Warn when timers longer than 1 min are set pending AlarmManager support

Summary:
These are bad since the app might not be foregrounded anymore and it also keeps the timing module awake. We could fix the latter but the former would require someone adding AlarmManager support.

Open to better/more helpful ideas for the warning message but there's not a ton we can tell them to do right now.

Reviewed By: achen1

Differential Revision: D4716273

fbshipit-source-id: c5d3a3ce8af53253b240477f2bde38094a138a02

Libraries/Core/Timers/JSTimers.js

@@ -15,6 +15,7 @@
 // in dependencies. NativeModules > BatchedBridge > MessageQueue > JSTimersExecution
 const RCTTiming = require('NativeModules').Timing;
 const JSTimersExecution = require('JSTimersExecution');
+const Platform = require('Platform');
 
 const parseErrorStack = require('parseErrorStack');
 
@@ -64,6 +65,14 @@ function _freeCallback(timerID: number) {
   }
 }
 
+const MAX_TIMER_DURATION_MS = 60 * 1000;
+const IS_ANDROID = Platform.OS === 'android';
+const ANDROID_LONG_TIMER_MESSAGE = 
+  'Setting a timer for a long period of time, i.e. multiple minutes, is a ' +
+  'performance and correctness issue on Android as it keeps the timer ' +
+  'module awake, and timers can only be called when the app is in the foreground. ' +
+  'See https://github.com/facebook/react-native/issues/12981 for more info.';
+
 /**
  * JS implementation of timer functions. Must be completely driven by an
  * external clock signal, all that's stored here is timerID, timer type, and
@@ -75,6 +84,11 @@ const JSTimers = {
    * @param {number} duration Number of milliseconds.
    */
   setTimeout: function(func: Function, duration: number, ...args?: any): number {
+    if (IS_ANDROID && duration > MAX_TIMER_DURATION_MS) {
+      console.warn(
+          ANDROID_LONG_TIMER_MESSAGE + '\n' + '(Saw setTimeout with duration ' +
+          duration + 'ms)');
+    }
     const id = _allocateCallback(() => func.apply(undefined, args), 'setTimeout');
     RCTTiming.createTimer(id, duration || 0, Date.now(), /* recurring */ false);
     return id;
@@ -85,6 +99,11 @@ const JSTimers = {
    * @param {number} duration Number of milliseconds.
    */
   setInterval: function(func: Function, duration: number, ...args?: any): number {
+    if (IS_ANDROID && duration > MAX_TIMER_DURATION_MS) {
+      console.warn(
+          ANDROID_LONG_TIMER_MESSAGE + '\n' + '(Saw setInterval with duration ' +
+          duration + 'ms)');
+    }
     const id = _allocateCallback(() => func.apply(undefined, args), 'setInterval');
     RCTTiming.createTimer(id, duration || 0, Date.now(), /* recurring */ true);
     return id;