 2010-01-03T04:10:17+00:00

Once upon a time, file and directory manipulation was considered very convenient. Compared to languages like C and Java, which consider I/O as some sort of distasteful act that should best be done behind at least 9 layers of abstraction, its positively enlightened. But once you use something like Ruby's File and Dir objects Perl starts to look a touch out of date.

In Perl, reading a file or directory is a three step process. Safe path manipulation requires the brilliant but cumbersome File::Spec. Even something like deleting a file requires special code to be safe. Want to reliably delete or create a directory? That's another module, File::Path. Copying a file? File::Copy. And so on.

The root of the problem is that Perl represents paths as just strings. And while that's enough to uniquely identify them, its not nearly enough to actually do anything with them. You want an object, files and directories which know how to do it all. Path::Class provides.

Created by Ken Williams, Path::Class is it. Short, convenient constructors, string overloading and providing just about everything you'd want to do with a path. Since its just sugar on top of all the pre-existing and well-built File modules, its extremely robust.

Here is why it is awesome.

Slurp a file.

# Perl open my $fh, "<", $file; my $content = do { local $/; <$fh> }; close $fh; # Path::Class my $contents = file($file)->slurp;

Iterate over every file in a directory.

# Perl opendir my $dh, $dir; for my $thing (grep { $_ ne '.' or $_ ne '..' } readdir $dh) { ... } closedir $dh; # Path::Class for my $thing (dir($dir)->children) { ... }

Change the subdir and file on a path (ie. from /some/path/foo/bar.txt to /some/path/baz/biff.txt)

# Perl my($vol, $dir, $file) = File::Spec->splitpath($path); my @dirs = File::Spec->splitdir($dir); pop @dirs; my $newpath = File::Spec->catpath($vol, @dirs, $newdir, $newfile); # Path::Class my $newpath = file($file)->parent->parent->subdir($newdir)->file($newfile);

That last example starts to demonstrate what happens once Path::Class objects become ubiquitous in your code. Rather than instantiating them when needed, they're just there and can be chained together for rapid manipulation. Since they're string overloaded there's no reason not to use them.

I neglected error handling in the examples above. Path::Class was written back when library functions calling die() was considered impolite. Before pjf hammered home (cleaved with a Bat'leth?) the point that exceptions are awesome. So you still have to do all the "or die ..." junk with Path::Class, you don't even get the convenience of autodie. Fortunately I hope to do something about that.

The next time you find yourself writing "use File::Spec" give Path::Class a shot.

I'm twittering my Perl stuff at http://twitter.com/briandfoy

brian_d_foy — 2010-01-02T13:06:32+00:00

I'll tweet at (http://twitter.com/briandfoy_perl) when I have something to say in 140 characters. I'll almost always use "Perl" when I post.

Effective Perl Programming master class at Frozen Perl

brian_d_foy — 2010-01-01T13:32:50+00:00

At Frozen Perl 2010 in Minneapolis, I'm teaching a new master class based on my latest book, Effective Perl Programming, 2nd Edition. Perl has changed quite a bit since Joseph Hall wrote the first edition over 10 years ago. Josh McAdams and I have added a lot of new information as well as updated the existing material. In the one-day class for intermediate Perl programmers, I'll cover selected topics from the book, including:

Working with Unicode in Perl
Tricks with filehandles
New regex features in Perl 5.10 and later
Playing with pack()
Using closures to make things simpler
and other topics as time allows

Although the book hasn't been published yet, it is available for pre-order, and attendees to the class can get a sneak peek at the working manuscript as well as a soft copy of the course slides.

Numbered test file abuse

schwern — 2009-12-29T01:43:23+00:00

I hate numbered test files. Not that it isn't useful to force the ordering of some tests, but because its not then necessary to force the ordering of EVERY test. At the worst case you're back to BASIC. Observe the test suite from SQL::Statement.

00error.t 01prepare.t 02executeDirect.t 03executeDBD.t 04names.t 05create.t 06group.t 07case.t 08join.t 09ops.t 10limit.t 11functions.t 12eval.t 13 call.t 14allcols.t 15naturaljoins.t 16morejoins.t 17quoting.t 18bigjoin.t 19idents.t 20pod.t 21pod_coverage.t

Now, how much of that is really trying to order the tests and how much of it is just the order it happened to be written? Does the limit test really have to go after the functions test? Why is there a quoting test in the middle of three join tests? I see three that make any kind of sense, 00error.t (since most of the tests use RaiseError), 20pod.t and 21pod_coverage.t, which maybe go last, though its honestly not important that they do.

What's the harm? It cripples command line completion. And you've got the old BASIC problem of renumbering. I want to add a new test, where does it go? Do I have to puzzle out the implied dependencies? Do I stick it at the end? But then the POD tests aren't last any more. Do I renumber everything? Do I use a duplicate number? Do I say the hell with it and cram it into an existing test file?

Not worth it.

Realistically most test dependencies really want to express two things: Run this first and run this last. For that you have 00foo.t and zz-bar.t. 00compile.t, 00setup.t, zz-teardown.t, zz-pod.t, etc... Anything else, just write it without the number. Or if you really do have a fixed order use Test::Manifest.

If you do have tests that would do better running in order, then instead of smashing them together into one arbitrary numbering system, group them. That is, stick them into a common subdirectory and then apply the first/last numbering again. A clear candidate in SQL-Statement would be t/join to contain naturaljoins.t, morejoins.t and bigjoin.t. This has the advantage of easily letting you run all one group's tests in one shot. "prove -lr t/join".

I don't mean to pick on SQL::Statement, its just what I'm patching right now. Lots of distributions obsessively number their test files to no real advantage.

