JS: fix RegExp::getSuccessor/getPredecessor for sequence end/starts

Author: esbena

javascript/ql/src/semmle/javascript/Regexp.qll

@@ -75,26 +75,41 @@ class RegExpTerm extends Locatable, @regexpterm {
 
   /** Gets the regular expression term that is matched (textually) before this one, if any. */
   RegExpTerm getPredecessor() {
-    exists(RegExpSequence seq, int i |
-      seq.getChild(i) = this and
-      seq.getChild(i - 1) = result
+    exists(RegExpTerm parent | parent = getParent() |
+      if parent instanceof RegExpSequence
+      then
+        exists(RegExpSequence seq, int i |
+          seq = parent and
+          seq.getChild(i) = this
+        |
+          seq.getChild(i - 1) = result
+          or
+          i = 0 and result = seq.getPredecessor()
+        )
+      else (
+        not parent instanceof RegExpSubPattern and
+        result = parent.getPredecessor()
+      )
     )
-    or
-    result = getParent().(RegExpTerm).getPredecessor()
   }
 
   /** Gets the regular expression term that is matched (textually) after this one, if any. */
   RegExpTerm getSuccessor() {
-    exists(RegExpSequence seq, int i |
-      seq.getChild(i) = this and
-      seq.getChild(i + 1) = result
-    )
-    or
-    exists(RegExpTerm parent |
-      parent = getParent() and
-      not parent instanceof RegExpSubPattern
-    |
-      result = parent.getSuccessor()
+    exists(RegExpTerm parent | parent = getParent() |
+      if parent instanceof RegExpSequence
+      then
+        exists(RegExpSequence seq, int i |
+          seq = parent and
+          seq.getChild(i) = this
+        |
+          seq.getChild(i + 1) = result
+          or
+          i = seq.getNumChild() - 1 and result = seq.getSuccessor()
+        )
+      else (
+        not parent instanceof RegExpSubPattern and
+        result = parent.getSuccessor()
+      )
     )
   }
 

javascript/ql/test/library-tests/RegExp/predecessors_and_successors/getPredecessor.expected

@@ -7,8 +7,6 @@
 | tst.js:5:2:5:2 | a | tst.js:5:3:5:8 | (b[c]) |
 | tst.js:5:2:5:2 | a | tst.js:5:4:5:4 | b |
 | tst.js:5:2:5:2 | a | tst.js:5:4:5:7 | b[c] |
-| tst.js:5:2:5:2 | a | tst.js:5:5:5:7 | [c] |
-| tst.js:5:2:5:2 | a | tst.js:5:6:5:6 | c |
 | tst.js:5:4:5:4 | b | tst.js:5:5:5:7 | [c] |
 | tst.js:5:4:5:4 | b | tst.js:5:6:5:6 | c |
 | tst.js:6:2:6:2 | a | tst.js:6:3:6:9 | (b\|[b]) |
@@ -20,8 +18,6 @@
 | tst.js:7:2:7:2 | a | tst.js:7:4:7:6 | [b] |
 | tst.js:7:2:7:2 | a | tst.js:7:4:7:9 | [b][c] |
 | tst.js:7:2:7:2 | a | tst.js:7:5:7:5 | b |
-| tst.js:7:2:7:2 | a | tst.js:7:7:7:9 | [c] |
-| tst.js:7:2:7:2 | a | tst.js:7:8:7:8 | c |
 | tst.js:7:4:7:6 | [b] | tst.js:7:7:7:9 | [c] |
 | tst.js:7:4:7:6 | [b] | tst.js:7:8:7:8 | c |
 | tst.js:8:2:8:2 | a | tst.js:8:3:8:13 | (b\|[b]\|[b]) |

javascript/ql/test/library-tests/RegExp/predecessors_and_successors/getSuccessor.expected

@@ -16,17 +16,13 @@
 | tst.js:13:3:13:4 | ab | tst.js:13:6:13:6 | c |
 | tst.js:14:2:14:7 | ([a]b) | tst.js:14:8:14:8 | c |
 | tst.js:14:3:14:5 | [a] | tst.js:14:6:14:6 | b |
-| tst.js:14:3:14:5 | [a] | tst.js:14:8:14:8 | c |
 | tst.js:14:3:14:6 | [a]b | tst.js:14:8:14:8 | c |
 | tst.js:14:4:14:4 | a | tst.js:14:6:14:6 | b |
-| tst.js:14:4:14:4 | a | tst.js:14:8:14:8 | c |
 | tst.js:14:6:14:6 | b | tst.js:14:8:14:8 | c |
 | tst.js:16:2:16:9 | ([a][b]) | tst.js:16:10:16:10 | c |
 | tst.js:16:3:16:5 | [a] | tst.js:16:6:16:8 | [b] |
-| tst.js:16:3:16:5 | [a] | tst.js:16:10:16:10 | c |
 | tst.js:16:3:16:8 | [a][b] | tst.js:16:10:16:10 | c |
 | tst.js:16:4:16:4 | a | tst.js:16:6:16:8 | [b] |
-| tst.js:16:4:16:4 | a | tst.js:16:10:16:10 | c |
 | tst.js:16:6:16:8 | [b] | tst.js:16:10:16:10 | c |
 | tst.js:16:7:16:7 | b | tst.js:16:10:16:10 | c |
 | tst.js:17:2:17:12 | ([a]\|[a]\|a) | tst.js:17:13:17:13 | b |