Fault-tolerant Date parsing for dashes

Summary: This is addressing a gap between Hermes and V8 regarding date parsing, raised in facebook#796 . There is whitespace allowed between M D Y. However, we should also support allowing a dash to be present as the first character in those gaps.

Reviewed By: jpporto

Differential Revision: D40368889

fbshipit-source-id: 5a9529300a221609ebb5c59dc44c4cf97a153700

lib/VM/JSLib/DateUtil.cpp

@@ -901,7 +901,7 @@ static double parseESDate(StringView str) {
 
  /// Reads the next \p len characters into `tok`,
  /// but instead of consuming \p len chars, it consumes a single word
- /// whatever how long it is (i.e. until a space is encountered).
+ /// whatever how long it is (i.e. until a space or dash is encountered).
  /// e.g.
  /// &str ="Garbage G MayG"
  /// scanStrAndSkipWord(3); consumeSpaces(); // &str="G MayG", &tok="Gar"
@@ -913,7 +913,7 @@ static double parseESDate(StringView str) {
  if (it + len > str.end())
  return false;
  tok = str.slice(it, it + len);
- while (it != str.end() && !std::isspace(*it))
+ while (it != str.end() && !std::isspace(*it) && *it != '-')
  it++;
  return true;
  };
@@ -931,6 +931,21 @@ static double parseESDate(StringView str) {
  ++it;
  };
 
+ /// Only one dash is ever allowed, and the dash must come first.
+ /// There is no limit to the number of spaces.
+ /// This is in line with V8's behavior.
+ auto consumeSpacesOrDash = [&]() {
+ auto first = true;
+ while (it != str.end()) {
+ if (std::isspace(*it) || (first && *it == '-')) {
+ ++it;
+ } else {
+ return;
+ }
+ first = false;
+ }
+ };
+
  // Weekday
  if (!scanStr(3))
  return nan;
@@ -964,7 +979,7 @@ static double parseESDate(StringView str) {
  // Day
  scanInt(it, end, d);
  // Month
- consumeSpaces();
+ consumeSpacesOrDash();
  // e.g. `Janwhatever` will get read as `Jan`
  if (!scanStrAndSkipWord(3))
  return nan;
@@ -980,7 +995,7 @@ static double parseESDate(StringView str) {
  // `tok` is now set to the Month candidate.
  if (tokIsMonth()) {
  // Day
- consumeSpaces();
+ consumeSpacesOrDash();
  if (!scanInt(it, end, d))
  return nan;
  break;
@@ -993,12 +1008,12 @@ static double parseESDate(StringView str) {
  }
 
  // Year
- consumeSpaces();
+ consumeSpacesOrDash();
  if (!scanInt(it, end, y))
  return nan;
 
  // Hour:minute:second.
- consumeSpaces();
+ consumeSpacesOrDash();
 
  if (it != end) {
  if (!scanInt(it, end, h))

test/hermes/date-constructor.js

@@ -313,6 +313,25 @@ print(Date.parse('Tue May 05 2020 00:00:00'.padEnd(60))); // trailing spaces.
 print(Date.parse('Tue May 05 2020'.padEnd(60)));
 // CHECK-NEXT: 1588662000000
 
+// Fault tolerance on dashes
+print(Date.parse("Friday, 02 Aug 2019 07:14:03 UTC"));
+// CHECK-NEXT: 1564730043000
+print(Date.parse("Friday, 02-Aug-2019-07:14:03 UTC"));
+// CHECK-NEXT: 1564730043000
+print(Date.parse("Friday, 02- Aug-2019-07:14:03 UTC"));
+// CHECK-NEXT: 1564730043000
+print(Date.parse("Friday, 02- Aug- 2019- 07:14:03 UTC"));
+// CHECK-NEXT: 1564730043000
+// Invalid use of dashes
+print(Date.parse("Friday, 02 - Aug-2019-07:14:03 UTC"));
+// CHECK-NEXT: NaN
+print(Date.parse("Friday, 02-Aug -2019-07:14:03 UTC"));
+// CHECK-NEXT: NaN
+print(Date.parse("Friday, 02-Aug-2019- -07:14:03 UTC"));
+// CHECK-NEXT: NaN
+print(Date.parse("Friday, 02-Aug-2019 -07:14:03 UTC"));
+// CHECK-NEXT: NaN
+
 // Quick check that getters work; internal functions are unit tested instead.
 print('getters');
 // CHECK-LABEL: getters