fix(GraphQL): Added error for case when multiple filter functions are…

… used in filter. (#7368)

we were having indeterministic behavior in the filter when we have multiple filter functions as below .

query {
  queryFoo(filter:{value:{eq:2 le:2}})
     {
      value
    }
  }

It was because we were selecting the first filter function from the list of functions whose order is not guaranteed.
Now we are returning an error for this.

(cherry picked from commit de2f4ab)

graphql/e2e/common/error_test.yaml

@@ -348,4 +348,18 @@
     { }
   errors:
     [ { "message": "Out of range value '2147483648', for type `Int`",
-        "locations": [ { "line": 2, "column": 53 } ] } ]
+        "locations": [ { "line": 2, "column": 53 } ] } ]
+
+- name: "Error when multiple filter functions are used"
+  gqlrequest: |
+    query {
+      queryBook(filter:{bookId: {eq:2 le:2}})
+         {
+          bookId
+        }
+      }
+  gqlvariables: |
+    { }
+  errors:
+    [ { "message": "Int64Filter filter expects only one filter function, got: 2",
+        "locations": [ { "line": 2, "column": 29 } ] } ]

graphql/schema/rules.go

@@ -47,6 +47,7 @@ func init() {
 	validator.AddRule("Check arguments of cascade directive", directiveArgumentsCheck)
 	validator.AddRule("Check range for Int type", intRangeCheck)
 	validator.AddRule("Input Coercion to List", listInputCoercion)
+	validator.AddRule("Check filter functions", filterCheck)
 
 }
 

graphql/schema/validation_rules.go

@@ -18,12 +18,17 @@ package schema
 
 import (
 	"errors"
+	"github.com/dgraph-io/dgraph/x"
 	"strconv"
 
 	"github.com/dgraph-io/gqlparser/v2/ast"
 	"github.com/dgraph-io/gqlparser/v2/validator"
 )
 
+var allowedFilters = []string{"StringHashFilter", "StringExactFilter", "StringFullTextFilter",
+	"StringRegExpFilter", "StringTermFilter", "DateTimeFilter", "FloatFilter", "Int64Filter", "IntFilter", "PointGeoFilter",
+	"ContainsFilter", "IntersectsFilter", "PolygonGeoFilter"}
+
 func listInputCoercion(observers *validator.Events, addError validator.AddErrFunc) {
 	observers.OnValue(func(walker *validator.Walker, value *ast.Value) {
 		if value.Definition == nil || value.ExpectedType == nil {
@@ -46,6 +51,18 @@ func listInputCoercion(observers *validator.Events, addError validator.AddErrFun
 	})
 }
 
+func filterCheck(observers *validator.Events, addError validator.AddErrFunc) {
+	observers.OnValue(func(walker *validator.Walker, value *ast.Value) {
+		if value.Definition == nil {
+			return
+		}
+
+		if x.HasString(allowedFilters, value.Definition.Name) && len(value.Children) > 1 {
+			addError(validator.Message("%s filter expects only one filter function, got: %d", value.Definition.Name, len(value.Children)), validator.At(value.Position))
+		}
+	})
+}
+
 func variableTypeCheck(observers *validator.Events, addError validator.AddErrFunc) {
 	observers.OnValue(func(walker *validator.Walker, value *ast.Value) {
 		if value.Definition == nil || value.ExpectedType == nil ||