NAME

Module::Build - Build and install Perl modules

SYNOPSIS

Standard process for building & installing modules:

  perl Build.PL
  ./Build
  ./Build test
  ./Build install

DESCRIPTION

This is a beta version of a new module set I've been working on, Module::Build. It is meant to be a replacement for ExtUtils::MakeMaker.

To install Module::Build, and any other module that uses Module::Build for its installation process, do the following:

perl Build.PL
./Build             # this script is created by 'perl Build.PL'
./Build test
./Build install

Actions defined so far include:

build                          help        
clean                          install     
dist                           manifest    
distcheck                      realclean   
distclean                      skipcheck   
distdir                        test        
disttest                       testdb      
fakeinstall                                

It's like the MakeMaker metaphor, except that Build is a short Perl script, not a long Makefile. State is stored in a directory called _build/.

Any customization can be done simply by subclassing Module::Build and adding a method called (for example) ACTION_test, overriding the default action. You could also add a method called ACTION_whatever, and then you could perform the action ./Build whatever.

More actions will certainly be added to the core - it should be easy to do everything that the MakeMaker process can do. It's going to take some time, though. In the meantime, I may implement some pass-through functionality so that unknown actions are passed to MakeMaker.

METHODS

I list here some of the most important methods in the Module::Build. As the interface is still very unstable, I must ask that for now, you read the source to get more information on them. Normally you won't need to deal with these methods unless you want to subclass Module::Build. But since one of the reasons I created this module in the first place was so that subclassing is possible (and easy), I will certainly write more docs as the interface stabilizes.

$m = Module::Build->new(...)

Creates a new Module::Build object. Arguments to the new() method are listed below. The only required argument is the module_name argument.

• module_name

  The module_name argument is required, and should be a string like 'Your::Module'. We use it for several purposes, including finding the version string for this distribution, and creating a suitably-named distribution directory.

• module_version

  The module_version argument is optional - if not explicitly provided, we'll look for the version string in the module specified by module_name, parsing it out according to the same rules as ExtUtils::MakeMaker and CPAN.pm.

• module_version_from

  Allows you to specify an alternate file for finding the module version, instead of looking in the file specified by module_name.

• prereq

  An optional prereq argument specifies any module prerequisites that the current module depends on. The prerequisites are given in a hash reference, where the keys are the module names and the values are version specifiers:

  prereq => {Foo::Module => '2.4',
             Bar::Module => 0,
             Ken::Module => '>= 1.2, != 1.5, < 2.0'},

  These three version specifiers have different effects. The value '2.4' means that at least version 2.4 of Foo::Module must be installed. The value 0 means that any version of Bar::Module is acceptable, even if Bar::Module doesn't define a version. The more verbose value '>= 1.2, != 1.5, < 2.0' means that Ken::Module's version must be at least 1.2, less than 2.0, and not equal to 1.5. The list of criteria is separated by commas, and all criteria must be satisfied.

• c_source

  An optional c_source argument specifies a directory which contains C source files that the rest of the build may depend on. Any .c files in the directory will be compiled to object files. The directory will be added to the search path during the compilation and linking phases of any C or XS files.

• autosplit

  An optional autosplit argument specifies a file which should be run through the Autosplit::autosplit() function. In general I don't consider this a great idea, and I may even go so far as to remove this feature later. Let me know if I shouldn't.

$m->add_to_cleanup

A Module::Build method may call $self->add_to_cleanup(@files) to tell Module::Build that certain files should be removed when the user performs the Build clean action. I decided to make this a dynamic method, rather than a static list of files, because these static lists can get difficult to manage. I preferred to keep the responsibility for registering temporary files close to the code that creates them.

Module::Build->resume

You'll probably never call this method directly, it's only called from the auto-generated Build script. The new() method is only called once, when the user runs perl Build.PL. Thereafter, when the user runs Build test or another action, the Module::Build object is created using the resume() method.

$m->dispatch

This method is also called from the auto-generated Build script. It parses the command-line arguments into an action and an argument list, then calls the appropriate routine to handle the action. Currently (though this may change), an action foo will invoke the ACTION_foo method. All arguments (including everything mentioned in ACTIONS below) are contained in the $self->{args} hash reference.

$m->os_type

If you're subclassing Module::Build and some code needs to alter its behavior based on the current platform, you may only need to know whether you're running on Windows, Unix, MacOS, VMS, etc. and not the fine-grained value of Perl's $^O variable. The os_type() method will return a string like Windows, Unix, MacOS, VMS, or whatever is appropriate. If you're running on an unknown platform, it will return undef - there shouldn't be many unknown platforms though.

