feat(swift): generate CONTRIBUTING.md for Swift SDKs

[Swimburger]

Description

Generate a Swift-specific CONTRIBUTING.md for Swift SDKs, using a new RootAsIsFiles pattern that extends the existing AsIs infrastructure for root-level files.

Changes Made

• Extended generators/swift/base/src/AsIs.ts with a RootAsIsFiles registry for root-level static files (no symbols needed, just filename + content loading)
• Added static generators/swift/base/src/asIs/Root/CONTRIBUTING.md with Swift-specific content:
  • Prerequisites: Swift 5.9+, Swift Package Manager
  • Install: swift package resolve
  • Build: swift build
  • Test: swift test
  • Format: swift format . / swiftformat .
  • Lint: swiftlint
  • References generators/swift/ as the generator path
  • Same overall structure as C# (Getting Started, About Generated Code with .fernignore, Making Changes, Questions, License)
• Wired up in generators/swift/sdk/src/SdkGeneratorCli.ts:
  • Added generateRootAsIsFiles method that loads and adds root AsIs files
  • Called from generateRootFiles() in parallel with README/reference generation, gated behind !context.config.whitelabel
  • Imports RootAsIsFiles from @fern-api/swift-base
• Added unit tests in generators/swift/sdk/src/__test__/ContributingGenerator.test.ts:
  • Tests for Swift commands, all sections, Fern info, generator path, prerequisites, filename, and a snapshot test (7 tests)
• Added changelog entry in generators/swift/sdk/changes/unreleased/add-contributing-md.yml

Testing

• Unit tests added/updated (7 tests, all passing)
• Biome check passes on all changed files
• pnpm format passes

Link to Devin session: https://app.devin.ai/sessions/e318dce18bb44560bd5859fb0d171213
Requested by: @Swimburger

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[devin-ai-integration]

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SDK Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-04-23T04:59:11Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
swift-sdk	square	41s (n=5)	290s (n=5)	45s	+4s (+9.8%)

main (generator): generator-only time via --skip-scripts (includes Docker image build, container startup, IR parsing, and code generation — this is the same Docker-based flow customers use via fern generate). main (E2E): full customer-observable time including build/test scripts (nightly baseline, informational). Delta is computed against generator-only baseline.
⚠️ = generation exited with a non-zero exit code (timing may not reflect a successful run).
Baseline from nightly runs on main (latest: 2026-04-23T04:59:11Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-05-04 20:54 UTC

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.

[devin-ai-integration]

Self-review: LGTM — No issues found. CI passing, code follows existing Swift generator patterns correctly. Generator path generators/swift/ is correct.

[Swimburger]

Is there no AsIs pattern to do this with copy/paste file?

[devin-ai-integration]

The AsIs pattern in Swift (SourceAsIsFiles/addSourceAsIsFile) is designed for .swift source files that get compiled into the module — they include symbol registration with the NameRegistry and are placed under Sources/. CONTRIBUTING.md is a root-level markdown file, so it follows the same addRootFiles(new File(...)) pattern used by README.md, reference.md, and Package.swift.

This also matches how C# and TypeScript handle it — both use a ContributingGenerator class with addRawFiles/addRootFiles rather than an AsIs file.

That said, if you'd prefer a different approach (e.g. a static .md file that gets copied), happy to refactor.

[kafkas]

Devin it shouldn't be difficult to extend this to allow root AsIs I think. We could just add RootAsIsFiles to AsIs.ts and then generate them in SdkGeneratorCLI generateRootFiles()? Could we not do that?

[devin-ai-integration]

Good call — refactored to use the AsIs pattern. I've:

1. Added RootAsIsFiles to generators/swift/base/src/AsIs.ts — a simpler variant of the existing AsIs registry (just filename + loadContents, no symbols/directory needed for root files)
2. Placed the static CONTRIBUTING.md at generators/swift/base/src/asIs/Root/CONTRIBUTING.md
3. Updated SdkGeneratorCli.ts to load via RootAsIsFiles.Contributing.loadContents() in generateRootAsIsFiles(), called in parallel with README/reference generation
4. Removed the ContributingGenerator class entirely

This makes it easy to add more root AsIs files in the future — just add an entry to RootAsIsFileSpecs and drop the file in asIs/Root/.