From 82999154a11b518001002d07c8bc71daa1fcf091 Mon Sep 17 00:00:00 2001
From: Martin Martinez Rivera <martinmr@users.noreply.github.com>
Date: Mon, 14 Oct 2019 10:33:37 -0700
Subject: [PATCH] Cherry pick PR #3205 into release/v1.0 branch. (#4143)

This fixes #3807.
---
 query/common_test.go |  4 +++
 query/query.go       | 35 +++++++++---------
 query/query3_test.go | 85 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 107 insertions(+), 17 deletions(-)

diff --git a/query/common_test.go b/query/common_test.go
index 0c6bf933821..11abda6c940 100644
--- a/query/common_test.go
+++ b/query/common_test.go
@@ -329,6 +329,7 @@ symbol                         : string @index(exact) .
 room                           : string @index(term) .
 office.room                    : uid .
 number                         : int @index(int) .
+node                           : uid .
 `
 
 	err := schema.ParseBytes([]byte(schemaStr), 1)
@@ -673,4 +674,7 @@ number                         : int @index(int) .
 	addEdgeToUID(t, "office.room", 4001, 4002, nil)
 	addEdgeToUID(t, "office.room", 4001, 4003, nil)
 	addEdgeToUID(t, "office.room", 4001, 4004, nil)
+
+	addEdgeToValue(t, "name", 11100, "expand", nil)
+	addEdgeToUID(t, "node", 11100, 11100, nil)
 }
diff --git a/query/query.go b/query/query.go
index c93c4cc3f64..a45c38d4c1c 100644
--- a/query/query.go
+++ b/query/query.go
@@ -1969,23 +1969,6 @@ func ProcessGraph(ctx context.Context, sg, parent *SubGraph, rch chan error) {
 		}
 	}
 
-	if sg.DestUIDs == nil || len(sg.DestUIDs.Uids) == 0 {
-		// Looks like we're done here. Be careful with nil srcUIDs!
-		if span != nil {
-			span.Annotatef(nil, "Zero uids for %q", sg.Attr)
-		}
-		out := sg.Children[:0]
-		for _, child := range sg.Children {
-			if child.IsInternal() && child.Attr == "expand" {
-				continue
-			}
-			out = append(out, child)
-		}
-		sg.Children = out // Remove any expand nodes we might have added.
-		rch <- nil
-		return
-	}
-
 	// Run filters if any.
 	if len(sg.Filters) > 0 {
 		// Run all filters in parallel.
@@ -2135,6 +2118,24 @@ func ProcessGraph(ctx context.Context, sg, parent *SubGraph, rch chan error) {
 			childErr = err
 		}
 	}
+
+	if sg.DestUIDs == nil || len(sg.DestUIDs.Uids) == 0 {
+		// Looks like we're done here. Be careful with nil srcUIDs!
+		if span != nil {
+			span.Annotatef(nil, "Zero uids for %q", sg.Attr)
+		}
+		out := sg.Children[:0]
+		for _, child := range sg.Children {
+			if child.IsInternal() && child.Attr == "expand" {
+				continue
+			}
+			out = append(out, child)
+		}
+		sg.Children = out // Remove any expand nodes we might have added.
+		rch <- nil
+		return
+	}
+
 	rch <- childErr
 }
 
diff --git a/query/query3_test.go b/query/query3_test.go
index 53625a1b4bf..251782b968d 100644
--- a/query/query3_test.go
+++ b/query/query3_test.go
@@ -1778,3 +1778,88 @@ func TestFilterRegex16(t *testing.T) {
 		`{"data": {"me":[{"name@ru":"Артём Ткаченко"}]}}`,
 		js)
 }
+
+func TestNestedExpandAll(t *testing.T) {
+	query := `{
+		q(func: has(node)) {
+			uid
+			expand(_all_) {
+				uid
+				node {
+					uid
+					expand(_all_)
+				}
+			}
+		}
+	}`
+	js := processToFastJsonNoErr(t, query)
+	require.JSONEq(t, `{"data": {
+    "q": [
+      {
+        "uid": "0x2b5c",
+        "name": "expand",
+        "node": [
+          {
+            "uid": "0x2b5c",
+            "node": [
+              {
+                "uid": "0x2b5c",
+                "name": "expand"
+              }
+            ]
+          }
+        ]
+      }
+    ]}}`, js)
+}
+
+func TestNoResultsFilter(t *testing.T) {
+	query := `{
+		q(func: has(nonexistent_pred)) @filter(le(name, "abc")) {
+			uid
+		}
+	}`
+	js := processToFastJsonNoErr(t, query)
+	require.JSONEq(t, `{"data": {"q": []}}`, js)
+}
+
+func TestNoResultsPagination(t *testing.T) {
+	query := `{
+		q(func: has(nonexistent_pred), first: 50) {
+			uid
+		}
+	}`
+	js := processToFastJsonNoErr(t, query)
+	require.JSONEq(t, `{"data": {"q": []}}`, js)
+}
+
+func TestNoResultsGroupBy(t *testing.T) {
+	query := `{
+		q(func: has(nonexistent_pred)) @groupby(name) {
+			count(uid)
+		}
+	}`
+	js := processToFastJsonNoErr(t, query)
+	require.JSONEq(t, `{"data": {}}`, js)
+}
+
+func TestNoResultsOrder(t *testing.T) {
+	query := `{
+		q(func: has(nonexistent_pred), orderasc: name) {
+			uid
+		}
+	}`
+	js := processToFastJsonNoErr(t, query)
+	require.JSONEq(t, `{"data": {"q": []}}`, js)
+}
+
+func TestNoResultsCount(t *testing.T) {
+	query := `{
+		q(func: has(nonexistent_pred)) {
+			uid
+			count(friend)
+		}
+	}`
+	js := processToFastJsonNoErr(t, query)
+	require.JSONEq(t, `{"data": {"q": []}}`, js)
+}