MA0042: add DbCommand await-using parity with DbConnection

docs/Rules/MA0042.md

@@ -55,7 +55,7 @@ public sealed class Sample
 
 The rule does not report a diagnostic for `IDbContextFactory<TContext>.CreateDbContext()`. The `CreateDbContextAsync()` overload was introduced only for specific edge-case scenarios where the factory itself must perform asynchronous initialization, and is not intended as a general-purpose replacement. See [dotnet/efcore#26630](https://github.com/dotnet/efcore/issues/26630) for more details.
 
-The rule will not report a diagnostic for a `using` statement on a `Stream` or `DbConnection` subclass that is directly instantiated with `new` when the concrete type does not override `DisposeAsync`. Both `Stream.DisposeAsync` and `DbConnection.DisposeAsync` merely call `Dispose()` synchronously by default, so switching to `await using` brings no benefit for such types. When the instance is obtained from a factory method rather than a direct `new` expression, the rule still reports a diagnostic because the runtime type may be a deeper subclass that does override `DisposeAsync`.
+The rule will not report a diagnostic for a `using` statement on a `Stream`, `DbConnection`, or `DbCommand` subclass that is directly instantiated with `new` when the concrete type does not override `DisposeAsync`. `Stream.DisposeAsync`, `DbConnection.DisposeAsync`, and `DbCommand.DisposeAsync` merely call `Dispose()` synchronously by default, so switching to `await using` brings no benefit for such types. When the instance is obtained from a factory method rather than a direct `new` expression, the rule still reports a diagnostic because the runtime type may be a deeper subclass that does override `DisposeAsync`.
 
 ````csharp
 public async Task Sample()
@@ -69,6 +69,12 @@ public async Task Sample()
 
     // Diagnostic: obtained from a factory, runtime type may override DisposeAsync.
     using var connection2 = CreateConnection();
+
+    // No diagnostic: SqlCommand does not override DisposeAsync.
+    using var command1 = new SqlCommand();
+
+    // Diagnostic: obtained from a factory, runtime type may override DisposeAsync.
+    using var command2 = CreateCommand();
 }
 ````
 

src/Meziantou.Analyzer/Rules/DoNotUseBlockingCallInAsyncContextAnalyzer.cs

@@ -77,6 +77,7 @@ public Context(Compilation compilation)
             ProcessSymbol = compilation.GetBestTypeByMetadataName("System.Diagnostics.Process");
             StreamSymbol = compilation.GetBestTypeByMetadataName("System.IO.Stream");
             DbConnectionSymbol = compilation.GetBestTypeByMetadataName("System.Data.Common.DbConnection");
+            DbCommandSymbol = compilation.GetBestTypeByMetadataName("System.Data.Common.DbCommand");
             CancellationTokenSymbol = compilation.GetBestTypeByMetadataName("System.Threading.CancellationToken");
             ObsoleteAttributeSymbol = compilation.GetBestTypeByMetadataName("System.ObsoleteAttribute");
 
@@ -126,6 +127,7 @@ public Context(Compilation compilation)
         private ISymbol? StreamSymbol { get; }
         private ISymbol? ProcessSymbol { get; }
         private INamedTypeSymbol? DbConnectionSymbol { get; }
+        private INamedTypeSymbol? DbCommandSymbol { get; }
         private ISymbol[] ConsoleErrorAndOutSymbols { get; }
         private INamedTypeSymbol? CancellationTokenSymbol { get; }
         private INamedTypeSymbol? ObsoleteAttributeSymbol { get; }
@@ -517,6 +519,17 @@ private bool CanBeAwaitUsing(IOperation operation)
                     return HasDisposeAsyncMethodDeclaredInSubclass(type, DbConnectionSymbol);
             }
 
+            // For DbCommand subclasses created directly (new T()), only report if the exact
+            // type being instantiated (or an intermediate subclass up to but not including
+            // DbCommand) actually overrides DisposeAsync. DbCommand.DisposeAsync just calls
+            // Dispose() synchronously, so it is not a meaningful async override.
+            if (DbCommandSymbol is not null && type.InheritsFrom(DbCommandSymbol))
+            {
+                var unwrapped = operation.UnwrapImplicitConversionOperations();
+                if (unwrapped is IObjectCreationOperation)
+                    return HasDisposeAsyncMethodDeclaredInSubclass(type, DbCommandSymbol);
+            }
+
             return HasDisposeAsyncMethod(type);
         }
 

tests/Meziantou.Analyzer.Test/Rules/DoNotUseBlockingCallInAsyncContextAnalyzer_AsyncContextTests.cs