What's your coolest Perl one-liner?

brian_d_foy — 2009-12-17T06:19:18+00:00

Josh and I are finishing up Effective Perl Programming, 2nd Edition, and the last part to finish off is the item on Perl one-liners.

Besides going through writing a one liner, we want to list a bunch of them too. Want to get your name in the book? Give us some one-liners that you wrote yourself and a couple of sentences about what it does. Make sure you tell us how you'd like your name to appear in the book, too. :)

gitPAN is complete!

schwern — 2009-12-14T22:27:48+00:00

The gitPAN import is complete.

From BackPAN
------------
118,752 files
10,440,348,937 bytes (measured by adding individual file size)
21987 distributions (I skipped perl, parrot and parrot-cfg)

To git
------
21,766 repositories
4,495,204 bytes (measured by total disk usage
after git gc with no checkout)
150 gigs on github (they have to index it)
12 days (lots of starts and stops)
1 laptop (1st gen Macbook)

I had to do it on a disk image because OS X's case-insensitive filesystem

I've written up a small FAQ. gitpan is reasonably stable, but you may have to rebase in the future.

Next, I take a break.

Then begins the second pass, mostly improving and adding tags. Here's the list of planned features. The second pass will be a rolling reimport of each distribution to bring everything up to the same standard, there was a lot of incremental improvements during the first pass. I expect this to be changes to commit logs and tags with very little content change.

The issue of PAUSE ownership I'm going to punt on. Its ugly and can be done entirely in parallel. If someone else makes available a historical distribution ownership database, gitPAN will use it.

MSCHWERN has a PAUSEID

schwern — 2009-12-13T07:36:42+00:00

ANDRE has a posse.

MSCHWERN has a PAUSEID.

Do you?

gitPAN and the PAUSE index

schwern — 2009-12-12T22:02:03+00:00

As you may or may not know, people on CPAN own modules (technically they own the namespace). Each Foo::Bar is owned by one or more CPAN accounts. Usually you gain ownership on a "first-come" basis, but it can also be transferred. Only the "official" tarball for a given namespace is indexed. So if the owner of Foo::Bar uploads Foo-Bar-1.23.tar.gz Foo::Bar will point at Foo-Bar-1.23.tar.gz. If I (presumably unauthorized) upload Foo-Bar-1.24.tar.gz the index will still point at Foo-Bar-1.23.tar.gz.

Here's the rub. Not owning a module doesn't stop you from uploading. It also says nothing about who owns the distribution. gitpan is by distribution. Now it gets a little more difficult to figure out who owns what. For example, look at MQSeries-1.30. All but two modules are unauthorized. BUT notice that MQSeries.pm is authorized. The CPAN index does point MQSeries at M/MQ/MQSERIES/MQSeries-1.30.tar.gz (everything else is at 1.29). Likely what we have here is a botched ownership transfer.

How do you mark that? search.cpan.org seems to take the strict approach, if anything's unauthorized its out. The CPAN uploads database I have available is the opposite, if anything is authorized its in. What to do?

Then there's stuff like lcwa. Looks like junk, but here's the thing. CPAN has a global module index to worry about, gitpan doesn't. Each distribution is its own distinct unit. So lcwa does no harm on gitpan, it can be recorded.

What does matter? The continuity of a distribution's releases, and this is precisely what CPAN does not track. It doesn't even have a concept of a distribution, just modules inside tarballs. CPAN authors playing nice with tarball naming conventions gives the illusion of a continuous distribution.

So... for a given release of a distribution (ie. a tarball), how does gitpan determine if the release should be included in the distribution's history? If we go strict, like search.cpan.org, we're going to lose legit releases and even entire distributions (like lcwa). If we let anything in gitpan is not showing an accurate history.

Add the complication that authorization changes. For example, the MQSeries module ownership will eventually be fixed. What then?

First pass through, gitpan is ignoring this problem. Its just chucking everything from BackPAN in. Second pass will rebuild individual repos with collected improvements. This is the first thing I'm not sure what to do about.

Suggestions?

Applying ideas from new languages in your old standbys

Aristotle — 2009-12-04T10:35:19+00:00

I just wrote the following Perl 5 code. Consider the bolded bits, and think about what the code would have looked like if I had tried to write it in any equally DRY way using map.

sub new { my $class = shift; my $self = bless { @_ }, $class; my $builder = $self->builder; my $content = $self->content; my ( @gather, @take ); for my $r ( XML::Builder::Util::is_raw_array( $content ) ? @$content : $content ) { @take = $r; if ( not Scalar::Util::blessed $r ) { @take = $builder->render( @_ ) if XML::Builder::Util::is_raw_array $r; next; } if ( not $r->isa( $builder->fragment_class ) ) { @take = $builder->stringify( $r ); next; } next if $builder == $r->builder; Carp::croak( 'Cannot merge XML::Builder fragments built with different namespace maps' ) if $r->depends_ns_scope; @take = $r->flatten; my ( $self_enc, $r_enc ) = map { lc $_->encoding } $builder, $r->builder; next if $self_enc eq $r_enc # be more permissive: ASCII is one-way compatible with UTF-8 and Latin-1 or 'us-ascii' eq $r_enc and grep { $_ eq $self_enc } 'utf-8', 'iso-8859-1'; Carp::croak( 'Cannot merge XML::Builder fragments with incompatible encodings' . " (have $self_enc, fragment has $r_enc)" ); } continue { push @gather, @take; } $self->{'content'} = \@gather; return $self; }

I don’t know whether this way of writing the code would have occurred to me if I hadn’t seen the construct in Perl 6. I suspect not.