Evaluate a project from the command line

[ltrzesniewski]

This is a feature request: Add a command line switch which would make MSBuild evaluate a project and output the value of a property or a list of items. No target would be called. This would be useful for scripting purposes.

Some examples of what I mean:

C:\Project> msbuild SomeProject.csproj -evaluate:'$(TargetPath)'
C:\Project\SomeProject\bin\Debug\SomeProject.exe

C:\Project> msbuild SomeProject.csproj -evaluate:'@(Compile)'
Program.cs
Foo.cs
Bar.cs

C:\Project> msbuild SomeProject.csproj -evaluate:'@(Compile->%(FileName))'
Program
Foo
Bar

Or a simpler version:

C:\Project> msbuild SomeProject.csproj -evaluateProperty:TargetPath
C:\Project\SomeProject\bin\Debug\SomeProject.exe

C:\Project> msbuild SomeProject.csproj -evaluateItems:Compile
Program.cs
Foo.cs
Bar.cs

[KirillOsenkov]

Take a look at MSBuildDumper and see if it fits your needs: https://github.com/KirillOsenkov/MSBuildTools

https://github.com/KirillOsenkov/MSBuildTools/blob/master/src/MSBuildDumper/MSBuildDumper.cs

[ltrzesniewski]

@KirillOsenkov thanks, but I know that getting the evaluated values is pretty easy with the MSBuild NuGet package.

To clarify, I simply thought that having this possibility from MSBuild itself (without requiring additional tools) would be a useful feature, and I think it would make sense to support that. I wished several times that MSBuild offered that.

I could contribute that feature if the MSBuild team thinks it would be valuable.

[rainersigwald]

Can you elaborate on "This would be useful for scripting purposes."? What specifically?

I would have sworn that we already had a work item for this but I don't see one. I think it's a fine idea and would help with various debugging scenarios. I would lean toward the simpler only-dump-values interface; I'm not sure how difficult plumbing the transform mechanism in would be and I think you could get most of the value from just items/properties. I'd suggest that the output should match the text logger, so combining requests would be more clear:

$ msbuild SomeProject.csproj -evaluateItems:Compile -evaluateProperty:TargetPath
TargetPath = s:\msbuild\artifacts\Debug\bin\Microsoft.Build.Framework\net472\Microsoft.Build.Framework.dll
Compile
    ..\Shared\BinaryWriterExtensions.cs
        Link = Shared\BinaryWriterExtensions.cs
    ..\Shared\Constants.cs
        Link = Shared\Constants.cs
    BuildEngineResult.cs
    BuildErrorEventArgs.cs
    BuildEventArgs.cs
    BuildEventContext.cs

[ltrzesniewski]

Can you elaborate on "This would be useful for scripting purposes."? What specifically?

I originally needed to get the OutDir property value in a script in order to zip the build output.

I couldn't just set my own OutDir because some referenced projects use multi-targeting and all targets would end up in the same output directory, thus overwriting each other. I ended up solving this issue differently, but I wished I had that feature nevertheless.

I'd suggest that the output should match the text logger, so combining requests would be more clear

The problem I see with this approach is that it's well suited for human inspection, but less useful for scripting. My idea was to make MSBuild behave like a Unix utility in this case: only output the desired value so it can be easily consumed by a script or by another tool which could be piped to the MSBuild output.

With this approach, a script would additionally have to strip the TargetPath = prefix, and there would probably be issues if the value is multi-line.

Also, given that the debugging experience is very good using the binary log viewer, I don't think a text output aimed at debuggability would provide a compelling benefit over that.

[rainersigwald]

That's interesting. What would you do about item metadata?

[ltrzesniewski]

Well, actually item metadata is the reason I suggested the "full" syntax (-evaluate) in the first place. I supposed it shouldn't be too hard to evaluate MSBuild expressions since they're also evaluated in the execution phase, and that this mode could be an alternate "execution phase" where you basically evaluate a single expression.

So suppose I want a list of linked files from your example, here's how I could get it:

$ msbuild SomeProject.csproj -evaluate:"@(Compile->'%(Identity):%(Link)')"
..\Shared\BinaryWriterExtensions.cs:Shared\BinaryWriterExtensions.cs
..\Shared\Constants.cs:Shared\Constants.cs
BuildEngineResult.cs:
BuildErrorEventArgs.cs:
BuildEventArgs.cs:
BuildEventContext.cs:

Line breaks could still be an issue though, but a unique delimiter could be inserted at the end of each line to handle these if needed.

[Scordo]

This would be super useful for us. We worked around that currently but our workaround broke and we now have lots of work backporting script-changes :-(