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Support variables in #:project directives #51108

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bc17aea
Support variables in `#:project` directives
jjonescz Oct 2, 2025
7a28231
Fix slashes
jjonescz Oct 2, 2025
bfba2dc
Fix typo in a comment
jjonescz Oct 2, 2025
b3dc5e4
Remove unnecessary `required`s
jjonescz Oct 9, 2025
2a0f51a
Preserve variables inside full paths
jjonescz Oct 9, 2025
ffa9443
Merge branch 'release/10.0.2xx' into sprint-project-vars
jjonescz Oct 30, 2025
4194017
Improve code
jjonescz Oct 30, 2025
f829602
Fix and test dependency on working directory
jjonescz Oct 30, 2025
9fd4539
Fix file name case in a test
jjonescz Oct 30, 2025
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6 changes: 6 additions & 0 deletions documentation/general/dotnet-run-file.md
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Original file line number Diff line number Diff line change
Expand Up @@ -245,6 +245,12 @@ The directives are processed as follows:
(because `ProjectReference` items don't support directory paths).
An error is reported if zero or more than one projects are found in the directory, just like `dotnet reference add` would do.

Directive values support MSBuild variables (like `$(..)`) normally as they are translated literally and left to MSBuild engine to process.
However, in `#:project` directives, variables might not be preserved during [grow up](#grow-up),
because there is additional processing of those directives that makes it technically challenging to preserve variables in all cases
(project directive values need to be resolved to be relative to the target directory
and also to point to a project file rather than a directory).

Because these directives are limited by the C# language to only appear before the first "C# token" and any `#if`,
dotnet CLI can look for them via a regex or Roslyn lexer without any knowledge of defined conditional symbols
and can do that efficiently by stopping the search when it sees the first "C# token".
Expand Down
51 changes: 41 additions & 10 deletions src/Cli/dotnet/Commands/Project/Convert/ProjectConvertCommand.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,8 @@ public override int Execute()

// Find directives (this can fail, so do this before creating the target directory).
var sourceFile = SourceFile.Load(file);
var directives = VirtualProjectBuildingCommand.FindDirectives(sourceFile, reportAllErrors: !_force, DiagnosticBag.ThrowOnFirst());
var diagnostics = DiagnosticBag.ThrowOnFirst();
var directives = VirtualProjectBuildingCommand.FindDirectives(sourceFile, reportAllErrors: !_force, diagnostics);

// Create a project instance for evaluation.
var projectCollection = new ProjectCollection();
Expand All @@ -42,6 +43,11 @@ public override int Execute()
};
var projectInstance = command.CreateProjectInstance(projectCollection);

// Evaluate directives.
directives = VirtualProjectBuildingCommand.EvaluateDirectives(projectInstance, directives, sourceFile, diagnostics);
command.Directives = directives;
projectInstance = command.CreateProjectInstance(projectCollection);

// Find other items to copy over, e.g., default Content items like JSON files in Web apps.
var includeItems = FindIncludedItems().ToList();

Expand Down Expand Up @@ -169,17 +175,42 @@ ImmutableArray<CSharpDirective> UpdateDirectives(ImmutableArray<CSharpDirective>

foreach (var directive in directives)
{
// Fixup relative project reference paths (they need to be relative to the output directory instead of the source directory).
if (directive is CSharpDirective.Project project &&
!Path.IsPathFullyQualified(project.Name))
{
var modified = project.WithName(Path.GetRelativePath(relativeTo: targetDirectory, path: project.Name));
result.Add(modified);
}
else
// Fixup relative project reference paths (they need to be relative to the output directory instead of the source directory,
// and preserve MSBuild interpolation variables like `$(..)`
// while also pointing to the project file rather than a directory).
if (directive is CSharpDirective.Project project)
{
result.Add(directive);
// If the path is absolute and it has some `$(..)` vars in it,
// turn it into a relative path (it might be in the form `$(ProjectDir)/../Lib`
// and we don't want that to be turned into an absolute path in the converted project).
if (Path.IsPathFullyQualified(project.Name))
{
// If the path is absolute and has no `$(..)` vars, just keep it.
if (project.UnresolvedName == project.OriginalName)
{
result.Add(project);
continue;
}

project = project.WithName(Path.GetRelativePath(relativeTo: targetDirectory, path: project.Name));
result.Add(project);
continue;
}

// If the original path is to a directory, just append the resolved file name
// but preserve the variables from the original, e.g., `../$(..)/Directory/Project.csproj`.
if (Directory.Exists(project.UnresolvedName))
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If I am understanding right, project.UnresolvedName could be relative, creating a dependency on the process current directory. I think we should avoid that, e.g. by explicitly resolving relative to some known absolute path, like the Path of the containing SourceFile, before doing this check.

