daikichiba9511/dotfiles/no-fallbacks

No Fallbacks

For experiment code, prioritize hypothesis purity and fail-fast behavior over backward compatibility.

Rules

• Do not add backward compatibility, aliases, compatibility layers, deprecated paths, silent fallbacks, or alternate execution paths unless the user explicitly asks for them.
• When replacing behavior, remove the old path. Do not keep historical traces, legacy branches, old config keys, or transitional aliases.
• Missing required config, missing dict keys, missing env vars, impossible states, and unsupported modes must fail fast with a clear error.
• Do not use default-value fallbacks for required values:
• dict.get(key, default)
• nested cfg.get("new", cfg.get("old"))
• os.getenv("NAME", default)
• kwargs.pop(name, default)
• value or default when a missing or falsey value would indicate a bug
• If a value is truly optional, name it as optional and handle None explicitly.
• If a default is a real domain constant, define it as an explicit constant, not as a fallback hidden inside lookup code.
• If an alias or migration path is explicitly required, make it loud:
• document why it exists
• count or report when it fires
• reject ambiguous mixed old/new keys
• include a removal condition

Experiment Code Guidance

• Prefer replacing the main path over adding a side path.
• Prefer deleting stale branches over preserving compatibility.
• Prefer one authoritative producer and one explicit consumer for each signal.
• Diagnostics should call production logic instead of reimplementing it.
• A fallback that keeps the run alive can invalidate the experiment result by hiding a disconnected or broken path.

Before Finishing

Report whether the change introduced any of the following:

• compatibility layer
• alias
• fallback path
• default value for missing config
• dict.get(..., default) for required data
• os.getenv(..., default)
• old branch left in place
• diagnostics reimplementing main logic

If any item is present, explain why it was explicitly required.