fix(swift): implement server-URL-templating support for multipleBaseUrls

[devin-ai-integration]

Description

Implements server-URL-templating (multiple base URLs) support in the Swift SDK generator, fixing the server-url-templating seed fixture so it compiles and passes. Removes that fixture from allowedFailures in seed/swift-sdk/seed.yml.

Previously, the Swift generator only handled singleBaseUrl environments. For APIs whose IR environments are multipleBaseUrls (each environment exposes several server URLs keyed by base-URL ID, e.g. Base for the API and Auth for an auth service), generation was unsupported and the fixture was listed under allowedFailures.

Changes Made

• Environment as a struct: For multipleBaseUrls, generate the environment as a struct exposing one String URL per base-URL ID plus a static property per named environment, instead of the enum used for singleBaseUrl. New MultipleBaseUrlsEnvironmentGenerator; environment symbol registration now branches on environmentType (singleBaseUrl | multipleBaseUrls).

  public struct ApiEnvironment: Equatable, Sendable {
      public let base: String
      public let auth: String
      public static let regionalApiServer = ApiEnvironment(
          base: "https://api.example.com/v1", auth: "https://auth.example.com")
  }

• Per-endpoint base-URL routing: RootClientGenerator builds a baseUrls map (["Base": environment.base, "Auth": environment.auth]) and passes it to ClientConfig. Each endpoint extracts its endpoint.baseUrl id and threads it as baseUrlId: into performRequest.
• Shared templates (ClientConfig.Template.swift, HTTPClient.Template.swift): added an optional baseUrls: [String: String]? to ClientConfig and an optional baseUrlId parameter through the performRequest / buildRequest / buildRequestURL chain. URL construction now resolves baseUrlId.flatMap { clientConfig.baseUrls?[$0] } ?? clientConfig.baseURL. Both additions are backward-compatible (default nil), so singleBaseUrl fixtures only pick up these additive lines.
• Removed server-url-templating (and its now-orphaned explanatory comment) from allowedFailures in seed/swift-sdk/seed.yml.
• Added changelog entry generators/swift/sdk/changes/unreleased/server-url-templating.yml (type fix).
• Regenerated all swift-sdk seed snapshots (shared-template additions are reflected across fixtures).

Testing

• pnpm run check (lint) passes
• TypeScript compiles (pnpm compile)
• Swift build + tests pass for the fixture via swift:6.1.2 Docker image (swift build, swift test — 20 tests pass)
• Verified representative singleBaseUrl fixtures still build with the additive template changes
• Manual testing completed

Link to Devin session: https://app.devin.ai/sessions/a956152e78d145269d8833856c161476
Requested by: @iamnamananand996

[devin-ai-integration]

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SDK Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-06-23T05:19:28Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
swift-sdk	square	58s (n=5)	431s (n=5)	60s	+2s (+3.4%)

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: 2026-06-23T05:19:28Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-06-23 12:06 UTC