Fix #3570: Support empty collection when using Contains (#3573)

src/Microsoft.OData.Client/ALinq/ExpressionWriter.cs

@@ -578,12 +578,8 @@ internal override Expression VisitConstant(ConstantExpression c)
                     listExpr.Append(uriLiteral);
                 }
 
-                // Contains cannot be used with an empty static collection
-                if (listExpr.Length == 0)
-                {
-                    throw new InvalidOperationException(SRResources.ALinq_ContainsNotValidOnEmptyCollection);
-                }
-
+                // An empty collection is translated to the empty 'in' collection literal, e.g. "Name in ()",
+                // which the OData query parser supports and evaluates to no matches.
                 listExpr.Insert(0, UriHelper.LEFTPAREN);
                 listExpr.Append(UriHelper.RIGHTPAREN);
 

src/Microsoft.OData.Client/SRResources.resx

@@ -665,9 +665,6 @@
   <data name="ALinq_TypeTokenWithNoTrailingNavProp" xml:space="preserve">
     <value>Found an illegal type token '{0}' without a trailing navigation property. </value>
   </data>
-  <data name="ALinq_ContainsNotValidOnEmptyCollection" xml:space="preserve">
-    <value>The Contains method cannot be used with an empty collection.</value>
-  </data>
   <data name="ALinq_AggregationMethodNotSupported" xml:space="preserve">
     <value>The aggregation method '{0}' is not supported.</value>
   </data>

test/UnitTests/Microsoft.OData.Client.Tests/DataServiceQueryProviderTests.cs

@@ -94,33 +94,33 @@ public void TranslatesEnumerableContainsWithSpecialCharactersToInOperator()
         }
 
         [Fact]
-        public void ThrowsForEnumerableContainsWithEmptyCollection()
+        public void TranslatesEnumerableContainsWithEmptyCollectionToEmptyInOperator()
         {
             // Arrange
             var sut = new DataServiceQueryProvider(dsc);
             var products = dsc.CreateQuery<Product>("Products")
                 .Where(product => Enumerable.Empty<string>().Contains(product.Name));
 
             // Act
-            var exception = Assert.ThrowsAny<InvalidOperationException>(() => sut.Translate(products.Expression));
+            var queryComponents = sut.Translate(products.Expression);
 
             // Assert
-            Assert.Equal(SRResources.ALinq_ContainsNotValidOnEmptyCollection, exception.Message);
+            Assert.Equal(@"http://root/Products?$filter=Name in ()", queryComponents.Uri.ToString());
         }
 
         [Fact]
-        public void ThrowsForEnumerableContainsWithEmptyEnumCollection()
+        public void TranslatesEnumerableContainsWithEmptyEnumCollectionToEmptyInOperator()
         {
             // Arrange
             var sut = new DataServiceQueryProvider(dsc);
             var products = dsc.CreateQuery<Product>("Products")
                 .Where(product => Enumerable.Empty<Color>().Contains(product.Color));
 
             // Act
-            var exception = Assert.ThrowsAny<InvalidOperationException>(() => sut.Translate(products.Expression));
+            var queryComponents = sut.Translate(products.Expression);
 
             // Assert
-            Assert.Equal(SRResources.ALinq_ContainsNotValidOnEmptyCollection, exception.Message);
+            Assert.Equal(@"http://root/Products?$filter=Color in ()", queryComponents.Uri.ToString());
         }
 
         [Fact]

test/UnitTests/Microsoft.OData.Client.Tests/Resources/SRResourcesTests.cs

@@ -39,7 +39,6 @@ public class SRResourcesTests
     [InlineData("ALinq_CollectionPropertyNotSupportedInWhere", new object[] { "Value" })]
     [InlineData("ALinq_ConditionalNotSupported", new object[] { })]
     [InlineData("ALinq_ConstantNotSupported", new object[] { "Value" })]
-    [InlineData("ALinq_ContainsNotValidOnEmptyCollection", new object[] { })]
     [InlineData("ALinq_CouldNotConvert", new object[] { "Value" })]
     [InlineData("ALinq_ExpressionCannotEndWithTypeAs", new object[] { "Value", "Value" })]
     [InlineData("ALinq_ExpressionNotSupportedInProjection", new object[] { "Value", "Value" })]