pythonnative/src/pythonnative/devserver/server.py at v0.43.1 · pythonnative/pythonnative · GitHub

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"""The dev server: HTTP for static assets, WebSocket for live peers.

One [`DevServer`][pythonnative.devserver.server.DevServer] runs on its

own thread with a private ``asyncio`` loop, so it works both inside

``pn start`` and in tests independently of the Python application

loop. It exposes:

- ``GET /``: the browser preview page.

- ``GET /static/<name>``: preview assets (JS, CSS).

- ``GET /manifest``: ``{"version", "entry", "files": {path: sha256}}``.

- ``GET /file/<path>``: raw bytes of one synced source file.

- ``GET /status``: server, project, and connected-peer information.

- ``WS /ws?role=client``: the dev-client protocol (see below).

- ``WS /ws?role=preview``: the browser preview's bridge channel; the

server only relays text frames between the page and the

[`PreviewChannel`][pythonnative.devserver.server.PreviewChannel]

handler installed by the preview.

Dev-client protocol (JSON objects, one per text frame):

- client -> server ``hello``: ``{"type": "hello", "platform", "device",

"app", "files": {path: sha256}}`` describing what the client already

holds in its overlay.

- server -> client ``sync``: ``{"type": "sync", "version", "entry",

"files": [{"path", "sha256", "content", "encoding"}], "removed": [...]}``

bringing the client up to date. The same shape is sent as

``"update"`` whenever the watcher sees a change.

- client -> server ``log`` (``level``, ``text``), ``error`` (``phase``,

``text``), ``reloaded`` (``version``, ``mode``, ``modules``): streamed

to the terminal.

"""

from __future__ import annotations

import asyncio

import base64

import json

import mimetypes

import os

import socket

import sys

import threading

import time

from dataclasses import dataclass, field

from typing import Any, AsyncIterator, Callable, Dict, List, Optional, Protocol, Sequence

from urllib.parse import parse_qs, unquote, urlsplit

from . import ws

from .watcher import FileWatcher, SourceChange, SourceSnapshot, snapshot_sources

__all__ = [

"DEFAULT_PORT",

"DevServer",

"PreviewChannel",

"PreviewPeer",

"ServerInfo",

"lan_addresses",

]

DEFAULT_PORT = 8765

"""Default port for ``pn start`` / ``pn preview``."""

_MAX_HEAD = 64 * 1024

_STATIC_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "static")

Logger = Callable[[str], None]

def lan_addresses() -> List[str]:

"""Best-effort list of this machine's non-loopback IPv4 addresses.

Used to print a URL a physical device on the same Wi-Fi can reach.

"""

found: List[str] = []

try:

probe = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

try:

# No packets are sent; connecting a UDP socket just selects

# the interface that routes to the internet.

probe.connect(("10.255.255.255", 1))

found.append(probe.getsockname()[0])

finally:

probe.close()

except OSError:

pass

try:

for info in socket.getaddrinfo(socket.gethostname(), None, socket.AF_INET):

addr = str(info[4][0])

if not addr.startswith("127.") and addr not in found:

found.append(addr)

except OSError:

pass

return found

@dataclass

class ServerInfo:

"""What the server is serving and where."""

host: str

port: int

project_root: str

entry_module: str

project_name: str = ""

def url(self, host: Optional[str] = None) -> str:

"""The HTTP base URL, substituting ``host`` for the bind address."""

return f"http://{host or self.display_host}:{self.port}"

def ws_url(self, host: Optional[str] = None) -> str:

"""The dev-client WebSocket URL."""

return f"ws://{host or self.display_host}:{self.port}/ws?role=client"

@property

def display_host(self) -> str:

"""A host suitable for a URL (``0.0.0.0`` becomes ``localhost``)."""

return "localhost" if self.host in ("", "0.0.0.0", "::") else self.host

# ======================================================================

# Preview channel

# ======================================================================

class PreviewPeer:

"""A connected browser preview page; ``send`` is safe from any thread."""

def __init__(self, server: "DevServer", writer: asyncio.StreamWriter) -> None:

self._server = server

self._writer = writer

self.closed = threading.Event()

def send(self, text: str) -> None:

"""Queue one text frame to the page (dropped once the peer is closed)."""

if self.closed.is_set():

return

self._server._call_soon(self._send_now, text)

def _send_now(self, text: str) -> None:

if self.closed.is_set():

return

try:

self._writer.write(ws.encode_frame(ws.TEXT, text.encode("utf-8")))

except Exception:

self.closed.set()

def close(self) -> None:

"""Ask the server to close this page's socket."""

self._server._call_soon(self._close_now)

def _close_now(self) -> None:

if self.closed.is_set():

return

self.closed.set()

try:

self._writer.write(ws.encode_close())

self._writer.close()

except Exception:

pass

class PreviewChannel(Protocol):

"""What the preview installs to receive the page's bridge traffic.