ACTIONS

There are some general principles at work here. First, each task when building a module is called an "action". These actions are listed above; they correspond to the building, testing, installing, packaging, etc. tasks.

Second, arguments are processed in a very systematic way. Arguments are always key=value pairs. They may be specified at perl Build.PL time (i.e. perl Build.PL sitelib=/my/secret/place), in which case their values last for the lifetime of the Build script. They may also be specified when executing a particular action (i.e. Build test verbose=1, in which case their values last only for the lifetime of that command. The build process also relies heavily on the Config.pm module, and all the key=value pairs in Config.pm are merged into the mix too. The precedence of parameters is, from highest to lowest: per-action parameters, Build.PL parameters, and Config.pm parameters.

The following build actions are provided by default.

• help

  This action will simply print out a message that is meant to help you use the build process. It will show you a list of available build actions too.

• build

  This is analogous to the MakeMaker 'make' target with no arguments. By default it just creates a blib/ directory and copies any .pm and .pod files from your lib/ directory into the blib/ directory. It also compiles any .xs files from lib/ and places them in blib/. Of course, you need a working C compiler (preferably the same one that built perl itself) for this to work properly.

  Note that in contrast to MakeMaker, this module only (currently) handles .pm, .pod, and .xs files. They must all be in the lib/ directory, in the directory structure that they should have when installed.

  If you run the Build script without any arguments, it runs the build action.

  In future releases of Module::Build the build action should be able to process .PL files. The .xs support is currently in alpha. Please let me know if it works for you.

• test

  This will use Test::Harness to run any regression tests and report their results. Tests can be defined in the standard places: a file called test.pl in the top-level directory, or several files ending with .t in a t/ directory.

  If you want tests to be 'verbose', i.e. show details of test execution rather than just summary information, pass the argument verbose=1.

  If you want to run tests under the perl debugger, pass the argument debugger=1.

  In addition, if a file called visual.pl exists in the top-level directory, this file will be executed as a Perl script and its output will be shown to the user. This is a good place to put speed tests or other tests that don't use the Test::Harness format for output.

• testdb

  This is a synonym for the 'test' action with the debugger=1 argument.

• clean

  This action will clean up any files that the build process may have created, including the blib/ directory (but not including the _build/ directory and the Build script itself).

• realclean

  This action is just like the clean action, but also removes the _build directory and the Build script. If you run the realclean action, you are essentially starting over, so you will have to re-create the Build script again.

• install

  This action will use ExtUtils::Install to install the files from blib/ into the correct system-wide module directory. The directory is determined from the sitelib entry in the Config.pm module. To install into a different directory, pass a different value for the sitelib parameter, like so:

  Build install sitelib=/my/secret/place/

  Alternatively, you could specify the sitelib parameter when you run the Build.PL script:

  perl Build.PL sitelib=/my/secret/place/

  Under normal circumstances, you'll need superuser privileges to install into the default sitelib directory.

• fakeinstall

  This is just like the install action, but it won't actually do anything, it will just report what it would have done if you had actually run the install action.

• manifest

  This is an action intended for use by module authors, not people installing modules. It will bring the MANIFEST up to date with the files currently present in the distribution. You may use a MANIFEST.SKIP file to exclude certain files or directories from inclusion in the MANIFEST. MANIFEST.SKIP should contain a bunch of regular expressions, one per line. If a file in the distribution directory matches any of the regular expressions, it won't be included in the MANIFEST.

  The following is a reasonable MANIFEST.SKIP starting point, you can add your own stuff to it:

  ^_build
  ^Build$
  ^blib
  ~$
  \.bak$
  ^MANIFEST\.SKIP$
  CVS

  See the distcheck and skipcheck actions if you want to find out what the manifest action would do, without actually doing anything.

• dist

  This action is helpful for module authors who want to package up their module for distribution through a medium like CPAN. It will create a tarball of the files listed in MANIFEST and compress the tarball using GZIP compression.

• distcheck

  Reports which files are in the build directory but not in the MANIFEST file, and vice versa. (See manifest for details)

• skipcheck

  Reports which files are skipped due to the entries in the MANIFEST.SKIP file (See manifest for details)

• distclean

  Performs the 'realclean' action and then the 'distcheck' action.

• distdir

  Creates a directory called $(DISTNAME)-$(VERSION) (if that directory already exists, it will be removed first). Then copies all the files listed in the MANIFEST file to that directory. This directory is what people will see when they download your distribution and unpack it.

