JS: Add SsaExplicitDefinition.getRhsNode

javascript/ql/src/semmle/javascript/SSA.qll

@@ -521,6 +521,27 @@ class SsaExplicitDefinition extends SsaDefinition, TExplicitDef {
   ) {
     getDef().getLocation().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
   }
+
+  /**
+   * Gets the data flow node representing the incoming value assigned at this definition,
+   * if any.
+   */
+  DataFlow::Node getRhsNode() {
+    exists(VarDef def | def = getDef() |
+      result = def.getSource().flow()
+      or
+      exists(VarRef ref |
+        ref = getSourceVariable().getAReference() and
+        def.getTarget().(BindingPattern).getABindingVarRef() = ref and
+        result = DataFlow::patternPropRead(ref)
+      )
+      or
+      result = DataFlow::parameterNode(def)
+      or
+      // Handle class, function, namespace, and enum declaration statement
+      result.getAstNode() = def.(Stmt)
+    )
+  }
 }
 
 /**

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

@@ -1089,6 +1089,27 @@ module DataFlow {
     nd = TExceptionalFunctionReturnNode(function)
   }
 
+  /**
+   * INTERNAL. DO NOT USE.
+   *
+   * Gets the `PropRead` node corresponding to the value stored in the given
+   * binding pattern due to destructuring.
+   *
+   * For example, in `let { p: value } = f()`, the `value` pattern maps to a `PropRead`
+   * extracting the `p` property.
+   */
+  DataFlow::PropRead patternPropRead(BindingPattern value) {
+    exists(PropertyPattern prop |
+      value = prop.getValuePattern() and
+      result = TPropNode(prop)
+    )
+    or
+    exists(ArrayPattern array |
+      value = array.getAnElement() and
+      result = TElementPatternNode(array, value)
+    )
+  }
+
   /**
    * A classification of flows that are not modeled, or only modeled incompletely, by
    * `DataFlowNode`:

javascript/ql/test/library-tests/SSA/GetRhsNode/GetRhsNode.expected

@@ -0,0 +1,14 @@
+| tst.js:2:7:2:13 | a = g() | a | tst.js:2:11:2:13 | g() |
+| tst.js:4:7:4:24 | { propB: b } = g() | b | tst.js:4:9:4:16 | propB: b |
+| tst.js:6:7:6:34 | { propC ... } = g() | c | tst.js:6:9:6:16 | propC: c |
+| tst.js:6:7:6:34 | { propC ... } = g() | d | tst.js:6:19:6:26 | propD: d |
+| tst.js:8:7:8:41 | { array ... } = g() | elm1 | tst.js:8:22:8:25 | elm1 |
+| tst.js:8:7:8:41 | { array ... } = g() | elm2 | tst.js:8:28:8:31 | elm2 |
+| tst.js:17:3:17:22 | ({ propB: b }) = g() | b | tst.js:17:6:17:13 | propB: b |
+| tst.js:19:3:19:32 | ({ prop ... ) = g() | c | tst.js:19:6:19:13 | propC: c |
+| tst.js:19:3:19:32 | ({ prop ... ) = g() | d | tst.js:19:16:19:23 | propD: d |
+| tst.js:21:3:21:22 | [ elm1, elm2 ] = g() | elm1 | tst.js:21:5:21:8 | elm1 |
+| tst.js:21:3:21:22 | [ elm1, elm2 ] = g() | elm2 | tst.js:21:11:21:14 | elm2 |
+| tst.js:31:12:31:23 | [elm1, elm2] | elm1 | tst.js:31:13:31:16 | elm1 |
+| tst.js:31:12:31:23 | [elm1, elm2] | elm2 | tst.js:31:19:31:22 | elm2 |
+| tst.js:31:26:31:40 | { prop: value } | value | tst.js:31:28:31:38 | prop: value |

javascript/ql/test/library-tests/SSA/GetRhsNode/GetRhsNode.ql

@@ -0,0 +1,4 @@
+import javascript
+
+from SsaExplicitDefinition def
+select def, def.getSourceVariable(), def.getRhsNode()

javascript/ql/test/library-tests/SSA/GetRhsNode/tst.js

@@ -0,0 +1,35 @@
+function f() {
+  let a = g();
+  
+  let { propB: b } = g();
+
+  let { propC: c, propD: d } = g();
+  
+  let { arrayProp: [ elm1, elm2 ] } = g();
+  
+  a; // Ensure variables are live.
+  b;
+  c;
+  d;
+  elm1;
+  elm2;
+
+  ({ propB: b }) = g();
+  
+  ({ propC: c, propD: d }) = g();
+  
+  [ elm1, elm2 ] = g();
+  
+  a;
+  b;
+  c;
+  d;
+  elm1;
+  elm2;
+}
+
+function h([elm1, elm2], { prop: value }) {
+  elm1;
+  elm2;
+  value;
+}