Every method is called on the server thread; implementations hop

to their own thread as needed.

"""

def on_preview_connected(self, peer: PreviewPeer, info: Dict[str, Any]) -> None:

"""A page connected (``info`` carries its query parameters)."""

def on_preview_message(self, peer: PreviewPeer, text: str) -> None:

"""A text frame arrived from the page."""

def on_preview_disconnected(self, peer: PreviewPeer) -> None:

"""The page went away."""

# ======================================================================

# Dev clients

# ======================================================================

@dataclass

class DevClient:

"""One connected on-device dev client."""

id: int

writer: asyncio.StreamWriter

platform: str = "unknown"

device: str = ""

app: str = ""

connected_at: float = field(default_factory=time.time)

files: Dict[str, str] = field(default_factory=dict)

def label(self) -> str:

"""A short human label for log lines."""

parts = [self.platform]

if self.device:

parts.append(self.device)

return " ".join(parts)

# ======================================================================

# The server

# ======================================================================

class DevServer:

"""Serve sources, assets, and the live protocol for one project.

Args:

project_root: Directory containing ``app/`` and ``pythonnative.toml``.

entry_module: The app's entry module (``"app.main"``).

host: Bind address. ``0.0.0.0`` so devices on the LAN can reach

it; pass ``127.0.0.1`` to stay local.

port: TCP port; ``0`` picks a free one.

project_name: Shown in the preview page and ``/status``.

static_dir: Where the preview page's assets live.

log: Where to print client logs and connection events.

watch: Whether to run the file watcher.

"""

def __init__(

self,

project_root: str,

entry_module: str = "app.main",

host: str = "0.0.0.0",

port: int = DEFAULT_PORT,

project_name: str = "",

static_dir: Optional[str] = None,

log: Optional[Logger] = None,

watch: bool = True,

) -> None:

self.project_root = os.path.abspath(project_root)

self.entry_module = entry_module

self.project_name = project_name

self.static_dir = static_dir or _STATIC_DIR

self.log: Logger = log or (lambda line: print(line, file=sys.stderr, flush=True))

self._host = host

self._port = port

self._watch = watch

self._loop: Optional[asyncio.AbstractEventLoop] = None

self._thread: Optional[threading.Thread] = None

self._server: Optional[asyncio.base_events.Server] = None

self._started = threading.Event()

self._start_error: Optional[BaseException] = None

self._clients: Dict[int, DevClient] = {}

self._client_ids = 0

self._preview: Optional[PreviewChannel] = None

self._preview_peer: Optional[PreviewPeer] = None

self._watcher: Optional[FileWatcher] = None

self._snapshot: SourceSnapshot = snapshot_sources(self.project_root)

self._snapshot_lock = threading.Lock()

self._change_listeners: List[Callable[[SourceChange, SourceSnapshot], None]] = []

self.info = ServerInfo(

host=host,

port=port,

project_root=self.project_root,

entry_module=entry_module,

project_name=project_name,

)

# -- lifecycle -------------------------------------------------------

def start(self) -> ServerInfo:

"""Bind the socket on a background thread and return the address.

Raises:

OSError: When the port is taken (the CLI prints a hint).

