From 5ecd0f75d2d2db813ebf9683031e0532eb112768 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Thu, 8 Apr 2021 10:04:20 -0400
Subject: [PATCH] fix: hoist variable declaration within do block

---
 .../variable-declaration-start.js             | 11 +++--
 .../variable-declaration-within-function.js   |  8 ++++
 packages/babel-traverse/package.json          |  1 +
 .../babel-traverse/src/path/replacement.ts    | 41 +++++--------------
 yarn.lock                                     |  1 +
 5 files changed, 28 insertions(+), 34 deletions(-)
 create mode 100644 packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-within-function.js

diff --git a/packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-start.js b/packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-start.js
index 5e5027c56c21..6f5c411593db 100644
--- a/packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-start.js
+++ b/packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-start.js
@@ -1,4 +1,7 @@
-expect(do {
-  var bar = "foo";
-  bar;
-}).toBe("foo");
+expect(
+  do {
+    var bar = "foo";
+    bar;
+  }
+).toBe("foo");
+expect(bar).toBe("foo");
diff --git a/packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-within-function.js b/packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-within-function.js
new file mode 100644
index 000000000000..a58b208ec7c6
--- /dev/null
+++ b/packages/babel-plugin-proposal-do-expressions/test/fixtures/do-expressions/variable-declaration-within-function.js
@@ -0,0 +1,8 @@
+expect(
+  () => do {
+    () => {
+      var bar = "foo";
+    };
+    bar;
+  }
+).toThrow(ReferenceError);
diff --git a/packages/babel-traverse/package.json b/packages/babel-traverse/package.json
index 1ce31ae23f74..3d28d4f61704 100644
--- a/packages/babel-traverse/package.json
+++ b/packages/babel-traverse/package.json
@@ -19,6 +19,7 @@
     "@babel/code-frame": "workspace:^7.12.13",
     "@babel/generator": "workspace:^7.13.9",
     "@babel/helper-function-name": "workspace:^7.12.13",
+    "@babel/helper-hoist-variables": "workspace:^7.13.0",
     "@babel/helper-split-export-declaration": "workspace:^7.12.13",
     "@babel/parser": "workspace:^7.13.13",
     "@babel/types": "workspace:^7.13.13",
diff --git a/packages/babel-traverse/src/path/replacement.ts b/packages/babel-traverse/src/path/replacement.ts
index abb5d0551481..3ff5de7f3ecb 100644
--- a/packages/babel-traverse/src/path/replacement.ts
+++ b/packages/babel-traverse/src/path/replacement.ts
@@ -6,35 +6,7 @@ import NodePath from "./index";
 import { path as pathCache } from "../cache";
 import { parse } from "@babel/parser";
 import * as t from "@babel/types";
-
-const hoistVariablesVisitor = {
-  Function(path) {
-    path.skip();
-  },
-
-  VariableDeclaration(path) {
-    if (path.node.kind !== "var") return;
-
-    const bindings = path.getBindingIdentifiers();
-    for (const key of Object.keys(bindings)) {
-      path.scope.push({ id: bindings[key] });
-    }
-
-    const exprs = [];
-
-    for (const declar of path.node.declarations as Array<any>) {
-      if (declar.init) {
-        exprs.push(
-          t.expressionStatement(
-            t.assignmentExpression("=", declar.id, declar.init),
-          ),
-        );
-      }
-    }
-
-    path.replaceWithMultiple(exprs);
-  },
-};
+import hoistVariables from "@babel/helper-hoist-variables";
 
 /**
  * Replace a node with an array of multiple. This method performs the following steps:
@@ -238,7 +210,16 @@ export function replaceExpressionWithStatements(
     t.CallExpression & { callee: t.ArrowFunctionExpression }
   >;
 
-  this.traverse(hoistVariablesVisitor);
+  // hoist variable declaration in do block
+  // `(do { var x = 1; x;})` -> `var x; (() => { x = 1; return x; })()`
+  const callee = (this as ThisType).get("callee");
+  hoistVariables(
+    callee.get("body"),
+    id => {
+      this.scope.push({ id });
+    },
+    "var",
+  );
 
   // add implicit returns to all ending expression statements
   const completionRecords: Array<NodePath> = (this as ThisType)
diff --git a/yarn.lock b/yarn.lock
index 605fda1024e0..2fdd7d652a53 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3492,6 +3492,7 @@ __metadata:
     "@babel/code-frame": "workspace:^7.12.13"
     "@babel/generator": "workspace:^7.13.9"
     "@babel/helper-function-name": "workspace:^7.12.13"
+    "@babel/helper-hoist-variables": "workspace:^7.13.0"
     "@babel/helper-plugin-test-runner": "workspace:*"
     "@babel/helper-split-export-declaration": "workspace:^7.12.13"
     "@babel/parser": "workspace:^7.13.13"