# NAME App::perlimports - Make implicit imports explicit # VERSION version 0.000004 # SYNOPSIS Update a file in place. (Make sure you can revert the file if you need to.) perlimports --filename test-data/foo.pl --inplace-edit If some of your imported modules are in local directories, you can give some hints as to where to find them: perlimports --filename test-data/foo.pl --inplace-edit --libs t/lib,/some/dir/lib Redirect output to a new file: perlimports --filename test-data/foo.pl > foo.new.pl ## VIM If you're a `vim` user, you can pipe your import statements to [perlimports](https://metacpan.org/pod/perlimports) directly. :vnoremap <silent> im :!perlimports --read-stdin --filename '%:p'<CR> The above statement will allow you to visually select one or more lines of code and have them updated in place by [perlimports](https://metacpan.org/pod/perlimports). Once you have selected the code enter `im` to have your imports (re)formatted. ## MOTIVATION Many Perl modules helpfully export functions and variables by default. These provide handy shortcuts when you're writing a quick or small script, but they can quickly become a maintenance burden as code grows organically. When code increases in complexity, it leads to greater costs in terms of development time. Conversely, reducing code complexity can speed up development. This tool aims to reduce complexity to further this goal. While importing symbols by default or using export tags provides a convenient shorthand for getting work done, this shorthand requires the developer to retain knowledge of these defaults and tags in order to understand the code. `perlimports` aims to allow you to develop your code as you see fit, while still giving you a viable option of tidying your imports automatically. In much the same way as you might use [perltidy](https://metacpan.org/pod/perltidy) to format your code, you can now automate the process of making your imports easier to understand. Let's look at some examples. - Where is this function defined? You may come across some code like this: use strict; use warnings; use HTTP::Request::Common; use LWP::UserAgent; my $ua = LWP::UserAgent->new; my $req = $ua->request( GET 'https://metacpan.org/' ); print $req->content; Where does `GET` come from? If you're not familiar with [HTTP::Request::Common](https://metacpan.org/pod/HTTP%3A%3ARequest%3A%3ACommon), you may not realize that the statement `use HTTP::Request::Common` has implicitly imported the functions `GET`, `HEAD`, `PUT`, `PATCH`, `POST` and `OPTIONS` into to this block of code. What would happen if we used `perlimports` to import all needed functions explicitly? It might look something like this: use strict; use warnings; use HTTP::Request::Common qw( GET ); use LWP::UserAgent (); my $ua = LWP::UserAgent->new; my $req = $ua->request( GET 'https://metacpan.org/' ); print $req->content; The code above makes it immediately obvious where `GET` originates, which in turn makes it easier for us to look up its documentation. It has the added bonus of also not importing `HEAD`, `PUT` or any of the other functions which [HTTP::Request::Common](https://metacpan.org/pod/HTTP%3A%3ARequest%3A%3ACommon) exports by default. So, those functions cannot unwittingly be used later in the code. This makes for more understandable code for present day you, future you and any others tasked with reading your code at some future point. Keep in mind that this simple act can save much time for developers who are not intimately familiar with Perl and the default exports of many CPAN modules. - Are we even using all of these imports? Imagine the following import statement use HTTP::Status qw( is_cacheable_by_default is_client_error is_error is_info is_redirect is_server_error is_success status_message ); followed by 3,000 lines of code. How do you know if all of these functions are actually being used? Were they ever used? You can grep all of these function names manually or you can remove them by trial and error to see what breaks. This is a doable solution, but it does not scale well to scripts and modules with many imports or to large code bases with many imports. Having an unmaintained list of imports is preferable to implicit imports, but it would be helpful to automate maintaining this