Xcode cannot generate Swift UI preview - build aborted due to an internal error: planningFailed

Question

I'm using Xcode 12 beta 2. I've packaged my libraries in Swift Packages. DataModel that appear in the error message is one of them, that my current package, WeatherView depends on.

I can build the package fine, but Swift UI preview fails

build aborted due to an internal error: planningFailed("multiple configured targets of \'DataModel\' are being created for iOS Simulator")

----------------------------------------

SchemeBuildError: Failed to build the scheme "WeatherView"

unexpected service error: build aborted due to an internal error: planningFailed("multiple configured targets of \'DataModel\' are being created for iOS Simulator")

Build system information:
error: unexpected service error: build aborted due to an internal error: planningFailed("multiple configured targets of \'DataModel\' are being created for iOS Simulator")

I lost an hour on something similar, but my case was because Xcode 12.4 opened instead of 12.5. After opening the right version, Preview got back to work. — Alexandre
– Alexandre, Commented Jul 19, 2021 at 21:34

Dharman · Accepted Answer · 2020-10-19 23:32:47Z

10

I found out that making the product library "dynamic" (instead of static) made my previews work from inside the package's targets.

let package = Package(
    name: "Modules",
    platforms: [
        .iOS(.v13)
    ],
    products: [
        .library(
            name: "Modules",
            type: .dynamic,
            targets: ["App"]
        ),
    ],
    dependencies: [],
    targets: [
        .target(
            name: "App",
            dependencies: []
        ),
        .testTarget(
            name: "AppTests",
            dependencies: ["App"]
        ),
    ]
)

One must also declare the package's platforms.

edited Oct 19, 2020 at 23:32

Dharman♦

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answered Oct 17, 2020 at 12:45

cicerocamargo

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1 Comment

swalkner Over a year ago

this did the trick for me as well, thanks! Do you know why this is the case?

Kevin · Accepted Answer · 2021-03-25 20:52:39Z

3

I got this same error when trying to preview my SwiftUI canvas for a view. I had multiple tabs open in Xcode. I closed all the other tabs but the one with my view and my canvas previews started working again.

answered Mar 25, 2021 at 20:52

Kevin

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2 Comments

Matteo Manferdini Over a year ago

This actually worked better for me than the accepted answer. Changing package libraries to dynamic created other problems with Xcode previews. Closing the other tab I had open in Xcode fixed the problem.

Pawel Zentala Over a year ago

I had two tabs opened at the same time (additional editor on right). I closed it and preview started working again.

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