Breaking change: Remove expand(_forward_) and expand(_reverse_). (#4119)

gql/parser.go

@@ -2804,9 +2804,9 @@ func godeep(it *lex.ItemIterator, gq *GraphQuery) error {
 				case "_all_":
 					child.Expand = "_all_"
 				case "_forward_":
-					child.Expand = "_forward_"
+					return item.Errorf("Argument _forward_ has been deprecated")
 				case "_reverse_":
-					child.Expand = "_reverse_"
+					return item.Errorf("Argument _reverse_ has been deprecated")
 				default:
 					return item.Errorf("Invalid argument %v in expand()", item.Val)
 				}

gql/parser_test.go

@@ -171,7 +171,8 @@ func TestParseQueryExpandForward(t *testing.T) {
 	}
 `
 	_, err := Parse(Request{Str: query})
-	require.NoError(t, err)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "Argument _forward_ has been deprecated")
 }
 
 func TestParseQueryExpandReverse(t *testing.T) {
@@ -185,7 +186,8 @@ func TestParseQueryExpandReverse(t *testing.T) {
 	}
 `
 	_, err := Parse(Request{Str: query})
-	require.NoError(t, err)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "Argument _reverse_ has been deprecated")
 }
 
 func TestParseQueryAliasListPred(t *testing.T) {

query/query.go

@@ -1820,7 +1820,7 @@ func expandSubgraph(ctx context.Context, sg *SubGraph) ([]*SubGraph, error) {
 		}
 
 		switch child.Params.Expand {
-		// It could be expand(_all_), expand(_forward_), expand(_reverse_) or expand(val(x)).
+		// It could be expand(_all_) or expand(val(x)).
 		case "_all_":
 			span.Annotate(nil, "expand(_all_)")
 			if len(types) == 0 {
@@ -1833,25 +1833,6 @@ func expandSubgraph(ctx context.Context, sg *SubGraph) ([]*SubGraph, error) {
 				return out, err
 			}
 			preds = append(preds, rpreds...)
-		case "_forward_":
-			span.Annotate(nil, "expand(_forward_)")
-			if len(types) == 0 {
-				break
-			}
-
-			preds = getPredicatesFromTypes(types)
-		case "_reverse_":
-			span.Annotate(nil, "expand(_reverse_)")
-			if len(types) == 0 {
-				break
-			}
-
-			typePreds := getPredicatesFromTypes(types)
-			rpreds, err := getReversePredicates(ctx, typePreds)
-			if err != nil {
-				return out, err
-			}
-			preds = append(preds, rpreds...)
 		default:
 			span.Annotate(nil, "expand default")
 			// We already have the predicates populated from the var.

query/query4_test.go

@@ -296,35 +296,6 @@ func TestTypeExpandAll(t *testing.T) {
 	]}}`, js)
 }
 
-func TestTypeExpandForward(t *testing.T) {
-	query := `{
-		q(func: eq(make, "Ford")) {
-			expand(_forward_) {
-				uid
-			}
-		}
-	}`
-	js := processQueryNoErr(t, query)
-	require.JSONEq(t, `{"data": {"q":[
-		{"make":"Ford","model":"Focus","year":2008},
-		{"make":"Ford","model":"Focus","year":2009, "previous_model": {"uid":"0xc8"}}
-	]}}`, js)
-}
-
-func TestTypeExpandReverse(t *testing.T) {
-	query := `{
-		q(func: eq(make, "Ford")) {
-			expand(_reverse_) {
-				uid
-			}
-		}
-	}`
-	js := processQueryNoErr(t, query)
-	require.JSONEq(t, `{"data": {"q":[
-		{"~previous_model": [{"uid":"0xc9"}]}
-	]}}`, js)
-}
-
 func TestTypeExpandLang(t *testing.T) {
 	query := `{
 		q(func: eq(make, "Toyota")) {

wiki/content/query-language/index.md

@@ -1797,18 +1797,12 @@ There are four ways to use the `expand` function.
 
 * Predicates can be stored in a variable and passed to `expand()` to expand all
   the predicates in the variable.
-* If `_all_` is passed as an argument to `expand()`, all the predicates for each
-  node at that level are retrieved. More levels can be specified in a nested
-  fashion under `expand()`.
-* If `_forward_` is passed as an argument to `expand()`, all predicates for each
-  node at that level (minus any reverse predicates) are retrieved.
-* If `_reverse_` is passed as an argument to `expand()`, only the reverse
-  predicates at each node in that level are retrieved.
-
-The last three keywords require that the nodes have types. Dgraph will look 
-for all the types that have been assigned to a node,
-query the types to check which attributes they have, and use those to compute
-the list of predicates to expand.
+* If `_all_` is passed as an argument to `expand()`, the predicates to be
+expanded will be the union of fields in the types assigned to a given node.
+
+The `_all_` keyword requires that the nodes have types. Dgraph will look for all
+the types that have been assigned to a node, query the types to check which
+attributes they have, and use those to compute the list of predicates to expand.
 
 For example, consider a node that has types `Animal` and `Pet`, which have 
 the following definitions:
@@ -2533,8 +2527,7 @@ err := c.Alter(context.Background(), &api.Operation{
 ### Expand queries and types
 
 Queries using [expand]({{< relref "#expand-predicates" >}}) (i.e.:
-`expand(_all_)`, `expand(_reverse_)`, or `expand(_forward_)`) require that the
-nodes to expand have types.
+`expand(_all_)`) require that the nodes to be expanded have types.
 
 ## Facets : Edge attributes