Do not process low-level command failed when the operation is SaveChanges. Fixes #96

Author: Giorgi

EntityFramework.Exceptions/Common/ExceptionFactory.cs

@@ -11,12 +11,16 @@ internal static Exception Create<T>(ExceptionProcessorInterceptor<T>.DatabaseErr
     {
         return error switch
         {
-            ExceptionProcessorInterceptor<T>.DatabaseError.CannotInsertNull => new CannotInsertNullException("Cannot insert null", exception.InnerException, entries),
-            ExceptionProcessorInterceptor<T>.DatabaseError.MaxLength => new MaxLengthExceededException("Maximum length exceeded", exception.InnerException, entries),
-            ExceptionProcessorInterceptor<T>.DatabaseError.NumericOverflow => new NumericOverflowException("Numeric overflow", exception.InnerException, entries),
-            ExceptionProcessorInterceptor<T>.DatabaseError.ReferenceConstraint => new ReferenceConstraintException("Reference constraint violation", exception.InnerException, entries),
-            ExceptionProcessorInterceptor<T>.DatabaseError.UniqueConstraint => new UniqueConstraintException("Unique constraint violation", exception.InnerException, entries),
-            ExceptionProcessorInterceptor<T>.DatabaseError.Deadlock => new DeadlockException("Deadlock", exception.InnerException, entries),
+            ExceptionProcessorInterceptor<T>.DatabaseError.CannotInsertNull => new CannotInsertNullException("Cannot insert null", exception, entries),
+            ExceptionProcessorInterceptor<T>.DatabaseError.MaxLength => new MaxLengthExceededException("Maximum length exceeded", exception, entries),
+            ExceptionProcessorInterceptor<T>.DatabaseError.NumericOverflow => new NumericOverflowException("Numeric overflow", exception, entries),
+            ExceptionProcessorInterceptor<T>.DatabaseError.ReferenceConstraint => new ReferenceConstraintException("Reference constraint violation", exception, entries),
+            ExceptionProcessorInterceptor<T>.DatabaseError.UniqueConstraint => new UniqueConstraintException("Unique constraint violation", exception, entries),
+            // DeadlockException intentionally has no InnerException. EF Core's ExecutionStrategy uses
+            // CallOnWrappedException to unwrap through DbUpdateException and check InnerException for
+            // transient errors. Setting a transient provider exception as InnerException would cause
+            // the execution strategy to wrap DeadlockException in InvalidOperationException.
+            ExceptionProcessorInterceptor<T>.DatabaseError.Deadlock => new DeadlockException("Deadlock", null, entries),
             _ => null,
         };
     }

EntityFramework.Exceptions/Common/ExceptionProcessorInterceptor.cs

@@ -43,13 +43,24 @@ public void SaveChangesFailed(DbContextErrorEventData eventData)
     /// <inheritdoc />
     public void CommandFailed(DbCommand command, CommandErrorEventData eventData)
     {
-        ProcessException(eventData.Exception, eventData.Context);
+        // Skip SaveChanges commands — CommandFailed fires before SaveChangesFailed and only receives
+        // the raw provider exception (no DbUpdateException, no Entries). Let SaveChangesFailed handle
+        // these so the typed exception preserves the full exception chain and entity entries.
+        if (eventData.CommandSource != CommandSource.SaveChanges)
+        {
+            ProcessException(eventData.Exception, eventData.Context);
+        }
     }
 
     /// <inheritdoc />
     public Task CommandFailedAsync(DbCommand command, CommandErrorEventData eventData, CancellationToken cancellationToken = new CancellationToken())
     {
-        ProcessException(eventData.Exception, eventData.Context);
+        // See comment in CommandFailed.
+        if (eventData.CommandSource != CommandSource.SaveChanges)
+        {
+            ProcessException(eventData.Exception, eventData.Context);
+        }
+
         return Task.CompletedTask;
     }
 
@@ -75,7 +86,7 @@ private void ProcessException(Exception eventException, DbContext eventContext)
         if (error == null) return;
 
         var updateException = eventException as DbUpdateException;
-        var exception = ExceptionFactory.Create(error.Value, eventException, updateException?.Entries);
+        var exception = ExceptionFactory.Create(error.Value, providerException, updateException?.Entries);
 
         switch (exception)
         {

EntityFramework.Exceptions/Tests/DatabaseTests.cs

@@ -4,6 +4,7 @@
 using Microsoft.EntityFrameworkCore;
 using MySql.EntityFrameworkCore.Extensions;
 using System;
+using System.Data.Common;
 using System.Linq;
 using System.Threading.Tasks;
 using Xunit;
@@ -22,7 +23,7 @@ protected DatabaseTests(DemoContext demoContext, SameNameIndexesContext sameName
         DemoContext = demoContext;
         SameNameIndexesContext = sameNameIndexesContext;
 
-        isMySql = MySQLDatabaseFacadeExtensions.IsMySql(DemoContext.Database);
+        isMySql = DemoContext.Database.IsMySql();
         isSqlite = demoContext.Database.IsSqlite();
     }
 
@@ -35,6 +36,9 @@ public virtual async Task UniqueColumnViolationThrowsUniqueConstraintException()
         var uniqueConstraintException = Assert.Throws<UniqueConstraintException>(() => DemoContext.SaveChanges());
         await Assert.ThrowsAsync<UniqueConstraintException>(() => DemoContext.SaveChangesAsync());
 
+        Assert.IsAssignableFrom<DbException>(uniqueConstraintException.InnerException);
+        Assert.NotEmpty(uniqueConstraintException.Entries);
+
         if (!isSqlite)
         {
             Assert.False(string.IsNullOrEmpty(uniqueConstraintException.ConstraintName));