avoid duplicating impure initializers in object rest destructuring

packages/babel-plugin-transform-object-rest-spread/src/index.js

@@ -81,8 +81,30 @@ export default function ({ types: t }) {
         const kind = path.parentPath.node.kind;
         const nodes = [];
 
-        path.traverse({
+        path.get("id").traverse({
           RestProperty(path) {
+            if (
+              // skip single-property case, e.g.
+              // const { ...x } = foo();
+              // since the RHS will not be duplicated
+              this.originalPath.node.id.properties.length > 1 &&
+              !t.isIdentifier(this.originalPath.node.init)
+            ) {
+              // const { a, ...b } = foo();
+              // to avoid calling foo() twice, as a first step convert it to:
+              // const _foo = foo();
+              // const { a, ...b } = _foo;
+              const initRef = path.scope.generateUidIdentifierBasedOnNode(this.originalPath.node.init, "ref");
+              // insert const _foo = foo()
+              this.originalPath.parentPath.insertBefore(t.variableDeclaration(kind, [
+                t.variableDeclarator(initRef, this.originalPath.node.init)
+              ]));
+              // replace foo() with _foo
+              this.originalPath.replaceWith(t.variableDeclarator(this.originalPath.node.id, initRef));
+
+              return;
+            }
+
             let ref = this.originalPath.node.init;
 
             path.findParent((path) => {

packages/babel-plugin-transform-object-rest-spread/test/fixtures/regression/gh-4904/actual.js

@@ -0,0 +1,7 @@
+const { s, ...t } = foo();
+
+const { s: { q1, ...q2 }, ...q3 } = bar();
+
+const { a } = foo(({ b, ...c }) => {
+  console.log(b, c);
+});

packages/babel-plugin-transform-object-rest-spread/test/fixtures/regression/gh-4904/expected.js

@@ -0,0 +1,18 @@
+const _foo = foo();
+
+const { s } = _foo;
+
+const t = babelHelpers.objectWithoutProperties(_foo, ["s"]);
+
+const _bar = bar();
+
+const { s: { q1 } } = _bar;
+
+const q2 = babelHelpers.objectWithoutProperties(_bar.s, ["q1"]);
+const q3 = babelHelpers.objectWithoutProperties(_bar, ["s"]);
+const { a } = foo((_ref) => {
+  let { b } = _ref;
+  let c = babelHelpers.objectWithoutProperties(_ref, ["b"]);
+
+  console.log(b, c);
+});

packages/babel-plugin-transform-object-rest-spread/test/fixtures/regression/options.json

@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "transform-object-rest-spread",
+    "external-helpers"
+  ]
+}