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codebase-design

Skill4 starsChanged 10 days agoMITView on GitHub

Design deep modules with small interfaces. Use when choosing seams, reducing file-hop friction, deepening modules, testing APIs, or applying shared design vocabulary.

194 other projects use a version of this.

Adopted by

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Used with

Projects with it also use setup-ts-deep-modules, decision-mapping and 3 more.

Other files people use alongside this one.

Files found in the same public projects as a version of this one, more often than they turn up anywhere else. Each project counts once, large collections count for less, and this file's own repository is left out.
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    setup-ts-deep-modules

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    decision-mapping

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    loop-me

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  • simo97Skill

    migrate-to-shoehorn

    Migrate test files from `as` type assertions to @total-typescript/shoehorn. Use when user mentions shoehorn, wants to replace `as` in tests, or needs partial test data.

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The file

We split this skill into the rules it gives an agent

5 rules. 0 are common, 3 are distinctive, and 2 are very specific to this project.

  • 0

    Common

    Most of the 181 edited versions we read keep these.

  • 3

    Distinctive

    This author's own choices. Worth a look.

  • 2

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Very specific:

    Use GLOSSARY.md terms, via GLOSSARY-MAP.md when present.

    line 9
  2. Distinctive:

    Ask whether methods/parameters can shrink and more complexity can hide.

    line 35
  3. Distinctive:

    Deletion test: if removal makes complexity vanish, the module was pass-through.

    line 40
  4. Distinctive:

    When two designs survive deletion, Call the Skill tool with "plan-arbiter": depth, locality, test surface, rollback.

    line 57
  5. Very specific:

    Read DEEPENING.md for cleanup/dependencies/tests.

    line 61

“Common” is measured: kept by at least 6 in 10 of the 181 edited versions of this file we could read. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

On interface/type/shared-state changes, read Poteto.

Design deep modules: substantial behavior behind a small, independently testable interface. Apply verifiability: caller leverage and locality, not implementation size. Use GLOSSARY.md terms, via GLOSSARY-MAP.md when present; respect ADRs.

Reduce caller knowledge/coordination; preserve required behavior.

Imports: checks.

Glossary

Use exactly:

Module -- interface plus implementation: function, class, package, slice.

Interface -- everything callers know: types, invariants, ordering, errors, config, performance; broader than signature.

Implementation -- module internals.

Depth -- interface leverage. Deep means small interface/large behavior; shallow means similar interface and implementation complexity.

Seam -- where behavior can vary without editing the caller; its interface lives here. Avoid: boundary, except DDD bounded context.

Adapter -- concrete implementation at a seam, named by role.

Leverage -- capability per interface learned.

Locality -- change, bugs, knowledge, verification concentrate together.

Ask whether methods/parameters can shrink and more complexity can hide.

Principles

  • Depth is an interface property, not line ratio; private seams need not leak.
  • Deletion test: if removal makes complexity vanish, the module was pass-through; if complexity spreads into callers/tests, it earned its keep.
  • The interface is the test surface: callers and tests cross the same seam. Testing past it signals a weak shape.
  • One adapter is a hypothetical seam; Two adapters means a real one.
  • Direct local code beats an abstraction that only moves code.

Caller-first sketch

For new/changed interfaces, sketch caller success and failure before types. Name state owner, invariant and failure result. Derive signatures; apply probe.

Testability

  1. Exercise the public interface with a focused command and repeatable fixture.
  2. Control dependencies at existing seams; return observable results and isolate state.
  3. Expose invariants and failure diagnostics; prove wrong behavior fails through the public interface.

When two designs survive deletion, Call the Skill tool with "plan-arbiter": depth, locality, test surface, rollback. Other hosts: dependency loading.

Reject depth-by-line-count, interface-as-TypeScript-keyword, and vague boundary wording.

Read DEEPENING.md for cleanup/dependencies/tests; DESIGN-IT-TWICE.md for alternatives.

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