[E2E] Log ready Swift preload cache hits

[kyle-schellen]

What changed

• Emit a debug-only diagnostic through Swift's configured Logger when presentation selects a matching cached WebView that reached .ready.
• Preserve the existing OSLog cache-hit message for dashboard compatibility.
• Reuse the Swift sample's existing FileLogger and Settings → Logs screen.
• Add SDK tests covering ready cache hits, matching entries that are still loading, non-debug logging, fresh presentation, and URL mismatch.

Why

preload-state-ready proves background preload completed, but not that presentation used that cached WebView. This diagnostic proves presentation selected the matching ready cache entry.

The two platforms differ only in transport. Android's equivalent cache-hit line is already available in BrowserStack's passing-test device logs; iOS passing logs are not, so the flow reads the diagnostic from the Swift sample's existing Logs screen instead.

Testing

• dev swift test CheckoutWebViewTests
• dev swift test sample
• dev swift lint
• dev swift api check — public API baseline unchanged
• Asserted end to end by [E2E] Prepare native preload ready-flow validation #631 on a physical iPhone: preload ready → present → real checkout content → close → Settings → Logs → cache-hit diagnostic.

Stack

1. [E2E] Expose native preload state markers #626 — preload state markers in the samples
2. [E2E] Log ready Swift preload cache hits #627 — this PR: Swift ready cache-hit diagnostic
3. [E2E] Prepare native preload ready-flow validation #631 — the E2E test, matrix wiring, and BrowserStack validation

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Before you merge

Important

• I've added tests to support my implementation
• I have read and agree with the Contribution Guidelines
• I have read and agree with the Code of Conduct
• I've updated the relevant platform README (platforms/swift/README.md and/or platforms/android/README.md)

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Releasing a new Swift version?

• I have bumped the version in ShopifyCheckoutKit.podspec
• I have bumped the version in platforms/swift/Sources/ShopifyCheckoutKit/ShopifyCheckoutKit.swift
• I have updated the SwiftPM/CocoaPods version snippets in platforms/swift/README.md (major version only)

Releasing a new Embedded Checkout Protocol version?

• I have bumped embeddedCheckoutProtocolAndroid in platforms/android/gradle/libs.versions.toml
• I have updated protocol/languages/kotlin/embedded-checkout-protocol/api/embedded-checkout-protocol.api if the public API changed

Releasing a new Android version?

• I have bumped checkoutKitAndroid in platforms/android/gradle/libs.versions.toml
• I have updated the Gradle/Maven version snippets in platforms/android/README.md

Tip

See the Contributing documentation for the full release process per platform.

[kyle-schellen]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [E2E] Prepare native preload ready-flow validation #631
• [E2E] Log ready Swift preload cache hits #627 👈 (View in Graphite)
• [E2E] Expose native preload state markers #626
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[bitrise]

Install this build

Open Tophat, select your target device, then click Install. Links open on the Mac running Tophat.

SDK	Install
Swift	Install with Tophat

Checkout Kit E2E results

Status	Suite	Target	Platform	OS version tag	Device
✅	tests/shared/launch-smoke.yaml	swift	ios	latest	iPhone 15 iOS 27 Beta

[kieran-osgood-shopify]

Dropping it here based on our slack convo
We're going to explore an approach using the log screen as this avoids us having to add conditional logs entries to the SDK