MSBuild giving "invalid version file" on F# - f#

Question

I'm recently unable to build F# with MSBuild. It is giving me an error "invalid version file". The generated compiler options below show --versionfile:version.htm being added, and I'm not sure why.
I did find that if I go to C:\Program Files (x86)\Microsoft SDKs\F#\4.0\Framework\v4.0\Microsoft.FSharp.targets, and remove the line VersionFile="$(VersionFile)" it starts working again. However I don't know where that file came from or why that line is there, and I don't want to be working with a non-standard dev box. Can anyone shed light on what's happening here?
Here's a dump of the whole output.
$ "C:\Program Files (x86)\MSBuild\14.0\Bin\MSBuild.exe" "C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj"
Microsoft (R) Build Engine version 14.0.25420.1
Copyright (C) Microsoft Corporation. All rights reserved.
Build started 5/4/2017 6:10:21 PM.
Project "C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj" on node 1 (default targets).
CoreCompile:
C:\Program Files (x86)\Microsoft SDKs\F#\4.0\Framework\v4.0\fsc.exe -o:obj\Debug\Library1.dll -g --debug:full --noframework --define:DEBUG --define
:TRACE --doc:bin\Debug\Library1.XML --optimize- --tailcalls- --versionfile:version.htm -r:"C:\Program Files (x86)\Reference Assemblies\Microsoft\FS
harp\.NETFramework\v4.0\4.4.0.0\FSharp.Core.dll" -r:"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6\mscorlib.dl
l" -r:"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6\System.Core.dll" -r:"C:\Program Files (x86)\Reference Ass
emblies\Microsoft\Framework\.NETFramework\v4.6\System.dll" -r:"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6\S
ystem.Numerics.dll" --target:library --warn:3 --warnaserror:76 --fullpaths --flaterrors --subsystemversion:6.00 --highentropyva+ "C:\Users\dafohl\A
ppData\Local\Temp\.NETFramework,Version=v4.6.AssemblyAttributes.fs" AssemblyInfo.fs Library1.fs
FSC : warning FS0075: The command-line option 'versionfile' is for test purposes only [C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1 \Library1\Library1.fsproj]
FSC : warning FS2015: The 'AssemblyVersionAttribute' has been ignored because a version was given using a command line option [C:\Users\dafohl\Docume nts\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj]
FSC : error FS0205: Invalid version file 'C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1\Library1\version.htm' [C:\Users\dafohl\Docum ents\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj]
Done Building Project "C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj" (default targets) -- FAILED.
Build FAILED.
"C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj" (default target) (1) ->
(CoreCompile target) ->
FSC : warning FS0075: The command-line option 'versionfile' is for test purposes only [C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Librar y1\Library1\Library1.fsproj]
FSC : warning FS2015: The 'AssemblyVersionAttribute' has been ignored because a version was given using a command line option [C:\Users\dafohl\Docu ments\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj]
"C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj" (default target) (1) ->
(CoreCompile target) ->
FSC : error FS0205: Invalid version file 'C:\Users\dafohl\Documents\Visual Studio 2015\Projects\Library1\Library1\version.htm' [C:\Users\dafohl\Doc uments\Visual Studio 2015\Projects\Library1\Library1\Library1.fsproj]
2 Warning(s)
1 Error(s)
Time Elapsed 00:00:00.68
Here are the original contents of Microsoft.FSharp.targets:
WARNING: DO NOT MODIFY this file unless you are knowledgeable about MSBuild and have
created a backup copy. Incorrect changes to this file will make it
impossible to load or build your projects from the command-line or the IDE.
This file defines the steps in the standard build process specific for F# .NET projects.
For example, it contains the step that actually calls the F# compiler. The remainder
of the build process is defined in Microsoft.Common.targets, which is imported by
this file.
Copyright (C) Microsoft Corporation. All rights reserved.