@@ -2589,4 +2589,166 @@ class DerivedConnection : BaseConnection { }
                 """)
               .ValidateAsync();
     }
+
+    [Fact]
+    public async Task UsingNewDbCommandSubclass_NoDisposeAsyncOverride_NoDiagnostic()
+    {
+        await CreateProjectBuilder()
+              .WithTargetFramework(TargetFramework.Net8_0)
+              .WithSourceCode("""
+                using System.Data;
+                using System.Data.Common;
+                using System.Threading.Tasks;
+
+                class Test
+                {
+                    public async Task A()
+                    {
+                        using var command = new MyDbCommand();
+                    }
+                }
+
+                class MyDbCommand : DbCommand
+                {
+                    public override string CommandText { get => throw null; set => throw null; }
+                    public override int CommandTimeout { get => throw null; set => throw null; }
+                    public override CommandType CommandType { get => throw null; set => throw null; }
+                    public override bool DesignTimeVisible { get => throw null; set => throw null; }
+                    public override UpdateRowSource UpdatedRowSource { get => throw null; set => throw null; }
+                    protected override DbConnection DbConnection { get => throw null; set => throw null; }
+                    protected override DbParameterCollection DbParameterCollection => throw null;
+                    protected override DbTransaction DbTransaction { get => throw null; set => throw null; }
+                    public override void Cancel() => throw null;
+                    public override int ExecuteNonQuery() => throw null;
+                    public override object ExecuteScalar() => throw null;
+                    public override void Prepare() => throw null;
+                    protected override DbParameter CreateDbParameter() => throw null;
+                    protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior) => throw null;
+                }
+                """)
+              .ValidateAsync();
+    }
+
+    [Fact]
+    public async Task UsingFactoryMethod_DbCommandSubclass_NoDisposeAsyncOverride_Diagnostic()
+    {
+        await CreateProjectBuilder()
+              .WithTargetFramework(TargetFramework.Net8_0)
+              .WithSourceCode("""
+                using System.Data;
+                using System.Data.Common;
+                using System.Threading.Tasks;
+
+                class Test
+                {
+                    public async Task A()
+                    {
+                        [|using var command = CreateCommand();|]
+                    }
+
+                    private MyDbCommand CreateCommand() => throw null;
+                }
+
+                class MyDbCommand : DbCommand
+                {
+                    public override string CommandText { get => throw null; set => throw null; }
+                    public override int CommandTimeout { get => throw null; set => throw null; }
+                    public override CommandType CommandType { get => throw null; set => throw null; }
+                    public override bool DesignTimeVisible { get => throw null; set => throw null; }
+                    public override UpdateRowSource UpdatedRowSource { get => throw null; set => throw null; }
+                    protected override DbConnection DbConnection { get => throw null; set => throw null; }
+                    protected override DbParameterCollection DbParameterCollection => throw null;
+                    protected override DbTransaction DbTransaction { get => throw null; set => throw null; }
+                    public override void Cancel() => throw null;
+                    public override int ExecuteNonQuery() => throw null;
+                    public override object ExecuteScalar() => throw null;
+                    public override void Prepare() => throw null;
+                    protected override DbParameter CreateDbParameter() => throw null;
+                    protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior) => throw null;
+                }
+                """)
+              .ValidateAsync();
+    }
+
+    [Fact]
+    public async Task UsingNewDbCommandSubclass_WithDisposeAsyncOverride_Diagnostic()
+    {
+        await CreateProjectBuilder()
+              .WithTargetFramework(TargetFramework.Net8_0)
+              .WithSourceCode("""
+                using System.Data;
+                using System.Data.Common;
+                using System.Threading.Tasks;
+
+                class Test
+                {
+                    public async Task A()
+                    {
+                        [|using var command = new MyDbCommand();|]
+                    }
+                }
+
+                class MyDbCommand : DbCommand
+                {
+                    public override string CommandText { get => throw null; set => throw null; }
+                    public override int CommandTimeout { get => throw null; set => throw null; }
+                    public override CommandType CommandType { get => throw null; set => throw null; }
+                    public override bool DesignTimeVisible { get => throw null; set => throw null; }
+                    public override UpdateRowSource UpdatedRowSource { get => throw null; set => throw null; }
+                    protected override DbConnection DbConnection { get => throw null; set => throw null; }
+                    protected override DbParameterCollection DbParameterCollection => throw null;
+                    protected override DbTransaction DbTransaction { get => throw null; set => throw null; }
+                    public override void Cancel() => throw null;
+                    public override int ExecuteNonQuery() => throw null;
+                    public override object ExecuteScalar() => throw null;
+                    public override void Prepare() => throw null;
+                    protected override DbParameter CreateDbParameter() => throw null;
+                    protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior) => throw null;
+                    public override ValueTask DisposeAsync() => throw null;
+                }
+                """)
+              .ValidateAsync();
+    }
+
+    [Fact]
+    public async Task UsingNewDbCommandSubclass_DisposeAsyncOverriddenInIntermediateBase_Diagnostic()
+    {
+        await CreateProjectBuilder()
+              .WithTargetFramework(TargetFramework.Net8_0)
+              .WithSourceCode("""
+                using System.Data;
+                using System.Data.Common;
+                using System.Threading.Tasks;
+
+                class Test
+                {
+                    public async Task A()
+                    {
+                        [|using var command = new DerivedDbCommand();|]
+                    }
+                }
+
+                class BaseDbCommand : DbCommand
+                {
+                    public override string CommandText { get => throw null; set => throw null; }
+                    public override int CommandTimeout { get => throw null; set => throw null; }
+                    public override CommandType CommandType { get => throw null; set => throw null; }
+                    public override bool DesignTimeVisible { get => throw null; set => throw null; }
+                    public override UpdateRowSource UpdatedRowSource { get => throw null; set => throw null; }
+                    protected override DbConnection DbConnection { get => throw null; set => throw null; }
+                    protected override DbParameterCollection DbParameterCollection => throw null;
+                    protected override DbTransaction DbTransaction { get => throw null; set => throw null; }
+                    public override void Cancel() => throw null;
+                    public override int ExecuteNonQuery() => throw null;
+                    public override object ExecuteScalar() => throw null;
+                    public override void Prepare() => throw null;
+                    protected override DbParameter CreateDbParameter() => throw null;
+                    protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior) => throw null;
+                    public override ValueTask DisposeAsync() => throw null;
+                }
+
+                class DerivedDbCommand : BaseDbCommand { }
+                """)
+              .ValidateAsync();
+    }
 }