dckcandClaude Opus 5.5
d1a9c88b30
A ": " inside a plain-scalar description is a parse error; use a folded block scalar instead. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
38 lines
2.0 KiB
Markdown
38 lines
2.0 KiB
Markdown
---
|
|
name: silent-failures-are-evil
|
|
description: >-
|
|
No silent failures — use when writing or reviewing error handling: catch blocks, promise rejections, fallbacks for unsupported features, or any branch that treats a result as "didn't work"; when a UI shows a failure with nothing logged; when someone says "silent failure". Every failure path leaves a trace in the logs, and no failure is invented without checking what the API actually returns.
|
|
---
|
|
|
|
# Silent failures are evil
|
|
|
|
A failure nobody can see is a failure nobody can fix. Every failure path
|
|
must leave a trace.
|
|
|
|
## the rules
|
|
|
|
- **Log every failure path**: a caught exception, a rejected promise, a
|
|
falsy result treated as "didn't work", an unsupported-feature
|
|
fallback. Changing a label on screen is not enough — log it, with an
|
|
`event` tag for grepping, and no secrets (no keys, cookies, header or
|
|
param values).
|
|
- **Don't invent failures.** Before branching on a result, check what
|
|
the API actually returns (the spec or MDN, not a guess). A success
|
|
misreported as failure is as bad as a failure reported as nothing.
|
|
- **Say only what you know.** When an API can't tell you the outcome,
|
|
report what it did tell you ("offered", not "saved").
|
|
- **Make it testable.** Pass the logger in (see
|
|
[no-ambient-authority](../no-ambient-authority/SKILL.md)) so a test can assert
|
|
that the failure path logged; a discovered silent failure is a goof
|
|
that owes a test ([lazy-tdd](../lazy-tdd/SKILL.md)).
|
|
|
|
## the goof that prompted this
|
|
|
|
diigo-cache's password-manager save button said "not saved", with
|
|
nothing in the console. The code read `c ? "saved" : "not saved"` on the
|
|
result of [`CredentialsContainer.store()`](https://developer.mozilla.org/en-US/docs/Web/API/CredentialsContainer/store),
|
|
which resolves with `undefined` per spec — even on success. So every
|
|
save was reported as a failure, silently. The fix
|
|
(`capsite/diigo-cache/src/pm-save.ts`) reports "offered", logs every
|
|
outcome, and is covered by `tests/pm-save.test.ts`.
|