From 7d2a14b8561ba115c635478af4f088c7c0bda1e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Mon, 23 Nov 2020 16:03:11 +0100
Subject: [PATCH] Initialize NodePath context when using `getSibling` (#12387)

---
 packages/babel-traverse/src/path/family.js |  2 +-
 packages/babel-traverse/test/family.js     | 27 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/packages/babel-traverse/src/path/family.js b/packages/babel-traverse/src/path/family.js
index 533b52722720..19479009e986 100644
--- a/packages/babel-traverse/src/path/family.js
+++ b/packages/babel-traverse/src/path/family.js
@@ -127,7 +127,7 @@ export function getSibling(key: string): NodePath {
     container: this.container,
     listKey: this.listKey,
     key: key,
-  });
+  }).setContext(this.context);
 }
 
 export function getPrevSibling(): NodePath {
diff --git a/packages/babel-traverse/test/family.js b/packages/babel-traverse/test/family.js
index 80d2d8955687..ef5fa0fac4d8 100644
--- a/packages/babel-traverse/test/family.js
+++ b/packages/babel-traverse/test/family.js
@@ -1,5 +1,6 @@
 import traverse from "../lib";
 import { parse } from "@babel/parser";
+import * as t from "@babel/types";
 
 describe("path/family", function () {
   describe("getBindingIdentifiers", function () {
@@ -81,6 +82,32 @@ describe("path/family", function () {
       expect(sibling.getAllNextSiblings()).toHaveLength(2);
       expect(lastSibling.getAllPrevSiblings()).toHaveLength(2);
     });
+
+    it("should initialize path.scope when needed", function () {
+      const ast = parse("if (0) {}");
+
+      let testHasScope = false;
+      let consequentHasScope = false;
+
+      traverse(ast, {
+        IfStatement(path) {
+          // @babel/traverse pre-traverses the whole tree to populate the initial
+          // scope. Thus, it pre-caches paths for all the original nodes.
+          // We need to introduce two new nodes to avoid using the cached paths
+          // that already have the path.scope property.
+          path.set("test", t.identifier("a"));
+          path.set("consequent", t.expressionStatement(t.identifier("b")));
+
+          const testPath = path.get("test");
+
+          testHasScope = !!testPath.scope;
+          consequentHasScope = !!testPath.getSibling("consequent").scope;
+        },
+      });
+
+      expect(testHasScope).toBe(true);
+      expect(consequentHasScope).toBe(true);
+    });
   });
 });