fix (graphql): disallowing field names with as (#6645)

This is related to GRAPHQL-564. as is Dgraph reserved keyword. It's being used by DQL to identify variables. This PR is to restrict the naming for fields with the name as.

graphql/schema/gqlschema_test.yml

@@ -2398,6 +2398,47 @@ invalid_schemas:
     {"message": "Subscription is a reserved word, so you can't declare a type with this name. Pick a different name for the type.", "locations": [{"line":1, "column":6}]},
     ]
 
+  -
+    name: "as is reserved keyword - type Name"
+    input: |
+      type As {
+        id: ID!
+        name: String
+      }
+    errlist: [
+      { "message": "As is a reserved word, so you can't declare a type with this name. Pick a different name for the type.", "locations": [ { "line": 1, "column": 6 } ] },
+    ]
+
+  - name: "as is reserved keyword - field name"
+    input: |
+      type X {
+        as: ID!
+        name: String
+      }
+    errlist: [
+      { "message": "Type X; Field as: as is a reserved keyword and you cannot declare a field with this name.", "locations": [ { "line": 2, "column": 3 } ] },
+    ]
+
+  - name: "as is reserved keyword - type name using @dgraph directive"
+    input: |
+      type X @dgraph(type:"as") {
+        id: ID!
+        name: String
+      }
+    errlist: [
+      { "message": "Type X; type argument 'as' for @dgraph directive is a reserved keyword.", "locations": [ { "line": 1, "column": 9 } ] },
+    ]
+
+  - name: "as is reserved keyword - field name using @dgraph directive"
+    input: |
+      type X {
+        id: ID!
+        name: String @dgraph(pred:"as")
+      }
+    errlist: [
+      { "message": "Type X; Field name: pred argument 'as' for @dgraph directive is a reserved keyword.", "locations": [ { "line": 3, "column": 17 } ] },
+    ]
+
 
 valid_schemas:
   - name: "@auth on interface implementation"

graphql/schema/rules.go

@@ -547,11 +547,19 @@ func dgraphDirectiveTypeValidation(schema *ast.Schema, typ *ast.Definition) gqle
 			dir.Position,
 			"Type %s; type argument for @dgraph directive should not be empty.", typ.Name)}
 	}
+
 	if typeArg.Value.Kind != ast.StringValue {
 		return []*gqlerror.Error{gqlerror.ErrorPosf(
 			dir.Position,
 			"Type %s; type argument for @dgraph directive should of type String.", typ.Name)}
 	}
+
+	if isReservedKeyWord(typeArg.Value.Raw) {
+		return []*gqlerror.Error{gqlerror.ErrorPosf(
+			dir.Position,
+			"Type %s; type argument '%s' for @dgraph directive is a reserved keyword.", typ.Name, typeArg.Value.Raw)}
+	}
+
 	return nil
 }
 
@@ -1048,13 +1056,23 @@ func dgraphDirectiveValidation(sch *ast.Schema, typ *ast.Definition, field *ast.
 			typ.Name, field.Name))
 		return errs
 	}
+
 	if predArg.Value.Kind != ast.StringValue {
 		errs = append(errs, gqlerror.ErrorPosf(
 			dir.Position,
 			"Type %s; Field %s: pred argument for @dgraph directive should of type String.",
 			typ.Name, field.Name))
 		return errs
 	}
+
+	if isReservedKeyWord(predArg.Value.Raw) {
+		errs = append(errs, gqlerror.ErrorPosf(
+			dir.Position,
+			"Type %s; Field %s: pred argument '%s' for @dgraph directive is a reserved keyword.",
+			typ.Name, field.Name, predArg.Value.Raw))
+		return errs
+	}
+
 	if strings.HasPrefix(predArg.Value.Raw, "~") || strings.HasPrefix(predArg.Value.Raw, "<~") {
 		if sch.Types[typ.Name].Kind == ast.Interface {
 			// We don't want to consider the field of an interface but only the fields with
@@ -1808,7 +1826,11 @@ func isReservedKeyWord(name string) bool {
 		"Subscription": true,
 	}
 
-	if isScalar(name) || isQueryOrMutation(name) || reservedTypeNames[name] {
+	caseInsensitiveKeywords := map[string]bool{
+		"as": true, // this is reserved keyword because DQL uses this for variables
+	}
+
+	if isScalar(name) || isQueryOrMutation(name) || reservedTypeNames[name] || caseInsensitiveKeywords[strings.ToLower(name)] {
 		return true
 	}
 

wiki/content/graphql/schema/reserved.md

@@ -4,7 +4,18 @@ title = "Reserved Names"
     parent = "schema"
     weight = 1   
 +++
+The following names are reserved and can't be used to define any other identifiers:
 
-Names `Int`, `Float`, `Boolean`, `String`, `DateTime` and `ID` are reserved and cannot be used to define any other identifiers.
+- `Int`
+- `Float`
+- `Boolean`
+- `String`
+- `DateTime`
+- `ID`
+- `uid`
+- `Subscription`
+- `as` (case-insensitive)
+- `Query`
+- `Mutation`
 
 For each type, Dgraph generates a number of GraphQL types needed to operate the GraphQL API, these generated type names also can't be present in the input schema.  For example, for a type `Author`, Dgraph generates `AuthorFilter`, `AuthorOrderable`, `AuthorOrder`, `AuthorRef`, `AddAuthorInput`, `UpdateAuthorInput`, `AuthorPatch`, `AddAuthorPayload`, `DeleteAuthorPayload` and `UpdateAuthorPayload`.  Thus if `Author` is present in the input schema, all of those become reserved type names.