Implement nullability computation for SqlFunctionExpression

src/EFCore.Relational/Query/SqlNullabilityProcessor.cs

@@ -1400,18 +1400,26 @@ protected virtual SqlExpression VisitSqlFunction(
             return sqlFunctionExpression.Update(sqlFunctionExpression.Instance, coalesceArguments);
         }
 
-        var instance = Visit(sqlFunctionExpression.Instance, out _);
-        nullable = sqlFunctionExpression.IsNullable;
+        var useNullabilityPropagation = sqlFunctionExpression is { InstancePropagatesNullability: true };
+
+        var instance = Visit(sqlFunctionExpression.Instance, out var nullableInstance);
+        var hasNullableArgument = nullableInstance && sqlFunctionExpression is { InstancePropagatesNullability: true };
 
         if (sqlFunctionExpression.IsNiladic)
         {
-            return sqlFunctionExpression.Update(instance, sqlFunctionExpression.Arguments);
+            sqlFunctionExpression = sqlFunctionExpression.Update(instance, sqlFunctionExpression.Arguments);
         }
-
-        var arguments = new SqlExpression[sqlFunctionExpression.Arguments.Count];
-        for (var i = 0; i < arguments.Length; i++)
+        else
         {
-            arguments[i] = Visit(sqlFunctionExpression.Arguments[i], out _);
+            var arguments = new SqlExpression[sqlFunctionExpression.Arguments.Count];
+            for (var i = 0; i < arguments.Length; i++)
+            {
+                arguments[i] = Visit(sqlFunctionExpression.Arguments[i], out var nullableArgument);
+                useNullabilityPropagation |= sqlFunctionExpression.ArgumentsPropagateNullability[i];
+                hasNullableArgument |= nullableArgument && sqlFunctionExpression.ArgumentsPropagateNullability[i];
+            }
+
+            sqlFunctionExpression = sqlFunctionExpression.Update(instance, arguments);
         }
 
         if (sqlFunctionExpression.IsBuiltIn
@@ -1420,12 +1428,15 @@ protected virtual SqlExpression VisitSqlFunction(
             nullable = false;
 
             return _sqlExpressionFactory.Coalesce(
-                sqlFunctionExpression.Update(instance, arguments),
+                sqlFunctionExpression,
                 _sqlExpressionFactory.Constant(0, sqlFunctionExpression.TypeMapping),
                 sqlFunctionExpression.TypeMapping);
         }
 
-        return sqlFunctionExpression.Update(instance, arguments);
+        // if some of the {Instance,Arguments}PropagateNullability are true, use
+        // the computed nullability information; otherwise rely only on IsNullable
+        nullable = sqlFunctionExpression.IsNullable && (!useNullabilityPropagation || hasNullableArgument);
+        return sqlFunctionExpression;
     }
 
     /// <summary>

test/EFCore.SqlServer.FunctionalTests/Query/FunkyDataQuerySqlServerTest.cs

@@ -158,7 +158,7 @@ public override async Task String_contains_on_argument_with_wildcard_column_nega
 SELECT [f].[FirstName] AS [fn], [f0].[LastName] AS [ln]
 FROM [FunkyCustomers] AS [f]
 CROSS JOIN [FunkyCustomers] AS [f0]
-WHERE NOT ([f].[FirstName] IS NOT NULL AND [f0].[LastName] IS NOT NULL AND (CHARINDEX([f0].[LastName], [f].[FirstName]) > 0 OR [f0].[LastName] LIKE N''))
+WHERE [f].[FirstName] IS NULL OR [f0].[LastName] IS NULL OR (CHARINDEX([f0].[LastName], [f].[FirstName]) <= 0 AND [f0].[LastName] NOT LIKE N'')
 """);
     }
 

test/EFCore.SqlServer.FunctionalTests/Query/GearsOfWarQuerySqlServerTest.cs

@@ -1162,10 +1162,7 @@ public override async Task Select_null_propagation_negative6(bool async)
         AssertSql(
             """
 SELECT CASE
-    WHEN [g].[LeaderNickname] IS NOT NULL THEN CASE
-        WHEN CAST(LEN([g].[LeaderNickname]) AS int) <> CAST(LEN([g].[LeaderNickname]) AS int) THEN CAST(1 AS bit)
-        ELSE CAST(0 AS bit)
-    END
+    WHEN [g].[LeaderNickname] IS NOT NULL THEN CAST(0 AS bit)
     ELSE NULL
 END
 FROM [Gears] AS [g]