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Good catch, thanks, I will add a test for this too.

{
var projectFileName = Path.GetFileName(project.Name);
project = project.WithName(Path.Join(project.OriginalName, projectFileName));
}

project = project.WithName(Path.GetRelativePath(relativeTo: targetDirectory, path: project.Name));
result.Add(project);
continue;
}

result.Add(directive);
}

return result.DrainToImmutable();
Expand Down
115 changes: 99 additions & 16 deletions src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs
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Expand Up @@ -6,6 +6,7 @@
using System.Collections.Immutable;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Security;
using System.Text.Json;
using System.Text.Json.Serialization;
Expand Down Expand Up @@ -164,14 +165,26 @@ public VirtualProjectBuildingCommand(
/// </summary>
public bool NoWriteBuildMarkers { get; init; }

private SourceFile EntryPointSourceFile
{
get
{
if (field == default)
{
field = SourceFile.Load(EntryPointFileFullPath);
}

return field;
}
}

public ImmutableArray<CSharpDirective> Directives
{
get
{
if (field.IsDefault)
{
var sourceFile = SourceFile.Load(EntryPointFileFullPath);
field = FindDirectives(sourceFile, reportAllErrors: false, DiagnosticBag.ThrowOnFirst());
field = FindDirectives(EntryPointSourceFile, reportAllErrors: false, DiagnosticBag.ThrowOnFirst());
Debug.Assert(!field.IsDefault);
}

Expand Down Expand Up @@ -1047,6 +1060,23 @@ public ProjectInstance CreateProjectInstance(ProjectCollection projectCollection
private ProjectInstance CreateProjectInstance(
ProjectCollection projectCollection,
Action<IDictionary<string, string>>? addGlobalProperties)
{
var project = CreateProjectInstance(projectCollection, Directives, addGlobalProperties);

var directives = EvaluateDirectives(project, Directives, EntryPointSourceFile, DiagnosticBag.ThrowOnFirst());
if (directives != Directives)
{
Directives = directives;
project = CreateProjectInstance(projectCollection, directives, addGlobalProperties);
}

return project;
}

private ProjectInstance CreateProjectInstance(
ProjectCollection projectCollection,
ImmutableArray<CSharpDirective> directives,
Action<IDictionary<string, string>>? addGlobalProperties)
{
var projectRoot = CreateProjectRootElement(projectCollection);

Expand All @@ -1069,7 +1099,7 @@ ProjectRootElement CreateProjectRootElement(ProjectCollection projectCollection)
var projectFileWriter = new StringWriter();
WriteProjectFile(
projectFileWriter,
Directives,
directives,
isVirtualProject: true,
targetFilePath: EntryPointFileFullPath,
artifactsPath: ArtifactsPath,
Expand Down Expand Up @@ -1589,6 +1619,28 @@ static bool Fill(ref WhiteSpaceInfo info, in SyntaxTriviaList triviaList, int in
}
}

/// <summary>
/// If there are any <c>#:project</c> <paramref name="directives"/>, expand <c>$()</c> in them and then resolve the project paths.
/// </summary>
public static ImmutableArray<CSharpDirective> EvaluateDirectives(
ProjectInstance? project,
ImmutableArray<CSharpDirective> directives,
SourceFile sourceFile,
DiagnosticBag diagnostics)
{
if (directives.OfType<CSharpDirective.Project>().Any())
{
return directives
.Select(d => d is CSharpDirective.Project p
? (project is null ? p : p.WithName(project.ExpandString(p.Name)))
.ResolveProjectPath(sourceFile, diagnostics)
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Nit: The original formatting here makes what ResolveProjectPath was being invoked on hard to see. Consider something more like this.

