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Choose Your Own Tutorial

Declaring and Detecting Prerequisites

The CPAN clients that will be used to install your distribution will first look at its META.yml or META.json files or interact with its install tool to decide what libraries, if any, have to be installed before your code can be built, tested, and installed. These are your dist's prereqs.

There are two common ways to set up your prerequisites. You can declare them explicitly, or you can let Dist::Zilla detect them by analyzing your code.

Declaring Your Prereqs

The Prereqs plugin is about as straightforward as it gets:

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[Prereqs]
Sub::Exporter = 0.979 ; to get INIT arg
Acme::ProgressBar = 1.002 ; includes needed bug fixes

 

If you need to declare special kind of prereqs, like prereqs only needed to test your dist, you could add either of the configuration sections in the following sample -- they'd have the same effect.

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[Prereqs]
-phase = test

Test::BinaryData = 0
Test::More = 0.88 ; for done_testing

 


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[Prereqs / TestRequires]
Test::BinaryData = 0
Test::More = 0.88 ; for done_testing

 

Because you can't have two sections with the same name, the second example will probably be simpler to use all around.

In general, the only prereq plugins you should need are RuntimeRequires (the default), TestRequires, ConfigureRequires, and BuildRequires. For more information about these, consult the CPAN META file specification.

Detecting Your Prereqs

The problem with maintaining your list of prerequisites in your dist.ini is the same as maintaining it in your Makefile.PL: the versions required in your code and your configuration diverge. The most common version of this is having a lot of bare use Some::Module lines in your code, but specific versions in your installer.

Dist::Zilla solves this problem by figuring out your prerequisites from your code. You specify the version in your use statement and Dist::Zilla requires that version. All you have to add to your configuration is:

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[AutoPrereqs]
 

It will look at all the use and require statements in your code, along with some special cases for Moose. Requirements found for code that's going to be installed (like programs or libraries) are made runtime prereqs. Requirements found for test libraries become test prereqs.

To specify particular versions of a prerequisite, you need to use the use MODULE VERSION form, which is actually a very good thing, because it means that we can no longer compile our code if the prereqs aren't met. It keeps our code and install data in sync. For example:

  use Moose 1.00;
  use JSON 2 (); # don't import any functions

(At this point, you'll probably want to make sure that you're requiring the right version in your code. Many dists require one version in the code and one in the prereq listing. Now that you've only got one place to list the required version, make sure you get it right.)

If AutoPrereqs makes mistakes, you can always tell it to skip things or add things manually with Prereqs:

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[AutoPrereqs]
skip = ^Library::Bogus$
skip = ^Bundled::

[Prereqs]
Something::AutoPrereqs::Misses = 1.234

 

Declaring Author Prereqs

Sometimes author prereqs (modules used by Dist::Zilla) are indirectly needed, e.g. via a Pod::Weaver configuration. You can declare them in dist.ini with

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; authordep Pod::Weaver::Plugin::StopWords
; authordep Pod::Weaver::Section::Support

 

You can fork and improve this documentation on GitHub!