test/EFCore.SqlServer.FunctionalTests/Query/NorthwindWhereQuerySqlServerTest.cs

@@ -878,7 +878,6 @@ public override async Task Where_datetime_today(bool async)
             """
 SELECT [e].[EmployeeID], [e].[City], [e].[Country], [e].[FirstName], [e].[ReportsTo], [e].[Title]
 FROM [Employees] AS [e]
-WHERE CONVERT(date, GETDATE()) = CONVERT(date, GETDATE())
 """);
     }
 

test/EFCore.SqlServer.FunctionalTests/Query/TPCGearsOfWarQuerySqlServerTest.cs

@@ -1638,10 +1638,7 @@ public override async Task Select_null_propagation_negative6(bool async)
         AssertSql(
             """
 SELECT CASE
-    WHEN [u].[LeaderNickname] IS NOT NULL THEN CASE
-        WHEN CAST(LEN([u].[LeaderNickname]) AS int) <> CAST(LEN([u].[LeaderNickname]) AS int) THEN CAST(1 AS bit)
-        ELSE CAST(0 AS bit)
-    END
+    WHEN [u].[LeaderNickname] IS NOT NULL THEN CAST(0 AS bit)
     ELSE NULL
 END
 FROM (

test/EFCore.SqlServer.FunctionalTests/Query/TPTGearsOfWarQuerySqlServerTest.cs

@@ -1392,10 +1392,7 @@ public override async Task Select_null_propagation_negative6(bool async)
         AssertSql(
             """
 SELECT CASE
-    WHEN [g].[LeaderNickname] IS NOT NULL THEN CASE
-        WHEN CAST(LEN([g].[LeaderNickname]) AS int) <> CAST(LEN([g].[LeaderNickname]) AS int) THEN CAST(1 AS bit)
-        ELSE CAST(0 AS bit)
-    END
+    WHEN [g].[LeaderNickname] IS NOT NULL THEN CAST(0 AS bit)
     ELSE NULL
 END
 FROM [Gears] AS [g]

test/EFCore.SqlServer.FunctionalTests/Query/TemporalGearsOfWarQuerySqlServerTest.cs

@@ -1785,10 +1785,7 @@ public override async Task Select_null_propagation_negative6(bool async)
         AssertSql(
             """
 SELECT CASE
-    WHEN [g].[LeaderNickname] IS NOT NULL THEN CASE
-        WHEN CAST(LEN([g].[LeaderNickname]) AS int) <> CAST(LEN([g].[LeaderNickname]) AS int) THEN CAST(1 AS bit)
-        ELSE CAST(0 AS bit)
-    END
+    WHEN [g].[LeaderNickname] IS NOT NULL THEN CAST(0 AS bit)
     ELSE NULL
 END
 FROM [Gears] FOR SYSTEM_TIME AS OF '2010-01-01T00:00:00.0000000' AS [g]

test/EFCore.Sqlite.FunctionalTests/Query/GearsOfWarQuerySqliteTest.cs

@@ -3791,7 +3791,7 @@ public override async Task Select_null_propagation_negative6(bool async)
         AssertSql(
             """
 SELECT CASE
-    WHEN "g"."LeaderNickname" IS NOT NULL THEN length("g"."LeaderNickname") <> length("g"."LeaderNickname")
+    WHEN "g"."LeaderNickname" IS NOT NULL THEN 0
     ELSE NULL
 END
 FROM "Gears" AS "g"

test/EFCore.Sqlite.FunctionalTests/Query/NorthwindWhereQuerySqliteTest.cs

@@ -82,7 +82,6 @@ public override async Task Where_datetime_today(bool async)
             """
 SELECT "e"."EmployeeID", "e"."City", "e"."Country", "e"."FirstName", "e"."ReportsTo", "e"."Title"
 FROM "Employees" AS "e"
-WHERE rtrim(rtrim(strftime('%Y-%m-%d %H:%M:%f', 'now', 'localtime', 'start of day'), '0'), '.') = rtrim(rtrim(strftime('%Y-%m-%d %H:%M:%f', 'now', 'localtime', 'start of day'), '0'), '.')
 """);
     }