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CSHARP-4742: Find and Aggregate Project should work with identity projection x => x on all server versions.
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4 files changed

+183
-4
lines changed

4 files changed

+183
-4
lines changed

‎src/MongoDB.Driver/Linq/Linq2Implementation/LinqProviderAdapterV2.cs

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@@ -152,6 +152,12 @@ internal override RenderedProjectionDefinition<TOutput> TranslateExpressionToPro
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IBsonSerializerRegistry serializerRegistry,
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ExpressionTranslationOptions translationOptions)
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{
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if (expression.Parameters.Count == 1 && expression.Body == expression.Parameters[0])
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{
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// handle x => x as a special case
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return new RenderedProjectionDefinition<TOutput>(null, (IBsonSerializer<TOutput>)inputSerializer);
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}
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return AggregateProjectTranslator.Translate<TInput, TOutput>(expression, inputSerializer, serializerRegistry, translationOptions);
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}
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}

‎src/MongoDB.Driver/Linq/Linq3Implementation/LinqProviderAdapterV3.cs

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@@ -166,6 +166,12 @@ private RenderedProjectionDefinition<TOutput> TranslateExpressionToProjection<TI
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Func<AggregationExpression, (IReadOnlyList<AstProjectStageSpecification>, IBsonSerializer)> projectionCreator,
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AstSimplifier simplifier)
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{
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if (expression.Parameters.Count == 1 && expression.Body == expression.Parameters[0])
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{
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// handle x => x as a special case
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return new RenderedProjectionDefinition<TOutput>(null, (IBsonSerializer<TOutput>)inputSerializer);
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}
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expression = (Expression<Func<TInput, TOutput>>)PartialEvaluator.EvaluatePartially(expression);
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var context = TranslationContext.Create(expression, inputSerializer);
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var translation = ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(context, expression, inputSerializer, asRoot: true);

‎src/MongoDB.Driver/PipelineStageDefinitionBuilder.cs

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1265,16 +1265,17 @@ public static PipelineStageDefinition<TInput, TOutput> Project<TInput, TOutput>(
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(s, sr, linqProvider) =>
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{
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var renderedProjection = projection.Render(s, sr, linqProvider);
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BsonDocument document;
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IEnumerable<BsonDocument> documents;
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if (renderedProjection.Document == null)
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{
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document = new BsonDocument();
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// renderedProjection.Document will be null for x => x (and perhaps other cases also in the future)
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documents = Array.Empty<BsonDocument>();
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}
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else
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{
1275-
document = new BsonDocument(operatorName, renderedProjection.Document);
1276+
documents = new[] { new BsonDocument(operatorName, renderedProjection.Document) };
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}
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return new RenderedPipelineStageDefinition<TOutput>(operatorName, document, renderedProjection.ProjectionSerializer);
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return new RenderedPipelineStageDefinition<TOutput>(operatorName, documents, renderedProjection.ProjectionSerializer);
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});
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12801281
return stage;

