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Perl import statements (like "
use POSIX;") allow you to import symbols into your package, but they also allow lots of other shenanigans to take place. We'll explore avoiding pitfalls when importing modules, implementing best practices when importing and how to automate this via
App::perlimports.
This talk will be made up of several parts.
How imports workThis will include a discussion of
Exporter,
Sub::Exporter and
Import::Into. It will probably include some examples of other unexpected behaviour that may take place when
Foo->import is called.
We will discuss why knowing what every CPAN module exports is almost impossible, but we'll review some techniques which we can use to maximize the number of modules we can reliably inspect for exports. There will be a brief discussion on how
Import::Into can be used to create your own pragmas, or even your own flavour of
Moose.
Why imports can introduce a maintenance burden on new and even experienced Perl programmersUnmanaged import statements allow many unused symbols to be imported into existing code. Bare import statements and even import tags make it hard to discover where functions and other symbols originate from. Managing existing import statements gives us a chance to make code more readable, clarify the origin of imported symbols, remove unused dependencies and even speed up code compilation.
There will be a brief discussion of existing
Perl::Critic policies which try to address this. We will look at using
dump-perl-exports as a tool to discover what a module really exports.
App::perlimportsBare imports and import tags provide the code author with a convenience, but this can come at the cost of readability for everyone else. We will walk through using
perlimports from the command line and see how it attempts to clean up import statements in a selection of a code, a file or even an entire codebase. We will discuss how to use similar techniques with a simple
vim integration, so that imports can be cleaned up directly in the
vim editor. If
perlimports does not present itself as a workable solution for an audience member, the preceding discussion should provide some food for thought as to how technical debt on an existing code base can be reduced through wise use of import statements.