"""

if self._thread is not None:

return self.info

self._thread = threading.Thread(target=self._run, name="pn-dev-server", daemon=True)

self._thread.start()

self._started.wait(timeout=10.0)

if self._start_error is not None:

error, self._start_error = self._start_error, None

self._thread = None

raise error

if self._watch:

self._watcher = FileWatcher(self.project_root, self._on_files_changed)

with self._snapshot_lock:

self._snapshot = self._watcher.snapshot

self._watcher.start()

return self.info

def stop(self) -> None:

"""Close every connection and stop the thread."""

watcher, self._watcher = self._watcher, None

if watcher is not None:

watcher.stop()

loop = self._loop

if loop is not None and not loop.is_closed():

loop.call_soon_threadsafe(self._shutdown)

thread, self._thread = self._thread, None

if thread is not None:

thread.join(timeout=5.0)

def _run(self) -> None:

loop = asyncio.new_event_loop()

self._loop = loop

asyncio.set_event_loop(loop)

try:

server = loop.run_until_complete(asyncio.start_server(self._handle_connection, self._host, self._port))

except BaseException as exc:

self._start_error = exc

self._started.set()

loop.close()

return

self._server = server

sockets: Sequence[Any] = server.sockets or []

if sockets:

self.info.port = int(sockets[0].getsockname()[1])

self._started.set()

try:

loop.run_forever()

finally:

try:

loop.run_until_complete(loop.shutdown_asyncgens())

except Exception:

pass

loop.close()

def _shutdown(self) -> None:

loop = self._loop

if self._server is not None:

self._server.close()

for client in list(self._clients.values()):

try:

client.writer.write(ws.encode_close())

client.writer.close()

except Exception:

pass

self._clients.clear()

if self._preview_peer is not None:

self._preview_peer._close_now()

if loop is not None:

loop.call_soon(loop.stop)

def _call_soon(self, fn: Callable[..., Any], *args: Any) -> None:

loop = self._loop

if loop is None or loop.is_closed():

return

try:

loop.call_soon_threadsafe(fn, *args)

except RuntimeError:

pass

# -- state -----------------------------------------------------------

@property

def snapshot(self) -> SourceSnapshot:

"""The current source snapshot."""

with self._snapshot_lock:

return self._snapshot

@property

def clients(self) -> List[DevClient]:

"""Connected dev clients (a copy)."""

return list(self._clients.values())

def set_preview_channel(self, channel: Optional[PreviewChannel]) -> None:

"""Install the handler for the browser preview's bridge traffic."""

self._preview = channel

def add_change_listener(self, listener: Callable[[SourceChange, SourceSnapshot], None]) -> Callable[[], None]:

"""Be told (on the watcher thread) when sources change; returns an unsubscribe."""

self._change_listeners.append(listener)

def _remove() -> None:

try:

self._change_listeners.remove(listener)

except ValueError:

pass

return _remove

def manifest(self) -> Dict[str, Any]:

"""The ``/manifest`` document."""

snap = self.snapshot

return {"version": snap.version, "entry": self.entry_module, "files": dict(snap.files)}

def status(self) -> Dict[str, Any]:

"""The ``/status`` document."""

snap = self.snapshot

return {

"name": self.project_name,

"entry": self.entry_module,

"project_root": self.project_root,

"version": snap.version,

"file_count": len(snap.files),

"clients": [

{"id": c.id, "platform": c.platform, "device": c.device, "app": c.app, "connected_at": c.connected_at}

for c in self._clients.values()

"preview_connected": self._preview_peer is not None and not self._preview_peer.closed.is_set(),

"lan": lan_addresses(),

"port": self.info.port,

}

# -- file changes ----------------------------------------------------

def _on_files_changed(self, change: SourceChange, snapshot: SourceSnapshot) -> None:

with self._snapshot_lock:

self._snapshot = snapshot

summary = ", ".join(change.changed + [f"-{p}" for p in change.removed])

self.log(f"[pn] changed: {summary}")

for listener in list(self._change_listeners):

try:

listener(change, snapshot)

except Exception as exc:

self.log(f"[pn] change listener failed: {exc!r}")

if self._clients:

message = self._sync_message("update", snapshot, change.changed, change.removed)

self._call_soon(self._broadcast, message)

def _sync_message(self, kind: str, snapshot: SourceSnapshot, paths: Sequence[str], removed: Sequence[str]) -> str:

files: List[Dict[str, Any]] = []

for path in paths:

data = snapshot.read(path)

if data is None:

continue

files.append(_encode_file(path, snapshot.files.get(path, ""), data))

return json.dumps(

{

"type": kind,

"version": snapshot.version,

"entry": self.entry_module,

"files": files,

"removed": list(removed),

}

)

def _broadcast(self, message: str) -> None:

frame = ws.encode_frame(ws.TEXT, message.encode("utf-8"))

for client in list(self._clients.values()):

try:

client.writer.write(frame)

except Exception:

self._drop_client(client)

def _drop_client(self, client: DevClient) -> None:

