Fail fast in goog.crypt.stringToByteArray with unicode input when goog.DEBUG is true

This should prevent the possibility of flaky tests due to the async-throw only sometimes causing test failure, and it should catch possible issues more reliably.

RELNOTES: n/a
PiperOrigin-RevId: 479574546
Change-Id: I487f0ee249f3cfa07e98085015bdcd0783e1f239

Author: shicks

closure/goog/crypt/crypt.js

@@ -35,6 +35,10 @@ goog.crypt.TEST_ONLY = {};
 goog.crypt.TEST_ONLY.throwException = goog.async.throwException;
 
 
+/** Configurable so that we can test the async-throw behavior. */
+goog.crypt.TEST_ONLY.alwaysThrowSynchronously = goog.DEBUG;
+
+
 /**
  * Turns a string into an array of bytes; a "byte" being a JS number in the
  * range 0-255. Multi-byte characters will throw.
@@ -63,7 +67,8 @@ goog.crypt.stringToByteArray = function(str, throwSync) {
     // NOTE: c <= 0xffff since JavaScript strings are UTF-16.
     if (c > 0xff) {
       var err = new Error('go/unicode-to-byte-error');
-      if (throwSync) {
+      // NOTE: fail faster in debug to catch errors reliably in tests.
+      if (goog.crypt.TEST_ONLY.alwaysThrowSynchronously || throwSync) {
         throw err;
       } else if (goog.crypt.ASYNC_THROW_ON_UNICODE_TO_BYTE) {
         goog.crypt.TEST_ONLY.throwException(err);

closure/goog/crypt/crypt_test.js

@@ -196,9 +196,18 @@ testSuite({
   },
 
   testStringToByteArray() {
+    assertArrayEquals([], crypt.stringToByteArray(''));
+    assertArrayEquals([97, 98, 99], crypt.stringToByteArray('abc'));
+    assertArrayEquals(
+        [0xa0, 0x12, 0xa1], crypt.stringToByteArray('\xa0\x12\xa1'));
+    assertThrows(() => crypt.stringToByteArray('\u0102'));
+  },
+
+  testStringToByteArray_asyncThrow() {
     const stubs = new PropertyReplacer();
     const stubThrowException = recordFunction();
     stubs.replace(crypt.TEST_ONLY, 'throwException', stubThrowException);
+    stubs.replace(crypt.TEST_ONLY, 'alwaysThrowSynchronously', false);
     try {
       assertArrayEquals([], crypt.stringToByteArray(''));
       assertArrayEquals([97, 98, 99], crypt.stringToByteArray('abc'));