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Merged
merged 3 commits into from
Jun 4, 2025
Merged

Extensions: Do not consider extension block methods as entry points, consider their implementation methods instead #78667

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dbb702b
Extensions: extension methods cannot be entry points
jcouv May 19, 2025
6aa6560
Add tests with instance extension method
jcouv May 28, 2025
5d70d8f
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jcouv May 28, 2025
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24 changes: 23 additions & 1 deletion src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1940,7 +1940,14 @@ internal EntryPoint GetEntryPointAndDiagnostics(CancellationToken cancellationTo
return scriptClass.GetScriptEntryPoint();
}

var mainTypeOrNamespace = globalNamespace.GetNamespaceOrTypeByQualifiedName(mainTypeName.Split('.')).OfMinimalArity();
var nameParts = mainTypeName.Split('.');
if (nameParts.Any(n => string.IsNullOrWhiteSpace(n)))
{
diagnostics.Add(ErrorCode.ERR_BadCompilationOptionValue, NoLocation.Singleton, nameof(CSharpCompilationOptions.MainTypeName), mainTypeName);
return null;
}

var mainTypeOrNamespace = globalNamespace.GetNamespaceOrTypeByQualifiedName(nameParts).OfMinimalArity();
if (mainTypeOrNamespace is null)
{
diagnostics.Add(ErrorCode.ERR_MainClassNotFound, NoLocation.Singleton, mainTypeName);
Expand Down Expand Up @@ -2157,6 +2164,21 @@ private static void AddEntryPointCandidates(
ArrayBuilder<MethodSymbol> entryPointCandidates, IEnumerable<Symbol> members)
{
foreach (var member in members)
{
if (member.GetIsNewExtensionMember())
{
if (member is MethodSymbol method && method.TryGetCorrespondingExtensionImplementationMethod() is { } implementationMethod)
{
addIfCandidate(entryPointCandidates, implementationMethod);
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@AlekseyTs AlekseyTs May 23, 2025 •
edited
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addIfCandidate(entryPointCandidates, implementationMethod);

It is not obvious why we need to do this. Wouldn't the implementation methods be enumerated as members of the enclosing class?

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The search for entry point uses GetSymbolsWithNameCore which relies on NameSymbolSearcher/AbstractSymbolSearcher which walks through the declaration tree (which doesn't include the implementation methods)

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Consider adding a comment explaining this.

}
}
else
{
addIfCandidate(entryPointCandidates, member);
}
}

static void addIfCandidate(ArrayBuilder<MethodSymbol> entryPointCandidates, Symbol member)
{
if (member is MethodSymbol method &&
method.IsEntryPointCandidate)
Expand Down
2 changes: 2 additions & 0 deletions src/Compilers/CSharp/Portable/Symbols/MethodSymbol.cs
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Expand Up @@ -710,6 +710,8 @@ internal bool IsEntryPointCandidate
{
get
{
Debug.Assert(!this.GetIsNewExtensionMember());

if (this.IsPartialDefinition() &&
this.PartialImplementationPart is null)
{
Expand Down
131 changes: 120 additions & 11 deletions src/Compilers/CSharp/Test/Emit3/Semantics/ExtensionTests.cs
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Expand Up @@ -35517,16 +35517,36 @@ static class E
}
""";
var comp = CreateCompilation(source, options: TestOptions.DebugExe);
comp.VerifyEmitDiagnostics();
// Tracked by https://github.com/dotnet/roslyn/issues/76130
// FindEntryPoint/NameSymbolSearcher skip "E" since it has not declaration named "Main"
// CompileAndVerify(comp, expectedOutput: "ran");
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
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@AlekseyTs AlekseyTs May 23, 2025 •
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CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();

It looks like this behavior is in disagreement with the PR title: "Extensions: extension methods cannot be entry points"

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Updated the title. The extension skeleton method cannot be considered, but the implementation method can (for portability from classic extension methods)

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Updated the title. The extension skeleton method cannot be considered, but the implementation method can (for portability from classic extension methods)

It looks like implementation methods were not considered before this change. I think it is important to reflect that they are considered now in the commit title. Also, I would avoid using the "skeleton" term. Something like: "Do not consider extension block methods as entry points, consider their implementation methods instead"


comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E"));
comp.VerifyEmitDiagnostics();
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact]
public void Validation_EntryPoint_02()
{
string source = """
static class E
{
extension(int)
{
public static System.Action Main => throw null;
}
}
""";
var comp = CreateCompilation(source, options: TestOptions.DebugExe);
comp.VerifyEmitDiagnostics(
// error CS5001: Program does not contain a static 'Main' method suitable for an entry point
Diagnostic(ErrorCode.ERR_NoEntryPoint).WithLocation(1, 1));

