SERVER-32784 Add $convert with typecast conversions.

2 files changed, 44 insertions, 0 deletions

diff --git a/src/mongo/bson/bsontypes.cpp b/src/mongo/bson/bsontypes.cpp
index a2dbcaaf334..a39470680d2 100644
--- a/src/mongo/bson/bsontypes.cpp
+++ b/src/mongo/bson/bsontypes.cpp
@@ -93,6 +93,37 @@ const char* typeName(BSONType type) {
     }
 }
 
+const StringMap<BSONType> kTypeAliasMap = {
+    {typeName(BSONType::NumberDouble), BSONType::NumberDouble},
+    {typeName(BSONType::String), BSONType::String},
+    {typeName(BSONType::Object), BSONType::Object},
+    {typeName(BSONType::Array), BSONType::Array},
+    {typeName(BSONType::BinData), BSONType::BinData},
+    {typeName(BSONType::Undefined), BSONType::Undefined},
+    {typeName(BSONType::jstOID), BSONType::jstOID},
+    {typeName(BSONType::Bool), BSONType::Bool},
+    {typeName(BSONType::Date), BSONType::Date},
+    {typeName(BSONType::jstNULL), BSONType::jstNULL},
+    {typeName(BSONType::RegEx), BSONType::RegEx},
+    {typeName(BSONType::DBRef), BSONType::DBRef},
+    {typeName(BSONType::Code), BSONType::Code},
+    {typeName(BSONType::Symbol), BSONType::Symbol},
+    {typeName(BSONType::CodeWScope), BSONType::CodeWScope},
+    {typeName(BSONType::NumberInt), BSONType::NumberInt},
+    {typeName(BSONType::bsonTimestamp), BSONType::bsonTimestamp},
+    {typeName(BSONType::NumberLong), BSONType::NumberLong},
+    {typeName(BSONType::NumberDecimal), BSONType::NumberDecimal},
+    {typeName(BSONType::MaxKey), BSONType::MaxKey},
+    {typeName(BSONType::MinKey), BSONType::MinKey}};
+
+BSONType typeFromName(StringData name) {
+    auto typeIt = kTypeAliasMap.find(name);
+    uassert(ErrorCodes::BadValue,
+            str::stream() << "Unknown type name: " << name,
+            typeIt != kTypeAliasMap.end());
+    return typeIt->second;
+}
+
 std::ostream& operator<<(std::ostream& stream, BSONType type) {
     return stream << typeName(type);
 }
diff --git a/src/mongo/bson/bsontypes.h b/src/mongo/bson/bsontypes.h
index 115e2d93aee..5ec96545772 100644
--- a/src/mongo/bson/bsontypes.h
+++ b/src/mongo/bson/bsontypes.h
@@ -34,6 +34,7 @@
 #include "mongo/config.h"
 #include "mongo/platform/decimal128.h"
 #include "mongo/util/assert_util.h"
+#include "mongo/util/string_map.h"
 
 namespace mongo {
 
@@ -108,12 +109,24 @@ enum BSONType {
     MaxKey = 127
 };
 
+/*
+ * Maps from the set of type aliases accepted by the $type query operator to the corresponding BSON
+ * types. Excludes "number", since this alias maps to a set of BSON types.
+ */
+extern const StringMap<BSONType> kTypeAliasMap;
+
 /**
  * returns the name of the argument's type
  */
 const char* typeName(BSONType type);
 
 /**
+ * Reverse mapping of typeName(). Throws an exception with error code BadValue when passed in
+ * invalid type name.
+ */
+BSONType typeFromName(StringData name);
+
+/**
  * Prints the name of the argument's type to the given stream.
  */
 std::ostream& operator<<(std::ostream& stream, BSONType type);