Stack trace when syntax errors in conf file

[ekr1]

I fabricated a syntax error in the config file (missing comma after the "600"):

...
agent-config: |
  {
    "command_timeout": 600
    "allowed_commands": [   
      "wc -l*"
    ]
...

I would expect it to tell me that a comma is missing at line $X. Instead, I am getting this stack trace:

Traceback (most recent call last):
  File "/Users/me/Documents/src/cecli-fork/cecli/coders/agent_coder.py", line 144, in _get_agent_config
    config = json.loads(self.args.agent_config)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/json/__init__.py", line 346, in loads
    return _default_decoder.decode(s)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/json/decoder.py", line 338, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/json/decoder.py", line 354, in raw_decode
    obj, end = self.scan_once(s, idx)
               ^^^^^^^^^^^^^^^^^^^^^^
json.decoder.JSONDecodeError: Expecting ',' delimiter: line 3 column 3 (char 29)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/me/.local/bin/cecli", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/Users/me/Documents/src/cecli-fork/cecli/main.py", line 494, in main
    return asyncio.run(main_async(argv, input, output, force_git_root, return_coder))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/asyncio/runners.py", line 195, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/asyncio/base_events.py", line 691, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/Users/me/Documents/src/cecli-fork/cecli/main.py", line 1035, in main_async
    coder = await Coder.create(
            ^^^^^^^^^^^^^^^^^^^
  File "/Users/me/Documents/src/cecli-fork/cecli/coders/base_coder.py", line 338, in create
    res = coder(main_model, io, args=args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/me/Documents/src/cecli-fork/cecli/coders/agent_coder.py", line 99, in __init__
    self.agent_config = self._get_agent_config()
                        ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/me/Documents/src/cecli-fork/cecli/coders/agent_coder.py", line 146, in _get_agent_config
    self.io.tool_warning(f"Failed to parse agent-config JSON: {e}")
    ^^^^^^^
AttributeError: 'AgentCoder' object has no attribute 'io'

Note how the user-facing error message is helpfully included in the middle (json.decoder.JSONDecodeError: Expecting ',' delimiter: line 3 column 3 (char 29)) so it should be reasonably easy to display that instead of the stack trace.

Note how this is the sub-parsing of the embedded JSON for the agent-config parameter. Syntax errors in the top-level YAML are reported correctly - breaking that, I get something like this:

cecli: error: Couldn't parse config file: while scanning a simple key
  in "/Users/me/.cecli.conf.yml", line 79, column 9
could not find expected ':'
  in "/Users/me/.cecli.conf.yml", line 81, column 1

Thanks for the awesome development!

cecli v0.100.6.dev8