Bug 1862922 - Run telemetry on day of week support r=arai

Differential Revision: https://phabricator.services.mozilla.com/D193367

dom/base/UseCounters.conf

@@ -71,6 +71,7 @@ custom onunderflow sets an element onunderflow event listener
 // JavaScript feature usage
 custom JS_asmjs uses asm.js
 custom JS_wasm uses WebAssembly
+custom JS_late_weekday parses a Date with day of week in an unexpected position
 
 // Console API
 method console.assert

js/public/friend/UsageStatistics.h

@@ -91,7 +91,7 @@ extern JS_PUBLIC_API void JS_SetAccumulateTelemetryCallback(
  * fixed member of the mozilla::UseCounter enum by the callback.
  */
 
-enum class JSUseCounter { ASMJS, WASM };
+enum class JSUseCounter { ASMJS, WASM, LATE_WEEKDAY };
 
 using JSSetUseCounterCallback = void (*)(JSObject*, JSUseCounter);
 

js/src/jsdate.cpp

@@ -1118,15 +1118,6 @@ static bool TryParseDashedDatePrefix(const CharT* s, size_t length,
                                      int* monOut, int* mdayOut) {
   size_t i = *indexOut;
 
-  if (*monOut != -1) {
-    // If the month has already been set by ParseDate, we'll be at a '-', we
-    // can skip it and start parsing the mday
-    if (i >= length || s[i] != '-') {
-      return false;
-    }
-    ++i;
-  }
-
   size_t pre = i;
   size_t mday;
   if (!ParseDigitsNOrLess(6, &mday, s, &i, length)) {
@@ -1355,7 +1346,8 @@ constexpr size_t MinKeywordLength(const CharsAndAction (&keywords)[N]) {
 
 template <typename CharT>
 static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
-                      size_t length, ClippedTime* result) {
+                      size_t length, ClippedTime* result,
+                      bool* countLateWeekday) {
   if (length == 0) {
     return false;
   }
@@ -1369,7 +1361,7 @@ static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
   bool seenMonthName = false;
 
   // Before we begin, we need to scrub any words from the beginning of the
-  // string that are not a month name
+  // string up to the first number, recording the month if we encounter it
   for (; index < length; index++) {
     int c = s[index];
 
@@ -1403,11 +1395,6 @@ static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
         break;
       }
     }
-    if (seenMonthName) {
-      // If we've found the month name, we're done with this loop, otherwise we
-      // move on to the next word
-      break;
-    }
   }
 
   if (index >= length) {
@@ -1430,6 +1417,8 @@ static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
   bool negativeYear = false;
   // Includes "GMT", "UTC", "UT", and "Z" timezone keywords
   bool seenGmtAbbr = false;
+  // For telemetry purposes
+  bool seenLateWeekday = false;
 
   // Try parsing the leading dashed-date.
   //
@@ -1676,6 +1665,7 @@ static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
         // Completely ignore days of the week, and don't derive any semantics
         // from them.
         if (action == 0) {
+          seenLateWeekday = true;
           break;
         }
 
@@ -1845,16 +1835,38 @@ static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
     date += tzOffset * msPerMinute;
   }
 
+  // Setting this down here so that it only counts the telemetry in
+  // the case of a successful parse.
+  if (seenLateWeekday) {
+    *countLateWeekday = true;
+  }
+
   *result = TimeClip(date);
   return true;
 }
 
 static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, JSLinearString* s,
-                      ClippedTime* result) {
-  AutoCheckCannotGC nogc;
-  return s->hasLatin1Chars()
-             ? ParseDate(forceUTC, s->latin1Chars(nogc), s->length(), result)
-             : ParseDate(forceUTC, s->twoByteChars(nogc), s->length(), result);
+                      ClippedTime* result, JSContext* cx) {
+  bool countLateWeekday = false;
+  bool success;
+
+  {
+    AutoCheckCannotGC nogc;
+    success = s->hasLatin1Chars()
+                  ? ParseDate(forceUTC, s->latin1Chars(nogc), s->length(),
+                              result, &countLateWeekday)
+                  : ParseDate(forceUTC, s->twoByteChars(nogc), s->length(),
+                              result, &countLateWeekday);
+  }
+
+  // We are running telemetry to see if support for day of week after
+  // mday can be dropped. It is being done here to keep
+  // JSRuntime::setUseCounter out of AutoCheckCannotGC's scope.
+  if (countLateWeekday) {
+    cx->runtime()->setUseCounter(cx->global(), JSUseCounter::LATE_WEEKDAY);
+  }
+
+  return success;
 }
 
 static bool date_parse(JSContext* cx, unsigned argc, Value* vp) {
@@ -1876,7 +1888,7 @@ static bool date_parse(JSContext* cx, unsigned argc, Value* vp) {
   }
 
