Properly redirect to the root page (#3369)

Co-authored-by: Nicolas Dorseuil <nicolas@gitbook.io>

packages/gitbook-v2/src/lib/links.test.ts

@@ -35,8 +35,9 @@ describe('toPathInSpace', () => {
         expect(variantInSection.toPathInSpace('some/path/')).toBe('/section/variant/some/path');
     });
 
-    it('should not add a trailing slash', () => {
-        expect(root.toPathInSpace('')).toBe('');
+    it('should not add an unnecessary trailing slash', () => {
+        // The index page should not be an empty path
+        expect(root.toPathInSpace('')).toBe('/');
         expect(variantInSection.toPathInSpace('')).toBe('/section/variant');
     });
 });
@@ -52,8 +53,9 @@ describe('toPathInSite', () => {
         expect(siteGitBookIO.toPathInSite('some/path/')).toBe('/sitename/some/path');
     });
 
-    it('should not add a trailing slash', () => {
-        expect(root.toPathInSite('')).toBe('');
+    it('should not add an unnecessary trailing slash', () => {
+        // The index page should not be an empty path
+        expect(root.toPathInSite('')).toBe('/');
         expect(siteGitBookIO.toPathInSite('')).toBe('/sitename');
     });
 });

packages/gitbook-v2/src/lib/links.ts

@@ -128,7 +128,8 @@ export function createLinker(
 function joinPaths(prefix: string, path: string): string {
     const prefixPath = prefix.endsWith('/') ? prefix : `${prefix}/`;
     const suffixPath = path.startsWith('/') ? path.slice(1) : path;
-    return removeTrailingSlash(prefixPath + suffixPath);
+    const pathWithoutTrailingSlash = removeTrailingSlash(prefixPath + suffixPath);
+    return pathWithoutTrailingSlash === '' ? '/' : pathWithoutTrailingSlash;
 }
 
 function removeTrailingSlash(path: string): string {