fix(NODE-6043): Binary.toString and Binary.toJSON output with respect to position

src/binary.ts

@@ -217,15 +217,15 @@ export class Binary extends BSONValue {
   }
 
   toJSON(): string {
-    return ByteUtils.toBase64(this.buffer);
+    return ByteUtils.toBase64(this.buffer.subarray(0, this.position));
   }
 
   toString(encoding?: 'hex' | 'base64' | 'utf8' | 'utf-8'): string {
-    if (encoding === 'hex') return ByteUtils.toHex(this.buffer);
-    if (encoding === 'base64') return ByteUtils.toBase64(this.buffer);
+    if (encoding === 'hex') return ByteUtils.toHex(this.buffer.subarray(0, this.position));
+    if (encoding === 'base64') return ByteUtils.toBase64(this.buffer.subarray(0, this.position));
     if (encoding === 'utf8' || encoding === 'utf-8')
-      return ByteUtils.toUTF8(this.buffer, 0, this.buffer.byteLength);
-    return ByteUtils.toUTF8(this.buffer, 0, this.buffer.byteLength);
+      return ByteUtils.toUTF8(this.buffer, 0, this.position);
+    return ByteUtils.toUTF8(this.buffer, 0, this.position);
   }
 
   /** @internal */

test/node/binary.test.ts

@@ -141,4 +141,68 @@ describe('class Binary', () => {
       });
     });
   });
+
+  context('toString()', () => {
+    context('when case is UTF8 (default)', () => {
+      it('should respect position when converting to string', () => {
+        const bin = new Binary();
+        expect(bin.toString()).to.equal('');
+        bin.put(1);
+        expect(bin.toString()).to.equal('\u0001');
+      });
+      it('should remain same after round trip', () => {
+        const bin = new BSON.Binary();
+        const serializedBin = BSON.serialize({ bin });
+        const roundTrippedBin = BSON.deserialize(serializedBin);
+        expect(roundTrippedBin.bin.toString()).to.equal(bin.toString());
+      });
+    });
+
+    context('when case is hex', () => {
+      it('should respect position when converting to string', () => {
+        const bin = new Binary();
+        expect(bin.toString('hex')).to.equal('');
+        bin.put(1);
+        expect(bin.toString('hex')).to.equal('01');
+      });
+      it('should remain same after round trip', () => {
+        const bin = new BSON.Binary();
+        const serializedBin = BSON.serialize({ bin });
+        const roundTrippedBin = BSON.deserialize(serializedBin);
+        expect(roundTrippedBin.bin.toString('hex')).to.equal(bin.toString('hex'));
+      });
+    });
+
+    context('when case is base64', () => {
+      it('should respect position when converting to string', () => {
+        const bin = new Binary();
+        expect(bin.toString('base64')).to.equal('');
+        bin.put(1);
+        expect(bin.toString('base64')).to.equal('AQ==');
+      });
+      it('should remain same after round trip', () => {
+        const bin = new BSON.Binary();
+        const serializedBin = BSON.serialize({ bin });
+        const roundTrippedBin = BSON.deserialize(serializedBin);
+        expect(roundTrippedBin.bin.toString('base64')).to.equal(bin.toString());
+      });
+    });
+  });
+
+  context('toJSON()', () => {
+    it('should respect position when converting to JSON', () => {
+      const bin = new Binary();
+      expect(bin.toJSON()).to.equal('');
+      bin.put(1);
+      // toJSON uses base64
+      expect(bin.toJSON()).to.equal('AQ==');
+    });
+
+    it('should remain same after round trip', () => {
+      const bin = new BSON.Binary();
+      const serializedBin = BSON.serialize({ bin });
+      const roundTrippedBin = BSON.deserialize(serializedBin);
+      expect(roundTrippedBin.bin.toJSON()).to.equal(bin.toJSON());
+    });
+  });
 });