Swift API Style Workflow

Swift API Style Workflow

Purpose

Make Swift APIs feel Swifty, ergonomic, intuitive, and human-friendly at the call site.

This skill owns language-level API style. Hand off to apple-dev-skills for Apple framework or Xcode project behavior, and to server-side-swift for Vapor, Hummingbird, SwiftNIO, deployment, persistence, observability, or auth behavior.

Source Check

Use repo-local guidance first. When general Swift API behavior needs a source, prefer the official Swift API Design Guidelines and current Swift documentation before community style guides.

Workflow

1. Inspect the current API surface:
   • public and internal symbols
   • call sites
   • result and error shapes
   • overloads, default arguments, and options structs
   • access control
   • naming consistency across sibling APIs
2. Classify the work:
   • new API design
   • API cleanup
   • call-site ergonomics review
   • error and result-shape repair
   • access-control tightening
3. Optimize for the caller:
   • prefer names that read naturally at the use site
   • keep labels meaningful instead of decorative
   • prefer domain values over ambiguous tuples, dictionaries, or strings
   • prefer defaulted parameters for small option sets
   • prefer request or options structs when public APIs reach four or more meaningful parameters
   • prefer enum-backed choices over boolean soups or stringly-typed modes
4. Tighten result and failure behavior:
   • use throws, typed domain errors, Result, or optional returns according to caller recovery needs
   • hand deeper failure-shape design to swift-error-handling-style-workflow
   • make invalid states hard to construct
   • include operation, source, likely cause, and next inspection point in operator-facing errors and logs
5. Remove accidental API weight:
   • collapse needless overloads
   • remove compatibility shims unless explicitly approved
   • replace broad managers with small support types when the current type owns unrelated jobs
   • keep dependency injection unidirectional and data flow straight

Style Defaults

• Prefer compact Swifty syntax when it is obvious.
• Prefer trailing closures, key paths, shorthand closure arguments, and fluent calls when they improve readability.
• Prefer named intermediate values when a chain needs a diagnostic boundary or the next reader would have to mentally execute it.
• Prefer small composable values, functions, and extensions over stateful orchestration types.
• Prefer complete cleanup passes over leaving duplicate long-term APIs behind.

Output Shape

Return:

1. API state: the current shape and main pain points.
2. Recommended surface: the target symbols, names, labels, and result shape.
3. Call-site examples: compact examples showing the intended feel.
4. Migration: compatibility impact and whether shims are being avoided or deliberately approved.
5. Validation: compile, test, or review checks needed.

Guardrails

• Do not rename public APIs casually when the repo has release or compatibility constraints.
• Do not add wrappers, managers, or service layers without a concrete near-term use case.
• Do not expand readable fluent Swift into verbose ceremony just to satisfy a generic style guide.
• Do not hide recoverable errors in logs or nil when the caller can do something useful.
• Do not keep duplicate old and new paths unless Gale explicitly approves that compromise.