fix(NODE-3815): update Decimal128 constructor validation

src/decimal128.ts

@@ -1,6 +1,7 @@
 import { Buffer } from 'buffer';
 import { BSONTypeError } from './error';
 import { Long } from './long';
+import { isUint8Array } from './parser/utils';
 
 const PARSE_STRING_REGEXP = /^(\+|-)?(\d+|(\d*\.\d*))?(E|e)?([-+])?(\d+)?$/;
 const PARSE_INF_REGEXP = /^(\+|-)?(Infinity|inf)$/i;
@@ -132,8 +133,13 @@ export class Decimal128 {
 
     if (typeof bytes === 'string') {
       this.bytes = Decimal128.fromString(bytes).bytes;
-    } else {
+    } else if (isUint8Array(bytes)) {
+      if (bytes.byteLength !== 16) {
+        throw new BSONTypeError('Decimal128 must take a Buffer of 16 bytes');
+      }
       this.bytes = bytes;
+    } else {
+      throw new BSONTypeError('Decimal128 must take a Buffer or string');
     }
   }
 

test/.eslintrc.json

@@ -31,6 +31,21 @@
       "error",
       "global"
     ],
-    "promise/no-native": "off"
+    "promise/no-native": "off",
+    "no-restricted-properties": [
+      "error",
+      {
+        "object": "describe",
+        "property": "only"
+      },
+      {
+        "object": "it",
+        "property": "only"
+      },
+      {
+        "object": "context",
+        "property": "only"
+      }
+    ]
   }
 }

test/node/decimal128_tests.js

@@ -1205,7 +1205,7 @@ describe('Decimal128', function () {
     done();
   });
 
-  it('accepts strings in the constructor', function (done) {
+  it('accepts strings in the constructor', () => {
     expect(new Decimal128('0').toString()).to.equal('0');
     expect(new Decimal128('00').toString()).to.equal('0');
     expect(new Decimal128('0.5').toString()).to.equal('0.5');
@@ -1216,6 +1216,30 @@ describe('Decimal128', function () {
     expect(new Decimal128('0.0011').toString()).to.equal('0.0011');
     expect(new Decimal128('0.00110').toString()).to.equal('0.00110');
     expect(new Decimal128('-1e400').toString()).to.equal('-1E+400');
-    done();
+  });
+
+  it('throws correct error for invalid constructor argument type', () => {
+    const constructorArgErrMsg = 'Decimal128 must take a Buffer or string';
+
+    expect(() => new Decimal128(-0)).to.throw(constructorArgErrMsg);
+    expect(() => new Decimal128(-1)).to.throw(constructorArgErrMsg);
+    expect(() => new Decimal128(10)).to.throw(constructorArgErrMsg);
+    expect(() => new Decimal128(1111111111111111)).to.throw(constructorArgErrMsg);
+  });
+
+  it('throws correct error for an invalid Buffer constructor argument', () => {
+    const byteLengthErrMsg = 'Decimal128 must take a Buffer of 16 bytes';
+
+    expect(() => new Decimal128(new Uint8Array(0))).to.throw(byteLengthErrMsg);
+    expect(() => new Decimal128(Buffer.alloc(0))).to.throw(byteLengthErrMsg);
+    expect(() => new Decimal128(new Uint8Array(3))).to.throw(byteLengthErrMsg);
+    expect(() => new Decimal128(Buffer.alloc(3))).to.throw(byteLengthErrMsg);
+    expect(() => new Decimal128(new Uint8Array(17))).to.throw(byteLengthErrMsg);
+    expect(() => new Decimal128(Buffer.alloc(17))).to.throw(byteLengthErrMsg);
+  });
+
+  it('does not throw error for an empty Buffer of correct length constructor argument', () => {
+    expect(() => new Decimal128(Buffer.alloc(16))).to.not.throw();
+    expect(() => new Decimal128(new Uint8Array(16))).to.not.throw();
   });
 });

test/node/extended_json_tests.js

@@ -227,7 +227,7 @@ describe('Extended JSON', function () {
       binary: new Binary(''),
       code: new Code('function() {}'),
       dbRef: new DBRef('tests', new Int32(1), 'test'),
-      decimal128: new Decimal128(128),
+      decimal128: new Decimal128('128'),
       double: new Double(10.1),
       int32: new Int32(10),
       long: new Long(234),
@@ -248,7 +248,7 @@ describe('Extended JSON', function () {
       binary: { $binary: { base64: '', subType: '00' } },
       code: { $code: 'function() {}' },
       dbRef: { $ref: 'tests', $id: { $numberInt: '1' }, $db: 'test' },
-      decimal128: { $numberDecimal: '0E-6176' },
+      decimal128: { $numberDecimal: '128' },
       double: { $numberDouble: '10.1' },
       int32: { $numberInt: '10' },
       long: { $numberLong: '234' },