‎tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Jira/CSharp4742Tests.cs

Lines changed: 166 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,166 @@
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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 FluentAssertions;
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using MongoDB.Bson.Serialization;
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using MongoDB.Driver.Linq;
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using MongoDB.TestHelpers.XunitExtensions;
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using Xunit;
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namespace MongoDB.Driver.Tests.Linq.Linq3Implementation.Jira
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{
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public class CSharp4742Tests : Linq3IntegrationTest
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{
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[Theory]
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[ParameterAttributeData]
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public void Find_with_identity_projection_should_work(
29+
[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
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{
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var collection = GetCollection(linqProvider);
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var projection = Builders<C>.Projection.Expression(x => x);
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var find = collection
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.Find("{}")
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.Project(projection);
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var renderedProjection = TranslateFindProjection(collection, find);
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renderedProjection.Should().BeNull();
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var result = find.Single();
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result.Id.Should().Be(1);
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result.X.Should().Be(2);
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}
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[Theory]
47+
[ParameterAttributeData]
48+
public void Aggregate_Project_with_identity_projection_should_work(
49+
[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
50+
{
51+
var collection = GetCollection(linqProvider);
52+
var projection = Builders<C>.Projection.Expression(x => x);
53+
54+
var aggregate = collection
55+
.Aggregate()
56+
.Project(projection);
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58+
var stages = Translate(collection, aggregate);
59+
stages.Should().BeEmpty();
60+
61+
var result = aggregate.Single();
62+
result.Id.Should().Be(1);
63+
result.X.Should().Be(2);
64+
}
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66+
[Theory]
67+
[ParameterAttributeData]
68+
public void ExpressionProjectionDefinition_with_identity_projection_Render_should_work(
69+
[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
70+
{
71+
var collection = GetCollection(linqProvider);
72+
var projection = new ExpressionProjectionDefinition<C, C>(x => x, translationOptions: null);
73+
var sourceSerializer = collection.DocumentSerializer;
74+
var serializerRegistry = BsonSerializer.SerializerRegistry;
75+
76+
var renderedProjection = projection.Render(sourceSerializer, serializerRegistry, linqProvider);
77+
78+
renderedProjection.Document.Should().BeNull();
79+
renderedProjection.ProjectionSerializer.Should().BeSameAs(sourceSerializer);
80+
}
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82+
[Theory]
83+
[ParameterAttributeData]
84+
public void ExpressionProjectionDefinition_with_identity_projection_RenderForFind_should_work(
85+
[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
86+
{
87+
var collection = GetCollection(linqProvider);
88+
var projection = new ExpressionProjectionDefinition<C, C>(x => x, translationOptions: null);
89+
var sourceSerializer = collection.DocumentSerializer;
90+
var serializerRegistry = BsonSerializer.SerializerRegistry;
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var renderedProjection = projection.RenderForFind(sourceSerializer, serializerRegistry, linqProvider);
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94+
renderedProjection.Document.Should().BeNull();
95+
if (linqProvider == LinqProvider.V2)
96+
{
97+
renderedProjection.ProjectionSerializer.ValueType.Should().Be(typeof(C));
98+
}
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else
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{
101+
renderedProjection.ProjectionSerializer.Should().BeSameAs(sourceSerializer);
102+
}
103+
}
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[Theory]
106+
[ParameterAttributeData]
107+
public void FindExpressionProjectionDefinition_with_identity_projection_Render_should_work(
108+
[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
109+
{
110+
var collection = GetCollection(linqProvider);
111+
var projection = new FindExpressionProjectionDefinition<C, C>(x => x);
112+
var sourceSerializer = collection.DocumentSerializer;
113+
var serializerRegistry = BsonSerializer.SerializerRegistry;
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115+
var renderedProjection = projection.Render(sourceSerializer, serializerRegistry, linqProvider);
116+
117+
renderedProjection.Document.Should().BeNull();
118+
if (linqProvider == LinqProvider.V2)
119+
{
120+
renderedProjection.ProjectionSerializer.ValueType.Should().Be(typeof(C));
121+
}
122+
else
123+
{
124+
renderedProjection.ProjectionSerializer.Should().BeSameAs(sourceSerializer);
125+
}
126+
}
127+
128+
[Theory]
129+
[ParameterAttributeData]
130+
public void FindExpressionProjectionDefinition_with_identity_projection_RenderForFind_should_work(
131+
[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
132+
{
133+
var collection = GetCollection(linqProvider);
134+
var projection = new FindExpressionProjectionDefinition<C, C>(x => x);
135+
var sourceSerializer = collection.DocumentSerializer;
136+
var serializerRegistry = BsonSerializer.SerializerRegistry;
137+
138+
var renderedProjection = projection.RenderForFind(sourceSerializer, serializerRegistry, linqProvider);
139+
140+
renderedProjection.Document.Should().BeNull();
141+
if (linqProvider == LinqProvider.V2)
142+
{
143+
renderedProjection.ProjectionSerializer.ValueType.Should().Be(typeof(C));
144+
}
145+
else
146+
{
147+
renderedProjection.ProjectionSerializer.Should().BeSameAs(sourceSerializer);
148+
}
149+
}
150+
151+
private IMongoCollection<C> GetCollection(LinqProvider linqProvider)
152+
{
153+
var collection = GetCollection<C>("test", linqProvider);
154+
CreateCollection(
155+
collection,
156+
new C { Id = 1, X = 2 });
157+
return collection;
158+
}
159+
160+
private class C
161+
{
162+
public int Id { get; set; }
163+
public int X { get; set; }
164+
}
165+
}
166+
}

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