[query] return 0 if there was at least one valid number

src/query/api/v1/handler/prometheus/native/common.go

@@ -442,9 +442,22 @@
 		jw.EndObject()
 
 		jw.BeginObjectField("value")
+
+		onlynans := true
+		for a := 0; a < length; a++ {
+			if !math.IsNaN(vals.ValueAt(a)) {
+				onlynans = false
+				break
+			}
+		}
+
 		jw.BeginArray()
 		jw.WriteInt(int(dp.Timestamp.Unix()))
-		jw.WriteString(utils.FormatFloat(dp.Value))
+		if math.IsNaN(dp.Value) && !onlynans {
+			jw.WriteString("0")
+		} else {
+			jw.WriteString(utils.FormatFloat(dp.Value))
+		}
 		jw.EndArray()
 		jw.EndObject()
 	}

src/query/test/testdata/functions.test

@@ -5,11 +5,10 @@ load 5m
 	http_requests{path="/biz"}	0 0 0 0 0 1 1 1 1 1
 
 # Tests for resets().
-# FAILING issue #16
-#eval instant at 50m resets(http_requests[5m])
-#	{path="/foo"} 0
-#	{path="/bar"} 0
-#	{path="/biz"} 0
+eval instant at 50m resets(http_requests[5m])
+	{path="/foo"} 0
+	{path="/bar"} 0
+	{path="/biz"} 0
 
 eval instant at 50m resets(http_requests[20m])
 	{path="/foo"} 1
@@ -29,11 +28,10 @@ eval instant at 50m resets(http_requests[50m])
 # FAILING. eval instant at 50m resets(nonexistent_metric[50m])
 
 # Tests for changes().
-# FAILING issue #17
-#eval instant at 50m changes(http_requests[5m])
-#	{path="/foo"} 0
-#	{path="/bar"} 0
-#	{path="/biz"} 0
+eval instant at 50m changes(http_requests[5m])
+	{path="/foo"} 0
+	{path="/bar"} 0
+	{path="/biz"} 0
 
 eval instant at 50m changes(http_requests[20m])
 	{path="/foo"} 3
@@ -45,10 +43,10 @@ eval instant at 50m changes(http_requests[30m])
 	{path="/bar"} 5
 	{path="/biz"} 1
 
-#eval instant at 50m changes(http_requests[50m])
-#	{path="/foo"} 8
-#	{path="/bar"} 9
-#	{path="/biz"} 1
+eval instant at 50m changes(http_requests[50m])
+	{path="/foo"} 8
+	{path="/bar"} 9
+	{path="/biz"} 1
 
 #eval instant at 50m changes((http_requests[50m]))
 #	{path="/foo"} 8
@@ -642,3 +640,4 @@ load 1m
 
 # FAILING. eval instant at 10m absent_over_time({job="ingress"}[4m])
 # FAILING. 	{job="ingress"} 1
+