# Coding Standards

The house standards every Rethink Studios project follows. They keep our code
consistent, readable, and predictable across the whole suite.

## Files and style

- Files end with a **single trailing newline** (LF / Unix line endings), and
  carry **no trailing whitespace** on any line.
- **4 spaces** for indentation by default. Respect language norms — TS/JS use
  **2 spaces**, Go uses **tabs** — and when editing an existing file, follow that
  file's existing indentation.
- **flake8 clean**, max line length **120**. **Type hints** on public functions.

A well-formed module — module docstring, type hints, lowercase-start docstring:

```python
"""async key/value store backed by a single json file"""

from pathlib import Path


def load_state(path: Path) -> dict[str, str]:
    """read the json state file, returning an empty dict if it's missing"""
    if not path.exists():
        return {}
    return _read_json(path)
```

flake8 tells you the moment you drift — keep the tree clean:

```text
$ flake8
./aiokv/store.py:14:80: E501 line too long (96 > 79 characters)
./aiokv/store.py:22:1: F401 'json' imported but unused
./aiokv/store.py:31:5: E303 too many blank lines (3)
```

!!! tip "Run it locally"
    Wire the shared config into an alias so every project lints the same way:
    `alias flake8='flake8 --config ~/.config/flake8'` (max line 120). See the
    [Workflow](workflow.md#handy-shell-setup) page.

## Documentation

- Public functions get a **docstring** — **lowercase-start, no trailing period**.
- Keep inline comments minimal; prefer docstrings. Use an inline comment only
  where the code is genuinely complex.
- Each module/file states its scope and purpose via a **module docstring**
  (header string) — **not** a license or copyright header.
- Every library and project has a **README** with the install line, what it does,
  and a usage example.

!!! note "Licensing — no per-file headers"
    Don't prepend license/copyright boilerplate to source files. If a repo needs a
    license, it's a single top-level **`LICENSE`** file — never repeated per file.
    Most internal repos don't carry one; add it only when a repo is meant for
    outside use and the terms are decided.

=== "Do"

    ```python
    def mask_secret(value: str, keep: int = 4) -> str:
        """mask all but the last ``keep`` characters of a secret"""
        if len(value) <= keep:
            return "*" * len(value)
        return "*" * (len(value) - keep) + value[-keep:]
    ```

=== "Don't"

    ```python
    # Masks a secret.   <- license-header-style noise, capitalized, trailing period
    def mask_secret(value, keep=4):   # no type hints
        # loop over the chars and hide them
        return "*" * (len(value) - keep) + value[-keep:]   # crashes if short
    ```

## Quality and error handling

**Fail loud** — never swallow exceptions. Catch the **specific** exception and
**log** it; don't paper over failures with a bare `except`.

=== "Do"

    ```python
    import logging

    log = logging.getLogger(__name__)


    def fetch(url: str) -> bytes:
        """fetch ``url``, logging and re-raising on failure"""
        try:
            return _client.get(url).content
        except TimeoutError:
            log.warning("fetch timed out: %s", url)
            raise
    ```

=== "Don't"

    ```python
    def fetch(url):
        try:
            return _client.get(url).content
        except Exception:
            pass   # swallowed — the caller has no idea anything broke
    ```

When something does break, a loud failure gives you a real traceback to act on:

```python-traceback
Traceback (most recent call last):
  File "run.py", line 42, in <module>
    data = fetch("https://example.test/feed")
  File "aioweb/session.py", line 88, in fetch
    return self._client.get(url).content
TimeoutError: request timed out after 30s
```

…and the log line that precedes it tells you where to look:

```text
2026-06-29 14:03:11,204 WARNING aioweb.session fetch timed out: https://example.test/feed
```

!!! note "Logging belongs to the app, not the library"
    Libraries **emit only** — `log = logging.getLogger(__name__)` and nothing
    else. Handlers, levels, and formatting are configured once at the
    application entry point, so a lib never dictates how its host logs.