list. [perlimports](https://metacpan.org/pod/perlimports) can, in many situations, clean up your import statements and automate this maintenance burden away. This makes it easier for you to write clean code, which is easier to understand. - Are we even using all of these modules? In cases where code is implicitly importing from modules or where explicit imports are not being curated, it can be hard to discover which modules are no longer being used in a script, module or even a code base. Removing unused modules from code can lead to gains in performance and decrease in consumption of resources. Removing entire modules from your code base can decrease the number of dependencies which you need to manage and decrease friction in your your deployment process. `perlimports` does not remove unused modules for you, but using it to actively tidy your imports can make this manual process much easier to manage. - Enforcing a consistent style Having a messy list of module imports makes your code harder to read. Imagine this: use Cpanel::JSON::XS; use Database::Migrator::Types qw( HashRef ArrayRef Object Str Bool Maybe CodeRef FileHandle RegexpRef ); use List::AllUtils qw( uniq any ); use LWP::UserAgent q{}; use Try::Tiny qw/ catch try /; use WWW::Mechanize q<>; [perlimports](https://metacpan.org/pod/perlimports) turns the above list into: use Cpanel::JSON::XS (); use Database::Migrator::Types qw( ArrayRef Bool CodeRef FileHandle HashRef Maybe Object RegexpRef Str ); use List::AllUtils qw( any uniq ); use LWP::UserAgent (); use Try::Tiny qw( catch try); use WWW::Mechanize (); Where possible, [perlimports](https://metacpan.org/pod/perlimports) will enforce a consistent style of parentheses and will also sort your imports and break up long lines. As mentioned above, if some imports are no longer in use, `perlimports` will helpfully remove these for you. - Import tags Import tags may obscure where symbols are coming from. While import tags provide a useful shorthand, they can contribute to code complexity by obscuring the origin of imported symbols. Consider: use HTTP::Status qw(:constants :is status_message); The above line imports the `status_message()` function as well \*some other things\* via `:constants` and `:is`. What exactly are these things? We'll need to read the documentation to know for sure. `perlimports` can audit your code and expand the line above to list the symbols which you are actually importing. So, the line above might now look something like: use HTTP::Status qw( HTTP_ACCEPTED HTTP_BAD_REQUEST HTTP_CONTINUE HTTP_I_AM_A_TEAPOT HTTP_MOVED_PERMANENTLY HTTP_NO_CODE HTTP_NOT_FOUND HTTP_OK HTTP_PAYLOAD_TOO_LARGE HTTP_PERMANENT_REDIRECT HTTP_RANGE_NOT_SATISFIABLE HTTP_REQUEST_ENTITY_TOO_LARGE HTTP_REQUEST_RANGE_NOT_SATISFIABLE HTTP_REQUEST_URI_TOO_LARGE HTTP_TOO_EARLY HTTP_UNORDERED_COLLECTION HTTP_URI_TOO_LONG is_cacheable_by_default is_client_error is_error is_info is_redirect is_server_error is_success status_message ); This is more verbose, but grepping your code will now reveal to you where something like `is_cacheable_by_default` gets defined. You have increased the lines of code, but you have also reduced complexity. # DESCRIPTION This distribution provides the [perlimports](https://metacpan.org/pod/perlimports) binary, which aims to automate the cleanup and maintenance of Perl import statements. # CAVEATS There are lots of shenanigans that Perl modules can get up to. This code will not find exports for all of those cases, but it should only attempt to rewrite imports which it knows how to handle. Please file a bug report in all other cases. # SEE ALSO [Perl::Critic::Policy::TooMuchCode::ProhibitUnusedImport](https://metacpan.org/pod/Perl%3A%3ACritic%3A%3APolicy%3A%3ATooMuchCode%3A%3AProhibitUnusedImport), [Perl::Critic::Policy::TooMuchCode::ProhibitUnusedInclude](https://metacpan.org/pod/Perl%3A%3ACritic%3A%3APolicy%3A%3ATooMuchCode%3A%3AProhibitUnusedInclude) and [Perl::Critic::Policy::TooMuchCode::ProhibitUnusedConstant](https://metacpan.org/pod/Perl%3A%3ACritic%3A%3APolicy%3A%3ATooMuchCode%3A%3AProhibitUnusedConstant) # AUTHOR Olaf Alders <olaf@wundercounter.com> # COPYRIGHT AND LICENSE This software is copyright (c) 2020 by Olaf Alders. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.