Linting event emitter returned by API can emit done before user listens it

[mondeja]

According to the example of the README, you must call lintSource to return a Linting instance and then listen the done event on that to check that the linting has been terminated. The problem is that Linting can have another state different to linting at that point.

These two tests are reproducing the behaviour:

svglint/test/valid.spec.js

Lines 57 to 65 in 3ce8e62

	it('should succeed when disabled for a valid SVG', function () {
	return testSucceeds('<svg></svg>', {rules: {valid: false}});
	});
	it('should succeed when disabled for an invalid SVG', function () {
	return testSucceeds(
	`<svg><path "M20.013 10.726l.001-.028A6.346"/></svg>`,
	{rules: {valid: false}},
	);
	});

That's the reason why I added this check to the tester before calling on('done', ... ):

svglint/test/helpers.js

Lines 25 to 38 in 3ce8e62

	// TODO: there is a race condition here. The this.lint() method
	// of the Linting class is called in the constructor, so it's possible
	// that the linting is already done before we call the on('done')
	// event listener. Removing the next condition will make some `valid`
	// rules tests fail.
	if (linting.state === linting.STATES.success) {
	resolve();
	} else if (linting.state !== linting.STATES.linting) {
	reject(
	new Error(
	`Linting failed (${linting.state}): ${inspect(config)}`,
	),
	);
	}

Is a race condition that happens because Linting.lint() is called at Linting constructor and can call Linting.emit('done') before the user listen the event. The most suitable solution is to not call this.lint() on Linting constructor and force to the user to call it after setting event listeners. This is a breaking change.