***********************************************************************************************
-->
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<UsingTask TaskName="Fsc" AssemblyFile="FSharp.Build.dll"/>
<UsingTask TaskName="CreateFSharpManifestResourceName" AssemblyFile="FSharp.Build.dll"/>
<PropertyGroup>
<ImportByWildcardBeforeMicrosoftFSharpTargets Condition="'$(ImportByWildcardBeforeMicrosoftFSharpTargets)' == ''">true</ImportByWildcardBeforeMicrosoftFSharpTargets>
<ImportByWildcardAfterMicrosoftFSharpTargets Condition="'$(ImportByWildcardAfterMicrosoftFSharpTargets)' == ''">true</ImportByWildcardAfterMicrosoftFSharpTargets>
</PropertyGroup>
<Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\$(MSBuildThisFile)\ImportBefore\*" Condition="'$(ImportByWildcardBeforeMicrosoftFSharpTargets)' == 'true' and exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\$(MSBuildThisFile)\ImportBefore')"/>
<PropertyGroup>
<MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
<DefaultLanguageSourceExtension>.fs</DefaultLanguageSourceExtension>
<Language>F#</Language>
<TargetRuntime>Managed</TargetRuntime>
<Tailcalls Condition="'$(Tailcalls)'==''">$(Optimize)</Tailcalls>
<FrameworkRegistryBase Condition="'$(TargetFrameworkIdentifier)'=='Silverlight'">Software\Microsoft\Microsoft SDKs\$(TargetFrameworkIdentifier)</FrameworkRegistryBase>
<!-- Visual studio requires a non-empty RootNamespace value for "Add New Item" to work. -->
<RootNamespace Condition="'$(RootNamespace)'==''">RootNamespace</RootNamespace>
<Actual32Bit Condition="'$(TargetFrameworkVersion)'=='v2.0' or '$(TargetFrameworkVersion)'=='v3.0' or '$(TargetFrameworkVersion)'=='v3.5' or '$(TargetFrameworkVersion)'=='v4.0'">false</Actual32Bit>
<Actual32Bit Condition="!('$(TargetFrameworkVersion)'=='v2.0' or '$(TargetFrameworkVersion)'=='v3.0' or '$(TargetFrameworkVersion)'=='v3.5' or '$(TargetFrameworkVersion)'=='v4.0')">$(Prefer32Bit)</Actual32Bit>
</PropertyGroup>
<!--
The CreateManifestResourceNames target create the manifest resource names from the .RESX
files.
[IN]
#(EmbeddedResource) - The list of EmbeddedResource items that have been pre-processed to add metadata about resource type
Expected Metadata "Type" can either be "Resx" or "Non-Resx"
[OUT]
#(EmbeddedResource) - EmbeddedResource items with metadata
For F# applications the transformation is like:
Resources1.resx => Resources1 => Build into main assembly
SubFolder\Resources1.resx => SubFolder.Resources1 => Build into main assembly
Resources1.fr.resx => Resources1.fr => Build into satellite assembly
Resources1.notaculture.resx => Resources1.notaculture => Build into main assembly
For other project systems, this transformation may be different.
