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.

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 {
@@ -51,6 +56,18 @@ 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 ||