NH-3787 - SQLite requires the cast in SQL

And SQLite cannot perform the NH-3787 test with so many digits (it does not have a true decimal type anyway).
To be squashed

Author: fredericDelaporte

src/NHibernate.Test/Async/NHSpecificTest/NH3787/TestFixture.cs

@@ -10,17 +10,23 @@
 
 using System.Linq;
 using NHibernate.Criterion;
+using NHibernate.Linq;
 using NHibernate.Transform;
+using NHibernate.Type;
 using NUnit.Framework;
-using NHibernate.Linq;
 
 namespace NHibernate.Test.NHSpecificTest.NH3787
 {
 	using System.Threading.Tasks;
 	[TestFixture]
 	public class TestFixtureAsync : BugTestCase
 	{
-		private const decimal _testRate = 12345.123456789M;
+		private const decimal _testRate = 12345.1234567890123M;
+
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return !TestDialect.HasBrokenDecimalType;
+		}
 
 		protected override void OnSetUp()
 		{
@@ -33,7 +39,7 @@ protected override void OnSetUp()
 				{
 					UsePreviousRate = true,
 					PreviousRate = _testRate,
-					Rate = 54321.123456789M
+					Rate = 54321.1234567890123M
 				};
 				s.Save(testEntity);
 				t.Commit();
@@ -76,7 +82,7 @@ public async Task TestLinqProjectionAsync()
 				var queryResult = await ((from test in s.Query<TestEntity>()
 				                   select new RateDto { Rate = test.UsePreviousRate ? test.PreviousRate : test.Rate }).ToListAsync());
 
-				// Check it has not been truncated to the default 5 positions of NHibernate.
+				// Check it has not been truncated to the default scale (10) of NHibernate.
 				Assert.That(queryResult[0].Rate, Is.EqualTo(_testRate));
 				await (t.CommitAsync());
 			}
@@ -90,9 +96,11 @@ public async Task TestLinqQueryOnExpressionAsync()
 			{
 				var queryResult = await (s
 					.Query<TestEntity>()
-					.Where(e => (e.UsePreviousRate ? e.PreviousRate : e.Rate) == _testRate)
+					.Where(
+						// Without MappedAs, the test fails for SQL Server because it would restrict its parameter to the dialect's default scale.
+						e => (e.UsePreviousRate ? e.PreviousRate : e.Rate) == _testRate.MappedAs(TypeFactory.Basic("decimal(18,13)")))
 					.ToListAsync());
-		
+
 				Assert.That(queryResult.Count, Is.EqualTo(1));
 				Assert.That(queryResult[0].PreviousRate, Is.EqualTo(_testRate));
 				await (t.CommitAsync());
@@ -113,13 +121,14 @@ public async Task TestQueryOverProjectionAsync()
 				var query = s
 					.QueryOver(() => testEntity)
 					.Select(
-						Projections.Alias(
-							           Projections.Conditional(
-								           Restrictions.Eq(Projections.Property(() => testEntity.UsePreviousRate), true),
-								           Projections.Property(() => testEntity.PreviousRate),
-								           Projections.Property(() => testEntity.Rate)),
-							           "Rate")
-						           .WithAlias(() => rateDto.Rate));
+						Projections
+							.Alias(
+								Projections.Conditional(
+									Restrictions.Eq(Projections.Property(() => testEntity.UsePreviousRate), true),
+									Projections.Property(() => testEntity.PreviousRate),
+									Projections.Property(() => testEntity.Rate)),
+								"Rate")
+							.WithAlias(() => rateDto.Rate));
 
 				var queryResult = await (query.TransformUsing(Transformers.AliasToBean<RateDto>()).ListAsync<RateDto>());
 

src/NHibernate.Test/NHSpecificTest/NH3787/TestFixture.cs

@@ -12,6 +12,11 @@ public class TestFixture : BugTestCase
 	{
 		private const decimal _testRate = 12345.1234567890123M;
 
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return !TestDialect.HasBrokenDecimalType;
+		}
+
 		protected override void OnSetUp()
 		{
 			base.OnSetUp();

src/NHibernate/Dialect/SQLiteDialect.cs

@@ -86,6 +86,9 @@ protected virtual void RegisterFunctions()
 			RegisterFunction("cast", new SQLiteCastFunction());
 
 			RegisterFunction("round", new StandardSQLFunction("round"));
+
+			// NH-3787: SQLite requires the cast in SQL too for not defaulting to string.
+			RegisterFunction("transparentcast", new CastFunction());
 		}
 
 		#region private static readonly string[] DialectKeywords = { ... }