Namespace, What and Why (original) (raw)
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2. ### Namespace on read https://bugs.ruby-lang.org/issues/19744
3. ### What is Namespace?
4. ### DEMO
5. ### 👏👏👏👏👏
6. ### Ruby Process Namespace Run methods de fi ned in a
space with de fi nitions in the space Namespace Application Code App::Func User Library Code DB::Client (v2) Library Code ActiveSupport (v7) Namespace Library Code DB::Client (v3) Namespace Application Code App::Func2 User Library Code ActiveSupport (v6) Application Code call call call
7. ### Why do we need Namespace?
8. ### Name Collisions No one can use a name in two
ways • Structured names • Foo::Bar::Baz • Major scenario: • Top-level “User” or “Configuration” classes (gems, apps, etc) • Two apps in a process (in the context of “Modular monolith”)
9. ### Definition Collisions De fi nitions can be modi fi ed,
globally, from anywhere • A single Module/Class instance • Example: Oj.default_options = {symbol_keys: true} • A single Module/Class definition • Process global open classes (monkey patches) • A single set of constants • A single set of global variables
10. ### Version Collisions Two di ff erent versions of a library
can’t be loaded • Application libraries and library dependencies • App uses X, and Y ver 2 • X depends on Y ver 1 • “Dependency hell” • App uses A and B • A depends on C ver 1 • B depends on C ver 2 App C ver 1 C ver 2 A B App Y ver 1 X Y ver 2
11. ### Why is the Namespace “on read”?
12. ### How can we implement Namespace?
13. ### Defining Classes/Modules Under a Namespace (NS) • Namespace as subclass
of Module • Use existing mechanism of load(file, module) • Load .rb fi les (A::B) under a module (M) → M::A::B • See also: “Multiverse Ruby” (RubyKaigi 2023, @shioyama) • Modify C API to de fi ne class/module: class_alloc (in class.c) • Create classes/modules (X) under a namespace (NS) → NS::X • To support extensions (.so/.dll/.bundle)
14. ### Having Class/Module Definitions Per namespace • Open class in NS
can modify built-in classes/modules • For monkey patches in namespace: class Object; def blank?; … • In other NSs: Object without #blank? • Class/Module de fi nition: classext (struct: rb_classext_t) • super, method table, constant table, instance variables, subclasses, … • Switching classext realizes a class with di ff erent de fi nitions! 🤪 (Thanks to @_ko1 and @mametter)
15. ### Where to go with Namespace in the future?
16. ### Modular-Monolith(-ish) Deployment Apps deployed on a (possible) app server •
Applications server based on Namespace • namespace per app • multiple apps are mounted using namespace • 2 or more applications on a single tenant (process) • Without con fl icts/collisions by namespace • Especially for development without containers on laptops App Server Namespace Web app Request Response Routing
17. ### “Packages” API (tentative) All libraries are required in namespace! (really?)
• Add a method to require gem as package, with implicit namespace p1 = require_package(‘my-awesome-client’) MyAwesomeClient = p1.export(:MyAwesomeClient) • Optional: default exports (in gemspec?) require_package ‘my-awesome-client’ MyAwesomeClient #=> NS::MyAwesomeClient • Optional: export-as require_package ‘my-awesome-client’, as: :MAClient MAClient #=> NS::MyAwesomeClient NEED DISCUSSIONS
18. ### When can we use Namespace?
19. ### When can we use Namespace? 🤔