if self._clients.pop(client.id, None) is not None:

self.log(f"[pn] {client.label()} disconnected")

try:

client.writer.close()

except Exception:

pass

# -- connections -----------------------------------------------------

async def _handle_connection(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:

try:

head = await reader.readuntil(b"\r\n\r\n")

except (asyncio.IncompleteReadError, asyncio.LimitOverrunError, ConnectionError):

writer.close()

return

if len(head) > _MAX_HEAD:

writer.close()

return

start_line, headers = ws.parse_http_headers(head)

parts = start_line.split()

if len(parts) < 2:

writer.close()

return

method, target = parts[0], parts[1]

url = urlsplit(target)

path = unquote(url.path)

query = {k: v[-1] for k, v in parse_qs(url.query).items()}

if "websocket" in headers.get("upgrade", "").lower():

await self._serve_websocket(reader, writer, headers, path, query)

return

try:

await self._serve_http(writer, method, path, query)

finally:

try:

writer.close()

except Exception:

pass

async def _serve_http(self, writer: asyncio.StreamWriter, method: str, path: str, query: Dict[str, str]) -> None:

if method not in ("GET", "HEAD"):

_respond(writer, 405, b"method not allowed", "text/plain")

return

if path in ("/", "/index.html"):

_respond_file(writer, os.path.join(self.static_dir, "index.html"))

return

if path == "/static/schema.js":

from ..sdk.schema import manifest

_respond(

writer, 200, ("export default " + json.dumps(manifest(), default=str) + ";").encode(), "text/javascript"

)

return

if path.startswith("/static/"):

name = path[len("/static/") :]

root = os.path.realpath(self.static_dir)

candidate = os.path.realpath(os.path.join(root, name))

if (

not name

or any(part.startswith(".") for part in name.split("/"))

or os.path.commonpath([root, candidate]) != root

_respond(writer, 404, b"not found", "text/plain")

return

_respond_file(writer, candidate)

return

if path == "/manifest":

_respond_json(writer, self.manifest())

return

if path == "/status":

_respond_json(writer, self.status())

return

if path.startswith("/file/"):

rel = path[len("/file/") :]

snap = self.snapshot

if rel not in snap.files:

_respond(writer, 404, b"not found", "text/plain")

return

data = snap.read(rel)

if data is None:

_respond(writer, 404, b"not found", "text/plain")

return

_respond(writer, 200, data, mimetypes.guess_type(rel)[0] or "application/octet-stream")

return

_respond(writer, 404, b"not found", "text/plain")

async def _serve_websocket(

self,

reader: asyncio.StreamReader,

writer: asyncio.StreamWriter,

headers: Dict[str, str],

path: str,

query: Dict[str, str],

) -> None:

try:

writer.write(ws.server_handshake(headers))

await writer.drain()

except (ws.HandshakeError, ConnectionError):

writer.close()

return

role = query.get("role", "client")

if path != "/ws":

writer.write(ws.encode_close(1008, "unknown path"))

writer.close()

return

if role == "preview":

await self._preview_session(reader, writer, query)

else:

await self._client_session(reader, writer)

async def _read_messages(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> AsyncIterator[str]:

"""Yield text messages until the peer closes; answers pings."""

decoder = ws.FrameDecoder()

while True:

try:

chunk = await reader.read(65536)

except (ConnectionError, asyncio.CancelledError, OSError):

return

if not chunk:

return

try:

messages = list(decoder.feed(chunk))

except ws.WebSocketError:

try:

writer.write(ws.encode_close(1002, "protocol error"))

except Exception:

pass

return

for opcode, payload in messages:

if opcode == ws.TEXT:

try:

yield payload.decode("utf-8")

except UnicodeDecodeError:

continue

elif opcode == ws.PING:

writer.write(ws.encode_frame(ws.PONG, payload))

elif opcode == ws.CLOSE:

try:

writer.write(ws.encode_close())

except Exception:

pass

return

async def _client_session(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:

self._client_ids += 1

client = DevClient(id=self._client_ids, writer=writer)

self._clients[client.id] = client

try:

async for text in self._read_messages(reader, writer):

try:

message = json.loads(text)

except ValueError:

continue

if isinstance(message, dict):

self._on_client_message(client, message)

finally:

self._drop_client(client)

def _on_client_message(self, client: DevClient, message: Dict[str, Any]) -> None:

