Add examples (palantir#8)

Author: gatesn

README.rst

@@ -20,9 +20,18 @@ Installation
 
 ``pip install -U python-jsonrpc-server``
 
-Usage
------
+Examples
+--------
 
+The examples directory contains two examples of running language servers over websockets. ``examples/langserver.py`` shows how to run a language server in-memory. ``examples/langserver_ext.py`` shows how to run a subprocess language server, in this case the `Python Language Server`_.
+
+Start by installing `tornado` and `python-language-server`
+
+``pip install python-language-server[all] tornado``
+
+Then running `python examples/langserver.py` or `python examples/langserver_ext.py` will host a websocket on ``ws://localhost:3000/python``.
+
+To setup a client, you can use the examples from `Monaco Language Client`_.
 
 Development
 -----------
@@ -39,3 +48,4 @@ This project is made available under the MIT License.
 .. _JSON RPC 2.0: http://www.jsonrpc.org/specification
 .. _Python Language Server: https://github.com/palantir/python-language-server
 .. _concurrent.futures backport: https://github.com/agronholm/pythonfutures
+.. _Monaco Language Client: https://github.com/TypeFox/monaco-languageclient

examples/langserver.py

@@ -0,0 +1,71 @@
+import json
+import logging
+
+from tornado import web, ioloop, websocket
+
+from jsonrpc import dispatchers, endpoint
+
+log = logging.getLogger(__name__)
+
+
+class LanguageServer(dispatchers.MethodDispatcher):
+    """Implement a JSON RPC method dispatcher for the language server protocol."""
+
+    def __init__(self):
+        # Endpoint is lazily set after construction
+        self.endpoint = None
+
+    def m_initialize(self, rootUri=None, **kwargs):
+        log.info("Got initialize params: %s", kwargs)
+        return {"capabilities": {
+            "textDocumentSync": {
+                "openClose": True,
+            }
+        }}
+
+    def m_text_document__did_open(self, textDocument=None, **_kwargs):
+        log.info("Opened text document %s", textDocument)
+        self.endpoint.notify('textDocument/publishDiagnostics', {
+            'uri': textDocument['uri'],
+            'diagnostics': [{
+                'range': {
+                    'start': {'line': 0, 'character': 0},
+                    'end': {'line': 1, 'character': 0},
+                },
+                'message': 'Some very bad Python code',
+                'severity': 1  # DiagnosticSeverity.Error
+            }]
+        })
+
+
+class LanguageServerWebSocketHandler(websocket.WebSocketHandler):
+    """Setup tornado websocket handler to host language server."""
+
+    def __init__(self, *args, **kwargs):
+        # Create an instance of the language server used to dispatch JSON RPC methods
+        langserver = LanguageServer()
+
+        # Setup an endpoint that dispatches to the ls, and writes server->client messages
+        # back to the client websocket
+        self.endpoint = endpoint.Endpoint(langserver, lambda msg: self.write_message(json.dumps(msg)))
+
+        # Give the language server a handle to the endpoint so it can send JSON RPC
+        # notifications and requests.
+        langserver.endpoint = self.endpoint
+
+        super(LanguageServerWebSocketHandler, self).__init__(*args, **kwargs)
+
+    def on_message(self, message):
+        """Forward client->server messages to the endpoint."""
+        self.endpoint.consume(json.loads(message))
+
+    def check_origin(self, origin):
+        return True
+
+
+if __name__ == "__main__":
+    app = web.Application([
+        (r"/python", LanguageServerWebSocketHandler),
+    ])
+    app.listen(3000, address='127.0.0.1')
+    ioloop.IOLoop.current().start()

examples/langserver_ext.py

@@ -0,0 +1,56 @@
+import json
+import logging
+import subprocess
+import threading
+
+from tornado import ioloop, process, web, websocket
+
+from jsonrpc import streams
+
+log = logging.getLogger(__name__)
+
+
+class LanguageServerWebSocketHandler(websocket.WebSocketHandler):
+    """Setup tornado websocket handler to host an external language server."""
+
+    writer = None
+
+    def open(self, *args, **kwargs):
+        log.info("Spawning pyls subprocess")
+
+        # Create an instance of the language server
+        proc = process.Subprocess(
+            ['pyls', '-v'],
+            stdin=subprocess.PIPE,
+            stdout=subprocess.PIPE
+        )
+
+        # Create a writer that formats json messages with the correct LSP headers
+        self.writer = streams.JsonRpcStreamWriter(proc.stdin)
+
+        # Create a reader for consuming stdout of the language server. We need to
+        # consume this in another thread
+        def consume():
+            # Start a tornado IOLoop for reading/writing to the process in this thread
+            ioloop.IOLoop()
+            reader = streams.JsonRpcStreamReader(proc.stdout)
+            reader.listen(lambda msg: self.write_message(json.dumps(msg)))
+
+        thread = threading.Thread(target=consume)
+        thread.daemon = True
+        thread.start()
+
+    def on_message(self, message):
+        """Forward client->server messages to the endpoint."""
+        self.writer.write(json.loads(message))
+
+    def check_origin(self, origin):
+        return True
+
+
+if __name__ == "__main__":
+    app = web.Application([
+        (r"/python", LanguageServerWebSocketHandler),
+    ])
+    app.listen(3000, address='127.0.0.1')
+    ioloop.IOLoop.current().start()