Method processFilter

build.go:174–298

processFilterNode builds query for the XPath filter predicate.

(root *filterNode, flags flag, props *builderProp)

// processFilterNode builds query for the XPath filter predicate.
func (b *builder) processFilter(root *filterNode, flags flag, props *builderProp) (query, error) {
	first := (flags & flagsEnum.Filter) == 0

	qyInput, err := b.processNode(root.Input, (flags | flagsEnum.Filter), props)
	if err != nil {
		return nil, err
	}
	firstInput := b.firstInput

	var propsCond builderProp
	cond, err := b.processNode(root.Condition, flags, &propsCond)
	if err != nil {
		return nil, err
	}

	// Checking whether is number
	if canBeNumber(cond) || ((propsCond & (builderProps.HasPosition | builderProps.HasLast)) != 0) {
		propsCond |= builderProps.HasPosition
		flags |= flagsEnum.PosFilter
	}

	if root.Input.Type() != nodeFilter {
		*props &= ^builderProps.PosFilter
	}

	if (propsCond & builderProps.HasPosition) != 0 {
		*props |= builderProps.PosFilter
	}

	if (propsCond & builderProps.HasPosition) != builderProps.None {
		if (propsCond & builderProps.HasLast) != 0 {
			// https://github.com/antchfx/xpath/issues/76
			// https://github.com/antchfx/xpath/issues/78
			if qyFunc, ok := cond.(*functionQuery); ok {
				switch qyFunc.Input.(type) {
				case *filterQuery:
					cond = &lastFuncQuery{Input: qyFunc.Input}
				case *groupQuery:
					cond = &lastFuncQuery{Input: qyFunc.Input}
				}
			}
		}
	}

	merge := (qyInput.Properties() & queryProps.Merge) != 0
	if first && firstInput != nil {
		if merge && ((*props & builderProps.PosFilter) != 0) {
			var (
				rootQuery = &contextQuery{}
				parent    query
			)
			switch axisQuery := firstInput.(type) {
			case *ancestorQuery:
				if _, ok := axisQuery.Input.(*contextQuery); !ok {
					parent = axisQuery.Input
					axisQuery.Input = rootQuery
				}
			case *attributeQuery: