JS: Add change note and deprecation member

Author: asger-semmle

change-notes/1.21/analysis-javascript.md

@@ -48,4 +48,7 @@
 * `RegExpLiteral` is now a `DataFlow::SourceNode`.
 * `JSDocTypeExpr` now has source locations and is a subclass of `Locatable` and `TypeAnnotation`.
 * Various predicates named `getTypeAnnotation()` now return `TypeAnnotation` instead of `TypeExpr`.
-  In rare cases, this may cause compilation errors. Cast the result to `TypeExpr` if this happens.
+  In rare cases, this may cause compilation errors in existing code. Cast the result to `TypeExpr` if this happens.
+* The `getALabel` predicate in `LabeledBarrierGuardNode` and `LabeledSanitizerGuardNode`
+  has been deprecated and overriding it no longer has any effect.
+  Instead use the 3-parameter version of `blocks` or `sanitizes`.

javascript/ql/src/semmle/javascript/dataflow/Configuration.qll

@@ -320,6 +320,13 @@ abstract class BarrierGuardNode extends DataFlow::Node {
  */
 abstract class LabeledBarrierGuardNode extends BarrierGuardNode {
   override predicate blocks(boolean outcome, Expr e) { none() }
+
+  /**
+   * DEPRECATED: Use `blocks(outcome, e, label)` or `sanitizes(outcome, e, label)` instead.
+   *
+   * Overriding this predicate has no effect.
+   */
+  deprecated FlowLabel getALabel() { none() }
 }
 
 /**