Add use-t-throws-async-well rule (#278)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

docs/rules/use-t-throws-async-well.md

@@ -0,0 +1,29 @@
+# Ensure that `t.throwsAsync()` and `t.notThrowsAsync()` are awaited
+
+When you use the `t.throwsAsync()` and `t.notThrowsAsync()` assertions, you must await the promise they return. If the test function completes before the assertions do, the test will fail.
+
+This rule is fixable inside `async` functions. It will insert `await` before `t.throwsAsync()` and `t.notThrowsAsync()`.
+
+## Fail
+
+```js
+import test from 'ava';
+
+test('main', t => {
+	t.throwsAsync(somePromise);
+	t.notThrowsAsync(somePromise);
+});
+```
+
+## Pass
+
+```js
+import test from 'ava';
+
+test('main', t => {
+	await t.throwsAsync(somePromise);
+	await t.notThrowsAsync(somePromise);
+	const p = t.throwsAsync(somePromise);
+	t.throwsAsync(somePromise).then(…);
+});
+```

index.js

@@ -48,6 +48,7 @@ module.exports = {
 				'ava/test-title-format': 'off',
 				'ava/use-t-well': 'error',
 				'ava/use-t': 'error',
+				'ava/use-t-throws-async-well': 'error',
 				'ava/use-test': 'error',
 				'ava/use-true-false': 'error'
 			}

readme.md

@@ -65,6 +65,7 @@ Configure it in `package.json`.
 			"ava/test-title": "error",
 			"ava/test-title-format": "off",
 			"ava/use-t": "error",
+			"ava/use-t-throws-async-well": "error",
 			"ava/use-t-well": "error",
 			"ava/use-test": "error",
 			"ava/use-true-false": "error"
@@ -105,6 +106,7 @@ The rules will only activate in test files.
 - [test-title](docs/rules/test-title.md) - Ensure tests have a title.
 - [test-title-format](docs/rules/test-title-format.md) - Ensure test titles have a certain format.
 - [use-t](docs/rules/use-t.md) - Ensure test functions use `t` as their parameter.
+- [use-t-throws-async-well](docs/rules/use-t-throws-async-well.md) - Ensure that `t.throwsAsync()` and `t.notThrowsAsync()` are awaited. *(partly fixable)*
 - [use-t-well](docs/rules/use-t-well.md) - Prevent the incorrect use of `t`. *(partly fixable)*
 - [use-test](docs/rules/use-test.md) - Ensure that AVA is imported with `test` as the variable name.
 - [use-true-false](docs/rules/use-true-false.md) - Ensure that `t.true()`/`t.false()` are used instead of `t.truthy()`/`t.falsy()`.

rules/use-t-throws-async-well.js

@@ -0,0 +1,47 @@
+'use strict';
+const {visitIf} = require('enhance-visitors');
+const util = require('../util');
+const createAvaRule = require('../create-ava-rule');
+
+const create = context => {
+	const ava = createAvaRule();
+
+	return ava.merge({
+		CallExpression: visitIf([
+			ava.isInTestFile,
+			ava.isInTestNode
+		])(node => {
+			if (
+				node.parent.type === 'ExpressionStatement' &&
+				node.callee.type === 'MemberExpression' &&
+				(node.callee.property.name === 'throwsAsync' || node.callee.property.name === 'notThrowsAsync') &&
+				node.callee.object.name === 't'
+			) {
+				const message = `Use \`await\` with \`t.${node.callee.property.name}()\`.`;
+				if (ava.isInTestNode().arguments[0].async) {
+					context.report({
+						node,
+						message,
+						fix: fixer => fixer.replaceText(node.callee, `await ${context.getSourceCode().getText(node.callee)}`)
+					});
+				} else {
+					context.report({
+						node,
+						message
+					});
+				}
+			}
+		})
+	});
+};
+
+module.exports = {
+	create,
+	meta: {
+		docs: {
+			url: util.getDocsUrl(__filename)
+		},
+		fixable: 'code',
+		type: 'problem'
+	}
+};

test/use-t-throws-async-well.js

@@ -0,0 +1,77 @@
+import test from 'ava';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/use-t-throws-async-well';
+
+const ruleTester = avaRuleTester(test, {
+	parserOptions: {
+		ecmaVersion: 2020
+	}
+});
+
+const header = 'const test = require(\'ava\');\n';
+
+function asyncTestCase(contents, prependHeader) {
+	const content = `test(async t => { ${contents} });`;
+
+	if (prependHeader !== false) {
+		return header + content;
+	}
+
+	return content;
+}
+
+function syncTestCase(contents, prependHeader) {
+	const content = `test(t => { ${contents} });`;
+
+	if (prependHeader !== false) {
+		return header + content;
+	}
+
+	return content;
+}
+
+ruleTester.run('use-t-throws-async-well', rule, {
+	valid: [
+		asyncTestCase('await t.throwsAsync(f)'),
+		asyncTestCase('await t.notThrowsAsync(f)'),
+		asyncTestCase('t.throws(f)'),
+		asyncTestCase('t.notThrows(f)'),
+		asyncTestCase('f(t.throwsAsync(f))'),
+		asyncTestCase('let p = t.throwsAsync(f)'),
+		asyncTestCase('p = t.throwsAsync(f)'),
+		asyncTestCase('t.throwsAsync(f)', false), // Shouldn't be triggered since it's not a test file
+		syncTestCase('t.throwsAsync(f)', false) // Shouldn't be triggered since it's not a test file
+	],
+	invalid: [
+		{
+			code: syncTestCase('t.throwsAsync(f)'),
+			errors: [{
+				ruleId: 'use-t-throws-async-well',
+				message: 'Use `await` with `t.throwsAsync()`.'
+			}]
+		},
+		{
+			code: syncTestCase('t.notThrowsAsync(f)'),
+			errors: [{
+				ruleId: 'use-t-throws-async-well',
+				message: 'Use `await` with `t.notThrowsAsync()`.'
+			}]
+		},
+		{
+			code: asyncTestCase('t.throwsAsync(f)'),
+			output: asyncTestCase('await t.throwsAsync(f)'),
+			errors: [{
+				ruleId: 'use-t-throws-async-well',
+				message: 'Use `await` with `t.throwsAsync()`.'
+			}]
+		},
+		{
+			code: asyncTestCase('t.notThrowsAsync(f)'),
+			output: asyncTestCase('await t.notThrowsAsync(f)'),
+			errors: [{
+				ruleId: 'use-t-throws-async-well',
+				message: 'Use `await` with `t.notThrowsAsync()`.'
+			}]
+		}
+	]
+});