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CSHARP-4858: Add IsMissing and IsNullOrMissing MongoDBFunctions.
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‎src/MongoDB.Driver/Linq/Linq3Implementation/Reflection/MqlMethod.cs

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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.Reflection;
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namespace MongoDB.Driver.Linq.Linq3Implementation.Reflection
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{
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internal static class MqlMethod
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{
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// private static fields
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private static readonly MethodInfo __exists;
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private static readonly MethodInfo __isMissing;
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private static readonly MethodInfo __isNullOrMissing;
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// static constructor
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static MqlMethod()
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{
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__exists = ReflectionInfo.Method((object field) => Mql.Exists(field));
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__isMissing = ReflectionInfo.Method((object field) => Mql.IsMissing(field));
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__isNullOrMissing = ReflectionInfo.Method((object field) => Mql.IsNullOrMissing(field));
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}
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// public properties
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public static MethodInfo Exists => __exists;
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public static MethodInfo IsMissing => __isMissing;
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public static MethodInfo IsNullOrMissing => __isNullOrMissing;
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}
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}

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodCallExpressionToAggregationExpressionTranslator.cs

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@@ -138,6 +138,10 @@ public static AggregationExpression Translate(TranslationContext context, Method
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case "IndexOfAny":
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return IndexOfAnyMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "IsMissing":
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case "IsNullOrMissing":
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return FieldExistsOrIsMissingMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "Log":
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case "Log10":
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return LogMethodToAggregationExpressionTranslator.Translate(context, expression);

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodTranslators/ExistsMethodToAggregationExpressionExpression.cs

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@@ -25,6 +25,11 @@ public static AggregationExpression Translate(TranslationContext context, Method
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{
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var method = expression.Method;
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if (method.Is(MqlMethod.Exists))
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{
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return FieldExistsOrIsMissingMethodToAggregationExpressionTranslator.Translate(context, expression);
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}
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if (method.Is(ArrayMethod.Exists) || ListMethod.IsExistsMethod(expression.Method))
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{
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return AnyMethodToAggregationExpressionTranslator.Translate(context, expression);

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodTranslators/FieldExistsOrIsMissingMethodToAggregationExpressionTranslator.cs

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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.Linq.Expressions;
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using System.Reflection;
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using MongoDB.Bson;
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using MongoDB.Bson.Serialization.Serializers;
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using MongoDB.Driver.Linq.Linq3Implementation.Ast;
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using MongoDB.Driver.Linq.Linq3Implementation.Ast.Expressions;
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using MongoDB.Driver.Linq.Linq3Implementation.Misc;
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using MongoDB.Driver.Linq.Linq3Implementation.Reflection;
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namespace MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.MethodTranslators
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{
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internal static class FieldExistsOrIsMissingMethodToAggregationExpressionTranslator
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{
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private static readonly MethodInfo[] __isMissingMethods =
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{
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MqlMethod.Exists,
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MqlMethod.IsMissing,
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MqlMethod.IsNullOrMissing,
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};
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public static AggregationExpression Translate(TranslationContext context, MethodCallExpression expression)
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{
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var method = expression.Method;
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var arguments = expression.Arguments;
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if (method.IsOneOf(__isMissingMethods))
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{
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var fieldExpression = arguments[0];
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var fieldTranslation = ExpressionToAggregationExpressionTranslator.Translate(context, fieldExpression);
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var fieldAst = fieldTranslation.Ast;
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if (fieldAst.NodeType != AstNodeType.GetFieldExpression)
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{
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throw new ExpressionNotSupportedException(expression, because: $"argument to {method.Name} must be a reference to a field");
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}
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var ast = method.Name switch
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{
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nameof(Mql.Exists) => AstExpression.Ne(AstExpression.Type(fieldAst), "missing"),
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nameof(Mql.IsMissing) => AstExpression.Eq(AstExpression.Type(fieldAst), "missing"),
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nameof(Mql.IsNullOrMissing) => AstExpression.In(AstExpression.Type(fieldAst), new BsonArray { "null", "missing" }),
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_ => throw new InvalidOperationException("Unexpected method."),
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};
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return new AggregationExpression(expression, ast, BooleanSerializer.Instance);
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}
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throw new ExpressionNotSupportedException(expression);
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}
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}
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}

