fix(NODE-3924): Change to throw at connect time

src/connection_string.ts

@@ -1096,30 +1096,10 @@ export const OPTIONS = {
     }
   },
   tlsCAFile: {
-    transform({ name, values: [value] }) {
-      if (typeof value !== 'string') {
-        throw new MongoParseError(`${name} must be of type string`);
-      }
-
-      if (value.length === 0) {
-        throw new MongoParseError(`${name} must be have non-zero length`);
-      }
-
-      return value;
-    }
+    type: 'string'
   },
   tlsCertificateKeyFile: {
-    transform({ name, values: [value] }) {
-      if (typeof value !== 'string') {
-        throw new MongoParseError(`${name} must be of type string`);
-      }
-
-      if (value.length === 0) {
-        throw new MongoParseError(`${name} must be have non-zero length`);
-      }
-
-      return value;
-    }
+    type: 'string'
   },
   tlsCertificateKeyFilePassword: {
     target: 'passphrase',

src/mongo_client.ts

@@ -435,10 +435,10 @@ export class MongoClient extends TypedEventEmitter<MongoClientEvents> {
     const options = this[kOptions];
 
     if (options.tls) {
-      if (options.tlsCAFile) {
+      if (typeof options.tlsCAFile === 'string') {
         options.ca ??= await fs.readFile(options.tlsCAFile, { encoding: 'utf8' });
       }
-      if (options.tlsCertificateKeyFile) {
+      if (typeof options.tlsCertificateKeyFile === 'string') {
         options.key ??= await fs.readFile(options.tlsCertificateKeyFile, { encoding: 'utf8' });
       }
     }

test/manual/tls_support.test.ts

@@ -37,15 +37,15 @@ describe('TLS Support', function () {
 
   context('when tls filepaths are provided', () => {
     let client: MongoClient;
+    afterEach(async () => {
+      if (client) await client.close();
+    });
+
     context('when tls filepaths have length > 0', () => {
       beforeEach(async () => {
         client = new MongoClient(CONNECTION_STRING, tlsSettings);
       });
 
-      afterEach(async () => {
-        if (client) await client.close();
-      });
-
       it('should read in files async at connect time', async () => {
         expect(client.options).property('tlsCAFile', TLS_CA_FILE);
         expect(client.options).property('tlsCertificateKeyFile', TLS_CERT_KEY_FILE);
@@ -73,6 +73,38 @@ describe('TLS Support', function () {
         });
       });
     });
+
+    context('when tlsCAFile has length === 0', () => {
+      beforeEach(() => {
+        client = new MongoClient(CONNECTION_STRING, {
+          tls: true,
+          tlsCAFile: '',
+          tlsCertificateKeyFile: TLS_CERT_KEY_FILE
+        });
+      });
+
+      it('should throw an error at connect time', async () => {
+        const err = await client.connect().catch(e => e);
+
+        expect(err).to.be.instanceof(Error);
+      });
+    });
+
+    context('when tlsCertificateKeyFile has length === 0', () => {
+      beforeEach(() => {
+        client = new MongoClient(CONNECTION_STRING, {
+          tls: true,
+          tlsCAFile: TLS_CA_FILE,
+          tlsCertificateKeyFile: ''
+        });
+      });
+
+      it('should throw an error at connect time', async () => {
+        const err = await client.connect().catch(e => e);
+
+        expect(err).to.be.instanceof(Error);
+      });
+    });
   });
 });
 

test/unit/mongo_client.test.js

@@ -455,26 +455,6 @@ describe('MongoOptions', function () {
     expect(optionsUndefined.checkServerIdentity).to.equal(undefined);
   });
 
-  context('when tlsCAPath is provided as an empty string', function () {
-    it('throws MongoParseError', function () {
-      expect(() => {
-        parseOptions('mongodb://localhost:27017/?tls=true', {
-          tlsCAFile: ''
-        });
-      }).to.throw(MongoParseError);
-    });
-  });
-
-  context('when tlsCertificateKeyFile is provided as an empty string', function () {
-    it('throws MongoParseError', function () {
-      expect(() => {
-        parseOptions('mongodb://localhost:27017/?tls=true', {
-          tlsCertificateKeyFile: ''
-        });
-      }).to.throw(MongoParseError);
-    });
-  });
-
   describe('compressors', function () {
     it('can be set when passed in as an array in the options object', function () {
       const clientViaOpt = new MongoClient('mongodb://localhost', {