microsoft · mxschmitt · Aug 26, 2021 · Aug 19, 2021 · Aug 19, 2021 · Aug 20, 2021
diff --git a/playwright/_impl/_browser_type.py b/playwright/_impl/_browser_type.py
@@ -15,7 +15,7 @@
 import asyncio
 import pathlib
 from pathlib import Path
-from typing import Dict, List, Optional, Union, cast
+from typing import TYPE_CHECKING, Dict, List, Optional, Union, cast
 
 from playwright._impl._api_structures import (
     Geolocation,
@@ -42,6 +42,9 @@
 from playwright._impl._transport import WebSocketTransport
 from playwright._impl._wait_helper import throw_on_timeout
 
+if TYPE_CHECKING:
+    from playwright._impl._playwright import Playwright
+
 
 class BrowserType(ChannelOwner):
     def __init__(
@@ -191,23 +194,22 @@ async def connect(
             self._connection._dispatcher_fiber,
             self._connection._object_factory,
             transport,
+            self._connection._loop,
         )
         connection._is_sync = self._connection._is_sync
-        connection._loop = self._connection._loop
         connection._loop.create_task(connection.run())
-        future = connection._loop.create_task(
-            connection.wait_for_object_with_known_name("Playwright")
-        )
+        playwright_future = connection.get_playwright_future()
+
         timeout_future = throw_on_timeout(timeout, Error("Connection timed out"))
         done, pending = await asyncio.wait(
-            {transport.on_error_future, future, timeout_future},
+            {transport.on_error_future, playwright_future, timeout_future},
             return_when=asyncio.FIRST_COMPLETED,
         )
-        if not future.done():
-            future.cancel()
+        if not playwright_future.done():
+            playwright_future.cancel()
         if not timeout_future.done():
             timeout_future.cancel()
-        playwright = next(iter(done)).result()
+        playwright: "Playwright" = next(iter(done)).result()
         self._connection._child_ws_connections.append(connection)
         pre_launched_browser = playwright._initializer.get("preLaunchedBrowser")
         assert pre_launched_browser

diff --git a/playwright/_impl/_connection.py b/playwright/_impl/_connection.py
@@ -16,14 +16,17 @@
 import sys
 import traceback
 from pathlib import Path
-from typing import Any, Callable, Dict, List, Optional, Union
+from typing import TYPE_CHECKING, Any, Callable, Dict, List, Optional, Union
 
 from greenlet import greenlet
 from pyee import AsyncIOEventEmitter
 
 from playwright._impl._helper import ParsedMessagePayload, parse_error
 from playwright._impl._transport import Transport
 
+if TYPE_CHECKING:
+    from playwright._impl._playwright import Playwright
+
 
 class Channel(AsyncIOEventEmitter):
     def __init__(self, connection: "Connection", guid: str) -> None:
@@ -119,7 +122,17 @@ def __init__(self, loop: asyncio.AbstractEventLoop) -> None:
 
 class RootChannelOwner(ChannelOwner):
     def __init__(self, connection: "Connection") -> None:
-        super().__init__(connection, "", "", {})
+        super().__init__(connection, "Root", "", {})
+
+    async def initialize(self) -> "Playwright":
+        return from_channel(
+            await self._channel.send(
+                "initialize",
+                {
+                    "sdkLanguage": "python",
+                },
+            )
+        )
 
 
 class Connection:
@@ -128,6 +141,7 @@ def __init__(
         dispatcher_fiber: Any,
         object_factory: Callable[[ChannelOwner, str, str, Dict], ChannelOwner],
         transport: Transport,
+        loop: asyncio.AbstractEventLoop,
     ) -> None:
         self._dispatcher_fiber = dispatcher_fiber
         self._transport = transport
@@ -140,6 +154,8 @@ def __init__(
         self._is_sync = False
         self._api_name = ""
         self._child_ws_connections: List["Connection"] = []
+        self._loop = loop
+        self._playwright_future: asyncio.Future["Playwright"] = loop.create_future()
 
     async def run_as_sync(self) -> None:
         self._is_sync = True
@@ -148,8 +164,17 @@ async def run_as_sync(self) -> None:
     async def run(self) -> None:
         self._loop = asyncio.get_running_loop()
         self._root_object = RootChannelOwner(self)
+
+        async def init() -> None:
+            self._playwright_future.set_result(await self._root_object.initialize())
+
+        await self._transport.connect()
+        self._loop.create_task(init())
         await self._transport.run()
 
+    def get_playwright_future(self) -> asyncio.Future:
+        return self._playwright_future
+
     def stop_sync(self) -> None:
         self._transport.request_stop()
         self._dispatcher_fiber.switch()
@@ -164,17 +189,6 @@ def cleanup(self) -> None:
         for ws_connection in self._child_ws_connections:
             ws_connection._transport.dispose()
 
