feat(NODE-3331): offer downleveled types for legacy typescript versio…

…ns (#2859)

.evergreen/run-checks.sh

@@ -1,9 +1,19 @@
 #!/bin/bash
-set -o errexit  # Exit the script with error if any of the commands fail
+set -o errexit # Exit the script with error if any of the commands fail
 
 export PROJECT_DIRECTORY="$(pwd)"
 NODE_ARTIFACTS_PATH="${PROJECT_DIRECTORY}/node-artifacts"
 export NVM_DIR="${NODE_ARTIFACTS_PATH}/nvm"
 [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
 
 npm run check:lint
+
+echo "Typescript $(npx tsc -v)"
+# check resolution uses the default latest types
+echo "import * as mdb from '.'" > file.ts && npx tsc --noEmit --traceResolution file.ts | grep 'mongodb.d.ts' && rm file.ts
+
+npm i --no-save typescript@4.0.2 # there is no 4.0.0
+echo "Typescript $(npx tsc -v)"
+npx tsc --noEmit mongodb.ts34.d.ts
+# check that resolution uses the downleveled types
+echo "import * as mdb from '.'" > file.ts && npx tsc --noEmit --traceResolution file.ts | grep 'mongodb.ts34.d.ts' && rm file.ts

README.md

@@ -41,6 +41,12 @@ For version compatibility matrices, please refer to the following links:
 - [MongoDB](https://docs.mongodb.com/drivers/node/compatibility#mongodb-compatibility)
 - [NodeJS](https://docs.mongodb.com/drivers/node/compatibility#language-compatibility)
 
+#### Typescript Version
+
+We recommend using the latest version of typescript, however we do provide a [downleveled](https://github.com/sandersn/downlevel-dts#readme) version of the type definitions that we test compiling against `typescript@4.0.2`.
+Since typescript [does not restrict breaking changes to major versions](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes) we consider this support best effort.
+If you run into any unexpected compiler failures please let us know and we will do our best to correct it.
+
 ## Installation
 
 The recommended way to get started using the Node.js 4.0 driver is by using the `npm` (Node Package Manager) to install the dependency in your project.