chore: single character url join

urlJoin now properly appends single characters

Author: danielntmd

yarn-project/foundation/src/string/index.test.ts

@@ -12,6 +12,15 @@ describe('string', () => {
     ])('removes duplicate slashes', (parts, url) => {
       expect(urlJoin(...parts)).toBe(url);
     });
+
+    it.each([
+      [['http://example.com', 'a'], 'http://example.com/a'],
+      [['http://example.com', 'a', 'b'], 'http://example.com/a/b'],
+      [['x', 'y', 'z'], 'x/y/z'],
+      [['http://example.com', '/a/'], 'http://example.com/a'],
+    ])('preserves single-character path segments %#', (parts, url) => {
+      expect(urlJoin(...parts)).toBe(url);
+    });
   });
 
   describe('hex prefix helpers', () => {

yarn-project/foundation/src/string/index.ts

@@ -58,7 +58,7 @@ export function urlJoin(...args: string[]): string {
       end--;
     }
 
-    if (start < end) {
+    if (start <= end) {
       processed.push(arg.slice(start, end + 1));
     }
   }