   ClippedTime result;
-  if (!ParseDate(ForceUTC(cx->realm()), linearStr, &result)) {
+  if (!ParseDate(ForceUTC(cx->realm()), linearStr, &result, cx)) {
     args.rval().setNaN();
     return true;
   }
@@ -3704,7 +3716,7 @@ static bool DateOneArgument(JSContext* cx, const CallArgs& args) {
         return false;
       }
 
-      if (!ParseDate(ForceUTC(cx->realm()), linearStr, &t)) {
+      if (!ParseDate(ForceUTC(cx->realm()), linearStr, &t, cx)) {
         t = ClippedTime::invalid();
       }
     } else {

js/xpconnect/src/XPCJSRuntime.cpp

@@ -2587,6 +2587,9 @@ static void SetUseCounterCallback(JSObject* obj, JSUseCounter counter) {
     case JSUseCounter::WASM:
       SetUseCounter(obj, eUseCounter_custom_JS_wasm);
       break;
+    case JSUseCounter::LATE_WEEKDAY:
+      SetUseCounter(obj, eUseCounter_custom_JS_late_weekday);
+      break;
     default:
       MOZ_ASSERT_UNREACHABLE("Unexpected JSUseCounter id");
   }

js/xpconnect/tests/browser/browser.toml

@@ -9,6 +9,8 @@ support-files = [
   "browser_promise_userInteractionHandling.html"
 ]
 
+["browser_date_telemetry.js"]
+
 ["browser_dead_object.js"]
 
 ["browser_exception_leak.js"]

js/xpconnect/tests/browser/browser_date_telemetry.js

@@ -0,0 +1,72 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+const HIST_ID = "USE_COUNTER2_JS_LATE_WEEKDAY_PAGE";
+
+const triggers = [
+  "Sep 26 Tues 1995",
+  "Sep 26 1995 Tues",
+  "Sep 26 1995 Tues 09:30",
+  "Sep 26 1995 09:Tues:30",
+  "Sep 26 1995 09:30 Tues GMT",
+  "Sep 26 1995 09:30 GMT Tues",
+
+  "26 Tues Sep 1995",
+  "26 Sep Tues 1995",
+  "26 Sep 1995 Tues",
+
+  "1995-09-26 Tues",
+
+  // Multiple occurences should only trigger 1 counter
+  "Sep 26 Tues 1995 Tues",
+];
+const nonTriggers = [
+  "Sep 26 1995",
+  "Tues Sep 26 1995",
+  "Sep Tues 26 1995",
+
+  // Invalid format shouldn't trigger the counter
+  "Sep 26 Tues 1995 foo",
+];
+
+function getCount() {
+  return Services.telemetry.getHistogramById(HIST_ID).snapshot().sum;
+}
+
+/**
+ * Opens and closes a browser tab with minimal JS code which parses
+ * the given Date format.
+ */
+async function parseFormat(format, call = "new Date") {
+  let newTab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    `data:text/html;charset=utf-8,<script>${call}("${format}")</script>`
+  );
+  BrowserTestUtils.removeTab(newTab);
+}
+
+add_task(async function test_date_telemetry() {
+  let sum = getCount();
+
+  // waitForCondition cannot be used to test if nothing has changed,
+  // so these tests aren't as reliable as the ones in the next loop.
+  // If you encounter an inexplicable failure in any of these tests,
+  // debug by adding a delay to the end of the parseFormat function.
+  for (const format of nonTriggers) {
+    await parseFormat(format);
+    const count = getCount();
+    is(count, sum, `${format} should not trigger telemetry`);
+    sum = count;
+  }
+
+  for (const [i, format] of triggers.entries()) {
+    // Alternate between Date constructor and Date.parse
+    await parseFormat(format, ["new Date", "Date.parse"][i % 2]);
+    await BrowserTestUtils.waitForCondition(() => getCount() > sum);
+    const count = getCount();
+    is(count, sum + 1, `${format} should trigger telemetry`);
+    sum = count;
+  }
+});