Added support for character class union in regex processing

javascript/extractor/src/com/semmle/js/ast/regexp/CharacterClassUnion.java

@@ -0,0 +1,22 @@
+package com.semmle.js.ast.regexp;
+
+import com.semmle.js.ast.SourceLocation;
+import java.util.List;
+
+public class CharacterClassUnion extends RegExpTerm {
+    private final List<RegExpTerm> union;
+
+    public CharacterClassUnion(SourceLocation loc, List<RegExpTerm> union) {
+        super(loc, "CharacterClassUnion");
+        this.union = union;
+    }
+
+    @Override
+    public void accept(Visitor v) {
+        v.visit(this);
+    }
+
+    public List<RegExpTerm> getUnion() {
+        return union;
+    }
+}

javascript/extractor/src/com/semmle/js/ast/regexp/Visitor.java

@@ -67,4 +67,6 @@ public interface Visitor {
   public void visit(CharacterClassIntersection nd);
 
   public void visit(CharacterClassSubtraction nd);
+
+  public void visit(CharacterClassUnion nd);
 }

javascript/extractor/src/com/semmle/js/extractor/RegExpExtractor.java

@@ -13,6 +13,7 @@
 import com.semmle.js.ast.regexp.CharacterClassQuotedString;
 import com.semmle.js.ast.regexp.CharacterClassRange;
 import com.semmle.js.ast.regexp.CharacterClassSubtraction;
+import com.semmle.js.ast.regexp.CharacterClassUnion;
 import com.semmle.js.ast.regexp.Constant;
 import com.semmle.js.ast.regexp.ControlEscape;
 import com.semmle.js.ast.regexp.ControlLetter;
@@ -98,6 +99,7 @@ public RegExpExtractor(TrapWriter trapwriter, LocationManager locationManager) {
     termkinds.put("CharacterClassQuotedString", 28);
     termkinds.put("CharacterClassIntersection", 29);
     termkinds.put("CharacterClassSubtraction", 30);
+    termkinds.put("CharacterClassUnion", 31);
   }
 
   private static final String[] errmsgs =
@@ -372,6 +374,14 @@ public void visit(CharacterClassSubtraction nd) {
       for (RegExpTerm element : nd.getSubtraction())
         visit(element, lbl, i++);
     }
+
+    @Override
+    public void visit(CharacterClassUnion nd) {
+      Label lbl = extractTerm(nd, parent, idx);
+      int i = 0;
+      for (RegExpTerm element : nd.getUnion())
+        visit(element, lbl, i++);
+    }
   }
 
   public void extract(String src, SourceMap sourceMap, Node parent, boolean isSpeculativeParsing, String flags) {

javascript/extractor/src/com/semmle/js/parser/RegExpParser.java

@@ -9,6 +9,7 @@
 import com.semmle.js.ast.regexp.CharacterClassQuotedString;
 import com.semmle.js.ast.regexp.CharacterClassRange;
 import com.semmle.js.ast.regexp.CharacterClassSubtraction;
+import com.semmle.js.ast.regexp.CharacterClassUnion;
 import com.semmle.js.ast.regexp.Constant;
 import com.semmle.js.ast.regexp.ControlEscape;
 import com.semmle.js.ast.regexp.ControlLetter;
@@ -568,6 +569,7 @@ private enum CharacterClassType {
     STANDARD,
     INTERSECTION,
     SUBTRACTION,
+    UNION
   }
 
   // ECMA 2024 `v` flag allows nested character classes.
@@ -599,12 +601,26 @@ else if (lookahead("--")) {
       }
     }
 
+    boolean containsComplex = elements.stream().anyMatch(term -> term instanceof UnicodePropertyEscape ||
+                                                        term instanceof CharacterClassQuotedString ||
+                                                        term instanceof CharacterClass);
+
+    // Set type to UNION only if:
+    // 1. We haven't already determined a specific type (intersection/subtraction)
+    // 2. We have more than one element
+    // 3. We have at least one complex element (i.e. a nested character class or a UnicodePropertyEscape)
+    if (containsComplex && classType == CharacterClassType.STANDARD && elements.size() > 1) {
+      classType = CharacterClassType.UNION;
+    }
+
     // Create appropriate RegExpTerm based on the detected class type
     switch (classType) {
       case INTERSECTION:
         return this.finishTerm(new CharacterClass(loc, Collections.singletonList(new CharacterClassIntersection(loc, elements)), inverted));
       case SUBTRACTION:
         return this.finishTerm(new CharacterClass(loc, Collections.singletonList(new CharacterClassSubtraction(loc, elements)), inverted));
+      case UNION:
+        return this.finishTerm(new CharacterClass(loc, Collections.singletonList(new CharacterClassUnion(loc, elements)), inverted));
       case STANDARD:
       default:
         return this.finishTerm(new CharacterClass(loc, elements, inverted));

javascript/extractor/tests/es2024/output/trap/regex_nested_character_class.js.trap