‎src/MongoDB.Driver/Mql.cs

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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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namespace MongoDB.Driver
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{
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/// <summary>
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/// Contains methods that can be used to access MongoDB specific functionality in LINQ queries.
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/// </summary>
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public static class Mql
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{
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/// <summary>
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/// Tests whether a field exists.
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/// </summary>
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/// <typeparam name="TField">The type of the field.</typeparam>
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/// <param name="field">The field.</param>
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/// <returns><c>true</c> if the field exists.</returns>
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public static bool Exists<TField>(TField field)
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{
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throw new NotSupportedException("This method is not functional. It is only usable in MongoDB LINQ queries.");
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}
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/// <summary>
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/// Tests whether a field is missing.
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/// </summary>
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/// <typeparam name="TField">The type of the field.</typeparam>
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/// <param name="field">The field.</param>
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/// <returns><c>true</c> if the field is missing.</returns>
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public static bool IsMissing<TField>(TField field)
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{
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throw new NotSupportedException("This method is not functional. It is only usable in MongoDB LINQ queries.");
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}
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/// <summary>
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/// Tests whether a field is null or missing.
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/// </summary>
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/// <typeparam name="TField">The type of the field.</typeparam>
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/// <param name="field">The field.</param>
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/// <returns><c>true</c> if the field is null or missing.</returns>
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public static bool IsNullOrMissing<TField>(TField field)
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{
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throw new NotSupportedException("This method is not functional. It is only usable in MongoDB LINQ queries.");
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}
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}
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}

‎tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodTranslators/FieldExistsOrIsMissingMethodToAggregationExpressionTranslatorTests.cs

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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.Linq;
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using FluentAssertions;
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using MongoDB.Bson;
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using MongoDB.Driver.Linq;
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using Xunit;
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namespace MongoDB.Driver.Tests.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.MethodTranslators
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{
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public class FieldExistsOrIsMissingMethodToAggregationExpressionTranslatorTests : Linq3IntegrationTest
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{
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[Fact]
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public void Select_Exists_should_work()
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{
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var collection = GetCollection();
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var queryable = collection.AsQueryable()
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.Select(x => Mql.Exists(x.S));
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var stages = Translate(collection, queryable);
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AssertStages(stages, "{ $project : { _v : { $ne : [{ $type : '$S' }, 'missing'] }, _id : 0 } }");
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var results = queryable.ToList();
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results.Should().Equal(false, true, true);
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}
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[Fact]
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public void Select_IsMissing_should_work()
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{
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var collection = GetCollection();
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var queryable = collection.AsQueryable()
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.Select(x => Mql.IsMissing(x.S));
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var stages = Translate(collection, queryable);
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AssertStages(stages, "{ $project : { _v : { $eq : [{ $type : '$S' }, 'missing'] }, _id : 0 } }");
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var results = queryable.ToList();
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results.Should().Equal(true, false, false);
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}
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[Fact]
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public void Select_IsNullOrMissing_should_work()
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{
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var collection = GetCollection();
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var queryable = collection.AsQueryable()
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.Select(x => Mql.IsNullOrMissing(x.S));
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var stages = Translate(collection, queryable);
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AssertStages(stages, "{ $project : { _v : { $in : [{ $type : '$S' }, ['null', 'missing']] }, _id : 0 } }");
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var results = queryable.ToList();
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results.Should().Equal(true, true, false);
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}
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private IMongoCollection<C> GetCollection()
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{
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var collection = GetCollection<C>("test");
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CreateCollection(
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GetCollection<BsonDocument>("test"),
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BsonDocument.Parse("{ _id : 1 }"),
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BsonDocument.Parse("{ _id : 2, S : null }"),
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BsonDocument.Parse("{ _id : 3, S : 'abc' }"));
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return collection;
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}
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private class C
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{
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public int Id { get; set; }
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public string S { get; set; }
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}
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}
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}

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