Merge pull request github#3023 from erik-krogh/RedundantUpdate

Approved by esbena

Author: semmle-qlci

change-notes/1.24/analysis-javascript.md

@@ -68,6 +68,7 @@
 | Syntax error (`js/syntax-error`) | Lower severity | This results of this query are now displayed with lower severity. |
 | Use of password hash with insufficient computational effort (`js/insufficient-password-hash`) | Fewer false positive results | This query now recognizes additional cases that do not require secure hashing. |
 | Useless regular-expression character escape (`js/useless-regexp-character-escape`) | Fewer false positive results | This query now distinguishes escapes in strings and regular expression literals. |
+| Identical operands (`js/redundant-operation`) | Fewer results | This query now recognizes cases where the operands change a value using ++/-- expressions. |
 
 ## Changes to libraries
 

javascript/ql/src/Expressions/RedundantExpression.ql

@@ -64,7 +64,10 @@ class RedundantIdemnecantOperand extends RedundantOperand {
  * arguments to integers. For example, `x&x` is a common idiom for converting `x` to an integer.
  */
 class RedundantIdempotentOperand extends RedundantOperand {
-  RedundantIdempotentOperand() { getParent() instanceof LogicalBinaryExpr }
+  RedundantIdempotentOperand() {
+    getParent() instanceof LogicalBinaryExpr and
+    not exists(UpdateExpr e | e.getParentExpr+() = this)
+  }
 }
 
 /**

javascript/ql/test/query-tests/Expressions/RedundantExpression/tst.js

@@ -6,4 +6,6 @@ x == 23 || x == 23;
 x & x;
 
 // this may actually be OK, but it's not good style
-pop() && pop();
+pop() && pop();
+
+foo[bar++] && foo[bar++] // OK