• disttest

  Performs the 'distdir' action, then switches into that directory and runs a perl Build.PL, followed by the 'build' and 'test' actions in that directory.

AUTOMATION

One advantage of Module::Build is that since it's implemented as Perl methods, you can invoke these methods directly if you want to install a module non-interactively. For instance, the following Perl script will invoke the entire build/install procedure:

my $m = new Module::Build (module_name => 'MyModule');
$m->dispatch('build');
$m->dispatch('test');
$m->dispatch('install');

If any of these steps encounters an error, it will throw a fatal exception.

You can also pass arguments as part of the build process:

my $m = new Module::Build (module_name => 'MyModule');
$m->dispatch('build');
$m->dispatch('test', verbose => 1);
$m->dispatch('install', sitelib => '/my/secret/place/');

Building and installing modules in this way skips creating the Build script.

STRUCTURE

Module::Build creates a class hierarchy conducive to customization. Here is the parent-child class hierarchy in classy ASCII art:

/--------------------\
|   Your::Parent     |  (If you subclass Module::Build)
\--------------------/
         |
         |
/--------------------\  (Doesn't define any functionality
|   Module::Build    |   of its own - just figures out what
\--------------------/   other modules to load.)
         |
         |
/-----------------------------------\  (Some values of $^O may
|   Module::Build::Platform::$^O    |   define specialized functionality.
\-----------------------------------/   Otherwise it's ...::Default, a
         |                              pass-through class.)
         |
/--------------------------\
|   Module::Build::Base    |  (Most of the functionality of 
\--------------------------/   Module::Build is defined here.)

Right now, if you want to subclass Module::Build you must do so by including an actual .pm file somewhere in your distribution. There will be much better ways to do this in the future. Can't do everything at once...

MOTIVATIONS

There are several reasons I wanted to start over, and not just fix what I didn't like about MakeMaker:

• I don't like the core idea of MakeMaker, namely that make should be involved in the build process. Here are my reasons:

  +

  When a person is installing a Perl module, what can you assume about their environment? Can you assume they have make? No, but you can assume they have some version of Perl.

  +

  When a person is writing a Perl module for intended distribution, can you assume that they know how to build a Makefile, so they can customize their build process? No, but you can assume they know Perl, and could customize that way.

  For years, these things have been a barrier to people getting the build/install process to do what they want.

• There are several architectural decisions in MakeMaker that make it very difficult to customize its behavior. For instance, when using MakeMaker you do use MakeMaker, but the object created in WriteMakefile() is actually blessed into a package name that's created on the fly, so you can't simply subclass ExtUtils::MakeMaker. There is a workaround MY package that lets you override certain MakeMaker methods, but only certain explicitly predefined (by MakeMaker) methods can be overridden. Also, the method of customization is very crude: you have to modify a string containing the Makefile text for the particular target.

• It is risky to make major changes to MakeMaker, since it does so many things, is so important, and generally works. Module::Build is an entirely seperate package so that I can work on it all I want, without worrying about backward compatibility.

• Finally, Perl is said to be a language for system administration. Could it really be the case that Perl isn't up to the task of building and installing software? Absolutely not - see the Cons package for one example, at "/www.dsmit.com/cons/"" in "http: .

Please contact me if you have any questions or ideas.

TO DO

Need to implement a prerequisite mechanism, similar to MakeMaker's PREREQ_PM stuff.

There will also be a subclassing mechanism that doesn't require as much module infrastructure to use. Something like this:

use Module::Build subclass => <<'EOF';
 sub ACTION_foo {
   ... implement the 'foo' action ...
 }
EOF

The current method of relying on time stamps to determine whether a derived file is out of date isn't likely to scale well, since it requires tracing all dependencies backward, it runs into problems on NFS, and it's just generally flimsy. It would be better to use an MD5 signature or the like, if available. See cons for an example.

The current dependency-checking for .xs files is prone to errors. You can make 'widowed' files by doing Build, perl Build.PL, and then Build realclean. Should be easy to fix, but it's got me wondering whether the dynamic declaration of dependencies is a good idea.

- make man pages and install them. - append to perllocal.pod - write .packlist in appropriate location (needed for un-install)

AUTHOR

Ken Williams, ken@mathforum.org

SEE ALSO

perl(1), ExtUtils::MakeMaker(3)

http://www.dsmit.com/cons/

cpanm Module::Build

perl -MCPAN -e shell
install Module::Build