PureXML/docs/rules/rules-swift/exp/build-performance.md

Build Performance Benefits

Why ExtremePackaging pays off in build time. Rationale, not rule. Read once for context.

Incremental Compilation

With ExtremePackaging:

• Change AppFont → Only AppFont rebuilds
• Change AppComponents → Only AppComponents + dependent targets rebuild
• Change SharedModels → More rebuilds (foundation layer), but still isolated

Without ExtremePackaging:

• Change any file → Entire monolith rebuilds

Parallel Builds

Build Graph (simplified):
SharedModels ─┬─> ApiClient ─┬─> AuthFeature ──> iosApp
              │               │
              └─> AppTheme ───┴─> AppFeature ───┘

SPM builds in parallel:
[SharedModels, AppFont] → [ApiClient, AppTheme, SharedViews] → [AuthFeature, AppFeature] → [iosApp]

SPM automatically parallelizes independent package builds.

CI/CD Optimization

# A CI runner can cache per-package
stages:
  - build-foundation
  - build-infrastructure
  - build-features
  - build-apps

build-foundation:
  script:
    - swift build --product SharedModels
    - swift build --product AppTheme
  # Cache: Only rebuild if foundation changed