Make loadPartialConfig's options optional

packages/babel-core/src/config/partial.js

@@ -157,8 +157,14 @@ type LoadPartialConfigOpts = {
 };
 
 export const loadPartialConfig = gensync<[any], PartialConfig | null>(
-  function* (inputOpts: LoadPartialConfigOpts): Handler<PartialConfig | null> {
-    const { showIgnoredFiles, ...opts } = inputOpts;
+  function* (opts?: LoadPartialConfigOpts): Handler<PartialConfig | null> {
+    let showIgnoredFiles = false;
+    // We only extract showIgnoredFiles if opts is an object, so that
+    // loadPrivatePartialConfig can throw the appropriate error if it's not.
+    if (typeof opts === "object" && opts !== null && !Array.isArray(opts)) {
+      ({ showIgnoredFiles, ...opts } = opts);
+    }
+
     const result: ?PrivPartialConfig = yield* loadPrivatePartialConfig(opts);
     if (!result) return null;
 

packages/babel-core/test/config-chain.js

@@ -1330,6 +1330,17 @@ describe("buildConfigChain", function () {
           ]),
         });
       });
+
+      it("loadPartialConfig can be called with no arguments", () => {
+        const cwd = process.cwd();
+
+        try {
+          process.chdir(fixture("config-files", "babelrc-extended"));
+          expect(() => babel.loadPartialConfig()).not.toThrow();
+        } finally {
+          process.chdir(cwd);
+        }
+      });
     });
 
     it("should throw when `test` presents but `filename` is not passed", () => {