CSHARP-4803: Refactor StringExpressionToRegexFilterTranslator.TryTranslate to not use an exception for flow control when possible.

Author: rstam

src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToFilterTranslators/ExpressionTranslators/StringExpressionToRegexFilterTranslator.cs

@@ -230,33 +230,52 @@ public static bool CanTranslate(Expression expression)
             return false;
         }
 
+        public static bool CanTranslateComparisonExpression(Expression leftExpression, AstComparisonFilterOperator comparisonOperator, Expression rightExpression)
+        {
+            return
+                IsGetCharsComparison(leftExpression) ||
+                IsStringEqualityComparison(leftExpression, comparisonOperator) ||
+                IsStringIndexOfComparison(leftExpression) ||
+                IsStringLengthComparison(leftExpression) || IsStringCountComparison(leftExpression);
+        }
+
         public static bool TryTranslate(TranslationContext context, Expression expression, out AstFilter filter)
         {
-            try
-            {
-                filter = Translate(context, expression);
-                return true;
-            }
-            catch (ExpressionNotSupportedException)
+            if (CanTranslate(expression))
             {
-                filter = null;
-                return false;
+                try
+                {
+                    filter = Translate(context, expression);
+                    return true;
+                }
+                catch (ExpressionNotSupportedException)
+                {
+                    // ignore exception and return false
+                }
             }
+
+            filter = null;
+            return false;
         }
 
         // caller is responsible for ensuring constant is on the right
         public static bool TryTranslateComparisonExpression(TranslationContext context, Expression expression, Expression leftExpression, AstComparisonFilterOperator comparisonOperator, Expression rightExpression, out AstFilter filter)
         {
-            try
-            {
-                filter = TranslateComparisonExpression(context, expression, leftExpression, comparisonOperator, rightExpression);
-                return true;
-            }
-            catch (ExpressionNotSupportedException)
+            if (CanTranslateComparisonExpression(leftExpression, comparisonOperator, rightExpression))
             {
-                filter = null;
-                return false;
+                try
+                {
+                    filter = TranslateComparisonExpression(context, expression, leftExpression, comparisonOperator, rightExpression);
+                    return true;
+                }
+                catch (ExpressionNotSupportedException)
+                {
+                    // ignore exception and return false
+                }
             }
+
+            filter = null;
+            return false;
         }
 
         public static AstFilter Translate(TranslationContext context, Expression expression)
@@ -287,9 +306,9 @@ public static AstFilter TranslateComparisonExpression(TranslationContext context
                 return TranslateGetCharsComparison(context, expression, leftExpression, comparisonOperator, rightExpression);
             }
 
-            if (IsStringComparison(leftExpression))
+            if (IsStringEqualityComparison(leftExpression, comparisonOperator))
             {
-                return TranslateStringComparison(context, expression, leftExpression, comparisonOperator, rightExpression);
+                return TranslateStringEqualityComparison(context, expression, leftExpression, comparisonOperator, rightExpression);
             }
 
             if (IsStringIndexOfComparison(leftExpression))
@@ -370,24 +389,19 @@ private static string GetEscapedTrimChars(MethodCallExpression trimExpression)
 
         private static bool IsGetCharsComparison(Expression leftExpression)
         {
-            if (leftExpression is UnaryExpression leftUnaryExpression &&
-                leftUnaryExpression.NodeType == ExpressionType.Convert &&
-                leftUnaryExpression.Type == typeof(int) &&
-                leftUnaryExpression.Operand is MethodCallExpression leftMethodCallExpression)
-            {
-                var method = leftMethodCallExpression.Method;
-                if (method.Is(StringMethod.GetChars))
-                {
-                    return true;
-                }
-            }
-
-            return false;
+            return
+                leftExpression is UnaryExpression leftConvertExpression &&
+                leftConvertExpression.NodeType == ExpressionType.Convert &&
+                leftConvertExpression.Type == typeof(int) &&
+                leftConvertExpression.Operand is MethodCallExpression leftGetCharsExpression &&
+                leftGetCharsExpression.Method.Is(StringMethod.GetChars);
         }
 
-        private static bool IsStringComparison(Expression leftExpression)
+        private static bool IsStringEqualityComparison(Expression leftExpression, AstComparisonFilterOperator comparisonOperator)
         {
-            return leftExpression.Type == typeof(string);
+            return
+                leftExpression.Type == typeof(string) &&
+                (comparisonOperator == AstComparisonFilterOperator.Eq || comparisonOperator == AstComparisonFilterOperator.Ne);
         }
 
         private static bool IsStringCountComparison(Expression leftExpression)
@@ -608,7 +622,7 @@ bool IsImpossibleMatch(Modifiers modifiers, string value)
             }
         }
 
-        private static AstFilter TranslateStringComparison(TranslationContext context, Expression expression, Expression leftExpression, AstComparisonFilterOperator comparisonOperator, Expression rightExpression)
+        private static AstFilter TranslateStringEqualityComparison(TranslationContext context, Expression expression, Expression leftExpression, AstComparisonFilterOperator comparisonOperator, Expression rightExpression)
         {
             var (field, modifiers) = TranslateField(context, expression, leftExpression);
             var comparand = rightExpression.GetConstantValue<string>(containingExpression: expression);

tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Jira/CSharp4803Tests.cs

@@ -0,0 +1,70 @@
+/* Copyright 2010-present MongoDB Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using System;
+using System.Linq.Expressions;
+using FluentAssertions;
+using MongoDB.Driver.Linq;
+using MongoDB.TestHelpers.XunitExtensions;
+using Xunit;
+
+namespace MongoDB.Driver.Tests.Linq.Linq3Implementation.Jira
+{
+    public class CSharp4803Tests : Linq3IntegrationTest
+    {
+        [Theory]
+        [ParameterAttributeData]
+        public void Find_filter_with_nonnullable_date_fields_should_work(
+            [Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
+        {
+            var collection = GetCollection(linqProvider);
+            var fromDate = new DateTime(2023, 9, 27, 0, 0, 0, DateTimeKind.Utc);
+            Expression<Func<C, bool>> filter = ft => ft.Date >= fromDate;
+
+            var find = collection.Find(filter);
+
+            var renderedFilter = TranslateFindFilter(collection, find);
+            renderedFilter.Should().Be("{ Date : { $gte : ISODate('2023-09-27T00:00:00Z') } }");
+        }
+
+        [Theory]
+        [ParameterAttributeData]
+        public void Find_filter_with_nullable_date_fields_should_work(
+            [Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
+        {
+            var collection = GetCollection(linqProvider);
+            var fromDate = new DateTime(2023, 9, 27, 0, 0, 0, DateTimeKind.Utc);
+            Expression<Func<C, bool>> filter = ft => ft.NullableDate >= fromDate;
+
+            var find = collection.Find(filter);
+
+            var renderedFilter = TranslateFindFilter(collection, find);
+            renderedFilter.Should().Be("{ NullableDate : { $gte : ISODate('2023-09-27T00:00:00Z') } }");
+        }
+
+        private IMongoCollection<C> GetCollection(LinqProvider linqProvider)
+        {
+            var collection = GetCollection<C>("test", linqProvider);
+            return collection;
+        }
+
+        private class C
+        {
+            public int Id { get; set; }
+            public DateTime Date { get; set; }
+            public DateTime? NullableDate { get; set; }
+        }
+    }
+}