fix race condition between inital fetch and immediate refetch

src/EventManager.js

@@ -38,8 +38,7 @@ function EventManager(options) { // assumed to be a calendar
 	var stickySource = { events: [] };
 	var sources = [ stickySource ];
 	var rangeStart, rangeEnd;
-	var currentFetchID = 0;
-	var pendingSourceCnt = 0; // for the current fetchID
+	var pendingSourceCnt = 0; // outstanding fetch requests, max one per source
 	var cache = []; // holds events that have already been expanded
 
 
@@ -69,53 +68,54 @@ function EventManager(options) { // assumed to be a calendar
 	function fetchEvents(start, end) {
 		rangeStart = start;
 		rangeEnd = end;
-		fetchEventSources(sources, true);
+		fetchEventSources(sources, 'reset');
 	}
 
 
 	// expects an array of event source objects (the originals, not copies)
-	function fetchEventSources(specificSources, shouldClearAll) {
-		var fetchID = ++currentFetchID;
-		var len = specificSources.length;
-		var i;
+	// `specialFetchType` is an optimization parameter that affects purging of the event cache.
+	function fetchEventSources(specificSources, specialFetchType) {
+		var i, source;
 
-		if (shouldClearAll) {
+		if (specialFetchType === 'reset') {
 			cache = [];
 		}
-		else {
+		else if (specialFetchType !== 'add') {
 			cache = excludeEventsBySources(cache, specificSources);
 		}
 
-		pendingSourceCnt = len;
-		for (i = 0; i < len; i++) {
-			fetchEventSource(specificSources[i], fetchID);
+		for (i = 0; i < specificSources.length; i++) {
+			source = specificSources[i];
+
+			// already-pending sources have already been accounted for in pendingSourceCnt
+			if (source._status !== 'pending') {
+				pendingSourceCnt++;
+			}
+
+			source._fetchId = (source._fetchId || 0) + 1;
+			source._status = 'pending';
 		}
-	}
 
+		for (i = 0; i < specificSources.length; i++) {
+			source = specificSources[i];
 
-	// returns a filtered array without events that are part of any of the given sources
-	function excludeEventsBySources(specificEvents, specificSources) {
-		return $.grep(specificEvents, function(event) {
-			for (var i = 0; i < specificSources.length; i++) {
-				if (event.source === specificSources[i]) {
-					return false; // exclude
-				}
-			}
-			return true; // keep
-		});
+			tryFetchEventSource(source, source._fetchId);
+		}
 	}
 
 
+	// fetches an event source and processes its result ONLY if it is still the current fetch.
 	// caller is responsible for incrementing pendingSourceCnt first.
-	// (done so that caller can increment in batch, preventing single
-	//  synchronous event source fetches from calling reportEvents immediately)
-	function fetchEventSource(source, fetchID) {
+	function tryFetchEventSource(source, fetchId) {
 		_fetchEventSource(source, function(eventInputs) {
 			var isArraySource = $.isArray(source.events);
 			var i, eventInput;
 			var abstractEvent;
 
-			if (fetchID == currentFetchID) {
+			// is this the source's most recent fetch?
+			if (fetchId === source._fetchId) {
+
+				source._status = 'resolved';
 
 				if (eventInputs) {
 					for (i = 0; i < eventInputs.length; i++) {
@@ -270,8 +270,7 @@ function EventManager(options) { // assumed to be a calendar
 		var source = buildEventSource(sourceInput);
 		if (source) {
 			sources.push(source);
-			pendingSourceCnt++;
-			fetchEventSource(source, currentFetchID); // will eventually call reportEvents
+			fetchEventSources([ source ], 'add'); // will eventually call reportEvents
 		}
 	}
 
@@ -346,6 +345,20 @@ function EventManager(options) { // assumed to be a calendar
 		) ||
 		source; // the given argument *is* the primitive
 	}
+
+
+	// util
+	// returns a filtered array without events that are part of any of the given sources
+	function excludeEventsBySources(specificEvents, specificSources) {
+		return $.grep(specificEvents, function(event) {
+			for (var i = 0; i < specificSources.length; i++) {
+				if (event.source === specificSources[i]) {
+					return false; // exclude
+				}
+			}
+			return true; // keep
+		});
+	}
 	
 	
 	

tests/automated/refetchEventSources.js

@@ -1,4 +1,4 @@
-ddescribe('refetchEventSources', function() {
+describe('refetchEventSources', function() {
 	var calendarEl;
 	var options;
 
@@ -101,10 +101,13 @@ ddescribe('refetchEventSources', function() {
 	});
 
 	describe('when called while initial fetch is still pending', function() {
-		it('rerenders the new events', function(done) {
+		it('keeps old events and rerenders new', function(done) {
 
 			options.eventAfterAllRender = function() {
 
+				// events from unaffected sources remain
+				expect($('.source2-7').length).toEqual(1);
+
 				// events from old fetch were cleared
 				expect($('.source1-7').length).toEqual(0);
 				expect($('.source3-7').length).toEqual(0);
@@ -132,34 +135,6 @@ ddescribe('refetchEventSources', function() {
 		});
 	});
 
-	describe('when called while initial fetch is still pending', function() {
-		// TODO: once this is fixed, merge with above test
-		xit('maintains old events', function(done) {
-
-			options.eventAfterAllRender = function() {
-
-				// events from unaffected sources remain
-				expect($('.source2-7').length).toEqual(1);
-
-				done();
-			};
-
-			fetchDelay = 100;
-			calendarEl.fullCalendar(options);
-
-			var allEventSources = calendarEl.fullCalendar('getEventSources');
-			var greenEventSources = $.grep(allEventSources, function(eventSource) {
-				return eventSource.color === 'green';
-			});
-
-			// increase the number of events for the refetched sources
-			eventCount = 2;
-			fetchId = 8;
-
-			calendarEl.fullCalendar('refetchEventSources', greenEventSources);
-		});
-	});
-
 	function createEventGenerator(classNamePrefix) {
 		return function(start, end, timezone, callback) {
 			var events = [];