Merge pull request #2344 from asger-semmle/element-pattern-prop-read

Approved by max-schaefer

Author: semmle-qlci

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

@@ -840,16 +840,18 @@ module DataFlow {
    * An array element pattern viewed as a property read; for instance, in
    * `var [ x, y ] = arr`, `x` is a read of property 0 of `arr` and similar
    * for `y`.
-   *
-   * Note: We currently do not expose the array index as the property name,
-   * instead treating it as a read of an unknown property.
    */
   private class ElementPatternAsPropRead extends PropRead, ElementPatternNode {
     override Node getBase() { result = TDestructuringPatternNode(pattern) }
 
     override Expr getPropertyNameExpr() { none() }
 
-    override string getPropertyName() { none() }
+    override string getPropertyName() {
+      exists (int i |
+        elt = pattern.getElement(i) and
+        result = i.toString()
+      )
+    }
   }
 
   /**

javascript/ql/test/library-tests/PropWrite/tests.expected

@@ -10,6 +10,9 @@ test_getAPropertyRead
 | tst.js:34:6:34:12 | vvv.ppp | tst.js:34:6:34:16 | vvv.ppp.qqq |
 | tst.js:44:3:44:9 | console | tst.js:44:3:44:13 | console.log |
 | tst.js:44:15:44:17 | obj | tst.js:44:15:44:20 | obj[p] |
+| tst.js:46:17:46:21 | array | tst.js:47:10:47:10 | x |
+| tst.js:46:17:46:21 | array | tst.js:47:13:47:13 | y |
+| tst.js:46:17:46:21 | array | tst.js:47:16:47:16 | z |
 test_getAPropertyReference
 | classes.ts:3:21:3:20 | this | classes.ts:4:3:4:24 | instanc ...  foo(); |
 | classes.ts:8:3:8:2 | this | classes.ts:8:15:8:35 | public  ... erField |
@@ -50,6 +53,9 @@ test_getAPropertyReference
 | tst.js:41:12:41:30 | ["a", ...arr3, "d"] | tst.js:41:27:41:29 | "d" |
 | tst.js:44:3:44:9 | console | tst.js:44:3:44:13 | console.log |
 | tst.js:44:15:44:17 | obj | tst.js:44:15:44:20 | obj[p] |
+| tst.js:46:17:46:21 | array | tst.js:47:10:47:10 | x |
+| tst.js:46:17:46:21 | array | tst.js:47:13:47:13 | y |
+| tst.js:46:17:46:21 | array | tst.js:47:16:47:16 | z |
 test_getAPropertySource
 | classes.ts:3:21:3:20 | this | instanceField | classes.ts:4:19:4:23 | foo() |
 | classes.ts:8:3:8:2 | this | parameterField | classes.ts:8:22:8:35 | parameterField |
@@ -92,6 +98,9 @@ test_getAPropertyRead2
 | tst.js:34:6:34:8 | vvv | ppp | tst.js:34:6:34:12 | vvv.ppp |
 | tst.js:34:6:34:12 | vvv.ppp | qqq | tst.js:34:6:34:16 | vvv.ppp.qqq |
 | tst.js:44:3:44:9 | console | log | tst.js:44:3:44:13 | console.log |
+| tst.js:46:17:46:21 | array | 0 | tst.js:47:10:47:10 | x |
+| tst.js:46:17:46:21 | array | 1 | tst.js:47:13:47:13 | y |
+| tst.js:46:17:46:21 | array | 2 | tst.js:47:16:47:16 | z |
 test_getAPropertyReference2
 | classes.ts:3:21:3:20 | this | instanceField | classes.ts:4:3:4:24 | instanc ...  foo(); |
 | classes.ts:8:3:8:2 | this | parameterField | classes.ts:8:15:8:35 | public  ... erField |
@@ -116,6 +125,9 @@ test_getAPropertyReference2
 | tst.js:34:6:34:8 | vvv | ppp | tst.js:34:6:34:12 | vvv.ppp |
 | tst.js:34:6:34:12 | vvv.ppp | qqq | tst.js:34:6:34:16 | vvv.ppp.qqq |
 | tst.js:44:3:44:9 | console | log | tst.js:44:3:44:13 | console.log |
+| tst.js:46:17:46:21 | array | 0 | tst.js:47:10:47:10 | x |
+| tst.js:46:17:46:21 | array | 1 | tst.js:47:13:47:13 | y |
+| tst.js:46:17:46:21 | array | 2 | tst.js:47:16:47:16 | z |
 test_hasPropertyWrite
 | classes.ts:3:21:3:20 | this | instanceField | classes.ts:4:19:4:23 | foo() |
 | classes.ts:8:3:8:2 | this | parameterField | classes.ts:8:22:8:35 | parameterField |

javascript/ql/test/library-tests/PropWrite/tst.js

@@ -42,3 +42,8 @@ var arr1 = ["a", "b", "c"],
 
 for (var p in obj)
   console.log(obj[p]);
+
+  function test(array) {
+    let [x, y, z] = array;
+  }
+