From d5f4505c7e90caf36c530f55165f4b3a0afc1edb Mon Sep 17 00:00:00 2001
From: Bogdan Savluk <savluk.bogdan@gmail.com>
Date: Mon, 18 Jul 2022 10:47:00 +0200
Subject: [PATCH] fix: allow exporting `TSDeclareFunction` as default (#14763)

---
 .../src/index.ts                              |  1 +
 .../src/ast-types/generated/index.ts          |  7 +++++-
 .../src/builders/generated/index.ts           |  6 ++++-
 packages/babel-types/src/definitions/core.ts  |  1 +
 .../typescript/exportDefaultDeclaration.js    | 23 +++++++++++++++++++
 5 files changed, 36 insertions(+), 2 deletions(-)
 create mode 100644 packages/babel-types/test/builders/typescript/exportDefaultDeclaration.js

diff --git a/packages/babel-plugin-transform-modules-systemjs/src/index.ts b/packages/babel-plugin-transform-modules-systemjs/src/index.ts
index f2cf1b4ee672..887adf4b5722 100644
--- a/packages/babel-plugin-transform-modules-systemjs/src/index.ts
+++ b/packages/babel-plugin-transform-modules-systemjs/src/index.ts
@@ -436,6 +436,7 @@ export default declare<PluginState>((api, options: Options) => {
                 }
                 removedPaths.push(path);
               } else {
+                // @ts-expect-error TSDeclareFunction is not expected here
                 path.replaceWith(buildExportCall("default", declar));
               }
             } else if (path.isExportNamedDeclaration()) {
diff --git a/packages/babel-types/src/ast-types/generated/index.ts b/packages/babel-types/src/ast-types/generated/index.ts
index ec419a324510..5b77c64d0714 100644
--- a/packages/babel-types/src/ast-types/generated/index.ts
+++ b/packages/babel-types/src/ast-types/generated/index.ts
@@ -813,7 +813,11 @@ export interface ExportAllDeclaration extends BaseNode {
 
 export interface ExportDefaultDeclaration extends BaseNode {
   type: "ExportDefaultDeclaration";
-  declaration: FunctionDeclaration | ClassDeclaration | Expression;
+  declaration:
+    | TSDeclareFunction
+    | FunctionDeclaration
+    | ClassDeclaration
+    | Expression;
   exportKind?: "value" | null;
 }
 
@@ -6722,6 +6726,7 @@ export interface ParentMaps {
   TSDeclareFunction:
     | BlockStatement
     | DoWhileStatement
+    | ExportDefaultDeclaration
     | ExportNamedDeclaration
     | ForInStatement
     | ForOfStatement
diff --git a/packages/babel-types/src/builders/generated/index.ts b/packages/babel-types/src/builders/generated/index.ts
index 5b07d9824037..acfef5336e0b 100644
--- a/packages/babel-types/src/builders/generated/index.ts
+++ b/packages/babel-types/src/builders/generated/index.ts
@@ -639,7 +639,11 @@ export function exportAllDeclaration(
   });
 }
 export function exportDefaultDeclaration(
-  declaration: t.FunctionDeclaration | t.ClassDeclaration | t.Expression,
+  declaration:
+    | t.TSDeclareFunction
+    | t.FunctionDeclaration
+    | t.ClassDeclaration
+    | t.Expression,
 ): t.ExportDefaultDeclaration {
   return validateNode<t.ExportDefaultDeclaration>({
     type: "ExportDefaultDeclaration",
diff --git a/packages/babel-types/src/definitions/core.ts b/packages/babel-types/src/definitions/core.ts
index c938999f717c..920078e0cfdc 100644
--- a/packages/babel-types/src/definitions/core.ts
+++ b/packages/babel-types/src/definitions/core.ts
@@ -1521,6 +1521,7 @@ defineType("ExportDefaultDeclaration", {
   fields: {
     declaration: {
       validate: assertNodeType(
+        "TSDeclareFunction",
         "FunctionDeclaration",
         "ClassDeclaration",
         "Expression",
diff --git a/packages/babel-types/test/builders/typescript/exportDefaultDeclaration.js b/packages/babel-types/test/builders/typescript/exportDefaultDeclaration.js
new file mode 100644
index 000000000000..8042f4323907
--- /dev/null
+++ b/packages/babel-types/test/builders/typescript/exportDefaultDeclaration.js
@@ -0,0 +1,23 @@
+import * as t from "../../../lib/index.js";
+
+describe("builders", function () {
+  describe("typescript", function () {
+    describe("exportDefaultDeclaration", function () {
+      it("accept TSDeclareFunction as argument for exportDefaultDeclaration", function () {
+        // this can be used when having function overrides for function exported as default
+        // export default function test();
+        // export default function test() {};
+        expect(() => {
+          t.exportDefaultDeclaration(
+            t.tsDeclareFunction(
+              t.identifier("test"),
+              null,
+              [],
+              t.tsTypeAnnotation(t.tsVoidKeyword()),
+            ),
+          );
+        }).not.toThrow();
+      });
+    });
+  });
+});