fix(v2): broken link checker should not report false positives when using encoded chars (#4407)

In order to create markdown links to URIs containing spaces, an
encoded space (%20) must be used. These types of links were not
properly resolved to doc files. This fix allows them to be
resolved by calling `decodeURI` on the links found in markdown files to
unescape characters such as spaces.

packages/docusaurus/src/server/__tests__/brokenLinks.test.ts

@@ -205,4 +205,54 @@ describe('brokenLinks', () => {
     });
     expect(result).toEqual(allCollectedLinksFiltered);
   });
+
+  describe('Encoded link', () => {
+    test('getAllBrokenLinks', async () => {
+      const routes: RouteConfig[] = [
+        {
+          path: '/docs',
+          component: '',
+          routes: [
+            {path: '/docs/some doc', component: ''},
+            {path: '/docs/some other doc', component: ''},
+            {path: '/docs/weird%20file%20name', component: ''},
+          ],
+        },
+        {
+          path: '*',
+          component: '',
+        },
+      ];
+
+      const allCollectedLinks = {
+        '/docs/some doc': [
+          // good - valid file with spaces in name
+          './some%20other%20doc',
+          // good - valid file with percent-20 in its name
+          './weird%20file%20name',
+          // bad - non-existant file with spaces in name
+          './some%20other%20non-existant%20doc',
+          // evil - trying to use ../../ but '/' won't get decoded
+          './break%2F..%2F..%2Fout',
+        ],
+      };
+
+      const expectedBrokenLinks = {
+        '/docs/some doc': [
+          {
+            link: './some%20other%20non-existant%20doc',
+            resolvedLink: '/docs/some%20other%20non-existant%20doc',
+          },
+          {
+            link: './break%2F..%2F..%2Fout',
+            resolvedLink: '/docs/break%2F..%2F..%2Fout',
+          },
+        ],
+      };
+
+      expect(getAllBrokenLinks({allCollectedLinks, routes})).toEqual(
+        expectedBrokenLinks,
+      );
+    });
+  });
 });

packages/docusaurus/src/server/brokenLinks.ts

@@ -48,7 +48,9 @@ function getPageBrokenLinks({
   }
 
   function isBrokenLink(link: string) {
-    const matchedRoutes = matchRoutes(toReactRouterRoutes(routes), link);
+    const matchedRoutes = [link, decodeURI(link)]
+      .map((l) => matchRoutes(toReactRouterRoutes(routes), l))
+      .reduce((prev, cur) => prev.concat(cur));
     return matchedRoutes.length === 0;
   }