Building `MetalKitEssentials.Mac` project from `mac-ios-samples` repo with
msbuild fails with:
```
"/Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/MetalKitEssentials.Mac.csproj" (default target) (1) ->
(_SmeltMetal target) ->
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Mac/Xamarin.Mac.Common.targets : error : Tool exited with code: 1. Output: warning: unable to open file obj/Debug/metal/../../../../../../../Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/Resources/Shaders.dia for serializing diagnostics (Error opening output file 'obj/Debug/metal/../../../../../../../Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/Resources/Shaders.dia': No such file or directory) [-Wserialized-diagnostics] [/Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/MetalKitEssentials.Mac.csproj]
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Mac/Xamarin.Mac.Common.targets : error : warning: '-std=osx-metal1.0' is equivalent to '-std=osx-metal1.1' [/Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/MetalKitEssentials.Mac.csproj]
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Mac/Xamarin.Mac.Common.targets : error : error: unable to open output file 'obj/Debug/metal/../../../../../../../Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/Resources/Shaders.air': 'Error opening output file 'obj/Debug/metal/../../../../../../../Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/Resources/Shaders.air': No such file or directory' [/Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/MetalKitEssentials.Mac.csproj]
```
The path
`obj/Debug/metal/../../../../../../../Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/Resources/Shaders.dia`
should be just `Resources/Shaders.dia`. This is from the `@(Metal)` item
passed to the `Metal` task as:
<Metal SourceFile="%(Metal.Identity)" ..
- This item is defined in the user's project file.
- And the task invocation is in
`/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Mac/Xamarin.Mac.Common.targets`.
- The `Metal` task (indirectly[2]) uses the `DefiningProjectFullPath`
metadata from that `SoureFile`, and expects to get the path to the
file that defined that `@(Metal)` item. But since we are using
`%(Metal.Identity)`, to use task batching, msbuild converts the
`%(Metal.Identity)` to a string and then "boxes" that as an ITaskItem,
and thus newly created item passed to `SourceFile` will have
`DefiningProjectFullPath` set to the `Xamarin.Mac.Common.targets`!
- And trying to create a relative path using that gives us
`obj/Debug/metal/../../../../../../../Users/ankit/dev/mac-ios-samples/MetalKitEssentials/MetalKitEssentials.Mac/Resources/Shaders.dia`
- The fix is to use `'%(Metal.Identity)` in the `Condition` to cause
task batching, but use `SourceFile="@(Metal)"` so that we get the
original item!
- Fixed for iOS targets too
---
1. The actual code is in `BundleResources.GetVirtualProjectPath`.
Other tasks using this were looked at and they are all using
`ITaskItem[]` and so passing `@(Items)` and thus get the original
items.
2. And the build works in xbuild, because it has `DefiningProjectFullPath`
for the "boxed" item set to `""`. And `GetVirtualProjectPath` works
around that.
05c8420f6c