Warn against reused context managers, and fix broken tests

nilmdb/client/client.py

@@ -144,6 +144,7 @@ class Client(object):
         ctx = StreamInserter(self, path, start, end)
         yield ctx
         ctx.finalize()
+        ctx.destroy()
 
     def stream_insert(self, path, data, start = None, end = None):
         """Insert rows of data into a stream.  data should be a string
@@ -293,6 +294,15 @@ class StreamInserter(object):
         self._block_data = []
         self._block_len = 0
 
+        self.destroyed = False
+
+    def destroy(self):
+        """Ensure this object can't be used again without raising
+        an error"""
+        def error(*args, **kwargs):
+            raise Exception("don't reuse this context object")
+        self._send_block = self.insert = self.finalize = self.send = error
+
     def insert(self, data):
         """Insert a chunk of ASCII formatted data in string form.  The
         overall data must consist of lines terminated by '\\n'."""

nilmdb/client/numpyclient.py

@@ -98,6 +98,7 @@ class NumpyClient(nilmdb.client.client.Client):
         ctx = StreamInserterNumpy(self, path, start, end, dtype)
         yield ctx
         ctx.finalize()
+        ctx.destroy()
 
     def stream_insert_numpy(self, path, data, start = None, end = None,
                             layout = None):

tests/test_client.py

@@ -621,7 +621,7 @@ class TestClient(object):
             pass
 
         # Try various things that might cause problems
-        with client.stream_insert_context("/empty/test", 1000, 1050):
+        with client.stream_insert_context("/empty/test", 1000, 1050) as ctx:
             ctx.finalize() # inserts [1000, 1050]
             ctx.finalize() # nothing
             ctx.finalize() # nothing

tests/test_numpyclient.py

@@ -310,7 +310,8 @@ class TestNumpyClient(object):
             pass
 
         # Try various things that might cause problems
-        with client.stream_insert_numpy_context("/empty/test", 1000, 1050):
+        with client.stream_insert_numpy_context("/empty/test",
+                                                1000, 1050) as ctx:
             ctx.finalize() # inserts [1000, 1050]
             ctx.finalize() # nothing
             ctx.finalize() # nothing