From a8ee22f73dc25ef75b592143ab98b255c112b331 Mon Sep 17 00:00:00 2001
From: Sang <11912225+hantatsang@users.noreply.github.com>
Date: Wed, 31 Mar 2021 09:24:31 +1100
Subject: [PATCH] "fix(services): convert to es6 module generate invalid code
 with .default" (#43309)

---
 src/services/codefixes/convertToEs6Module.ts  | 28 +++++++++++++------
 ...vertToEs6Module_import_es6DefaultImport.ts | 19 +++++++++++++
 2 files changed, 38 insertions(+), 9 deletions(-)
 create mode 100644 tests/cases/fourslash/refactorConvertToEs6Module_import_es6DefaultImport.ts

diff --git a/src/services/codefixes/convertToEs6Module.ts b/src/services/codefixes/convertToEs6Module.ts
index 963f8923ee6..e15c507a4ef 100644
--- a/src/services/codefixes/convertToEs6Module.ts
+++ b/src/services/codefixes/convertToEs6Module.ts
@@ -436,7 +436,9 @@ namespace ts.codefix {
 
     /**
      * Convert `import x = require("x").`
-     * Also converts uses like `x.y()` to `y()` and uses a named import.
+     * Also:
+     * - Convert `x.default()` to `x()` to handle ES6 default export
+     * - Converts uses like `x.y()` to `y()` and uses a named import.
      */
     function convertSingleIdentifierImport(name: Identifier, moduleSpecifier: StringLiteralLike, checker: TypeChecker, identifiers: Identifiers, quotePreference: QuotePreference): ConvertedImports {
         const nameSymbol = checker.getSymbolAtLocation(name);
@@ -454,15 +456,23 @@ namespace ts.codefix {
 
             const { parent } = use;
             if (isPropertyAccessExpression(parent)) {
-                const { expression, name: { text: propertyName } } = parent;
-                Debug.assert(expression === use, "Didn't expect expression === use"); // Else shouldn't have been in `collectIdentifiers`
-                let idName = namedBindingsNames.get(propertyName);
-                if (idName === undefined) {
-                    idName = makeUniqueName(propertyName, identifiers);
-                    namedBindingsNames.set(propertyName, idName);
-                }
+                const { name: { text: propertyName } } = parent;
+                if (propertyName === "default") {
+                    needDefaultImport = true;
 
-                (useSitesToUnqualify ??= new Map()).set(parent, factory.createIdentifier(idName));
+                    const importDefaultName = use.getText();
+                    (useSitesToUnqualify ??= new Map()).set(parent, factory.createIdentifier(importDefaultName));
+                }
+                else {
+                    Debug.assert(parent.expression === use, "Didn't expect expression === use"); // Else shouldn't have been in `collectIdentifiers`
+                    let idName = namedBindingsNames.get(propertyName);
+                    if (idName === undefined) {
+                        idName = makeUniqueName(propertyName, identifiers);
+                        namedBindingsNames.set(propertyName, idName);
+                    }
+
+                    (useSitesToUnqualify ??= new Map()).set(parent, factory.createIdentifier(idName));
+                }
             }
             else {
                 needDefaultImport = true;
diff --git a/tests/cases/fourslash/refactorConvertToEs6Module_import_es6DefaultImport.ts b/tests/cases/fourslash/refactorConvertToEs6Module_import_es6DefaultImport.ts
new file mode 100644
index 00000000000..9fe26a24010
--- /dev/null
+++ b/tests/cases/fourslash/refactorConvertToEs6Module_import_es6DefaultImport.ts
@@ -0,0 +1,19 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+// @target: esnext
+
+// @Filename: /a.js
+////const x = require('x');
+////x.default();
+////const y = require('y').default;
+////y();
+
+verify.codeFix({
+    description: "Convert to ES6 module",
+    newFileContent:
+`import x from 'x';
+x();
+import y from 'y';
+y();`,
+});