[major] Throw an error if the connection URL is invalid

Make the `WebSocket` constructor throw a `SyntaxError` if the URL
contains a fragment identifier or if the URL's protocol is not one of
`'ws:'`, `'wss:'`, or `'ws+unix:'`.

lib/websocket.js

@@ -613,18 +613,32 @@ function initAsClient(websocket, address, protocols, options) {
     parsedUrl = address;
     websocket._url = address.href;
   } else {
-    parsedUrl = new URL(address);
+    try {
+      parsedUrl = new URL(address);
+    } catch (e) {
+      throw new SyntaxError(`Invalid URL: ${address}`);
+    }
+
     websocket._url = address;
   }
 
+  const isSecure = parsedUrl.protocol === 'wss:';
   const isUnixSocket = parsedUrl.protocol === 'ws+unix:';
 
-  if (!parsedUrl.host && (!isUnixSocket || !parsedUrl.pathname)) {
-    throw new Error(`Invalid URL: ${websocket.url}`);
+  if (parsedUrl.protocol !== 'ws:' && !isSecure && !isUnixSocket) {
+    throw new SyntaxError(
+      'The URL\'s protocol must be one of "ws:", "wss:", or "ws+unix:"'
+    );
+  }
+
+  if (isUnixSocket && !parsedUrl.pathname) {
+    throw new SyntaxError("The URL's pathname is empty");
+  }
+
+  if (parsedUrl.hash) {
+    throw new SyntaxError('The URL contains a fragment identifier');
   }
 
-  const isSecure =
-    parsedUrl.protocol === 'wss:' || parsedUrl.protocol === 'https:';
   const defaultPort = isSecure ? 443 : 80;
   const key = randomBytes(16).toString('base64');
   const get = isSecure ? https.get : http.get;

test/websocket.test.js

@@ -20,9 +20,24 @@ class CustomAgent extends http.Agent {
 describe('WebSocket', () => {
   describe('#ctor', () => {
     it('throws an error when using an invalid url', () => {
+      assert.throws(
+        () => new WebSocket('foo'),
+        /^SyntaxError: Invalid URL: foo$/
+      );
+
+      assert.throws(
+        () => new WebSocket('https://echo.websocket.org'),
+        /^SyntaxError: The URL's protocol must be one of "ws:", "wss:", or "ws\+unix:"$/
+      );
+
       assert.throws(
         () => new WebSocket('ws+unix:'),
-        /^Error: Invalid URL: ws\+unix:$/
+        /^SyntaxError: The URL's pathname is empty$/
+      );
+
+      assert.throws(
+        () => new WebSocket('wss://echo.websocket.org#foo'),
+        /^SyntaxError: The URL contains a fragment identifier$/
       );
     });