# BuildToolPlugin/XcodeBuildToolPlugin for generating Swift wrappers from Metal

**URL:** <https://forums.swift.org/t/buildtoolplugin-xcodebuildtoolplugin-for-generating-swift-wrappers-from-metal/78044>\
**Category:** Using Swift\
**Tags:** packagemanager\
**Created:** [February 23, 2025, 12:50am UTC](https://forums.swift.org/t/buildtoolplugin-xcodebuildtoolplugin-for-generating-swift-wrappers-from-metal/78044 "2025-02-23T00:50:47Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![audulus](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/audulus/32/40637_2.png) [@audulus](https://forums.swift.org/u/audulus)\
**Post date:** [February 23, 2025, 12:50am UTC](https://forums.swift.org/t/buildtoolplugin-xcodebuildtoolplugin-for-generating-swift-wrappers-from-metal/78044/1 "2025-02-23T00:50:47Z")

</div>

I've got a command line tool which generates Swift wrappers for my Metal kernels ([GitHub - audulus/Anodize: Type safety for Metal 🤘](https://github.com/audulus/Anodize)).

I would like to integrate it with Xcode so I don't have to run it manually. Ideally, it should run on `default.metallib` which Xcode creates whenever you have a metal file in your project. That way, I wouldn't have to redundantly compile all the metal files to generate another metallib to load just for reflection of the kernel functions.

The metallib file isn't part of the `XcodeTarget`'s `inputFiles`. Perhaps I can still construct a path to it?

I tried this:

```swift
#if canImport(XcodeProjectPlugin)
import XcodeProjectPlugin

extension AnodizePlugin: XcodeBuildToolPlugin {

    /// This entry point is called when operating on an Xcode project.
    func createBuildCommands(context: XcodePluginContext, target: XcodeTarget) throws -> [Command] {
        let inputFiles = target.inputFiles.filter { $0.url.pathExtension == "metallib" }
        // inputFiles is empty!
        let outputURL = context.pluginWorkDirectoryURL.appending(path: "Anodized.swift")

        return [
            .buildCommand(displayName: "Anodizing",
                          executable: try context.tool(named: "Anodize").url,
                          arguments: inputFiles.map { $0.url.path() },
                          inputFiles: inputFiles.map { $0.url },
                          outputFiles: [outputURL])
        ]
    }

}
#endif

```

---

<div class="post-metadata">

**Author:** ![audulus](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/audulus/32/40637_2.png) [@audulus](https://forums.swift.org/u/audulus)\
**Post date:** [February 23, 2025, 7:54pm UTC](https://forums.swift.org/t/buildtoolplugin-xcodebuildtoolplugin-for-generating-swift-wrappers-from-metal/78044/2 "2025-02-23T19:54:34Z")

</div>

Ok, it seems like the `BuildToolPlugin` sandbox doesn't allow an `MTLDevice` to be created, so I can't use Metal's reflection.

Would be nice if there was a way to load and and use reflection on a metallib without needing an `MTLDevice`, but that doesn't seem to be the case.