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CSHARP-5540: Fix exception when using AsQueryable().Last() (#1649)
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Diff for: ‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToExecutableQueryTranslators/LastMethodToExecutableQueryTranslator.cs

+2-1
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@@ -75,10 +75,11 @@ public static ExecutableQuery<TDocument, TOutput> Translate<TDocument>(MongoQuer
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pipeline.OutputSerializer);
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}
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pipeline = pipeline.AddStage(
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pipeline = pipeline.AddStages(
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AstStage.Group(
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id: BsonNull.Value,
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fields: AstExpression.AccumulatorField("_last", AstUnaryAccumulatorOperator.Last, AstExpression.RootVar)),
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AstStage.ReplaceRoot(AstExpression.GetField(AstExpression.RootVar, "_last")),
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pipeline.OutputSerializer);
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var finalizer = method.Name == "LastOrDefault" ? __singleOrDefaultFinalizer : __singleFinalizer;

Diff for: ‎tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Translators/ExpressionToExecutableQueryTranslators/LastMethodToExecutableQueryTranslatorTests.cs

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@@ -0,0 +1,199 @@
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/* Copyright 2010-present MongoDB Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using FluentAssertions;
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using MongoDB.Driver.Linq;
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using MongoDB.Driver.TestHelpers;
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using Xunit;
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namespace MongoDB.Driver.Tests.Linq.Linq3Implementation.Translators.ExpressionToExecutableQueryTranslators
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{
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public class LastMethodToExecutableQueryTranslator : LinqIntegrationTest<LastMethodToExecutableQueryTranslator.ClassFixture>
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{
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public LastMethodToExecutableQueryTranslator(ClassFixture fixture)
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: base(fixture)
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{
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}
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[Fact]
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public void Last_should_work()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable().OrderBy(t => t.Id);
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var result = queryable.Last();
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $sort : { _id : 1 } }",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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result.Id.Should().Be(3);
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}
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[Fact]
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public void Last_with_no_matching_documents_should_throw()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable().Where(t => t.Id > 5);
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var exception = Record.Exception(() => queryable.Last());
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $match : { _id : { $gt : 5 } }}",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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exception.Should().BeOfType<InvalidOperationException>();
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exception.Message.Should().Contain("Sequence contains no elements");
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}
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[Fact]
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public void LastOrDefault_should_work()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable().OrderBy(t => t.Id);
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var result = queryable.LastOrDefault();
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $sort : { _id : 1 } }",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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result.Should().NotBeNull();
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result.Id.Should().Be(3);
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}
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[Fact]
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public void LastOrDefault_with_no_matching_documents_should_work()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable().Where(t => t.Id > 5);
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var result = queryable.LastOrDefault();
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $match : { _id : { $gt : 5 } }}",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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result.Should().BeNull();
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}
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[Fact]
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public void LastOrDefaultWithPredicate_should_work()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable().OrderBy(t => t.Id);
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var result = queryable.LastOrDefault(t => t.Id > 1);
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $sort : { _id : 1 } }",
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"{ $match : { _id : { $gt : 1 } }}",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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result.Should().NotBeNull();
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result.Id.Should().Be(3);
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}
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[Fact]
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public void LastOrDefaultWithPredicate_with_no_matching_documents_should_work()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable();
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var result = queryable.LastOrDefault(t => t.Id > 4);
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $match : { _id : { $gt : 4 } }}",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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result.Should().BeNull();
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}
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[Fact]
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public void LastWithPredicate_should_work()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable().OrderBy(t => t.Id);
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var result = queryable.Last(t => t.Id > 1);
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $sort : { _id : 1 } }",
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"{ $match : { _id : { $gt : 1 } }}",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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result.Id.Should().Be(3);
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}
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[Fact]
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public void LastWithPredicate_with_no_matching_documents_should_throw()
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{
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var collection = Fixture.Collection;
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var queryable = collection.AsQueryable();
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var exception = Record.Exception(() => queryable.Last(t => t.Id > 4));
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var stages = queryable.GetMongoQueryProvider().LoggedStages;
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AssertStages(
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stages,
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"{ $match : { _id : { $gt : 4 } }}",
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"{ $group : { _id : null, _last : { $last : '$$ROOT' } } }",
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"{ $replaceRoot : { newRoot : '$_last' } }");
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exception.Should().BeOfType<InvalidOperationException>();
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exception.Message.Should().Contain("Sequence contains no elements");
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}
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public class TestClass
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{
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public int Id { get; set; }
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public string StringProperty { get; set; }
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}
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public sealed class ClassFixture : MongoCollectionFixture<TestClass>
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{
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protected override IEnumerable<TestClass> InitialData { get; } =
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[
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new TestClass { Id = 1, StringProperty = "A" },
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new TestClass { Id = 2, StringProperty = "B" },
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new TestClass { Id = 3, StringProperty = "C" }
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];
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}
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}
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}

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