affaan-m/ECC · error · ConfigError

Invalid JSON in config

Error message

Invalid JSON in config: {path}

What it means

Illustrative pattern from the python-patterns skill: the config file was opened successfully but json parsing failed, so the contents are not valid JSON and a ConfigError with the path is raised (chained from JSONDecodeError). The file's contents, not its absence, are the problem.

Solutions

1. Report line/column from the chained JSONDecodeError to the user
2. Validate configs against a schema after parsing
3. Fail fast at startup instead of returning partially initialized config

When it happens

Trigger: Thrown at skills/python-patterns/SKILL.md:153 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of affaan-m/ECC@d8409a4b08 (2026-08-26). Data as JSON: /api/errors/95fee8ce8247bee5. Report an issue: GitHub.

Appendix: source

Thrown at skills/python-patterns/SKILL.md:153

def render_all(items: list[Renderable]) -> str:
    """Render all items that implement the Renderable protocol."""
    return "\n".join(item.render() for item in items)
```

## Error Handling Patterns

### Specific Exception Handling

```python
# Good: Catch specific exceptions
def load_config(path: str) -> Config:
    try:
        with open(path) as f:
            return Config.from_json(f.read())
    except FileNotFoundError as e:
        raise ConfigError(f"Config file not found: {path}") from e
    except json.JSONDecodeError as e:
        raise ConfigError(f"Invalid JSON in config: {path}") from e

# Bad: Bare except
def load_config(path: str) -> Config:
    try:
        with open(path) as f:
            return Config.from_json(f.read())
    except:
        return None  # Silent failure!
```

### Exception Chaining

```python
def process_data(data: str) -> Result:
    try:
        parsed = json.loads(data)
    except json.JSONDecodeError as e:
        # Chain exceptions to preserve the traceback

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