Fix KeyError on malformed Bitcoin Core RPC responses

[Copilot]

BitcoinRPC.__getattr__ crashes with KeyError: 'error' when Bitcoin Core returns malformed JSON-RPC responses. The code blindly accessed r['error']['message'] without validating response structure.

Changes

RPC error handling (rpc.py)

• Validate response is dict before accessing keys
• Handle error field as non-dict (e.g., plain strings)
• Handle missing 'message' key in error dicts
• Check 'result' field exists before access
• Fix RpcError.init_via_response() to handle both Response objects and dicts

Test coverage (test_rpc.py)

• Add test_BitcoinRpc_malformed_response covering 6 malformed response scenarios

Example

Before:

# Crashes with KeyError if response = {"error": "Connection refused"}
r = self.multi([(method, *args)], **kwargs)[0]
if r.get("error") is not None:
    raise RpcError(f"...: {r['error']['message']}", r)  # KeyError

After:

if not isinstance(r, dict):
    raise RpcError(f"Invalid response format (expected dict, got {type(r).__name__})", ...)

error = r.get("error")
if error is not None:
    error_message = error.get("message", str(error)) if isinstance(error, dict) else str(error)
    raise RpcError(f"...: {error_message}", r)

All valid JSON-RPC 2.0 responses continue to work unchanged.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https tgresql cal/bin/rustc ver -plu�� hon3.12 -plugin-opt=/usr/libexec/gcc/x86_64-linux-gnu/13/lto-wrapper de/node/bin/bash -plugin-opt=-pascut tgresql -plugin-opt=-pass-through=-lc /x86_64-linux-gnu/13/cc1 -I xml2 hon3.12 p/bin/git -I -x86_64-cpython--rs tgresql as (dns block)
• httpbin.org
  • Triggering command: /usr/bin/python3 python3 /usr/include/pos--force-confdef -I as ctly�� /usr/include/pyt--print-foreign-architectures -I nfig/composer/vendor/bin/lsb_release -I /usr/include/pos-x -I hg root�� p/specter-desktop/.git --gdwarf-5 lsb_release -o build/temp.linux--listfiles /tmp/cc4LLc0S.s git (dns block)
  • Triggering command: /usr/bin/python3 python3 /usr/include/pos--force-confdef -I as -I rd -I k/_temp/ghcca-no--force-confdef -I /usr/include/pos--fsys-tarfile -I git rev-�� p/specter-desktop/.git --gdwarf-5 ame -o e response struccall /tmp/ccna9yb6.s bash (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Exception Error</issue_title>
<issue_description>Details

version: v2.0.5
Traceback (most recent call last):
File "flask/app.py", line 1823, in full_dispatch_request
File "flask/app.py", line 1799, in dispatch_request
File "flask_login/utils.py", line 290, in decorated_view
File "cryptoadvance/specter/server_endpoints/nodes.py", line 68, in node_settings_new_node_get
File "cryptoadvance/specter/node.py", line 348, in from_json
File "cryptoadvance/specter/node.py", line 327, in init
File "cryptoadvance/specter/node.py", line 395, in _get_rpc
File "cryptoadvance/specter/rpc.py", line 219, in autodetect_rpc_confs
File "cryptoadvance/specter/rpc.py", line 508, in fn
KeyError: 'error'

This is what it says when I connected to bitcoin core. How do fix this?</issue_description>

<agent_instructions>Improve error management more or less as described and check how we can potentially test it within the existing test framework.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Exception Error #2506

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[al-munazzim]

✅ LGTM - solid defensive coding.

The KeyError crash when Bitcoin Core returns malformed responses is a real issue. This PR:

1. ✅ Validates response is a dict before accessing keys
2. ✅ Handles error field as non-dict (e.g., plain strings)
3. ✅ Handles missing message key in error dicts
4. ✅ Good test coverage with 6 malformed response scenarios

The error messages are now informative instead of cryptic KeyErrors. Good work.