-->
<PropertyGroup>
<CreateManifestResourceNamesDependsOn></CreateManifestResourceNamesDependsOn>
</PropertyGroup>
<Target
Name="CreateManifestResourceNames"
Condition="'#(EmbeddedResource)' != ''"
DependsOnTargets="$(CreateManifestResourceNamesDependsOn)"
>
<ItemGroup>
<_Temporary Remove="#(_Temporary)" />
</ItemGroup>
<!-- Create manifest names for culture and non-culture Resx files, and for non-culture Non-Resx resources -->
<CreateFSharpManifestResourceName
ResourceFiles="#(EmbeddedResource)"
RootNamespace="$(RootNamespace)"
Condition="'%(EmbeddedResource.ManifestResourceName)' == '' and ('%(EmbeddedResource.WithCulture)' == 'false' or '%(EmbeddedResource.Type)' == 'Resx')">
<Output TaskParameter="ResourceFilesWithManifestResourceNames" ItemName="_Temporary" />
</CreateFSharpManifestResourceName>
<!-- Create manifest names for all culture non-resx resources -->
<CreateFSharpManifestResourceName
ResourceFiles="#(EmbeddedResource)"
RootNamespace="$(RootNamespace)"
PrependCultureAsDirectory="false"
Condition="'%(EmbeddedResource.ManifestResourceName)' == '' and '%(EmbeddedResource.WithCulture)' == 'true' and '%(EmbeddedResource.Type)' == 'Non-Resx'">
<Output TaskParameter="ResourceFilesWithManifestResourceNames" ItemName="_Temporary" />
</CreateFSharpManifestResourceName>
<ItemGroup>
<EmbeddedResource Remove="#(EmbeddedResource)" Condition="'%(EmbeddedResource.ManifestResourceName)' == ''"/>
<EmbeddedResource Include="#(_Temporary)" />
<_Temporary Remove="#(_Temporary)" />
</ItemGroup>
</Target>
<ItemGroup>
<DocFileItem Include="$(DocumentationFile)" Condition="'$(DocumentationFile)'!=''"/>
</ItemGroup>
<ItemGroup Condition="'$(_DebugSymbolsProduced)' == 'true' and '$(PdbFile)' != ''">
<_DebugSymbolsIntermediatePathTemporary Include="$(PdbFile)"/>
<!-- Add any missing .pdb extension, as the compiler does -->
<_DebugSymbolsIntermediatePath Include="#(_DebugSymbolsIntermediatePathTemporary->'%(RootDir)%(Directory)%(Filename).pdb')"/>
</ItemGroup>
<PropertyGroup>
<CoreCompileDependsOn>_ComputeNonExistentFileProperty</CoreCompileDependsOn>
</PropertyGroup>
<Target
Name="CoreCompile"
Inputs="$(MSBuildAllProjects);
#(CompileBefore);
#(Compile);
#(CompileAfter);
#(_CoreCompileResourceInputs);
$(ApplicationIcon);
$(AssemblyOriginatorKeyFile);
#(ReferencePath);
#(CompiledLicenseFile);
#(EmbeddedDocumentation);
$(Win32Resource);
$(Win32Manifest);
#(CustomAdditionalCompileInputs);
$(VersionFile);
$(KeyOriginatorFile)"
Outputs="#(DocFileItem);
#(IntermediateAssembly);
#(_DebugSymbolsIntermediatePath);
$(NonExistentFile);
#(CustomAdditionalCompileOutputs)"
Returns=""
DependsOnTargets="$(CoreCompileDependsOn)"
>
<Error
Condition="'$(SilverlightVersion)' != '' and '$(SilverlightVersion)' != 'v5.0'"
Text="In this version of Visual Studio, F# for Silverlight can only target Silverlight v5.0. Use a prior version of Visual Studio to target previous versions of Silverlight with F#."
/>
<Warning
Condition="'$(Win32ResourceFile)' != '' "
Text="The property <Win32ResourceFile> has been renamed to <Win32Resource>. Update your project file to ensure that the correct value is passed via the --win32res option to the F# compiler."
