fix(v2): normalizeUrl edge cases (#3427)

* fix(utils): cover normalizeUrl edge cases

* fix(utils): normalizeUrl new edge cases

packages/docusaurus-utils/src/__tests__/index.test.ts

@@ -258,6 +258,22 @@ describe('load utils', () => {
 
   test('normalizeUrl', () => {
     const asserts = [
+      {
+        input: ['/', ''],
+        output: '/',
+      },
+      {
+        input: ['', '/'],
+        output: '/',
+      },
+      {
+        input: ['/'],
+        output: '/',
+      },
+      {
+        input: [''],
+        output: '',
+      },
       {
         input: ['/', '/'],
         output: '/',
@@ -306,6 +322,34 @@ describe('load utils', () => {
         input: ['http://foobar.com', '', 'test', '/'],
         output: 'http://foobar.com/test/',
       },
+      {
+        input: ['/', '', 'hello', '', '/', '/', '', '/', '/world'],
+        output: '/hello/world',
+      },
+      {
+        input: ['', '', '/tt', 'ko', 'hello'],
+        output: '/tt/ko/hello',
+      },
+      {
+        input: ['', '///hello///', '', '///world'],
+        output: '/hello/world',
+      },
+      {
+        input: ['', '/hello/', ''],
+        output: '/hello/',
+      },
+      {
+        input: ['', '/', ''],
+        output: '/',
+      },
+      {
+        input: ['///', '///'],
+        output: '/',
+      },
+      {
+        input: ['/', '/hello/world/', '///'],
+        output: '/hello/world/',
+      },
     ];
     asserts.forEach((testCase) => {
       expect(normalizeUrl(testCase.input)).toBe(testCase.output);

packages/docusaurus-utils/src/index.ts

@@ -282,6 +282,9 @@ export function normalizeUrl(rawUrls: string[]): string {
   const urls = rawUrls;
   const resultArray = [];
 
+  let hasStartingSlash = false;
+  let hasEndingSlash = false;
+
   // If the first part is a plain protocol, we combine it with the next part.
   if (urls[0].match(/^[^/:]+:\/*$/) && urls.length > 1) {
     const first = urls.shift();
@@ -302,19 +305,30 @@ export function normalizeUrl(rawUrls: string[]): string {
     }
 
     if (component === '') {
+      if (i === urls.length - 1 && hasEndingSlash) {
+        resultArray.push('/');
+      }
       // eslint-disable-next-line
       continue;
     }
 
+    if (component !== '/') {
       if (i > 0) {
         // Removing the starting slashes for each component but the first.
-      component = component.replace(/^[/]+/, '');
+        component = component.replace(
+          /^[/]+/,
+          // Special case where the first element of rawUrls is empty ["", "/hello"] => /hello
+          component[0] === '/' && !hasStartingSlash ? '/' : '',
+        );
       }
 
+      hasEndingSlash = component[component.length - 1] === '/';
       // Removing the ending slashes for each component but the last.
       // For the last component we will combine multiple slashes to a single one.
       component = component.replace(/[/]+$/, i < urls.length - 1 ? '' : '/');
+    }
 
+    hasStartingSlash = true;
     resultArray.push(component);
   }