business-logic-entry-point-colocate-types
Colocate Types with Business Logic Entry Points
Goal
When a business-logic entry point has parameters or return values whose types are declared by the project, those types must live in the same file as the entry point, as long as the project stack allows it.
This keeps each entry point self-contained: opening one file reveals the full signature, including the shape of its inputs and outputs, without navigating to other files.
What Counts as In Scope
Apply this skill to code that does one or more of these things:
- declares a business-logic entry point with project-declared parameter types or return types
- places command types, query types, success types, or error types in separate files from the entry point that uses them
- creates shared type modules or barrel exports for types that belong to a single entry point
- imports project-declared signature types from another file into an entry point module
What Counts as a Project-Declared Type
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