/>
<!-- Condition is to filter out the _CoreCompileResourceInputs so that it doesn't pass in culture resources to the compiler -->
<Fsc Condition=" '%(_CoreCompileResourceInputs.WithCulture)' != 'true' "
BaseAddress="$(BaseAddress)"
CodePage="$(CodePage)"
DebugSymbols="$(DebugSymbols)"
DebugType="$(DebugType)"
DefineConstants="$(DefineConstants)"
DisabledWarnings="$(NoWarn)"
DocumentationFile="$(DocumentationFile)"
GenerateInterfaceFile="$(GenerateInterfaceFile)"
KeyFile="$(KeyOriginatorFile)"
LCID="$(LCID)"
NoFramework="true"
Optimize="$(Optimize)"
OtherFlags="$(OtherFlags)"
OutputAssembly="#(IntermediateAssembly)"
PdbFile="$(PdbFile)"
Platform="$(PlatformTarget)"
Prefer32Bit="$(Actual32Bit)"
References="#(ReferencePath)"
ReferencePath="$(ReferencePath)"
Resources="#(_CoreCompileResourceInputs);#(CompiledLicenseFile);#(AdditionalEmbeddedResource)"
Sources="#(CompileBefore);#(Compile);#(CompileAfter)"
Tailcalls="$(Tailcalls)"
TargetType="$(OutputType)"
ToolExe="$(FscToolExe)"
ToolPath="$(FscToolPath)"
TreatWarningsAsErrors="$(TreatWarningsAsErrors)"
Utf8Output="$(Utf8Output)"
VersionFile="$(VersionFile)"
VisualStudioStyleErrors="$(VisualStudioStyleErrors)"
WarningLevel="$(WarningLevel)"
WarningsAsErrors="$(WarningsAsErrors)"
Win32ManifestFile="$(Win32Manifest)"
Win32ResourceFile="$(Win32Resource)"
SubsystemVersion="$(SubsystemVersion)"
HighEntropyVA="$(HighEntropyVA)"
TargetProfile="$(TargetProfile)"
SqmSessionGuid="$(SqmSessionGuid)"
/>
<ItemGroup>
<_CoreCompileResourceInputs Remove="#(_CoreCompileResourceInputs)" />
</ItemGroup>
</Target>
<Import Project="$(MSBuildBinPath)\Microsoft.Common.targets"/>
<!--
============================================================
GenerateTargetFrameworkMonikerAttribute
Emit the target framework moniker attribute as a code fragment into a temporary source file for the compiler.
============================================================
-->
<Target Name="GenerateTargetFrameworkMonikerAttribute" BeforeTargets="BeforeCompile" DependsOnTargets="PrepareForBuild;GetReferenceAssemblyPaths" Inputs="$(MSBuildThisFileFullPath)" Outputs="$(TargetFrameworkMonikerAssemblyAttributesPath)" Condition="'$(GenerateTargetFrameworkAttribute)' == 'true'">
<PropertyGroup>
<!-- This attribute is only available in mscorlib v4 and later -->
<AdditionalSourcesText Condition="'$(TargetFrameworkMoniker)' != '' and '$(TargetingClr2Framework)' != 'true'">
$(AdditionalSourcesText)
namespace Microsoft.BuildSettings
[<System.Runtime.Versioning.TargetFrameworkAttribute("$(TargetFrameworkMoniker)", FrameworkDisplayName="$(TargetFrameworkMonikerDisplayName)")>]
do ()
</AdditionalSourcesText>
</PropertyGroup>
<!-- This is a file shared between projects so we have to take care to handle simultaneous writes (by ContinueOnError)
and a race between clean from one project and build from another (by not adding to FilesWritten so it doesn't clean) -->
<WriteLinesToFile
File="$(TargetFrameworkMonikerAssemblyAttributesPath)"
Lines="$(AdditionalSourcesText)"
Condition="'$(AdditionalSourcesText)' != ''"
ContinueOnError="true"
Overwrite="true"/>
<ItemGroup>
<CompileBefore Include="$(TargetFrameworkMonikerAssemblyAttributesPath)" Condition="'$(AdditionalSourcesText)' != ''"/>
</ItemGroup>
</Target>
<Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\$(MSBuildThisFile)\ImportAfter\*" Condition="'$(ImportByWildcardAfterMicrosoftFSharpTargets)' == 'true' and exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\$(MSBuildThisFile)\ImportAfter')"/>
</Project>

Answer 1

Silly me, this was caused by some CoreXT setting in my work environment when launching VS from the command line where CoreXT had been loaded. When starting VS from a fresh command line or from the start menu the problem goes away.
No idea what setting exactly got changed by CoreXT or where, but that was definitely the culprit.