Issue building UWP app using MSBuild (GENERATEPROJECTPRIFILE) - msbuild

Question

I am trying to build a UWP app from the command-line in an effort to automate the builds from check-in to publishing to the store. Everything works fine when running the builds from within Visual Studio and when I create app packages, it all works fine (but takes too long, 15 minutes or so).
While invoking msbuild per platform (x86, x64 & ARM), only ARM seems to fail with the following error:
_CreatePriConfigXmlForSplitting
"C:\Source\MyProject\src\MyProject\MyProject.csproj" (Build target) (1) ->
(_SplitResourcesPri target) ->
error PRI175 : 0x80070002 - Processing Resources failed with error : The system cannot find the file specified. [C:\Source\MyProject\src\MyProject\MyProject.csproj]
GENERATEPROJECTPRIFILE : error PRI252: 0xdef00071 - File C:\Source\MyProject\output\Release\x86\arm\MyProject\resources.pri not found. [C:\Source\MyProject\src\MyProject\MyProject.csproj]
0 Warning(s)
2 Error(s)
As you probably noticed, it's using x86\arm directory instead of arm, hence the build is failing.
I am using Cake to build this, below is (relevant part of) the script:
Task("Build")
.IsDependentOn("Clean")
.IsDependentOn("UpdateVersion")
.IsDependentOn("RestorePackages")
.Does(() =>
{
var platforms = new Dictionary<string, PlatformTarget>();
platforms["ARM"] = PlatformTarget.ARM;
platforms["x86"] = PlatformTarget.x86;
platforms["x64"] = PlatformTarget.x64;
foreach (var platform in platforms)
{
Information("Building project for platform {0}", platform.Key);
var outputDirectory = "../../" + outputRootDirectory + "/" + platform.Value.ToString();
var projectFileName = string.Format("./src/{0}/{0}.csproj", solutionName);
var msBuildSettings = new MSBuildSettings {
Verbosity = Verbosity.Diagnostic, // Verbosity.Minimal
ToolVersion = MSBuildToolVersion.VS2017,
Configuration = configurationName,
MSBuildPlatform = MSBuildPlatform.x86, // Always require x86, see platform for actual target platform
PlatformTarget = platform.Value
};
// Need special path since this is relative to the project file, not the cake build directory
//msBuildSettings.Properties["OutputPath"] = new List<string>(new [] { outputDirectory });
// We don't create native builds, we will use MSIL builds which the store will recompile,
// for more info see https://oren.codes/2015/12/03/continuous-integration-for-uwp-projects-making-builds-faster/
msBuildSettings.Properties["UseDotNetNativeToolchain"] = new List<string>(new [] { "false" });
msBuildSettings.Properties["BuildAppxUploadPackageForUap"] = new List<string>(new [] { "true" });
//msBuildSettings.Properties["AppxPackageArtifactsDir"] = new List<string>(new [] { outputDirectory });
// Fix for broken targets
//msBuildSettings.Properties["ProjectPriFileName"] = new List<string>(new [] { "resources.pri" });
//msBuildSettings.Properties["ProjectPriFullPath"] = new List<string>(new [] { outputDirectory + "/resources.pri" });
//msBuildSettings.Properties["_TransformedProjectPriFullPath"] = new List<string>(new [] { outputDirectory + "/resources.pri" });
MSBuild(projectFileName, msBuildSettings);
}
});
A. As you can see I am experimenting a bit by manually overriding the ms build properties, but no luck so far.
B. At first I thought it was GenerateProjectPriFile task that was failing. However, after some investigation I found out that creating the split files already show use the wrong startIndexAt value:
<?xml version="1.0" encoding="utf-8"?>
<resources targetOsVersion="10.0.0" majorVersion="1">
<packaging>
<autoResourcePackage qualifier="Language" />
<autoResourcePackage qualifier="Scale" />
<autoResourcePackage qualifier="DXFeatureLevel" />
<omitSchemaFromResourcePacks />
</packaging>
<index root="\" startIndexAt="C:\Source\MyProject\output\Release\x86\arm\MyProject\resources.pri">
<default>
<qualifier name="Language" value="en-US" />
<qualifier name="Contrast" value="standard" />
<qualifier name="Scale" value="200" />
<qualifier name="HomeRegion" value="001" />
<qualifier name="TargetSize" value="256" />
<qualifier name="LayoutDirection" value="LTR" />
<qualifier name="DXFeatureLevel" value="DX9" />
<qualifier name="Configuration" value="" />
<qualifier name="AlternateForm" value="" />
<qualifier name="Platform" value="UAP" />
</default>
<indexer-config type="PRI" />
</index>
</resources>
I have no idea why it prepends x86 before ARM when building for ARM. Any help is appreciated. In the meantime I'll continue investigating and update this post if I find something new.

Answer 1

It looks like I have to specify the sln file, not the csproj file. This is a bit unfortunate since now it builds much more than it needs to (there are multiple projects in the same solution), but I can get around that by creating a custom MyProject.Build.sln file