CSHARP-1661: support for $indexOfXXX.

Author: craiggwilson

src/MongoDB.Driver/Linq/Translators/AggregateLanguageTranslator.cs

@@ -976,6 +976,46 @@ private bool TryTranslateStringMethodCall(MethodCallExpression node, out BsonVal
                         }
                     }
                     break;
+                case "IndexOf":
+                    var args = new BsonArray { field };
+                    if (node.Arguments[0].Type == typeof(char)
+                        && node.Arguments[0].NodeType == ExpressionType.Constant)
+                    {
+                        args.Add(new BsonString(((ConstantExpression)node.Arguments[0]).Value.ToString()));
+                    }
+                    else
+                    {
+                        args.Add(TranslateValue(node.Arguments[0]));
+                    }
+
+                    if (node.Arguments.Count > 1)
+                    {
+                        if (node.Arguments[1].Type != typeof(int))
+                        {
+                            throw new NotSupportedException("The StringComparison parameter is not supported in IndexOf.");
+                        }
+
+                        args.Add(TranslateValue(node.Arguments[1]));
+                    }
+
+                    if (node.Arguments.Count > 2)
+                    {
+                        if (node.Arguments[2].Type != typeof(int))
+                        {
+                            throw new NotSupportedException("The StringComparison parameter is not supported in IndexOf.");
+                        }
+
+                        var count = TranslateValue(node.Arguments[2]);
+                        args.Add(new BsonDocument("$add", new BsonArray { args[2], count }));
+                    }
+
+                    if (node.Arguments.Count > 3)
+                    {
+                        throw new NotSupportedException("The StringComparison parameter is not supported in IndexOf.");
+                    }
+
+                    result = new BsonDocument("$indexOfBytes", args);
+                    return true;
                 case "Split":
                     if (node.Arguments.Count < 1 || node.Arguments.Count > 2)
                     {

tests/MongoDB.Driver.Tests/Linq/Translators/AggregateProjectTranslatorTests.cs

@@ -548,6 +548,36 @@ public void Should_translate_hour()
             result.Value.Result.Should().Be(13);
         }
 
+        [SkippableFact]
+        public void Should_translate_indexOf()
+        {
+            RequireServer.Where(minimumVersion: "3.3.6");
+
+            var result = Project(x => new { Result = x.A.IndexOf('e') });
+            result.Projection.Should().Be("{ Result: { \"$indexOfBytes\": [\"$A\", \"e\"] }, _id: 0 }");
+            result.Value.Result.Should().Be(2);
+
+            result = Project(x => new { Result = x.A.IndexOf("e") });
+            result.Projection.Should().Be("{ Result: { \"$indexOfBytes\": [\"$A\", \"e\"] }, _id: 0 }");
+            result.Value.Result.Should().Be(2);
+
+            result = Project(x => new { Result = x.A.IndexOf('e', 4) });
+            result.Projection.Should().Be("{ Result: { \"$indexOfBytes\": [\"$A\", \"e\", 4] }, _id: 0 }");
+            result.Value.Result.Should().Be(6);
+
+            result = Project(x => new { Result = x.A.IndexOf("e", 4) });
+            result.Projection.Should().Be("{ Result: { \"$indexOfBytes\": [\"$A\", \"e\", 4] }, _id: 0 }");
+            result.Value.Result.Should().Be(6);
+
+            result = Project(x => new { Result = x.A.IndexOf('e', 4, 2) });
+            result.Projection.Should().Be("{ Result: { \"$indexOfBytes\": [\"$A\", \"e\", 4, { $add: [4, 2] }] }, _id: 0 }");
+            result.Value.Result.Should().Be(-1);
+
+            result = Project(x => new { Result = x.A.IndexOf("e", 4, 2) });
+            result.Projection.Should().Be("{ Result: { \"$indexOfBytes\": [\"$A\", \"e\", 4, { $add: [4, 2] }] }, _id: 0 }");
+            result.Value.Result.Should().Be(-1);
+        }
+
         [Fact]
         public void Should_translate_less_than()
         {