fix(pg): throw on invalid Date instead of serializing NaN string

new Date(undefined) and new Date('invalid') produce an invalid Date
object whose getTime() returns NaN.  Previously prepareValue() would
pass such a date straight through to dateToString() / dateToStringUTC()
which format each NaN component with padStart(), producing the
meaningless string '0NaN-NaN-NaNTNaN:NaN:NaN.NaN+NaN:NaN' that Postgres
cannot parse.

Add an isNaN(val.getTime()) guard in the isDate branch of prepareValue()
and throw an informative error immediately, so callers discover the bug
at the JS level rather than receiving a cryptic Postgres error.

Fixes #3318

Author: terminalchai

packages/pg/lib/utils.js

@@ -64,6 +64,9 @@ const prepareValue = function (val, seen) {
       return buf.slice(val.byteOffset, val.byteOffset + val.byteLength) // Node.js v4 does not support those Buffer.from params
     }
     if (isDate(val)) {
+      if (isNaN(val.getTime())) {
+        throw new Error('date is invalid')
+      }
       if (defaults.parseInputDatesAsUTC) {
         return dateToStringUTC(val)
       } else {

packages/pg/test/unit/utils-tests.js

@@ -94,6 +94,22 @@ test('prepareValues: undefined prepared properly', function () {
   assert.strictEqual(out, null)
 })
 
+test('prepareValues: invalid date throws an error', function () {
+  const invalidDate = new Date(undefined)
+  assert.throws(
+    () => utils.prepareValue(invalidDate),
+    /date is invalid/
+  )
+})
+
+test('prepareValues: invalid date (NaN) does not produce NaN string', function () {
+  const invalidDate = new Date('not a date')
+  assert.throws(
+    () => utils.prepareValue(invalidDate),
+    /date is invalid/
+  )
+})
+
 test('prepareValue: null prepared properly', function () {
   const out = utils.prepareValue(null)
   assert.strictEqual(out, null)