Check for telnet BrokenPipeError, better match on bad telnet cmd

coverage multiprocessing concurrency

flightgear_python/fg_if.py

@@ -423,7 +423,10 @@ def _telnet_str(in_str: str) -> ByteString:
         return f'{in_str}\r\n'.encode()
 
     def _send_cmd_get_resp(self, cmd_str: str, buflen: int = 512) -> str:
-        self.sock.sendall(self._telnet_str(cmd_str))
+        try:
+            self.sock.sendall(self._telnet_str(cmd_str))
+        except BrokenPipeError as e:
+            raise FGCommunicationError('Failed to send data. Did you call .connect()?') from e
 
         # FG telnet always ends with a prompt (`cwd`> ), and since we always
         # operate relative to the root directory, it should always be the same prompt
@@ -438,7 +441,7 @@ def _send_cmd_get_resp(self, cmd_str: str, buflen: int = 512) -> str:
         resp_bytes = strip_end(resp_bytes, b'\r\n' + ending_bytes)  # trim the prompt
 
         resp_str = resp_bytes.decode()
-        if resp_str.startswith('-ERR'):
+        if resp_str.startswith('-ERR') or resp_str.startswith('Valid commands are'):
             raise FGCommunicationError(f'Bad telnet command "{cmd_str}". Response: "{resp_str}"')
         return resp_str
 

pyproject.toml

@@ -58,3 +58,8 @@ addopts = '-m "not fg_integration"'
 filterwarnings = [
     'ignore::DeprecationWarning:setuptools:2',
 ]
+
+[tool.coverage.run]
+branch = true
+timid = true
+concurrency = ['multiprocessing']

tests/test_integration_FG_telnet.py

@@ -3,7 +3,7 @@
 import pytest
 
 from flightgear_python.fg_if import TelnetConnection
-from flightgear_python.fg_util import FGConnectionError
+from flightgear_python.fg_util import FGConnectionError, FGCommunicationError
 
 
 pytestmark = pytest.mark.fg_integration
@@ -49,3 +49,23 @@ def test_telnet_wrong_port():
     t_con = TelnetConnection('localhost', 123)
     with pytest.raises(FGConnectionError):
         t_con.connect()
+
+
+def test_telnet_no_connect():
+    t_con = TelnetConnection('localhost', 5500)
+    with pytest.raises(FGCommunicationError):
+        t_con.get_prop('/controls/flight/rudder')
+
+
+def test_telnet_bad_path_cmd():
+    t_con = TelnetConnection('localhost', 5500)
+    t_con.connect()
+    with pytest.raises(FGCommunicationError):
+        t_con.list_props('/aaa/bbb/ccc')
+
+
+def test_telnet_bad_internal_cmd():
+    t_con = TelnetConnection('localhost', 5500)
+    t_con.connect()
+    with pytest.raises(FGCommunicationError):
+        t_con._send_cmd_get_resp('what a bad command')