Register binding for newly created vars for commonjs transforms

packages/babel-plugin-transform-modules-commonjs/src/index.ts

@@ -235,6 +235,12 @@ export default declare((api, options) => {
 
           ensureStatementsHoisted(headers);
           path.unshiftContainer("body", headers);
+          path.get("body").forEach(path => {
+            if (headers.indexOf(path.node) === -1) return;
+            if (path.isVariableDeclaration()) {
+              path.scope.registerDeclaration(path);
+            }
+          });
         },
       },
     },

packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/binding-for-new-vars/input.mjs

@@ -0,0 +1,5 @@
+import {x} from './foo.js';
+var y = true;
+function f() {
+return [x, y, console];
+}

packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/binding-for-new-vars/options.json

@@ -0,0 +1,4 @@
+{
+    "sourceType": "module",
+    "plugins": ["transform-modules-commonjs", "./plugin"]
+}

packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/binding-for-new-vars/output.js

@@ -0,0 +1,15 @@
+"use strict";
+
+var _foo = require("./foo.js");
+
+var y = true;
+
+function f() {
+  return [
+  /* _foo hasBinding, getBinding */
+  _foo.x,
+  /* y hasBinding, getBinding */
+  y,
+  /* console no hasBinding, no getBinding */
+  console];
+}

packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/binding-for-new-vars/plugin.js

@@ -0,0 +1,29 @@
+module.exports = function () {
+  return {
+    visitor: {
+      Program: {
+        exit(programPath) {
+          // Sub-traversal to ensure runs after ESM->CJS transform
+          programPath.traverse({
+            ReferencedIdentifier(path) {
+              if (!path.findParent(p => p.isFunction())) return;
+              const varName = path.node.name;
+              path.addComment(
+                "leading",
+                ` ${varName} ${
+                  path.scope.hasBinding(varName)
+                    ? "hasBinding"
+                    : "no hasBinding"
+                }, ${
+                  path.scope.getBinding(varName)
+                    ? "getBinding"
+                    : "no getBinding"
+                } `
+              );
+            },
+          });
+        },
+      },
+    },
+  };
+};