kind = message.get("type")

if kind == "hello":

client.platform = str(message.get("platform") or "unknown")

client.device = str(message.get("device") or "")

client.app = str(message.get("app") or "")

files = message.get("files")

client.files = {str(k): str(v) for k, v in files.items()} if isinstance(files, dict) else {}

self.log(f"[pn] {client.label()} connected")

snap = self.snapshot

changed = sorted(p for p, digest in snap.files.items() if client.files.get(p) != digest)

removed = sorted(p for p in client.files if p not in snap.files)

try:

client.writer.write(

ws.encode_frame(ws.TEXT, self._sync_message("sync", snap, changed, removed).encode("utf-8"))

)

except Exception:

self._drop_client(client)

return

if kind == "log":

level = str(message.get("level") or "info")

text = str(message.get("text") or "").rstrip("\n")

prefix = f"[{client.label()}]"

if level in ("error", "warn", "warning"):

prefix = f"[{client.label()} {level}]"

for line in text.split("\n"):

self.log(f"{prefix} {line}")

return

if kind == "error":

phase = str(message.get("phase") or "runtime")

text = str(message.get("text") or "").rstrip("\n")

self.log(f"[{client.label()}] error during {phase}:")

for line in text.split("\n"):

self.log(f" {line}")

return

if kind == "reloaded":

mode = str(message.get("mode") or "reload")

modules = message.get("modules") or []

what = ", ".join(str(m) for m in modules) if isinstance(modules, list) and modules else "app"

self.log(f"[{client.label()}] {mode}: {what}")

return

async def _preview_session(

self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter, query: Dict[str, str]

) -> None:

channel = self._preview

if channel is None:

writer.write(ws.encode_close(1013, "no preview running"))

writer.close()

return

previous = self._preview_peer

if previous is not None and not previous.closed.is_set():

# One page at a time: the newest tab takes over the app.

try:

previous._send_now(json.dumps(["dev", {"type": "superseded"}]))

except Exception:

pass

previous._close_now()

channel.on_preview_disconnected(previous)

peer = PreviewPeer(self, writer)

self._preview_peer = peer

channel.on_preview_connected(peer, dict(query))

try:

async for text in self._read_messages(reader, writer):

channel.on_preview_message(peer, text)

finally:

peer.closed.set()

if self._preview_peer is peer:

self._preview_peer = None

channel.on_preview_disconnected(peer)

try:

writer.close()

except Exception:

pass

# ======================================================================

# HTTP helpers

# ======================================================================

def _encode_file(path: str, digest: str, data: bytes) -> Dict[str, Any]:

try:

return {"path": path, "sha256": digest, "content": data.decode("utf-8"), "encoding": "utf8"}

except UnicodeDecodeError:

return {"path": path, "sha256": digest, "content": base64.b64encode(data).decode("ascii"), "encoding": "base64"}

_STATUS_TEXT = {200: "OK", 404: "Not Found", 405: "Method Not Allowed", 500: "Internal Server Error"}

def _respond(writer: asyncio.StreamWriter, status: int, body: bytes, content_type: str) -> None:

head = (

f"HTTP/1.1 {status} {_STATUS_TEXT.get(status, 'OK')}\r\n"

f"Content-Type: {content_type}\r\n"

f"Content-Length: {len(body)}\r\n"

"Cache-Control: no-store\r\n"

"Access-Control-Allow-Origin: *\r\n"

"Connection: close\r\n"

"\r\n"

).encode("ascii")

try:

writer.write(head + body)

except Exception:

pass

def _respond_json(writer: asyncio.StreamWriter, document: Any) -> None:

_respond(writer, 200, json.dumps(document).encode("utf-8"), "application/json; charset=utf-8")

def _respond_file(writer: asyncio.StreamWriter, path: str) -> None:

try:

with open(path, "rb") as handle:

data = handle.read()

except OSError:

_respond(writer, 404, b"not found", "text/plain")

return

content_type = mimetypes.guess_type(path)[0] or "application/octet-stream"

if path.endswith(".js"):

content_type = "text/javascript"

if content_type.startswith("text/") and "charset" not in content_type:

content_type += "; charset=utf-8"

_respond(writer, 200, data, content_type)

pythonnative/src/pythonnative/devserver/server.py at v0.43.1 · pythonnative/pythonnative · GitHub

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