gitlab-org--gitlab-foss/doc/development/directory_structure.md

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Backend directory structure

Use namespaces to define bounded contexts

A healthy application is divided into macro and sub components that represent the contexts at play, whether they are related to business domain or infrastructure code.

As GitLab code has so many features and components it's hard to see what contexts are involved. We should expect any class to be defined inside a module/namespace that represents the contexts where it operates.

When we namespace classes inside their domain:

• Similar terminology becomes unambiguous as the domain clarifies the meaning: For example, MergeRequests::Diff and Notes::Diff.
• Top-level namespaces could be associated to one or more groups identified as domain experts.
• We can better identify the interactions and coupling between components. For example, several classes inside MergeRequests:: domain interact more with Ci:: domain and less with ImportExport::.

# bad
class MyClass
end

# good
module MyDomain
  class MyClass
  end
end