Interfaces in Perl5 at The Perl Conference 2019 in Pittsburgh

1. Interfaces in Perl5 kobaken a.k.a @kfly8 The Perl Conference 2019 #TPCiP
2. me • kobaken a.k.a @kfly8 • leader Gotanda.pm • orgnize YAPC::Tokyo 2019
11. I ❤ Perl
12. Interfaces in Perl5
13. DBI
14. my $dbh = DBI->connect(...); my $items = $dbh->selectrow_arrayref(…);
15. Unified Interface independent of datastore
16. Unified Interface provides values
17. Limitation makes value
18. Agenda 1.DEMO & Features 2.Goal 3.Example: TODO app 4.Internal 5.Performance
19. Function::Interface is Java-like interface
20. DEMO
21. Features of Function::Interface 1.Typed interface definition 2.Check at compile time
22. What is Goal ?
23. To maintain large Perl apps
24. Interface is good for large apps
25. 1. Be easier to fix implementation
26. 2. Stable dependencies
27. Goal • To maintain large apps. • Interface is good for large apps 1. Easy to fix implementation 2. Stable Dependencies
28. Example: TODO app
29. Case: “Inheritance”
30. package TodoRepository; use parent qw(DBI); sub new { my $class = shift; $class->connect(…); }
31. package TodoRepository; … 
 sub select { my ($self, $user_id) = @_; $self->selectall_arrayref( ‘SELECT * FROM todos WHERE user_id = ?’, $user_id ); }
32. package TodoApp; use TodoRepository; my $repo = TodoRepository->new;
33. package TodoApp; use TodoRepository; my $repo = TodoRepository->new(…); sub my_todo_list {
 my $self = shift; my $todos = $repo->select($self->user_id); return $self->render($todos); }
34. TodoApp TodoRepository DBI TODO table
35. TodoApp TodoRepository DBI TODO table
36. TodoApp TodoRepository DBI TODO table Unstable Dependencies
37. package TodoApp; use TodoRepository; my $repo = TodoRepository->new;
 sub evil_method { $repo->do(“ANY QUERY!!!!”); }
38. package TodoApp; use TodoRepository; my $repo = TodoRepository->new;
 sub evil_method { $repo->do(“ANY QUERY!!!!”); } Too many features
39. easy to test?
40. my $mock = mock TodoRepository => ( select => sub { … } ); my $app = TodoApp->new; test $app->my_todo_list;
41. my $mock = mock TodoRepository => ( select => sub { … } ); my $app = TodoApp->new; test $app->my_todo_list; messy to test
42. Problems of “Inheritance” case 1.Unstable dependencies 2.Too many features 3.messy to test
43. “Role” case
44. package TodoRepositoryInterface; use Moo::Role; requires qw(select);
45. package TodoRepository;
 use Moo; with qw( TodoRepositoryInterface ); has dbh => ( isa => ‘DBI::db’ );
46. package TodoRepository; use Moo; with qw( TodoRepositoryInterface ); has dbh => ( isa => ‘DBI::db’ );
47. package TodoRepository; … sub select { my ($self, $user_id) = @_; $self->dbh->selectall_arrayref( ‘SELECT * FROM todos WHERE user_id = ?’, $user_id ); }
48. package TodoApp; use Moo; has todo_repo => ( is => ‘ro’, does => ‘TodoRepositoryInterface’ );
49. package TodoApp; … sub my_todo_list {
 my $self = shift; my $repo = $self->todo_repo; my $todos = $repo->select($self->user_id); return $self->render($todos); }
50. TodoApp TodoRepository DBI TODO table TodoRepositoryInterface
51. TodoApp TodoRepository DBI TODO table TodoRepositoryInterface NOT!
52. TodoApp TodoRepository DBI TODO table TodoRepositoryInterface more stable
53. Problems of “Inheritance” case 1.Unstable dependencies 2.Too many features 3.messy to test
54. package TodoApp; use Moo; has todo_repo => ( is => ‘ro’, does => ‘TodoRepositoryInterface’ );
 sub evil_method { $todo_repo->do(“ANY QUERY!!!!”); }
55. package TodoApp; use Moo; has todo_repo => ( is => ‘ro’, does => ‘TodoRepositoryInterface’ );
 sub evil_method { $todo_repo->do(“ANY QUERY!!!!”); }
56. package TodoApp; use Moo; has todo_repo => ( is => ‘ro’, does => ‘TodoRepositoryInterface’ );
 sub evil_method { $todo_repo->do(“ANY QUERY!!!!”); } Necessary and sufficient features
57. Problems of “Inheritance” case 1.Unstable dependencies 2.Too many features 3.messy to test
58. easy to test?
59. package TestTodoRepository;
 use Moo; with qw( TodoRepositoryInterface ); sub select { … }
60. package TestTodoRepository;
 use Moo; with qw( TodoRepositoryInterface ); sub select { … } Be easier to test
61. Problems of “Inheritance” case 1.Unstable dependencies 2.Too many features 3.messy to test
62. no problem at all?
