The catalogue

Utility functions you copy into your project, each verified against a public, executable contract. Not a dependency: the source lands in your repository and it is yours.

npx toopo add domain/function

Every contract carries its own command, on its own page. This is the shape of all of them.

A contract is the whole behavioural specification of one function — its signature, the invariants that must hold for every input, and every edge case named, settled and argued for. Anything that satisfies it can replace anything else that does, which is what makes an implementation a detail. The contract is what this project publishes; the code is what it hands you.

5 contracts in 4 domains

number

parse

date

array

group-by — turned down

string

How we verify

692 defect cells injected

659 caught by the suite

19 batteries, replayable

A test suite that has never failed proves nothing. Every contract here is measured by breaking the implementation on purpose and requiring the suite to notice — and what those measurements did not catch is published beside what they did. They measure what the tests notice, which is not the same as what the code does.

What the command does

It copies files. Nothing is added to your package.json, nothing of ours runs in your build, and a lockfile records what was served and what was written — so a file you edited is never overwritten and one that moved is named.

init — configure where features go.

add — install a feature and what it imports.

remove — show what would go, then take it out.

update — show what would change, then write it.

list — what this project holds.

search — find a contract, or list the catalogue.

What a contract is

The whole specification of one function: its signature, the invariants that must hold for every input, and every edge case named, settled and argued for. A contribution can be an implementation, or an input where ours is wrong — never a contract.