Function customDirectiveValidation

graphql/schema/rules.go:1663–2327

(sch *ast.Schema,
	typ *ast.Definition,
	field *ast.FieldDefinition,
	dir *ast.Directive,
	secrets map[string]x.Sensitive)

}

func customDirectiveValidation(sch *ast.Schema,
	typ *ast.Definition,
	field *ast.FieldDefinition,
	dir *ast.Directive,
	secrets map[string]x.Sensitive) gqlerror.List {
	var errs []*gqlerror.Error

	// 1. Validating custom directive itself
	search := field.Directives.ForName(searchDirective)
	if search != nil {
		errs = append(errs, gqlerror.ErrorPosf(
			dir.Position,
			"Type %s; Field %s; custom directive not allowed along with @search directive.",
			typ.Name, field.Name))
	}

	dgraph := field.Directives.ForName(dgraphDirective)
	if dgraph != nil {
		errs = append(errs, gqlerror.ErrorPosf(
			dir.Position,
			"Type %s; Field %s; custom directive not allowed along with @dgraph directive.",
			typ.Name, field.Name))
	}

	defn := sch.Types[typ.Name]
	id := getIDField(defn, nil)
	xid := getXIDField(defn, nil)
	if !isQueryOrMutationType(typ) {
		if len(id) == 0 && len(xid) == 0 {
			errs = append(errs, gqlerror.ErrorPosf(
				dir.Position,
				"Type %s; Field %s; @custom directive is only allowed on fields where the type"+
					" definition has a field with type ID! or a field with @id directive.",
				typ.Name, field.Name))
		}
	}

	// 2. Validating arguments to custom directive
	l := len(dir.Arguments)
	if l == 0 || l > 1 {
		errs = append(errs, gqlerror.ErrorPosf(
			dir.Position,
			"Type %s; Field %s: has %d arguments for @custom directive, "+
				"it should contain exactly one of `http` or `dql` arguments.",
			typ.Name, field.Name, l))
	}

	httpArg := dir.Arguments.ForName(httpArg)
	dqlArg := dir.Arguments.ForName(dqlArg)

	if httpArg == nil && dqlArg == nil {
		errs = append(errs, gqlerror.ErrorPosf(
			dir.Position,
			"Type %s; Field %s: one of `http` or `dql` arguments must be present for @custom"+
				" directive.",
			typ.Name, field.Name))
		return errs
	}