fix(NODE-6102): Double.fromString prohibiting '+' character and prohibiting exponential notation (#674)

Author: aditi-khare-mongoDB

src/double.ts

@@ -38,29 +38,32 @@ export class Double extends BSONValue {
    *
    * This method will throw a BSONError on any string input that is not representable as a IEEE-754 64-bit double.
    * Notably, this method will also throw on the following string formats:
-   * - Strings in non-decimal formats (exponent notation, binary, hex, or octal digits)
+   * - Strings in non-decimal and non-exponential formats (binary, hex, or octal digits)
    * - Strings with characters other than numeric, floating point, or leading sign characters (Note: 'Infinity', '-Infinity', and 'NaN' input strings are still allowed)
    * - Strings with leading and/or trailing whitespace
    *
    * Strings with leading zeros, however, are also allowed
    *
-   * @param value - the string we want to represent as an double.
+   * @param value - the string we want to represent as a double.
    */
   static fromString(value: string): Double {
     const coercedValue = Number(value);
-    const nonFiniteValidInputs = ['Infinity', '-Infinity', 'NaN'];
 
+    if (value === 'NaN') return new Double(NaN);
+    if (value === 'Infinity') return new Double(Infinity);
+    if (value === '-Infinity') return new Double(-Infinity);
+
+    if (!Number.isFinite(coercedValue)) {
+      throw new BSONError(`Input: ${value} is not representable as a Double`);
+    }
     if (value.trim() !== value) {
       throw new BSONError(`Input: '${value}' contains whitespace`);
-    } else if (value === '') {
+    }
+    if (value === '') {
       throw new BSONError(`Input is an empty string`);
-    } else if (/[^-0-9.]/.test(value) && !nonFiniteValidInputs.includes(value)) {
-      throw new BSONError(`Input: '${value}' contains invalid characters`);
-    } else if (
-      (!Number.isFinite(coercedValue) && !nonFiniteValidInputs.includes(value)) ||
-      (Number.isNaN(coercedValue) && value !== 'NaN')
-    ) {
-      throw new BSONError(`Input: ${value} is not representable as a Double`); // generic case
+    }
+    if (/[^-0-9.+eE]/.test(value)) {
+      throw new BSONError(`Input: '${value}' is not in decimal or exponential notation`);
     }
     return new Double(coercedValue);
   }

test/node/double.test.ts

@@ -239,21 +239,33 @@ describe('BSON Double Precision', function () {
         ['-Infinity', '-Infinity', -Infinity],
         ['NaN', 'NaN', NaN],
         ['basic floating point', '-4.556000', -4.556],
-        ['negative zero', '-0', -0]
+        ['negative zero', '-0', -0],
+        ['explicit plus zero', '+0', 0],
+        ['explicit plus decimal', '+78.23456', 78.23456],
+        ['explicit plus leading zeros', '+00000000000001.11', 1.11],
+        ['exponentiation notation', '1.34e16', 1.34e16],
+        ['exponentiation notation with negative exponent', '1.34e-16', 1.34e-16],
+        ['exponentiation notation with explicit positive exponent', '1.34e+16', 1.34e16],
+        ['exponentiation notation with negative base', '-1.34e16', -1.34e16],
+        ['exponentiation notation with capital E', '-1.34E16', -1.34e16]
       ];
 
       const errorInputs = [
-        ['commas', '34,450', 'contains invalid characters'],
-        ['exponentiation notation', '1.34e16', 'contains invalid characters'],
-        ['octal', '0o1', 'contains invalid characters'],
-        ['binary', '0b1', 'contains invalid characters'],
-        ['hex', '0x1', 'contains invalid characters'],
+        ['commas', '34,450', 'is not representable as a Double'],
+        ['octal', '0o1', 'is not in decimal or exponential notation'],
+        ['binary', '0b1', 'is not in decimal or exponential notation'],
+        ['hex', '0x1', 'is not in decimal or exponential notation'],
         ['empty string', '', 'is an empty string'],
         ['leading and trailing whitespace', '    89   ', 'contains whitespace'],
-        ['fake positive infinity', '2e308', 'contains invalid characters'],
-        ['fake negative infinity', '-2e308', 'contains invalid characters'],
-        ['fraction', '3/4', 'contains invalid characters'],
-        ['foo', 'foo', 'contains invalid characters']
+        ['fake positive infinity', '2e308', 'is not representable as a Double'],
+        ['fake negative infinity', '-2e308', 'is not representable as a Double'],
+        ['fraction', '3/4', 'is not representable as a Double'],
+        ['foo', 'foo', 'is not representable as a Double'],
+        [
+          'malformed number without invalid characters',
+          '9.0.+76',
+          'is not representable as a Double'
+        ]
       ];
 
       for (const [testName, value, expectedDouble] of acceptedInputs) {
@@ -262,7 +274,7 @@ describe('BSON Double Precision', function () {
             if (value === 'NaN') {
               expect(isNaN(Double.fromString(value))).to.be.true;
             } else {
-              expect(Double.fromString(value).value).to.equal(expectedDouble);
+              expect(Double.fromString(value).value).to.deep.equal(expectedDouble);
             }
           });
         });