Building templates on a non-Windows machine is broken

[eerhardt]

Description

When building on a macOS machine, we are using MSBuild to template some .json files. These .json files have backslashes in them \":

maui/src/Templates/src/templates/maui-blazor/.template.config/template.json

Line 24 in 7b3c187

"condition": "(HostIdentifier != \"dotnetcli\" && HostIdentifier != \"dotnetcli-preview\")",

However, when we run this file through WriteLinesToFile task in MSBuild, the backslashes are getting flipped to front slashes:

maui/src/Templates/src/Microsoft.Maui.Templates.csproj

Lines 29 to 48 in 7b3c187

	<Target Name="_UpdateTemplateVersions" DependsOnTargets="SetVersions">
	<ItemGroup>
	<_TemplateJsonFile Include="templates\*\.template.config\template.json" />
	<_TemplateJsonFileWithContent
	Include="@(_TemplateJsonFile)"
	Contents="$([System.IO.File]::ReadAllText('%(FullPath)')
	.Replace('WINDOWSAPPSDK_VERSION_VALUE', '$(MicrosoftWindowsAppSDKPackageVersion)')
	.Replace('WIN2D_VERSION_VALUE', '$(MicrosoftGraphicsWin2DPackageVersion)'))" />
	<_TemplateCsprojFile Include="templates\*\*.csproj" />
	<_TemplateCsprojFileWithContent
	Include="@(_TemplateCsprojFile)"
	Contents="$([System.IO.File]::ReadAllText('%(FullPath)')
	.Replace('DOTNET_TFM_VALUE', '$(_MauiDotNetTfm)'))" />
	<_TemplateReplacedFile Include="@(_TemplateJsonFile);@(_TemplateCsprojFile)" />
	<_TemplateReplacedFileWithContent Include="@(_TemplateJsonFileWithContent);@(_TemplateCsprojFileWithContent)" />
	</ItemGroup>
	<WriteLinesToFile
	File="@(_TemplateReplacedFileWithContent -> '$(IntermediateOutputPath)%(Identity)')"
	Lines="%(Contents)"
	Overwrite="true" />

In the binlog I see:

but that is getting flipped in the parameter to Lines:

To fix this, we might need to make our own "replacement" task that doesn't flip the slashes.

See dotnet/msbuild#1622 for more details on the underlying MSBuild bug.

Steps to Reproduce

1. Build dotnet/maui on a macOS machine: dotnet cake --configuration="Release"
2. Set your $PATH to include $REPO_ROOT/bin/dotnet
3. dotnet new maui

Results

Error: Failed to load template from /Users/eerhardt/git/maui/bin/dotnet/template-packs/microsoft.maui.templates.6.0.200-dev.nupkg(/content/templates/maui-blazor/.template.config/template.json).
Details: Newtonsoft.Json.JsonReaderException: After parsing a value an unexpected character was encountered: d. Path 'primaryOutputs[0].condition', line 17, position 43.
   at Newtonsoft.Json.JsonTextReader.ParsePostValue(Boolean ignoreComments)
   at Newtonsoft.Json.JsonTextReader.Read()
   at Newtonsoft.Json.Linq.JContainer.ReadContentFrom(JsonReader r, JsonLoadSettings settings)
   at Newtonsoft.Json.Linq.JContainer.ReadTokenFrom(JsonReader reader, JsonLoadSettings options)
   at Newtonsoft.Json.Linq.JObject.Load(JsonReader reader, JsonLoadSettings settings)
   at Newtonsoft.Json.Linq.JObject.Load(JsonReader reader)
   at Microsoft.TemplateEngine.JExtensions.ReadJObjectFromIFile(IFile file)
   at Microsoft.TemplateEngine.Orchestrator.RunnableProjects.RunnableProjectGenerator.GetTemplatesAndLangpacksFromDir(IMountPoint source, IList`1& localizations)

Version with bug

Unknown/Other (please specify)

Last version that worked well

Unknown/Other

Affected platforms

macOS

Affected platform versions

All macOS versions

Did you find any workaround?

Use the template packages from a Windows build. Or use a Windows build to make the templated app and copy it to the macOS.

Relevant log output

No response