From 46efc78e925ddfc5f566cf61b4350fea711a68f3 Mon Sep 17 00:00:00 2001
From: Jan Jones <janjones@microsoft.com>
Date: Wed, 1 Oct 2025 12:03:10 +0200
Subject: [PATCH 1/2] Allow empty file-level directive values

---
 .../Run/VirtualProjectBuildingCommand.cs      | 12 ++++-
 .../Convert/DotnetProjectConvertTests.cs      | 44 +++++++++++++++++++
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs b/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs
index 6997b8052a0c..a8105509dd52 100644
--- a/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs
+++ b/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs
@@ -1738,12 +1738,20 @@ private static (string, string?)? ParseOptionalTwoParts(in ParseContext context,
             return context.Diagnostics.AddError<(string, string?)?>(context.SourceFile, context.Info.Span, string.Format(CliCommandStrings.InvalidDirectiveName, directiveKind, separator));
         }
 
-        var secondPart = i < 0 ? [] : context.DirectiveText.AsSpan((i + 1)..).TrimStart();
-        if (i < 0 || secondPart.IsWhiteSpace())
+        if (i < 0)
         {
             return (firstPart.ToString(), null);
         }
 
+        var secondPart = context.DirectiveText.AsSpan((i + 1)..).TrimStart();
+        if (secondPart.IsWhiteSpace())
+        {
+            Debug.Assert(secondPart.Length == 0,
+                "We have trimmed the second part, so if it's white space, it should be actually empty.");
+
+            return (firstPart.ToString(), string.Empty);
+        }
+
         return (firstPart.ToString(), secondPart.ToString());
     }
 
diff --git a/test/dotnet.Tests/CommandTests/Project/Convert/DotnetProjectConvertTests.cs b/test/dotnet.Tests/CommandTests/Project/Convert/DotnetProjectConvertTests.cs
index 27bf71fa48dc..faaba8746189 100644
--- a/test/dotnet.Tests/CommandTests/Project/Convert/DotnetProjectConvertTests.cs
+++ b/test/dotnet.Tests/CommandTests/Project/Convert/DotnetProjectConvertTests.cs
@@ -889,6 +889,50 @@ public void Directives_EmptyName(
             expectedWildcardPattern: RunFileTests.DirectiveError("/app/Program.cs", 1, CliCommandStrings.MissingDirectiveName, directive));
     }
 
+    [Theory]
+    [InlineData("")]
+    [InlineData(" ")]
+    public void Directives_EmptyValue(string value)
+    {
+        VerifyConversion(
+            inputCSharp: $"""
+                #:property TargetFramework={value}
+                #:property Prop1={value}
+                #:sdk First@{value}
+                #:sdk Second@{value}
+                #:package P1@{value}
+                """,
+            expectedProject: """
+                <Project Sdk="First/">
+
+                  <Sdk Name="Second" Version="" />
+
+                  <PropertyGroup>
+                    <OutputType>Exe</OutputType>
+                    <ImplicitUsings>enable</ImplicitUsings>
+                    <Nullable>enable</Nullable>
+                    <PublishAot>true</PublishAot>
+                    <PackAsTool>true</PackAsTool>
+                    <TargetFramework></TargetFramework>
+                    <Prop1></Prop1>
+                  </PropertyGroup>
+
+                  <ItemGroup>
+                    <PackageReference Include="P1" Version="" />
+                  </ItemGroup>
+
+                </Project>
+
+                """,
+            expectedCSharp: "");
+
+        VerifyConversionThrows(
+            inputCSharp: $"""
+                #:project{value}
+                """,
+            expectedWildcardPattern: RunFileTests.DirectiveError("/app/Program.cs", 1, CliCommandStrings.MissingDirectiveName, "project"));
+    }
+
     [Fact]
     public void Directives_MissingPropertyValue()
     {

From 9635141863099c23647e4596f0ffd7942a6e4cb7 Mon Sep 17 00:00:00 2001
From: Jan Jones <janjones@microsoft.com>
Date: Tue, 7 Oct 2025 10:55:36 +0200
Subject: [PATCH 2/2] Clarify separator index variable name

---
 .../dotnet/Commands/Run/VirtualProjectBuildingCommand.cs  | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs b/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs
index a8105509dd52..3efd5305ae2a 100644
--- a/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs
+++ b/src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs
@@ -1723,8 +1723,8 @@ public readonly struct ParseContext
 
     private static (string, string?)? ParseOptionalTwoParts(in ParseContext context, char separator)
     {
-        var i = context.DirectiveText.IndexOf(separator, StringComparison.Ordinal);
-        var firstPart = (i < 0 ? context.DirectiveText : context.DirectiveText.AsSpan(..i)).TrimEnd();
+        var separatorIndex = context.DirectiveText.IndexOf(separator, StringComparison.Ordinal);
+        var firstPart = (separatorIndex < 0 ? context.DirectiveText : context.DirectiveText.AsSpan(..separatorIndex)).TrimEnd();
 
         string directiveKind = context.DirectiveKind;
         if (firstPart.IsWhiteSpace())
@@ -1738,12 +1738,12 @@ private static (string, string?)? ParseOptionalTwoParts(in ParseContext context,
             return context.Diagnostics.AddError<(string, string?)?>(context.SourceFile, context.Info.Span, string.Format(CliCommandStrings.InvalidDirectiveName, directiveKind, separator));
         }
 
-        if (i < 0)
+        if (separatorIndex < 0)
         {
             return (firstPart.ToString(), null);
         }
 
-        var secondPart = context.DirectiveText.AsSpan((i + 1)..).TrimStart();
+        var secondPart = context.DirectiveText.AsSpan((separatorIndex + 1)..).TrimStart();
         if (secondPart.IsWhiteSpace())
         {
             Debug.Assert(secondPart.Length == 0,