fix(search): return results even if doc is empty (#3457)

* fix(search): return results even if doc is empty

"If a relevant key expires while a query is running, an attempt to load
the key's value will return a null array. However, the key is still
counted in the total number of results." - Redis Search return
documentation

* fix(doctest): fix assertions in doctests

Author: ndyakov

doctests/geo_index_test.go

@@ -199,11 +199,11 @@ func ExampleClient_geoindex() {
 	// OK
 	// OK
 	// OK
-	// {1 [{product:46885 <nil> <nil> <nil> map[$:{"city":"Denver","description":"Navy Blue Slippers","location":"-104.991531, 39.742043","price":45.99}]}]}
+	// {1 [{product:46885 <nil> <nil> <nil> map[$:{"city":"Denver","description":"Navy Blue Slippers","location":"-104.991531, 39.742043","price":45.99}] <nil>}]}
 	// OK
 	// OK
 	// OK
 	// OK
 	// OK
-	// {1 [{shape:4 <nil> <nil> <nil> map[$:[{"geom":"POINT (2 2)","name":"Purple Point"}]]}]}
+	// {1 [{shape:4 <nil> <nil> <nil> map[$:[{"geom":"POINT (2 2)","name":"Purple Point"}]] <nil>}]}
 }

doctests/home_json_example_test.go

@@ -219,7 +219,7 @@ func ExampleClient_search_json() {
 	// STEP_END
 
 	// Output:
-	// {1 [{user:3 <nil> <nil> <nil> map[$:{"age":35,"city":"Tel Aviv","email":"[email protected]","name":"Paul Zamir"}]}]}
+	// {1 [{user:3 <nil> <nil> <nil> map[$:{"age":35,"city":"Tel Aviv","email":"[email protected]","name":"Paul Zamir"}] <nil>}]}
 	// London
 	// Tel Aviv
 	// 0
@@ -329,5 +329,5 @@ func ExampleClient_search_hash() {
 	// STEP_END
 
 	// Output:
-	// {1 [{huser:3 <nil> <nil> <nil> map[age:35 city:Tel Aviv email:[email protected] name:Paul Zamir]}]}
+	// {1 [{huser:3 <nil> <nil> <nil> map[age:35 city:Tel Aviv email:[email protected] name:Paul Zamir] <nil>}]}
 }

doctests/search_quickstart_test.go

@@ -257,6 +257,6 @@ func ExampleClient_search_qs() {
 
 	// Output:
 	// Documents found: 10
-	// {1 [{bicycle:0 <nil> <nil> <nil> map[$:{"brand":"Velorim","condition":"new","description":"Small and powerful, the Jigger is the best ride for the smallest of tikes! This is the tiniest kids’ pedal bike on the market available without a coaster brake, the Jigger is the vehicle of choice for the rare tenacious little rider raring to go.","model":"Jigger","price":270}]}]}
-	// {1 [{bicycle:4 <nil> <nil> <nil> map[$:{"brand":"Noka Bikes","condition":"used","description":"Whether you want to try your hand at XC racing or are looking for a lively trail bike that's just as inspiring on the climbs as it is over rougher ground, the Wilder is one heck of a bike built specifically for short women. Both the frames and components have been tweaked to include a women’s saddle, different bars and unique colourway.","model":"Kahuna","price":3200}]}]}
+	// {1 [{bicycle:0 <nil> <nil> <nil> map[$:{"brand":"Velorim","condition":"new","description":"Small and powerful, the Jigger is the best ride for the smallest of tikes! This is the tiniest kids’ pedal bike on the market available without a coaster brake, the Jigger is the vehicle of choice for the rare tenacious little rider raring to go.","model":"Jigger","price":270}] <nil>}]}
+	// {1 [{bicycle:4 <nil> <nil> <nil> map[$:{"brand":"Noka Bikes","condition":"used","description":"Whether you want to try your hand at XC racing or are looking for a lively trail bike that's just as inspiring on the climbs as it is over rougher ground, the Wilder is one heck of a bike built specifically for short women. Both the frames and components have been tweaked to include a women’s saddle, different bars and unique colourway.","model":"Kahuna","price":3200}] <nil>}]}
 }

search_commands.go

@@ -474,6 +474,7 @@ type Document struct {
 	Payload *string
 	SortKey *string
 	Fields  map[string]string
+	Error   error
 }
 
 type AggregateQuery []interface{}
@@ -1654,7 +1655,13 @@ func parseFTSearch(data []interface{}, noContent, withScores, withPayloads, with
 		if i < len(data) {
 			fields, ok := data[i].([]interface{})
 			if !ok {
-				return FTSearchResult{}, fmt.Errorf("invalid document fields format")
+				if data[i] == proto.Nil || data[i] == nil {
+					doc.Error = proto.Nil
+					doc.Fields = map[string]string{}
+					fields = []interface{}{}
+				} else {
+					return FTSearchResult{}, fmt.Errorf("invalid document fields format")
+				}
 			}
 
 			for j := 0; j < len(fields); j += 2 {