@@ -137,75 +137,81 @@ regexpterm(#20042,23,#20041,0,"[ [] [ [] [] ] ]")
 locations_default(#20043,#10000,3,2,3,17)
 hasLocation(#20042,#20043)
 #20044=*
-regexpterm(#20044,14,#20042,0," ")
-#20045=@"loc,{#10000},3,3,3,3"
-locations_default(#20045,#10000,3,3,3,3)
-hasLocation(#20044,#20045)
-regexp_const_value(#20044," ")
-#20046=*
-regexpterm(#20046,23,#20042,1,"[]")
-#20047=@"loc,{#10000},3,4,3,5"
-locations_default(#20047,#10000,3,4,3,5)
-hasLocation(#20046,#20047)
-#20048=*
-regexpterm(#20048,14,#20042,2," ")
-#20049=@"loc,{#10000},3,6,3,6"
-locations_default(#20049,#10000,3,6,3,6)
-hasLocation(#20048,#20049)
-regexp_const_value(#20048," ")
-#20050=*
-regexpterm(#20050,23,#20042,3,"[ [] [] ]")
-#20051=@"loc,{#10000},3,7,3,15"
-locations_default(#20051,#10000,3,7,3,15)
-hasLocation(#20050,#20051)
-#20052=*
-regexpterm(#20052,14,#20050,0," ")
-#20053=@"loc,{#10000},3,8,3,8"
-locations_default(#20053,#10000,3,8,3,8)
-hasLocation(#20052,#20053)
-regexp_const_value(#20052," ")
+regexpterm(#20044,31,#20042,0,"[ [] [ [] [] ] ]")
+hasLocation(#20044,#20043)
+#20045=*
+regexpterm(#20045,14,#20044,0," ")
+#20046=@"loc,{#10000},3,3,3,3"
+locations_default(#20046,#10000,3,3,3,3)
+hasLocation(#20045,#20046)
+regexp_const_value(#20045," ")
+#20047=*
+regexpterm(#20047,23,#20044,1,"[]")
+#20048=@"loc,{#10000},3,4,3,5"
+locations_default(#20048,#10000,3,4,3,5)
+hasLocation(#20047,#20048)
+#20049=*
+regexpterm(#20049,14,#20044,2," ")
+#20050=@"loc,{#10000},3,6,3,6"
+locations_default(#20050,#10000,3,6,3,6)
+hasLocation(#20049,#20050)
+regexp_const_value(#20049," ")
+#20051=*
+regexpterm(#20051,23,#20044,3,"[ [] [] ]")
+#20052=@"loc,{#10000},3,7,3,15"
+locations_default(#20052,#10000,3,7,3,15)
+hasLocation(#20051,#20052)
+#20053=*
+regexpterm(#20053,31,#20051,0,"[ [] [] ]")
+hasLocation(#20053,#20052)
 #20054=*
-regexpterm(#20054,23,#20050,1,"[]")
-#20055=@"loc,{#10000},3,9,3,10"
-locations_default(#20055,#10000,3,9,3,10)
+regexpterm(#20054,14,#20053,0," ")
+#20055=@"loc,{#10000},3,8,3,8"
+locations_default(#20055,#10000,3,8,3,8)
 hasLocation(#20054,#20055)
+regexp_const_value(#20054," ")
 #20056=*
-regexpterm(#20056,14,#20050,2," ")
-#20057=@"loc,{#10000},3,11,3,11"
-locations_default(#20057,#10000,3,11,3,11)
+regexpterm(#20056,23,#20053,1,"[]")
+#20057=@"loc,{#10000},3,9,3,10"
+locations_default(#20057,#10000,3,9,3,10)
 hasLocation(#20056,#20057)
-regexp_const_value(#20056," ")
 #20058=*
-regexpterm(#20058,23,#20050,3,"[]")
-#20059=@"loc,{#10000},3,12,3,13"
-locations_default(#20059,#10000,3,12,3,13)
+regexpterm(#20058,14,#20053,2," ")
+#20059=@"loc,{#10000},3,11,3,11"
+locations_default(#20059,#10000,3,11,3,11)
 hasLocation(#20058,#20059)
+regexp_const_value(#20058," ")
 #20060=*
-regexpterm(#20060,14,#20050,4," ")
-#20061=@"loc,{#10000},3,14,3,14"
-locations_default(#20061,#10000,3,14,3,14)
+regexpterm(#20060,23,#20053,3,"[]")
+#20061=@"loc,{#10000},3,12,3,13"
+locations_default(#20061,#10000,3,12,3,13)
 hasLocation(#20060,#20061)
-regexp_const_value(#20060," ")
 #20062=*
-regexpterm(#20062,14,#20042,4," ")
-#20063=@"loc,{#10000},3,16,3,16"
-locations_default(#20063,#10000,3,16,3,16)
+regexpterm(#20062,14,#20053,4," ")
+#20063=@"loc,{#10000},3,14,3,14"
+locations_default(#20063,#10000,3,14,3,14)
 hasLocation(#20062,#20063)
 regexp_const_value(#20062," ")
 #20064=*
-entry_cfg_node(#20064,#20001)
-#20065=@"loc,{#10000},1,1,1,0"
-locations_default(#20065,#10000,1,1,1,0)
+regexpterm(#20064,14,#20044,4," ")
+#20065=@"loc,{#10000},3,16,3,16"
+locations_default(#20065,#10000,3,16,3,16)
 hasLocation(#20064,#20065)
+regexp_const_value(#20064," ")
 #20066=*
-exit_cfg_node(#20066,#20001)
-hasLocation(#20066,#20023)
+entry_cfg_node(#20066,#20001)
+#20067=@"loc,{#10000},1,1,1,0"
+locations_default(#20067,#10000,1,1,1,0)
+hasLocation(#20066,#20067)
+#20068=*
+exit_cfg_node(#20068,#20001)
+hasLocation(#20068,#20023)
 successor(#20040,#20041)
-successor(#20041,#20066)
+successor(#20041,#20068)
 successor(#20032,#20033)
 successor(#20033,#20040)
 successor(#20025,#20027)
 successor(#20027,#20032)
-successor(#20064,#20025)
+successor(#20066,#20025)
 numlines(#10000,3,3,1)
 filetype(#10000,"javascript")