Summary

• Add a new context initializer to support ClientEncryption.encryptExpression().
  • Require queryType to be "rangePreview"
• Error if queryType "rangePreview" is passed to the context for ClientEncryption.Encrypt().

Background & Motivation

The DBX Scope: Driver Support for Range Index currently proposes this API:

   // encryptExpression encrypts an expression to query a range index.
   // `expr` is expected to be a BSON document of one of the following forms:
   // 1. A Match Expression of this form:
   //   {$and: [{<field>: {$gt: <value1>}}, {<field>: {$lt: <value2> }}]}
   // 2. An Aggregate Expression of this form:
   //   {$and: [{$gt: [<fieldpath>, <value1>]}, {$lt: [<fieldpath>, <value2>]}]
   // $gt may also be $gte. $lt may also be $lte.
   // Only supported for queryType "rangePreview"
   encryptExpression(expr: BsonDocument, opts: EncryptOpts): BsonDocument;

ClientEncryption.Encrypt() uses mongocrypt_ctx_explicit_encrypt_init.

mongocrypt_ctx_explicit_encrypt_init currently supports encrypting the Match Expression or Aggregate Expression, and returns a BSON document.

A separate initializer (perhaps named mongocrypt_ctx_explicit_encrypt_expression_init) can mirror the driver API. It can check for the required queryType=rangePreview.