Suggested change
? (project is null ? p : p.WithName(project.ExpandString(p.Name)))
.ResolveProjectPath(sourceFile, diagnostics)
? (project is null
? p
: p.WithName(project.ExpandString(p.Name)))
.ResolveProjectPath(sourceFile, diagnostics)

: d)
.ToImmutableArray();
}

return directives;
}

public static SourceText? RemoveDirectivesFromFile(ImmutableArray<CSharpDirective> directives, SourceText text)
{
if (directives.Length == 0)
Expand Down Expand Up @@ -1867,8 +1919,26 @@ public sealed class Package(in ParseInfo info) : Named(info)
/// <summary>
/// <c>#:project</c> directive.
/// </summary>
public sealed class Project(in ParseInfo info) : Named(info)
public sealed class Project : Named
{
[SetsRequiredMembers]
public Project(in ParseInfo info, string name) : base(info)
{
Name = name;
OriginalName = name;
UnresolvedName = name;
}

/// <summary>
/// Preserved across <see cref="WithName"/> calls.
/// </summary>
public required string OriginalName { get; init; }

/// <summary>
/// Preserved across <see cref="ResolveProjectPath"/> calls.
/// </summary>
public required string UnresolvedName { get; init; }

public static new Project? Parse(in ParseContext context)
{
var directiveText = context.DirectiveText;
Expand All @@ -1878,11 +1948,32 @@ public sealed class Project(in ParseInfo info) : Named(info)
return context.Diagnostics.AddError<Project?>(context.SourceFile, context.Info.Span, string.Format(CliCommandStrings.MissingDirectiveName, directiveKind));
}

return new Project(context.Info, directiveText);
}

public Project WithName(string name, bool preserveUnresolvedName = false)
{
return name == Name
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It feels like we would also want to create a new instance if !preserveUnresolvedName && UnresolvedName != name. If we don't expect this to occur, it would probably be good to add an assertion to that effect.

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Good catch, forgot to update this when adding the parameter.

? this
: new Project(Info, name)
{
OriginalName = OriginalName,
UnresolvedName = preserveUnresolvedName ? UnresolvedName : name,
};
}

/// <summary>
/// If the directive points to a directory, returns a new directive pointing to the corresponding project file.
/// </summary>
public Project ResolveProjectPath(SourceFile sourceFile, DiagnosticBag diagnostics)
{
var directiveText = Name;

try
{
// If the path is a directory like '../lib', transform it to a project file path like '../lib/lib.csproj'.
// Also normalize blackslashes to forward slashes to ensure the directive works on all platforms.
var sourceDirectory = Path.GetDirectoryName(context.SourceFile.Path) ?? ".";
// Also normalize backslashes to forward slashes to ensure the directive works on all platforms.
var sourceDirectory = Path.GetDirectoryName(sourceFile.Path) ?? ".";
var resolvedProjectPath = Path.Combine(sourceDirectory, directiveText.Replace('\\', '/'));
if (Directory.Exists(resolvedProjectPath))
{
Expand All @@ -1900,18 +1991,10 @@ public sealed class Project(in ParseInfo info) : Named(info)
}
catch (GracefulException e)
{
context.Diagnostics.AddError(context.SourceFile, context.Info.Span, string.Format(CliCommandStrings.InvalidProjectDirective, e.Message), e);
diagnostics.AddError(sourceFile, Info.Span, string.Format(CliCommandStrings.InvalidProjectDirective, e.Message), e);
}

return new Project(context.Info)
{
Name = directiveText,
};
}

public Project WithName(string name)
{
return new Project(Info) { Name = name };
return WithName(directiveText, preserveUnresolvedName: true);
}

public override string ToString() => $"#:project {Name}";
Expand Down
78 changes: 71 additions & 7 deletions test/dotnet.Tests/CommandTests/Project/Convert/DotnetProjectConvertTests.cs
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Expand Up @@ -73,11 +73,14 @@ public void SameAsTemplate()
}

[Theory] // https://github.com/dotnet/sdk/issues/50832
[InlineData("File", "Lib", "../Lib", "Project", "../Lib/lib.csproj")]
[InlineData(".", "Lib", "./Lib", "Project", "../Lib/lib.csproj")]
[InlineData(".", "Lib", "Lib/../Lib", "Project", "../Lib/lib.csproj")]
[InlineData("File", "Lib", "../Lib", "File/Project", "../../Lib/lib.csproj")]
[InlineData("File", "Lib", "..\\Lib", "File/Project", "../../Lib/lib.csproj")]
[InlineData("File", "Lib", "../Lib", "Project", "..{/}Lib{/}lib.csproj")]
[InlineData(".", "Lib", "./Lib", "Project", "..{/}Lib{/}lib.csproj")]
[InlineData(".", "Lib", "Lib/../Lib", "Project", "..{/}Lib{/}lib.csproj")]
[InlineData("File", "Lib", "../Lib", "File/Project", "..{/}..{/}Lib{/}lib.csproj")]
[InlineData("File", "Lib", @"..\Lib", "File/Project", @"..{/}..\Lib{/}lib.csproj")]
[InlineData("File", "Lib", "../$(LibProjectName)", "File/Project", "..{/}..{/}$(LibProjectName){/}lib.csproj")]
[InlineData("File", "Lib", @"..\$(LibProjectName)", "File/Project", @"..{/}..\$(LibProjectName){/}lib.csproj")]
[InlineData("File", "Lib", "$(MSBuildProjectDirectory)/../$(LibProjectName)", "File/Project", "..{/}..{/}Lib{/}lib.csproj")]
public void ProjectReference_RelativePaths(string fileDir, string libraryDir, string reference, string outputDir, string convertedReference)
{
var testInstance = _testAssetsManager.CreateTestDirectory();
Expand Down Expand Up @@ -105,6 +108,7 @@ public static void M()
Directory.CreateDirectory(fileDirFullPath);
File.WriteAllText(Path.Join(fileDirFullPath, "app.cs"), $"""
#:project {reference}
#:property LibProjectName=Lib
C.M();
""");

