[intl] Change the r/w order of fractionalSecondDigits

1. read and output into option after timeZoneName
2. Not output into resolvedOptions if dateStyle or timeStyle is presented.
3. Add unit test

Spec: https://github.com/tc39/ecma402/pull/347

Bug: v8:10438
Change-Id: Ie7fecdb5b6dc83dc9a6dfd8ced26679a4051c833
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2161509
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67344}

src/objects/js-date-time-format.cc

@@ -545,6 +545,7 @@ MaybeHandle<JSObject> JSDateTimeFormat::ResolvedOptions(
   //    [[Minute]]           "minute"
   //    [[Second]]           "second"
   //    [[TimeZoneName]]     "timeZoneName"
+  //    [[FractionalSecondDigits]]     "fractionalSecondDigits"
   CHECK(JSReceiver::CreateDataProperty(isolate, options,
                                        factory->locale_string(), locale,
                                        Just(kDontThrow))
@@ -615,6 +616,13 @@ MaybeHandle<JSObject> JSDateTimeFormat::ResolvedOptions(
         }
       }
     }
+    if (FLAG_harmony_intl_dateformat_fractional_second_digits) {
+      int fsd = FractionalSecondDigitsFromPattern(pattern);
+      CHECK(JSReceiver::CreateDataProperty(
+                isolate, options, factory->fractionalSecondDigits_string(),
+                factory->NewNumberFromInt(fsd), Just(kDontThrow))
+                .FromJust());
+    }
   }
 
   // dateStyle
@@ -634,14 +642,6 @@ MaybeHandle<JSObject> JSDateTimeFormat::ResolvedOptions(
               Just(kDontThrow))
               .FromJust());
   }
-  if (FLAG_harmony_intl_dateformat_fractional_second_digits) {
-    int fsd = FractionalSecondDigitsFromPattern(pattern);
-    CHECK(JSReceiver::CreateDataProperty(
-              isolate, options, factory->fractionalSecondDigits_string(),
-              factory->NewNumberFromInt(fsd), Just(kDontThrow))
-              .FromJust());
-  }
-
   return options;
 }
 

test/intl/regress-10438.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony_intl_dateformat_fractional_second_digits
+
+assertEquals(
+    0,
+    (new Intl.DateTimeFormat("en", {fractionalSecondDigits: 0}))
+        .resolvedOptions().fractionalSecondDigits);
+
+assertEquals(
+    1,
+    (new Intl.DateTimeFormat("en", {fractionalSecondDigits: 1}))
+        .resolvedOptions().fractionalSecondDigits);
+
+assertEquals(
+    2,
+    (new Intl.DateTimeFormat("en", {fractionalSecondDigits: 2}))
+        .resolvedOptions().fractionalSecondDigits);
+
+assertEquals(
+    3,
+    (new Intl.DateTimeFormat("en", {fractionalSecondDigits: 3}))
+        .resolvedOptions().fractionalSecondDigits);
+
+// When timeStyle and dateStyle is not present, GetNumberOption will fallback
+// to 0 as default regardless fractionalSecondDigits is present in the option or
+// not.
+assertEquals(
+    0,
+    (new Intl.DateTimeFormat()).resolvedOptions().fractionalSecondDigits);
+
+assertEquals(
+    0,
+    (new Intl.DateTimeFormat("en", {fractionalSecondDigits: undefined}))
+        .resolvedOptions().fractionalSecondDigits);
+
+// When timeStyle or dateStyle is present, the code should not read
+// fractionalSecondDigits from the option.
+assertEquals(
+    undefined,
+    (new Intl.DateTimeFormat(
+        "en", {timeStyle: "short", fractionalSecondDigits: 3}))
+        .resolvedOptions().fractionalSecondDigits);
+
+assertEquals(
+    undefined,
+    (new Intl.DateTimeFormat(
+        "en", {dateStyle: "short", fractionalSecondDigits: 3}))
+        .resolvedOptions().fractionalSecondDigits);