-    async def wait_for_object_with_known_name(self, guid: str) -> ChannelOwner:
-        if guid in self._objects:
-            return self._objects[guid]
-        callback: asyncio.Future[ChannelOwner] = self._loop.create_future()
-
-        def callback_wrapper(result: ChannelOwner) -> None:
-            callback.set_result(result)
-
-        self._waiting_for_object[guid] = callback_wrapper
-        return await callback
-
     def call_on_object_with_known_name(
         self, guid: str, callback: Callable[[ChannelOwner], None]
     ) -> None:

diff --git a/playwright/_impl/_transport.py b/playwright/_impl/_transport.py
@@ -60,6 +60,10 @@ def dispose(self) -> None:
     async def wait_until_stopped(self) -> None:
         pass
 
+    @abstractmethod
+    async def connect(self) -> None:
+        pass
+
     @abstractmethod
     async def run(self) -> None:
         pass
@@ -91,14 +95,15 @@ def __init__(
         self._driver_executable = driver_executable
 
     def request_stop(self) -> None:
+        assert self._output
         self._stopped = True
         self._output.close()
 
     async def wait_until_stopped(self) -> None:
         await self._stopped_future
         await self._proc.wait()
 
-    async def run(self) -> None:
+    async def connect(self) -> None:
         self._stopped_future: asyncio.Future = asyncio.Future()
         # Hide the command-line window on Windows when using Pythonw.exe
         creationflags = 0
@@ -111,7 +116,7 @@ async def run(self) -> None:
             if getattr(sys, "frozen", False):
                 env["PLAYWRIGHT_BROWSERS_PATH"] = "0"
 
-            self._proc = proc = await asyncio.create_subprocess_exec(
+            self._proc = await asyncio.create_subprocess_exec(
                 str(self._driver_executable),
                 "run-driver",
                 stdin=asyncio.subprocess.PIPE,
@@ -123,20 +128,21 @@ async def run(self) -> None:
             )
         except Exception as exc:
             self.on_error_future.set_exception(exc)
-            return
+            raise exc
 
-        assert proc.stdout
-        assert proc.stdin
-        self._output = proc.stdin
+        self._output = self._proc.stdin
 
+    async def run(self) -> None:
+        assert self._proc.stdout
+        assert self._proc.stdin
         while not self._stopped:
             try:
-                buffer = await proc.stdout.readexactly(4)
+                buffer = await self._proc.stdout.readexactly(4)
                 length = int.from_bytes(buffer, byteorder="little", signed=False)
                 buffer = bytes(0)
                 while length:
                     to_read = min(length, 32768)
-                    data = await proc.stdout.readexactly(to_read)
+                    data = await self._proc.stdout.readexactly(to_read)
                     length -= to_read
                     if len(buffer):
                         buffer = buffer + data
@@ -151,6 +157,7 @@ async def run(self) -> None:
         self._stopped_future.set_result(None)
 
     def send(self, message: Dict) -> None:
+        assert self._output
         data = self.serialize_message(message)
         self._output.write(
             len(data).to_bytes(4, byteorder="little", signed=False) + data
@@ -184,15 +191,16 @@ def dispose(self) -> None:
     async def wait_until_stopped(self) -> None:
         await self._connection.wait_closed()
 
-    async def run(self) -> None:
+    async def connect(self) -> None:
         try:
             self._connection = await websocket_connect(
                 self.ws_endpoint, extra_headers=self.headers
             )
         except Exception as exc:
             self.on_error_future.set_exception(Error(f"websocket.connect: {str(exc)}"))
-            return
+            raise exc
 
+    async def run(self) -> None:
         while not self._stopped:
             try:
                 message = await self._connection.recv()
@@ -220,7 +228,7 @@ async def run(self) -> None:
                 break
 
     def send(self, message: Dict) -> None:
-        if self._stopped or self._connection.closed:
+        if self._stopped or (hasattr(self, "_connection") and self._connection.closed):
             raise Error("Playwright connection closed")
         data = self.serialize_message(message)
         self._loop.create_task(self._connection.send(data))
diff --git a/playwright/async_api/_context_manager.py b/playwright/async_api/_context_manager.py
@@ -32,12 +32,11 @@ async def __aenter__(self) -> AsyncPlaywright:
             None,
             create_remote_object,
             PipeTransport(loop, compute_driver_executable()),
+            loop,
         )
-        self._connection._loop = loop
         loop.create_task(self._connection.run())
-        playwright_future = loop.create_task(
-            self._connection.wait_for_object_with_known_name("Playwright")
-        )
+        playwright_future = self._connection.get_playwright_future()
+
         done, pending = await asyncio.wait(
             {self._connection._transport.on_error_future, playwright_future},
             return_when=asyncio.FIRST_COMPLETED,

diff --git a/playwright/async_api/_generated.py b/playwright/async_api/_generated.py
@@ -2748,18 +2748,18 @@ async def goto(
         Returns the main resource response. In case of multiple redirects, the navigation will resolve with the response of the
         last redirect.
 
-        `frame.goto` will throw an error if:
+        The method will throw an error if:
         - there's an SSL error (e.g. in case of self-signed certificates).
         - target URL is invalid.
         - the `timeout` is exceeded during navigation.
         - the remote server does not respond or is unreachable.
         - the main resource failed to load.
 
