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.emacs.d/elpa/elpy-20171206.847/elpy/rpc.py

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+"""A simple JSON-RPC-like server.
+
+The server will read and write lines of JSON-encoded method calls and
+responses.
+
+See the documentation of the JSONRPCServer class for further details.
+
+"""
+
+import json
+import sys
+import traceback
+
+
+class JSONRPCServer(object):
+    """Simple JSON-RPC-like server.
+
+    This class will read single-line JSON expressions from stdin,
+    decode them, and pass them to a handler. Return values from the
+    handler will be JSON-encoded and written to stdout.
+
+    To implement a handler, you need to subclass this class and add
+    methods starting with "rpc_". Methods then will be found.
+
+    Method calls should be encoded like this:
+
+    {"id": 23, "method": "method_name", "params": ["foo", "bar"]}
+
+    This will call self.rpc_method("foo", "bar").
+
+    Responses will be encoded like this:
+
+    {"id": 23, "result": "foo"}
+
+    Errors will be encoded like this:
+
+    {"id": 23, "error": "Simple error message"}
+
+    See http://www.jsonrpc.org/ for the inspiration of the protocol.
+
+    """
+
+    def __init__(self, stdin=None, stdout=None):
+        """Return a new JSON-RPC server object.
+
+        It will read lines of JSON data from stdin, and write the
+        responses to stdout.
+
+        """
+        if stdin is None:
+            self.stdin = sys.stdin
+        else:
+            self.stdin = stdin
+        if stdout is None:
+            self.stdout = sys.stdout
+        else:
+            self.stdout = stdout
+
+    def read_json(self):
+        """Read a single line and decode it as JSON.
+
+        Can raise an EOFError() when the input source was closed.
+
+        """
+        line = self.stdin.readline()
+        if line == '':
+            raise EOFError()
+        return json.loads(line)
+
+    def write_json(self, **kwargs):
+        """Write an JSON object on a single line.
+
+        The keyword arguments are interpreted as a single JSON object.
+        It's not possible with this method to write non-objects.
+
+        """
+        self.stdout.write(json.dumps(kwargs) + "\n")
+        self.stdout.flush()
+
+    def handle_request(self):
+        """Handle a single JSON-RPC request.
+
+        Read a request, call the appropriate handler method, and
+        return the encoded result. Errors in the handler method are
+        caught and encoded as error objects. Errors in the decoding
+        phase are not caught, as we can not respond with an error
+        response to them.
+
+        """
+        request = self.read_json()
+        if 'method' not in request:
+            raise ValueError("Received a bad request: {0}"
+                             .format(request))
+        method_name = request['method']
+        request_id = request.get('id', None)
+        params = request.get('params') or []
+        try:
+            method = getattr(self, "rpc_" + method_name, None)
+            if method is not None:
+                result = method(*params)
+            else:
+                result = self.handle(method_name, params)
+            if request_id is not None:
+                self.write_json(result=result,
+                                id=request_id)
+        except Fault as fault:
+            error = {"message": fault.message,
+                     "code": fault.code}
+            if fault.data is not None:
+                error["data"] = fault.data
+            self.write_json(error=error, id=request_id)
+        except Exception as e:
+            error = {"message": str(e),
+                     "code": 500,
+                     "data": {"traceback": traceback.format_exc()}}
+            self.write_json(error=error, id=request_id)
+
+    def handle(self, method_name, args):
+        """Handle the call to method_name.
+
+        You should overwrite this method in a subclass.
+        """
+        raise Fault("Unknown method {0}".format(method_name))
+
+    def serve_forever(self):
+        """Serve requests forever.
+
+        Errors are not caught, so this is a slight misnomer.
+
+        """
+        while True:
+            try:
+                self.handle_request()
+            except (KeyboardInterrupt, EOFError, SystemExit):
+                break
+
+
+class Fault(Exception):
+    """RPC Fault instances.
+
+    code defines the severity of the warning.
+
+    2xx: Normal behavior lead to end of operation, i.e. a warning
+    4xx: An expected error occurred
+    5xx: An unexpected error occurred (usually includes a traceback)
+    """
+    def __init__(self, message, code=500, data=None):
+        super(Fault, self).__init__(message)
+        self.message = message
+        self.code = code
+        self.data = data