fixup! Support evaluation of Guid.NewGuid() on db side

Add an option for failing or falling back in case of lack of dialect
support

Author: fredericDelaporte

src/NHibernate.Test/Async/Linq/PreEvaluationTests.cs

@@ -330,14 +330,28 @@ public async Task CanQueryByNewGuidAsync()
 			if (!TestDialect.SupportsSqlType(SqlTypeFactory.Guid))
 				Assert.Ignore("Guid are not supported by the target database");
 
+			var isSupported = IsFunctionSupported("new_uuid");
 			using (var spy = new SqlLogSpy())
 			{
-				var guid = Guid.NewGuid();
-				var x = await (db.Orders.CountAsync(o => guid != Guid.NewGuid()));
+				try
+				{
+					var guid = Guid.NewGuid();
+					var x = await (db.Orders.CountAsync(o => guid != Guid.NewGuid()));
 
-				Assert.That(x, Is.GreaterThan(0));
-				AssertFunctionInSql("new_uuid", spy);
+					Assert.That(x, Is.GreaterThan(0));
+					AssertFunctionInSql("new_uuid", spy);
+				}
+				catch (QueryException)
+				{
+					if (!isSupported && !FallbackOnPreEvaluation)
+						// Expected failure
+						return;
+					throw;
+				}
 			}
+
+			if (!isSupported && !FallbackOnPreEvaluation)
+				Assert.Fail("The test should have thrown a QueryException, but has not thrown anything");
 		}
 
 		[Test]
@@ -346,16 +360,30 @@ public async Task CanSelectNewGuidAsync()
 			if (!TestDialect.SupportsSqlType(SqlTypeFactory.Guid))
 				Assert.Ignore("Guid are not supported by the target database");
 
+			var isSupported = IsFunctionSupported("new_uuid");
 			using (var spy = new SqlLogSpy())
 			{
-				var x =
-					await (db
-						.Orders.Select(o => new { id = o.OrderId, g = Guid.NewGuid() })
-						.OrderBy(o => o.id).Take(1).ToListAsync());
+				try
+				{
+					var x =
+						await (db
+							.Orders.Select(o => new { id = o.OrderId, g = Guid.NewGuid() })
+							.OrderBy(o => o.id).Take(1).ToListAsync());
 
-				Assert.That(x, Has.Count.GreaterThan(0));
-				AssertFunctionInSql("new_uuid", spy);
+					Assert.That(x, Has.Count.GreaterThan(0));
+					AssertFunctionInSql("new_uuid", spy);
+				}
+				catch (QueryException)
+				{
+					if (!isSupported && !FallbackOnPreEvaluation)
+						// Expected failure
+						return;
+					throw;
+				}
 			}
+
+			if (!isSupported && !FallbackOnPreEvaluation)
+				Assert.Fail("The test should have thrown a QueryException, but has not thrown anything");
 		}
 
 		private void AssertFunctionInSql(string functionName, SqlLogSpy spy)

src/NHibernate.Test/Linq/PreEvaluationTests.cs

@@ -318,14 +318,28 @@ public void CanQueryByNewGuid()
 			if (!TestDialect.SupportsSqlType(SqlTypeFactory.Guid))
 				Assert.Ignore("Guid are not supported by the target database");
 
+			var isSupported = IsFunctionSupported("new_uuid");
 			using (var spy = new SqlLogSpy())
 			{
-				var guid = Guid.NewGuid();
-				var x = db.Orders.Count(o => guid != Guid.NewGuid());
+				try
+				{
+					var guid = Guid.NewGuid();
+					var x = db.Orders.Count(o => guid != Guid.NewGuid());
 
-				Assert.That(x, Is.GreaterThan(0));
-				AssertFunctionInSql("new_uuid", spy);
+					Assert.That(x, Is.GreaterThan(0));
+					AssertFunctionInSql("new_uuid", spy);
+				}
+				catch (QueryException)
+				{
+					if (!isSupported && !FallbackOnPreEvaluation)
+						// Expected failure
+						return;
+					throw;
+				}
 			}
+
+			if (!isSupported && !FallbackOnPreEvaluation)
+				Assert.Fail("The test should have thrown a QueryException, but has not thrown anything");
 		}
 
 		[Test]
@@ -334,16 +348,30 @@ public void CanSelectNewGuid()
 			if (!TestDialect.SupportsSqlType(SqlTypeFactory.Guid))
 				Assert.Ignore("Guid are not supported by the target database");
 
+			var isSupported = IsFunctionSupported("new_uuid");
 			using (var spy = new SqlLogSpy())
 			{
-				var x =
-					db
-						.Orders.Select(o => new { id = o.OrderId, g = Guid.NewGuid() })
-						.OrderBy(o => o.id).Take(1).ToList();
+				try
+				{
+					var x =
+						db
+							.Orders.Select(o => new { id = o.OrderId, g = Guid.NewGuid() })
+							.OrderBy(o => o.id).Take(1).ToList();
 
-				Assert.That(x, Has.Count.GreaterThan(0));
-				AssertFunctionInSql("new_uuid", spy);
+					Assert.That(x, Has.Count.GreaterThan(0));
+					AssertFunctionInSql("new_uuid", spy);
+				}
+				catch (QueryException)
+				{
+					if (!isSupported && !FallbackOnPreEvaluation)
+						// Expected failure
+						return;
+					throw;
+				}
 			}
+
+			if (!isSupported && !FallbackOnPreEvaluation)
+				Assert.Fail("The test should have thrown a QueryException, but has not thrown anything");
 		}
 
 		private void AssertFunctionInSql(string functionName, SqlLogSpy spy)

src/NHibernate/Linq/Functions/NewGuidHqlGenerator.cs

@@ -6,6 +6,7 @@
 using NHibernate.Hql.Ast;
 using NHibernate.Linq.Visitors;
 using NHibernate.Util;
+using Environment = NHibernate.Cfg.Environment;
 
 namespace NHibernate.Linq.Functions
 {
@@ -31,8 +32,17 @@ public override HqlTreeNode BuildHql(
 
 		public bool AllowPreEvaluation(MemberInfo member, ISessionFactoryImplementor factory)
 		{
-			// When not supported, allow pre-evaluation on client side as a fallback.
-			return !factory.Dialect.Functions.ContainsKey("new_uuid");
+			if (factory.Dialect.Functions.ContainsKey("new_uuid"))
+				return false;
+
+			if (factory.Settings.LinqToHqlFallbackOnPreEvaluation)
+				return true;
+
+			throw new QueryException(
+				"Cannot translate NewGuid: new_uuid is " +
+				$"not supported by {factory.Dialect}. Either enable the fallback on pre-evaluation " +
+				$"({Environment.LinqToHqlFallbackOnPreEvaluation}) or evaluate NewGuid " +
+				"outside of the query.");
 		}
 	}
 }