63. package TodoRepositoryInterface; use Moo::Role; requires qw(select); sub surprised_method { .. do anything }
64. package TodoRepositoryInterface; use Moo::Role; requires qw(select); sub surprised_method { .. do anything } Implementation reusable
65. package TodoRepositoryInterface; use Moo::Role; requires qw(select);
66. select($id) ? select(id => $id) ? select({ id => $id }) ?
67. select($id) # => arrayref of Todo ? # => iterator of Todo ?
68. select($id) # => arrayref of Todo ? # => iterator of Todo ? Ambiguous interface input / output
69. Problems of “Role” case 1.Implementation reusable 2.Ambiguous interface input / output
70. “Function::Interface” case
71. package TodoRepositoryInterface; use Function::Interface; use TodoTypes; method select(UserID $user_id) :Return(ArrayRef[Todo]);
72. Problems of “Role” case 1.Implementation reusable 2.Ambiguous interface input / output
73. package TodoRepositoryInterface; use Function::Interface; use TodoTypes; method select(UserID $user_id) :Return(ArrayRef[Todo]); sub surprising_method {
 … do anything }
74. package TodoRepositoryInterface; use Function::Interface; use TodoTypes; method select(UserID $user_id) :Return(ArrayRef[Todo]); sub surprising_method {
 … do anything }
75. Problems of “Role” case 1.Implementation reusable 2.Ambiguous interface input / output
76. package TodoRepository; use TodoTypes; use Function::Interface::Impl qw( TodoRepositoryInterface ); has dbh => ( … ); method select(UserID $user_id) :Return(ArrayRef[Todo]) { … }
77. package TodoApp; use Moo; use TodoTypes; has todo_repo => ( isa => ImplOf["TodoRepositoryInterface"], ); sub my_todo_list { … }
78. Looks Good!
79. Internal
80. requirements 1.function implementation 2.function interface 3.check if interface is implmented 4.interface type
81. 1. function implementation
82. Function::Parameters • subroutine signatures • developed by MAUKE
83. use Function::Parameters; use Types::Standard -types; fun add(Int $a, Int $b) { return $a + $b }
84. my $info = Function::Parameters::info(\&add); $info->positional_required; # => Int $a, Int $b
85. Function::Return • specify function return types • created by myself
86. sub add :Return(Int) { 3.14 } add(); # ERROR! Invalid type
87. my $info = Function::Return::info(\&add); $info->types; # => Int
88. Appendix about Function::Return
89. sub multi :Return(Num, Str) { 3.14, ‘message' } my ($pi, $msg) = multi();
90. sub multi :Return(Num, Str) { 3.14, ‘message' } my ($pi, $msg) = multi(); my $count = multi(); # ERROR!
91. requirements 1.function implementation 2.function interface 3.check if interface is implemented 4.interface type
92. 2. function interface
93. Function::Interface • Keyword::Simple • PPR
94. Deparse fun hello() :Return(Str);
95. sub BEGIN { Function::Interface::_register_info({ package => ‘HelloInterface', keyword => ‘fun', subname => ‘message', params => [], return => [&Str()]} ); }
96. my $info = Function::Interface::info(“HelloInterface”); $info->functions; # => hello(Str $msg) :Return(Str)
97. requirements 1.function implementation 2.function interface 3.check if interface is implemented 4.interface type
98. 3.check if interface is implemented
99. use Function::Interface::Impl qw(
 FooInterface BarInterface BazInterface );
100. F::Parameters#info F::Return#info F::Interface#info
101. F::Parameters#info F::Return#info F::Interface#info
102. requirements 1.function implementation 2.function interface 3.check if interface is implemented 4.interface type
103. use Function::Interface::Types; my $type = ImplOF[‘FooInterface’]; # Foo is implements of FooInterface my $foo = Foo->new; $type->check($foo);
104. requirements 1.function implementation 2.function interface 3.check if interface is implemented 4.interface type
105. Performance
106. F::I::Impl runs at compile time
107. F::Return has `no_check` option
108. Let’s benchmark
109. F::P + F::R + F::I F::P + F::R no_check + F::I F::P + F::R no_check F::P Case1 Case4 Case2 Case3
110. F::P + F::R + F::I F::P + F::R no_check + F::I F::P + F::R no_check F::P 360653.77/s 1499189.22/s 1499189.22/s 1499189.22/s Case1 Case4 Case2 Case3
111.      $BTF $BTF $BTF $BTF
112. Conclusion
113. Features of F::Interface 1.Typed interface definition 2.Check at compile time
114. Goal • To maintain large apps. • Interface is good for large apps 1. Easy to fix implementation 2. Stable Dependencies
115. Internal • function implementation • Function::Parameters + Function:\:Return • function interface • Keyword::Simple + PPR • compare meta infos at compile time
116. Performance • The same speed as using only F::Parameters • Function::Interface::Impl runs at CHECK phase • Function::Return has `no_check` option
117. Questions?
118. Thank you!