room power-levels should fail gracefully when Synapse not reachable

[JOJ0]

$ synadm room power-levels
ERROR ConnectionError while querying Synapse: HTTPConnectionPool(host='localhost', port=8008): Max retries exceeded with url: /_synapse/admin/v1/rooms?from=0&limit=10 (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x10405aa90>: Failed to establish a new connection: [Errno 61] Connection refused'))
...
...

  File "/Users/user/git/synadm/synadm/api.py", line 849, in room_power_levels
    for i, room in enumerate(rooms["rooms"]):
                             ~~~~~^^^^^^^^^
TypeError: 'NoneType' object is not subscriptable

[JacksonChen666]

I've removed the "good first issue" label because glancing over how stuff is handled, it doesn't seem easy. The easiest thing is adding conditions to check if it's None, but that's code that'll be repeated everywhere. The API code also queries Synapse for more stuff in a loop, and then that gets trickier to handle because we have to handle retries now (everywhere as well, also would not recommend) and it's multiple requests in a single "API" function as well.

Retries are already handled apparently, just from reading your logs:

ERROR ConnectionError while querying Synapse: HTTPConnectionPool(host='localhost', port=8008): Max retries exceeded with url: /_synapse/admin/v1/rooms?from=0&limit=10 (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x10405aa90>: Failed to establish a new connection: [Errno 61] Connection refused'))

It's just that we don't have a nice way of displaying requests errors and complain (I think, could we do fatal logging?), and instead the query function just returns None. Maybe the query function should throw an exception but I'm not sure if that's good API design (throwing exceptions).

Also should point out that the rest of the codebase has a similar issue with failed requests handling: It doesn't. Here's an output from npx pyright (yes, a Python type checker in JS. I'm aware 🙃):

/Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:329:12 - error: Operator "in" not supported for types "Literal['room_id']" and "Any | None"
    Operator "in" not supported for types "Literal['room_id']" and "None" (reportOperatorIssue)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:330:20 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:473:30 - error: "get" is not a known attribute of "None" (reportOptionalMemberAccess)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:819:30 - error: "get" is not a known attribute of "None" (reportOptionalMemberAccess)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:866:34 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:867:13 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:869:22 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:875:25 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:879:25 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:889:26 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:891:9 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1069:23 - error: "before_ts" is possibly unbound (reportPossiblyUnboundVariable)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1071:53 - error: "before_ts" is possibly unbound (reportPossiblyUnboundVariable)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1074:12 - error: "before_ts" is possibly unbound (reportPossiblyUnboundVariable)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1076:30 - error: "before_ts" is possibly unbound (reportPossiblyUnboundVariable)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1117:23 - error: "before_ts" is possibly unbound (reportPossiblyUnboundVariable)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1119:53 - error: "before_ts" is possibly unbound (reportPossiblyUnboundVariable)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1123:34 - error: "before_ts" is possibly unbound (reportPossiblyUnboundVariable)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1400:16 - error: Operator "not in" not supported for types "Literal['users']" and "Any | None"
    Operator "not in" not supported for types "Literal['users']" and "None" (reportOperatorIssue)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1403:29 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1412:20 - error: Operator "not in" not supported for types "Literal['next_token']" and "Any | None"
    Operator "not in" not supported for types "Literal['next_token']" and "None" (reportOperatorIssue)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/api.py:1414:43 - error: Object of type "None" is not subscriptable (reportOptionalSubscript)
/Users/jackson/projects/github.com/JOJ0/synadm/synadm/cli/_helper.py
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/cli/_helper.py:251:31 - error: Cannot access attribute "target" for class "list[Unknown]"
    Attribute "target" is unknown (reportAttributeAccessIssue)
  /Users/jackson/projects/github.com/JOJ0/synadm/synadm/cli/_helper.py:251:49 - error: Cannot access attribute "port" for class "list[Unknown]"
    Attribute "port" is unknown (reportAttributeAccessIssue)
24 errors, 0 warnings, 0 informations

If it mentions None, it's probably not correctly handling the API's None responses correctly. pyright also doesn't detect API usages because of the click helper thing, so this is not complete as it misses CLI stuff.

So some of my ideas with how to proceed with this codebase-wise:

• Continue as-is, and handle a potential lack of response completely every time (if not obvious, this is not the case even within this codebase)
• Throw exceptions in the query function in the API, creating a breaking change to handling failed requests (no clear design about this yet)
  • Log fatally, exiting the program early, when querying Synapse
• Something else

I'm currently not sure. Might think about this later.

(Also please don't cut off stacktraces!)

[JOJ0]

Log fatally, exiting the program early, when querying Synapse

This seems like the best idea here.

A try/except wrapper around "everything" (not sure yet what everything is) or maybe just around the query function? Would that work?

Another idea would be to more precisely return what Synapse/requests "experiences". Elsewhere (and I know it's a very basic and maybe not the most sophisticated strategy) I had requests functions like query return a 3-valued tuple (respone|None, errcode|None, errdetail|None) (or could also be a named tuple or dataclass). At least this would give an easy opportunity on the CLI level to put simple "early returns" and end the program:

if errcode != 200:  # or check for only "fatal" errorcodes/errortypes
    log.error(errdetail)
    sys.exit()

Again, this is very basic, also it would mean we would have to change every CLI and every API function. But once we had it in place, it might help with "reacting" to other less-fatal errors and work with that. And yes I'm aware of that this is something similar or maybe just a little better as what you point out in "- Continue as-is ....." , but still more control....and we still would have to finally do it everywhere

For fatal-only probably putting a "global" wrapper "somewhere" and simply ending sounds easier to implement.

[JOJ0]

...and now that you mention typing.....we should talk about that too ;-)