SERVER-43860 Always upsert exact source document for pipeline-insert $merge

2 files changed, 120 insertions, 1 deletions

diff --git a/src/mongo/idl/basic_types.h b/src/mongo/idl/basic_types.h
new file mode 100644
index 00000000000..8eb66c53629
--- /dev/null
+++ b/src/mongo/idl/basic_types.h
@@ -0,0 +1,107 @@
+/**
+ *    Copyright (C) 2019 MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <boost/optional.hpp>
+
+#include "mongo/base/string_data.h"
+#include "mongo/bson/bsonobjbuilder.h"
+
+namespace mongo {
+
+/**
+ * Wraps a boost::optional<bool> to provide consistent semantics. A standard boost::optional<bool>
+ * can introduce ambiguity because its 'operator bool' will resolve to 'true' if the optional is
+ * populated, even if is populated with boolean 'false'. By contrast, an instance of this class
+ * always resolves to the populated value, or false if not yet populated. This class will also
+ * serialize to BSON via the IDL only if the value has been explicitly set.
+ */
+class OptionalBool {
+public:
+    static OptionalBool parseFromBSON(BSONElement element) {
+        uassert(ErrorCodes::BadValue,
+                str::stream() << "Field '" << element.fieldNameStringData()
+                              << "' should be a boolean value, but found: " << element.type(),
+                !element || element.type() == BSONType::Bool);
+        return element ? OptionalBool{element.boolean()} : OptionalBool{};
+    }
+
+    OptionalBool(boost::optional<bool> value) : _value(std::move(value)) {}
+    OptionalBool(bool value) : _value(value) {}
+
+    OptionalBool() : OptionalBool(boost::none) {}
+
+    /**
+     * Returns true only if _value is populated with a value of true.
+     */
+    operator bool() const {
+        return _value.value_or(false);
+    }
+
+    /**
+     * Returns true if the value has been populated, false otherwise.
+     */
+    bool has_value() const {
+        return _value.has_value();
+    }
+
+    /**
+     * Serialize this object as a field in a document. If _value is empty, omit the field.
+     */
+    void serializeToBSON(StringData fieldName, BSONObjBuilder* builder) const {
+        if (_value) {
+            builder->appendBool(fieldName, *_value);
+        }
+    }
+
+    /**
+     * Serialize this object as an element of a BSON array. If _value is empty, omit the entry.
+     */
+    void serializeToBSON(BSONArrayBuilder* builder) const {
+        if (_value) {
+            builder->append(*_value);
+        }
+    }
+
+    /**
+     * Returns a string representation of the current value.
+     */
+    std::string toString() const {
+        return *this ? "1" : "0";
+    }
+    operator std::string() const {
+        return toString();
+    }
+
+private:
+    boost::optional<bool> _value;
+};
+
+}  // namespace mongo
diff --git a/src/mongo/idl/basic_types.idl b/src/mongo/idl/basic_types.idl
index 7ebee57fb3f..fda3a56df0d 100644
--- a/src/mongo/idl/basic_types.idl
+++ b/src/mongo/idl/basic_types.idl
@@ -31,6 +31,7 @@ global:
     cpp_namespace: "mongo"
     cpp_includes:
         - "mongo/db/namespace_string.h"
+        - "mongo/idl/basic_types.h"
         - "mongo/util/uuid.h"
 
 types:
@@ -92,10 +93,21 @@ types:
         cpp_type: bool
         deserializer: "mongo::BSONElement::trueValue"
 
+    optionalBool:
+        bson_serialization_type: any
+        description: "An optional bool type that does not serialize unless explicitly set. Can be
+                      used in place of boost::optional<bool> to provide more intuitive semantics,
+                      since the standard optional will coerce to true if populated regardless of
+                      its internal value."
+        cpp_type: "mongo::OptionalBool"
+        default: "mongo::OptionalBool()"
+        deserializer: "mongo::OptionalBool::parseFromBSON"
+        serializer: "mongo::OptionalBool::serializeToBSON"
+
     bindata_generic:
         bson_serialization_type: bindata
         bindata_subtype: generic
-        description: "A BSON bindata of "
+        description: "A BSON bindata of generic sub type"
         cpp_type: "std::vector<std::uint8_t>"
         deserializer: "mongo::BSONElement::_binDataVector"