url: fix setting `url.search` to the empty string

PR-URL: https://github.com/nodejs/node/pull/11105
Fixes: https://github.com/nodejs/node/issues/11101
Fixes: 98bb65f641 "url: improving URLSearchParams"
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

lib/internal/url.js

@@ -188,12 +188,7 @@ function onParseSearchComplete(flags, protocol, username, password,
   if (flags & binding.URL_FLAGS_FAILED)
     return;
   const ctx = this[context];
-  if (query) {
   ctx.query = query;
-    ctx.flags |= binding.URL_FLAGS_HAS_QUERY;
-  } else {
-    ctx.flags &= ~binding.URL_FLAGS_HAS_QUERY;
-  }
 }
 
 function onParseHashComplete(flags, protocol, username, password,
@@ -486,13 +481,15 @@ Object.defineProperties(URL.prototype, {
       if (!search) {
         ctx.query = null;
         ctx.flags &= ~binding.URL_FLAGS_HAS_QUERY;
-        this[searchParams][searchParams] = {};
-        return;
-      }
+      } else {
         if (search[0] === '?') search = search.slice(1);
         ctx.query = '';
+        ctx.flags |= binding.URL_FLAGS_HAS_QUERY;
+        if (search) {
           binding.parse(search, binding.kQuery, null, ctx,
                         onParseSearchComplete.bind(this));
+        }
+      }
       initSearchParams(this[searchParams], search);
     }
   },
@@ -610,9 +607,11 @@ function update(url, params) {
   }
 }
 
-// Reused by the URL parse function invoked by
-// the href setter, and the URLSearchParams constructor
 function initSearchParams(url, init) {
+  if (!init) {
+    url[searchParams] = [];
+    return;
+  }
   url[searchParams] = getParamsFromObject(querystring.parse(init));
 }
 

test/parallel/test-whatwg-url-searchparams.js

@@ -21,6 +21,10 @@ assert(sp.has('a'));
 assert.strictEqual(sp.get('a'), '[object Object]');
 sp.delete('a');
 assert(!sp.has('a'));
+
+m.search = '';
+assert.strictEqual(sp.toString(), '');
+
 values.forEach((i) => sp.append('a', i));
 assert(sp.has('a'));
 assert.strictEqual(sp.getAll('a').length, 6);