alamofire/rdar-urlsessiontaskmetrics

This repository is a small sample project created by the team behind Alamofire, a popular Swift library for handling web requests. Its purpose is to demonstrate a specific bug: when building an app for the Apple Watch using watchOS 3.0 or later, a feature called URLSessionTaskMetrics fails to compile correctly. URLSessionTaskMetrics is essentially a tool that provides detailed timing information about web requests, like how long a download took. The problem is a "linker error," which is a technical roadblock that happens when a project is being packaged and prepared to run. In this case, simply trying to use these timing measurement tools on the Apple Watch causes the build process to completely fail. The README notes that the exact root cause is unknown, but the team discovered a workaround: by simply defining a global property with an availability check (a way to tell the app to only use certain features on specific operating system versions), the build suddenly succeeds. The primary audience for this project is Apple's own engineering team. When developers find bugs in Apple's software or tools, they submit them through a system called Radar (hence the "rdar" in the project name). This sample app serves as a concrete, easily testable example that Apple engineers can run to see the bug in action. It was filed with Apple in December 2017, and according to the project notes, the issue remains unresolved. For non-developers, this repository isn't something you would use directly in your own work. It is essentially a bug report published openly so that the broader developer community can track the issue. It demonstrates a common practice in software development where teams isolate a tricky problem into a small, shareable project to help platform owners identify and fix the underlying flaw.