fix regression to allow for empty-string paths

packages/react-router/modules/__tests__/matchPath-test.js

@@ -9,6 +9,23 @@ describe("matchPath", () => {
     });
   });
 
+  describe('with path=""', () => {
+    it('returns correct url at "/"', () => {
+      const path = "";
+      const pathname = "/";
+      const match = matchPath(pathname, path);
+      // TODO: why is match.url "/" instead of ""?
+      expect(match.url).toBe("/");
+    });
+
+    it('returns correct url at "/somewhere/else"', () => {
+      const path = "";
+      const pathname = "/somewhere/else";
+      const match = matchPath(pathname, path);
+      expect(match.url).toBe("");
+    });
+  });
+
   describe('with path="/"', () => {
     it('returns correct url at "/"', () => {
       const path = "/";

packages/react-router/modules/matchPath.js

@@ -35,7 +35,7 @@ function matchPath(pathname, options = {}) {
   const paths = [].concat(path);
 
   return paths.reduce((matched, path) => {
-    if (!path) return null;
+    if (!path && path !== "") return null;
     if (matched) return matched;
 
     const { regexp, keys } = compilePath(path, {