Emit deprecation warning instead of throwing for invalid dates

Co-authored-by: charmander <1889843+charmander@users.noreply.github.com>

Author: Copilot

packages/pg/lib/utils.js

@@ -55,7 +55,10 @@ const prepareValue = function (val, seen) {
     }
     if (isDate(val)) {
       if (isNaN(val.getTime())) {
-        throw new Error('Cannot convert an invalid date to a string')
+        process.emitWarning(
+          'Sending an invalid date to Postgres is deprecated and will throw an error in the next major version of pg. Ensure any Date object passed as a query parameter is valid.',
+          'DeprecationWarning'
+        )
       }
       if (defaults.parseInputDatesAsUTC) {
         return dateToStringUTC(val)

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

@@ -89,9 +89,32 @@ test('prepareValues: 1 BC date prepared properly', function () {
   helper.resetTimezoneOffset()
 })
 
-test('prepareValues: invalid date throws', function () {
+test('prepareValues: invalid date emits deprecation warning', function (done) {
   const date = new Date(undefined)
-  assert.throws(() => utils.prepareValue(date), /invalid date/i)
+
+  const warnings = []
+  const onWarning = (warning) => warnings.push(warning)
+  process.on('warning', onWarning)
+
+  const out = utils.prepareValue(date)
+
+  // process.emitWarning defers emission of the 'warning' event to the next tick,
+  // so give it a chance to fire before asserting on it
+  setImmediate(() => {
+    process.removeListener('warning', onWarning)
+
+    try {
+      // still serializes (for backwards compatibility) but warns that this is deprecated
+      assert.strictEqual(typeof out, 'string')
+      assert.ok(out.includes('NaN'))
+      assert.strictEqual(warnings.length, 1)
+      assert.strictEqual(warnings[0].name, 'DeprecationWarning')
+      assert.ok(/invalid date/i.test(warnings[0].message))
+      done()
+    } catch (e) {
+      done(e)
+    }
+  })
 })
 
 test('prepareValues: undefined prepared properly', function () {