ddd-ts-kit/clean-function-size

Architecture id: clean/function-size. Default severity: warn in recommended, error in strict.

Applies to: every linted file.

Why

A function with more than three parameters hides a concept that has no name yet; a function longer than a screen does more than one thing.

Reported

• more than maxParameters parameters (default 3); constructors are exempt, a this parameter is not counted
• more than maxLines lines of code in the body (default 30, never above 100); blank lines and comment lines are not counted

Incorrect:

function charge(amount: Amount, card: Card, at: Date, retries: number): void {}

Correct:

function charge(payment: Payment, policy: RetryPolicy): void {}

Details

The module file of a context (<context>.module.ts) is exempt from the line limit: a composition grows with the context. So is the callback of describe, suite and context: it holds tests, not steps. Both are still held by the hard ceiling of 100 lines, which is the companion rule clean-function-ceiling, an error whatever the severity of this one.

Options

[{ "maxParameters": 3, "maxLines": 30 }]. When an option is absent, limits.maxParameters and limits.maxFunctionLines of ddd-ts-kit.config.json apply, then the defaults. A maxLines or a limits.maxFunctionLines above 100 is read as 100.

rules."clean/function-size" in ddd-ts-kit.config.json set to off silences the rule, and // ddd-ts-kit-disable-next-line clean/function-size -- <reason> silences one line, exactly as for ddd-ts-kit check.

Limits

• The standard max-params and max-lines-per-function are not enabled by the presets: they cannot exempt constructors nor read the limits of the config, and would report twice.
• A nested function counts in the length of the function around it.

With the CLI checker

ddd-ts-kit check approximates this rule on the text of the file and stays the fast edit-time guard. This rule is the authority.