Validation

A value can be the wrong type wherever it came from. seniority's validation knows where it came from, so the message points at the place to fix it: the file and line, the flag the user typed, or the variable.

import { check, resolve, validate } from 'seniority';

const specs = { out: { type: 'string' }, mode: { type: 'string' }, retries: { type: 'number' }, token: { type: 'string' } };
const shape = { out: { type: 'string' }, mode: { choices: ['fast', 'safe'] }, retries: { type: 'number' }, token: { required: true } };

const result = resolve(specs, {
  flags: { mode: 'quick' },
  env: { APP_RETRIES: 'three' },
  envPrefix: 'APP',
  config: { path: 'mytool.config.json', data: { out: 4 }, lines: { out: 3 } },
});

for (const violation of validate(shape, result)) console.log(violation.message);

try {
  check(shape, result);
} catch (error) {
  console.log(`${error.constructor.name}, ${error.message.split('\n').length} lines`);
}

`out` must be a string; `mytool.config.json:3` set it to `4`
`mode` must be one of fast, safe; `--mode` set it to `"quick"`
`retries` must be a number; `APP_RETRIES` set it to `"three"`
`token` is required, and no source set it
ConfigError, 4 lines

• Every violation, not just the first. A config with four mistakes is fixed in one pass.
• validate never throws. No violations is an empty array. check is the throwing form: one ConfigError listing them all, or the values when there is nothing to say.
• A shape reads type, choices, required and default. An option with no declared type is not type-checked: a shape that says nothing asserts nothing.
• Each violation is data too: { key, message, expected, value, provenance }, so --json can carry it without parsing the sentence.

The line comes from the layer. discover records the line of each top-level key in a JSON config. A JavaScript config has no line to give, so its violations name the file alone.

What is testedCopy Anchor Link

• validate.test.ts:
  • the sentence, line and all;
  • no line when the source has none;
  • a flag named as the user typed it;
  • choices listed;
  • a required option with no provenance;
  • every violation reported;
  • check throws one CONFIG error.