Expand All @@ -130,7 +134,7 @@ public static void M()

File.ReadAllText(Path.Join(outputDirFullPath, "app.csproj"))
.Should().Contain($"""
<ProjectReference Include="{convertedReference.Replace('/', Path.DirectorySeparatorChar)}" />
<ProjectReference Include="{convertedReference.Replace("{/}", Path.DirectorySeparatorChar.ToString())}" />
""");
}

Expand Down Expand Up @@ -191,6 +195,64 @@ public static void M()
""");
}

[Fact]
public void ProjectReference_FullPath_WithVars()
{
var testInstance = _testAssetsManager.CreateTestDirectory();

var libraryDirFullPath = Path.Join(testInstance.Path, "Lib");
Directory.CreateDirectory(libraryDirFullPath);
File.WriteAllText(Path.Join(libraryDirFullPath, "lib.cs"), """
public static class C
{
public static void M()
{
System.Console.WriteLine("Hello from library");
}
}
""");
File.WriteAllText(Path.Join(libraryDirFullPath, "lib.csproj"), $"""
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>{ToolsetInfo.CurrentTargetFramework}</TargetFramework>
</PropertyGroup>
</Project>
""");

var fileDirFullPath = Path.Join(testInstance.Path, "File");
Directory.CreateDirectory(fileDirFullPath);
File.WriteAllText(Path.Join(fileDirFullPath, "app.cs"), $"""
#:project {fileDirFullPath}/../$(LibProjectName)
#:property LibProjectName=Lib
C.M();
""");

var expectedOutput = "Hello from library";

new DotnetCommand(Log, "run", "app.cs")
.WithWorkingDirectory(fileDirFullPath)
.Execute()
.Should().Pass()
.And.HaveStdOut(expectedOutput);

var outputDirFullPath = Path.Join(testInstance.Path, "File/Project");
new DotnetCommand(Log, "project", "convert", "app.cs", "-o", outputDirFullPath)
.WithWorkingDirectory(fileDirFullPath)
.Execute()
.Should().Pass();

new DotnetCommand(Log, "run")
.WithWorkingDirectory(outputDirFullPath)
.Execute()
.Should().Pass()
.And.HaveStdOut(expectedOutput);

File.ReadAllText(Path.Join(outputDirFullPath, "app.csproj"))
.Should().Contain($"""
<ProjectReference Include="{"../../Lib/lib.csproj".Replace('/', Path.DirectorySeparatorChar)}" />
""");
}

[Fact]
public void DirectoryAlreadyExists()
{
Expand Down Expand Up @@ -1551,7 +1613,9 @@ public void Directives_VersionedSdkFirst()
private static void Convert(string inputCSharp, out string actualProject, out string? actualCSharp, bool force, string? filePath)
{
var sourceFile = new SourceFile(filePath ?? "/app/Program.cs", SourceText.From(inputCSharp, Encoding.UTF8));
var directives = VirtualProjectBuildingCommand.FindDirectives(sourceFile, reportAllErrors: !force, DiagnosticBag.ThrowOnFirst());
var diagnostics = DiagnosticBag.ThrowOnFirst();
var directives = VirtualProjectBuildingCommand.FindDirectives(sourceFile, reportAllErrors: !force, diagnostics);
directives = VirtualProjectBuildingCommand.EvaluateDirectives(project: null, directives, sourceFile, diagnostics);
var projectWriter = new StringWriter();
VirtualProjectBuildingCommand.WriteProjectFile(projectWriter, directives, isVirtualProject: false);
actualProject = projectWriter.ToString();
Expand Down
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