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E"));
comp.VerifyDiagnostics(
// (1,14): error CS1558: 'E' does not have a suitable static 'Main' method
// static class E
Diagnostic(ErrorCode.ERR_NoMainInClass, "E").WithArguments("E").WithLocation(1, 14));
}

[Fact]
public void Validation_EntryPoint_03()
{
Expand All @@ -35535,14 +35555,19 @@ static class E
{
extension(int i)
{
public static void Main() { System.Console.Write("ran"); }
public static void Main() => throw null;
}
}
""";
var comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E.<>E__0"));
comp.VerifyEmitDiagnostics(
// error CS1555: Could not find 'E.<>E__0' specified for Main method
Diagnostic(ErrorCode.ERR_MainClassNotFound).WithArguments("E.<>E__0").WithLocation(1, 1));

Assert.Equal("<>E__0", comp.GetTypeByMetadataName("E").GetTypeMembers().Single().ExtensionName);

// Tracked by https://github.com/dotnet/roslyn/issues/76130 : we should find the unspeakable nested type
Assert.Null(comp.GetTypeByMetadataName("E+<>E__0"));
}

[Fact]
Expand All @@ -35557,13 +35582,97 @@ public static void Main() { }
}
}
""";
// Tracked by https://github.com/dotnet/roslyn/issues/76130
// FindEntryPoint should not attempt to find types with an empty name
var comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E."));
comp.VerifyEmitDiagnostics(
// (3,5): error CS1556: 'E.extension(int)' specified for Main method must be a non-generic class, record, struct, or interface
// extension(int i)
Diagnostic(ErrorCode.ERR_MainClassNotClass, "extension").WithArguments("E.extension(int)").WithLocation(3, 5));
// error CS7088: Invalid 'MainTypeName' value: 'E.'.
Diagnostic(ErrorCode.ERR_BadCompilationOptionValue).WithArguments("MainTypeName", "E.").WithLocation(1, 1));

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E. "));
comp.VerifyEmitDiagnostics(
// error CS7088: Invalid 'MainTypeName' value: 'E. '.
Diagnostic(ErrorCode.ERR_BadCompilationOptionValue).WithArguments("MainTypeName", "E. ").WithLocation(1, 1));

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName(""));
comp.VerifyEmitDiagnostics(
Diagnostic(ErrorCode.ERR_BadCompilationOptionValue).WithArguments("MainTypeName", "").WithLocation(1, 1));

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName(" "));
comp.VerifyEmitDiagnostics(
// error CS7088: Invalid 'MainTypeName' value: ' '.
Diagnostic(ErrorCode.ERR_BadCompilationOptionValue).WithArguments("MainTypeName", " ").WithLocation(1, 1));

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName(".A"));
comp.VerifyEmitDiagnostics(
// error CS7088: Invalid 'MainTypeName' value: '.A'.
Diagnostic(ErrorCode.ERR_BadCompilationOptionValue).WithArguments("MainTypeName", ".A").WithLocation(1, 1));
}

[Fact]
public void Validation_EntryPoint_05()
{
string source = """
static class E
{
extension(int i)
{
public static async System.Threading.Tasks.Task<int> Main() { System.Console.Write("ran"); await System.Threading.Tasks.Task.Yield(); return 0; }
}
}
""";
var comp = CreateCompilation(source, options: TestOptions.DebugExe);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E"));
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact]
public void Validation_EntryPoint_06()
{
string source = """
static class E
{
extension(string[] args)
{
public void Main() { System.Console.Write("ran"); }
}
}
""";
var comp = CreateCompilation(source, options: TestOptions.DebugExe);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E"));
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact]
public void Validation_EntryPoint_07()
{
string source = """
static class E
{
extension(int i)
{
public void Main() => throw null;
}
}
""";
var comp = CreateCompilation(source, options: TestOptions.DebugExe);
comp.VerifyEmitDiagnostics(
// error CS5001: Program does not contain a static 'Main' method suitable for an entry point
Diagnostic(ErrorCode.ERR_NoEntryPoint).WithLocation(1, 1),
// (5,21): warning CS0028: 'E.Main(int)' has the wrong signature to be an entry point
// public void Main() => throw null;
Diagnostic(ErrorCode.WRN_InvalidMainSig, "Main").WithArguments("E.Main(int)").WithLocation(5, 21));

comp = CreateCompilation(source, options: TestOptions.ReleaseExe.WithMainTypeName("E"));
comp.VerifyEmitDiagnostics(
// (1,14): error CS1558: 'E' does not have a suitable static 'Main' method
// static class E
Diagnostic(ErrorCode.ERR_NoMainInClass, "E").WithArguments("E").WithLocation(1, 14),
// (5,21): warning CS0028: 'E.Main(int)' has the wrong signature to be an entry point
// public void Main() => throw null;
Diagnostic(ErrorCode.WRN_InvalidMainSig, "Main").WithArguments("E.Main(int)").WithLocation(5, 21));
}

[Fact]
Expand Down