Match zero-length match at end of string, even if the start node is an assertion (end of string, lookarounds, etc.)

matching.go

@@ -34,10 +34,10 @@ func takeZeroState(states []*State) (rtv []*State, isZero bool) {
 }
 
 // zeroMatchPossible returns true if a zero-length match is possible
-// from any of the given states.
+// from any of the given states, given the string and our position in it.
 // It uses the same algorithm to find zero-states as the one inside the loop,
 // so I should probably put it in a function.
-func zeroMatchPossible(states ...*State) bool {
+func zeroMatchPossible(str []rune, idx int, states ...*State) bool {
 	zerostates, iszero := takeZeroState(states)
 	tempstates := make([]*State, 0, len(zerostates)+len(states))
 	tempstates = append(tempstates, states...)
@@ -51,7 +51,7 @@ func zeroMatchPossible(states ...*State) bool {
 		}
 	}
 	for _, state := range tempstates {
-		if state.isEmpty && state.assert == NONE && state.isLast {
+		if state.isEmpty && (state.assert == NONE || state.checkAssertion(str, idx)) && state.isLast {
 			return true
 		}
 	}
@@ -117,8 +117,8 @@ func findAllMatchesHelper(start *State, str []rune, offset int) (bool, MatchInde
 	if offset == len(str) {
 		// Get all zero-state matches. If we can get to a zero-state without matching anything, we
 		// can add a zero-length match. This is all true only if the start state itself matches nothing.
-		if start.isEmpty && start.assert == NONE {
-			if zeroMatchPossible(start) {
+		if start.isEmpty {
+			if zeroMatchPossible(str, offset, start) {
 				return true, MatchIndex{offset, offset}, offset + 1
 			}
 		}
@@ -196,7 +196,7 @@ func findAllMatchesHelper(start *State, str []rune, offset int) (bool, MatchInde
 		}
 		// Check if we can find a zero-length match
 		if foundPath == false {
-			if zeroMatchPossible(currentStates...) {
+			if zeroMatchPossible(str, i, currentStates...) {
 				tempIndices, _ = unique_append(tempIndices, MatchIndex{startIdx, startIdx})
 			}
 			// If we haven't moved in the string, increment the counter by 1