-        `frame.goto` will not throw an error when any valid HTTP status code is returned by the remote server, including 404
-        \"Not Found\" and 500 \"Internal Server Error\".  The status code for such responses can be retrieved by calling
+        The method will not throw an error when any valid HTTP status code is returned by the remote server, including 404 \"Not
+        Found\" and 500 \"Internal Server Error\".  The status code for such responses can be retrieved by calling
         `response.status()`.
 
-        > NOTE: `frame.goto` either throws an error or returns a main resource response. The only exceptions are navigation to
+        > NOTE: The method either throws an error or returns a main resource response. The only exceptions are navigation to
         `about:blank` or navigation to the same URL with a different hash, which would succeed and return `null`.
         > NOTE: Headless mode doesn't support navigation to a PDF document. See the
         [upstream issue](https://bugs.chromium.org/p/chromium/issues/detail?id=761295).
@@ -4936,7 +4936,42 @@ async def register(
         An example of registering selector engine that queries elements based on a tag name:
 
         ```py
-        # FIXME: add snippet
+        import asyncio
+        from playwright.async_api import async_playwright
+
+        async def run(playwright):
+            tag_selector = \"\"\"
+              {
+                  // Returns the first element matching given selector in the root's subtree.
+                  query(root, selector) {
+                      return root.querySelector(selector);
+                  },
+                  // Returns all elements matching given selector in the root's subtree.
+                  queryAll(root, selector) {
+                      return Array.from(root.querySelectorAll(selector));
+                  }
+              }\"\"\"
+
+            # Register the engine. Selectors will be prefixed with \"tag=\".
+            await playwright.selectors.register(\"tag\", tag_selector)
+            browser = await playwright.chromium.launch()
+            page = await browser.new_page()
+            await page.set_content('<div><button>Click me</button></div>')
+
+            # Use the selector prefixed with its name.
+            button = await page.query_selector('tag=button')
+            # Combine it with other selector engines.
+            await page.click('tag=div >> text=\"Click me\"')
+            # Can use it in any methods supporting selectors.
+            button_count = await page.eval_on_selector_all('tag=button', 'buttons => buttons.length')
+            print(button_count)
+            await browser.close()
+
+        async def main():
+            async with async_playwright() as playwright:
+                await run(playwright)
+
+        asyncio.run(main())
         ```
 
         Parameters
@@ -6389,18 +6424,18 @@ async def goto(
         Returns the main resource response. In case of multiple redirects, the navigation will resolve with the response of the
         last redirect.
 
-        `page.goto` will throw an error if:
+        The method will throw an error if:
         - there's an SSL error (e.g. in case of self-signed certificates).
         - target URL is invalid.
         - the `timeout` is exceeded during navigation.
         - the remote server does not respond or is unreachable.
         - the main resource failed to load.
 
-        `page.goto` will not throw an error when any valid HTTP status code is returned by the remote server, including 404 \"Not
+        The method will not throw an error when any valid HTTP status code is returned by the remote server, including 404 \"Not
         Found\" and 500 \"Internal Server Error\".  The status code for such responses can be retrieved by calling
         `response.status()`.
 
-        > NOTE: `page.goto` either throws an error or returns a main resource response. The only exceptions are navigation to
+        > NOTE: The method either throws an error or returns a main resource response. The only exceptions are navigation to
         `about:blank` or navigation to the same URL with a different hash, which would succeed and return `null`.
         > NOTE: Headless mode doesn't support navigation to a PDF document. See the
         [upstream issue](https://bugs.chromium.org/p/chromium/issues/detail?id=761295).
@@ -10144,7 +10179,8 @@ async def launch(
             Network proxy settings.
         downloads_path : Union[pathlib.Path, str, NoneType]
             If specified, accepted downloads are downloaded into this directory. Otherwise, temporary directory is created and is
-            deleted when browser is closed.
+            deleted when browser is closed. In either case, the downloads are deleted when the browser context they were created in
+            is closed.
         slow_mo : Union[float, NoneType]
             Slows down Playwright operations by the specified amount of milliseconds. Useful so that you can see what is going on.
         traces_dir : Union[pathlib.Path, str, NoneType]
@@ -10283,7 +10319,8 @@ async def launch_persistent_context(
             Network proxy settings.
         downloads_path : Union[pathlib.Path, str, NoneType]
             If specified, accepted downloads are downloaded into this directory. Otherwise, temporary directory is created and is
-            deleted when browser is closed.
+            deleted when browser is closed. In either case, the downloads are deleted when the browser context they were created in
+            is closed.
         slow_mo : Union[float, NoneType]
             Slows down Playwright operations by the specified amount of milliseconds. Useful so that you can see what is going on.
         viewport : Union[{width: int, height: int}, NoneType]

diff --git a/playwright/sync_api/_context_manager.py b/playwright/sync_api/_context_manager.py
@@ -56,6 +56,7 @@ def greenlet_main() -> None:
             dispatcher_fiber,
             create_remote_object,
             PipeTransport(loop, compute_driver_executable()),
+            loop,
         )
 
         g_self = greenlet.getcurrent()