Dist::Zilla::Plugins:: Best Practices

You've already written your own Dist::Zilla plugin (or you plan to write one)? Your dzil build are slow and you want to know why? This is for you.

In this talk I will expose a few tips that will help you to avoid adding more bloat to Dist::Zilla:
- how to discover performance issues (tools...)
- how to write efficient InlineFiles-based Test:: plugin
- best pratices to inject dependencies

Transcript

1. August 22th, 2014 YAPC::EU::2014
   Dist::Zilla::Plugin::
   Best Practices
   for authors
   

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2. Olivier Mengué
   DOLMEN - @omengue
   ●
   IoT software engineer at IJENKO
   ●
   Perl embeded in a gateway between a Home Area
   Network (HAN) and the Internet ; ZigBee, M-Bus,
   EnOcean…
   ●
   Member of the Perl Toolchain Gang
   ●
   Open Source:
   – 20+ dists on CPAN
   – 300+ tickets filled on rt.cpan.org ;
   – Maintainer of LiquidPrompt github:nojhan/liquidprompt
   – Personal projects : github-keygen, angel-PS1
   – 72 commits in Dist::Zilla core (committer #3)
   

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3. Plan
   ●
   dzil plugins overview
   ●
   Profiling your build
   ●
   Advices
   

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4. Dist::Zilla plugins
   ●
   Dist::Zilla::Plugin::*
   – Plugins referenced from dist.ini
   – Methods called during « phases »
   – dist.ini: [Name]
   ●
   Dist::Zilla::Plugin::Test::*
   – Plugins that inject files test scripts in t/ or xt/
   ●
   Dist::Zilla::PluginBundle::*
   – Group of plugins, with settings, packaged
   – dist.ini: [@Name]
   ●
   Dist::Zilla::App::Command::*
   – For dzil sub commands
   

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5. dzil performance : profiling
   ●
   List modules loaded by dzil
   perl ­d:TraceUse=output:out.txt ­S dzil nop
   ●
   Check dzil run flamegraph to find major hot
   spots
   perl ­d:NYTProf ­S dzil listdeps
   nytprofhtml ­­open
   

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6. dzil profiling
   dzil nop
   dzil listdeps
   dzil build
   dzil test
   

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7. ?? POLL ??
   How many modules are loaded by
   dzil nop
   for
   [@Milla]
   Dist::Milla is bundle that provides a useful set of plugins.
   Reply is system dependent as it depends on plugins installed.
   

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9. ...but down from
   672
   with my patches
   https://github.com/miyagawa/Dist-Milla/issues/24
   

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10. Solution: lazy loading
    Replace... with...
    use Foo::Bar;
    sub foo
    {
    my $foo = Foo::Bar­>new;
    }
    sub foo
    {
    require Foo::Bar;
    my $foo = Foo::Bar­>new;
    }
    use Foo::Bar qw< bar >;
    sub foo
    {
    bar(…);
    }
    sub foo
    {
    require Foo::Bar;
    Foo::Bar::bar(…);
    }
    

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11. Dist::Zilla::App::Command::*
    ●
    All plugins are loaded every time you run 'dzil',
    whatever the command
    ●
    Impacts all builds of all your projects
    ●
    Fix : delay loading of dependencies to the
    execute method
    

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12. Dist::Zilla::Plugin::*
    ●
    Executed by phase (see
    Dist::Zilla::App::Command::dumpphases)
    ●
    But loaded always
    ●
    Delay dependencies loading!
    

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13. Dist::Zilla::Plugin::*
    ●
    Use your plugin for the build of the distribution
    of the plugin
    – Eat your own dog food
    – Find issues early
    – Just building the dist is one more test!
    ●
    How to:
    – Use the plugin in dist.ini
    – But use [Bootstrap::lib] before
    else you use the last installed one in @INC, not the one in
    development
    

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14. Dist::Zilla::Plugin::*
    ●
    Since dzil v5
    ->content vs ->encoded_content
    

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15. Dist::Zilla::Plugin::Test::*
    ●
    If the generated script uses a module, inject the module
    as a prereq so it appears in
    dzil listdeps ­­author
    – Author, release tests must inject as 'develop' prereq
    – Others tests as 'test' prereq
    ●
    The test script must fail (loudly) if the prereq is missing
    – « Soft failure » (skip the test if prereq missing) is a failure of
    the plugin author as that makes the plugin useless
    ●
    How to:
    – Use Dist::Zilla::Role::PrereqSource
    – Example: Dist::Zilla::Plugin::Test::NoTabs
    

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16. Dist::Zilla::PluginBundle::*
    ●
    Eat your own dog food
    … after [Bootstrap::lib]
    ●
    Use
    Dist::Zilla::Role::PluginBundle::PluginRemover
    – Convenient for users of the bundle
    

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17. Summary
    ●
    As a dzil user, profile your own builds, report
    issues to plugin authors
    ●
    As a plugin author, delay dependency loading
    

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18. Questions?
    dolmen@cpan.org
    Twitter: @omengue
    IRC: dolmen in #distzilla
    Slides : not yet on...
    http://o.mengue.free.fr/presentations/
    Https://speakerdeck.com/dolmen
    

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