Function parseFunction

dql/parser.go:1735–2111

(it *lex.ItemIterator, gq *GraphQuery)

}

func parseFunction(it *lex.ItemIterator, gq *GraphQuery) (*Function, error) {
	function := &Function{}
	var expectArg, seenFuncArg, expectLang, isDollar bool
L:
	for it.Next() {
		item := it.Item()
		if item.Typ != itemName {
			return nil, item.Errorf("Expected a function but got %q", item.Val)

		}

		name := collectName(it, item.Val)
		function.Name = strings.ToLower(name)
		var similarToOptSeen map[string]struct{}
		if function.Name == similarToFn {
			similarToOptSeen = make(map[string]struct{})
		}
		if _, ok := tryParseItemType(it, itemLeftRound); !ok {
			return nil, it.Errorf("Expected ( after func name [%s]", function.Name)
		}

		attrItemsAgo := -1
		expectArg = true
		for it.Next() {
			itemInFunc := it.Item()
			if attrItemsAgo >= 0 {
				attrItemsAgo++
			}
			var val string
			switch itemInFunc.Typ {
			case itemRightRound:
				break L
			case itemComma:
				if expectArg {
					return nil, itemInFunc.Errorf("Invalid use of comma.")
				}
				if isDollar {
					return nil, itemInFunc.Errorf("Invalid use of comma after dollar.")
				}
				expectArg = true
				continue
			case itemLeftRound:
				// Function inside a function.
				if seenFuncArg {
					return nil, itemInFunc.Errorf("Multiple functions as arguments not allowed")
				}
				it.Prev()
				it.Prev()
				nestedFunc, err := parseFunction(it, gq)
				if err != nil {
					return nil, err
				}
				seenFuncArg = true
				switch nestedFunc.Name {
				case valueFunc:
					if len(nestedFunc.NeedsVar) > 1 {
						return nil, itemInFunc.Errorf("Multiple variables not allowed in a function")
					}