add a JS implementation of RegexTreeViewSig

javascript/ql/lib/semmle/javascript/security/regexp/RegexTreeView.qll

@@ -0,0 +1,73 @@
+/**
+ * Provides JavaScript-specific definitions for use in the NfaUtils module.
+ */
+
+private import codeql.regex.nfa.NfaUtils as NfaUtils
+private import codeql.regex.RegexTreeView
+
+/** An implementation that parses a regular expression into a tree of `RegExpTerm`s. */
+module RegexTreeView implements RegexTreeViewSig {
+  import javascript
+
+  class Top = Locatable;
+
+  /**
+   * Holds if `term` is an escape class representing e.g. `\d`.
+   * `clazz` is which character class it represents, e.g. "d" for `\d`.
+   */
+  predicate isEscapeClass(RegExpTerm term, string clazz) {
+    exists(RegExpCharacterClassEscape escape | term = escape | escape.getValue() = clazz)
+  }
+
+  /**
+   * Holds if `term` is a possessive quantifier.
+   * As javascript's regexes do not support possessive quantifiers, this never holds, but is used by the shared library.
+   */
+  predicate isPossessive(RegExpQuantifier term) { none() }
+
+  /**
+   * Holds if the regex that `term` is part of is used in a way that ignores any leading prefix of the input it's matched against.
+   * Not yet implemented for JavaScript.
+   */
+  predicate matchesAnyPrefix(RegExpTerm term) { any() }
+
+  /**
+   * Holds if the regex that `term` is part of is used in a way that ignores any trailing suffix of the input it's matched against.
+   * Not yet implemented for JavaScript.
+   */
+  predicate matchesAnySuffix(RegExpTerm term) { any() }
+
+  /**
+   * Holds if the regular expression should not be considered.
+   *
+   * For javascript we make the pragmatic performance optimization to ignore minified files.
+   */
+  predicate isExcluded(RegExpParent parent) { parent.(Expr).getTopLevel().isMinified() }
+
+  /**
+   * Holds if `root` has the `i` flag for case-insensitive matching.
+   */
+  predicate isIgnoreCase(RegExpTerm root) { RegExp::isIgnoreCase(getFlags(root)) }
+
+  /**
+   * Gets the flags for `root`, or the empty string if `root` has no flags.
+   */
+  private string getFlags(RegExpTerm root) {
+    root.isRootTerm() and
+    exists(DataFlow::RegExpCreationNode node | node.getRoot() = root |
+      result = node.getFlags()
+      or
+      not exists(node.getFlags()) and
+      result = ""
+    )
+    or
+    exists(RegExpPatternSource source | source.getRegExpTerm() = root |
+      result = source.getARegExpObject().(DataFlow::RegExpCreationNode).getFlags()
+    )
+  }
+
+  /**
+   * Holds if `root` has the `s` flag for multi-line matching.
+   */
+  predicate isDotAll(RegExpTerm root) { RegExp::isDotAll(getFlags(root)) }
+}