Can a binaryTarget use the package access modifier in SwiftPM?

Development Package Manager
1

I’m trying to understand how the package access modifier works with binary targets in Swift Package Manager.

Here’s a simplified example of my Package.swift:

import PackageDescription

let package = Package(
    name: "MyLib",
    platforms: [
        .iOS(.v13),
    ],
    products: [
        .library(
            name: "MyLib",
            targets: ["MyLibWrapper"]
        ),
    ],
    dependencies: [],
    targets: [
        .binaryTarget(
            name: "MyLibCore", // package_name: MyLibInternal
            path: "Frameworks/MyLibCore.xcframework"
        ),
        .binaryTarget(
            name: "MyLibAuth", // package_name: MyLibInternal
            path: "Frameworks/MyLibAuth.xcframework"
        ),
        .target(
            name: "MyLibWrapper",
            dependencies: [
                .target(name: "MyLibCore"),
                .target(name: "MyLibAuth"),
            ],
            packageAccess: true
        )
    ]
)

When using this package in another project that has the same SWIFT_PACKAGE_NAME (MyLibInternal), I get the following error:

Module 'MyLib' is in package 'MyLibInternal' but was built from a non-package interface;
modules of the same package can only be loaded if built from source or package interface:
.../MyLibCore.framework/Modules/MyLibCore.swiftmodule/arm64-apple-ios-simulator.private.swiftinterface

However, if I look inside the .xcframework, there is a arm64-apple-ios-simulator.package.swiftinterface alongside the private interface. So it seems SwiftPM is choosing the .private.swiftinterface even though a .package.swiftinterface exists.

So my question is:

Are binary targets fundamentally unable to use the package access modifier (and package-level visibility), or is there some way to build or configure a binary target so that SwiftPM treats it as having a package interface?

Any insight into whether this is by design or if there’s a possible workaround would be greatly appreciated.

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2

The issue was that the consuming target hadn’t enabled the -experimental-package-interface-load flag in OTHER_SWIFT_FLAGS. Once I added that flag, the compiler was able to locate and load the .package.swiftinterface files correctly.

Reference: swiftlang/swift#69733

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