Dependencies Unavailable to Plugins

[filip-sakel]

Description

Adding local target dependencies or external dependencies to my plugin doesn't result in an error when declared in the package manifest. However, importing these dependencies in the plugin code makes SwiftPM complain that it can't find these modules.

Expected behavior

I'd expect to declare dependencies and be able to actually import them.

Actual behavior

An error is emitted when importing a module that was declared as a dependency in the plugin code. This is the case for both build tools and command tools.

Steps to reproduce

1. Create a TestPackage directory, cd into it, and run swift package init.
2. Add the following target in the package manifest:

    .plugin(name: "MyPlugin", capability: .buildTool(), dependencies: [.target(name: "TestPackage")]),

3. Create a Plugins/MyPlugin/Plugin.swift containing:

   import TestPackage
   import PackagePlugin
   
   @main
   struct Plugin: BuildToolPlugin {
       func createBuildCommands(context: PackagePlugin.PluginContext, target: PackagePlugin.Target) async throws -> [PackagePlugin.Command] {
           []
       }
   }

Swift Package Manager version/commit hash

Swift Package Manager - Swift 5.7.0

Swift & OS version (output of swift --version && uname -a)

swift-driver version: 1.55.1 Apple Swift version 5.7 (swiftlang-5.7.0.113.202 clang-1400.0.16.2)
Target: arm64-apple-macosx13.0
Darwin Filip-MacBook-Air.local 22.0.0 Darwin Kernel Version 22.0.0: Tue May 24 20:30:32 PDT 2022; root:xnu-8792.0.50.111.3~5/RELEASE_ARM64_T8103 arm64

[tomerd]

@abertelrud are missing validation here?

[abertelrud]

Yes, I think so. This isn't currently supported and thus there should be up-front validation. In the long run we should make it work, but that will require some build system changes (we either have to be able to do parts of the build before plugins run, or interleave running plugins are part of the build).