feat(prefer-implicit-assert): adding new rule (#815)

Closes #743 * feat(prefer-implicit-assert): adding new rule * feat(prefer-implicit-assert): increment number of rules * feat(prefer-implicit-assert): reduce duplication * feat(prefer-implicit-assert): add recommened rule by library, more test cases, update docs * feat(prefer-implicit-assert): added findBy link * feat(prefer-implicit-assert): added line and column checks * feat(prefer-implicit-assert): use existing utils * feat(prefer-implicit-assert): remove unnecessary checks
testing-library · Oct 12, 2023 · 56a1900 · 56a1900
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diff --git a/README.md b/README.md
@@ -228,6 +228,7 @@ module.exports = {
 | [no-wait-for-snapshot](docs/rules/no-wait-for-snapshot.md)                       | Ensures no snapshot is generated inside of a `waitFor` call                                  | ![badge-angular][] ![badge-dom][] ![badge-marko][] ![badge-react][] ![badge-vue][] |                                                                     |     |
 | [prefer-explicit-assert](docs/rules/prefer-explicit-assert.md)                   | Suggest using explicit assertions rather than standalone queries                             |                                                                                    |                                                                     |     |
 | [prefer-find-by](docs/rules/prefer-find-by.md)                                   | Suggest using `find(All)By*` query instead of `waitFor` + `get(All)By*` to wait for elements | ![badge-angular][] ![badge-dom][] ![badge-marko][] ![badge-react][] ![badge-vue][] |                                                                     | 🔧  |
+| [prefer-implicit-assert](docs/rules/prefer-implicit-assert.md)                   | Suggest using implicit assertions for getBy* & findBy* queries                               |                                                                                    |                                                                     |     |
 | [prefer-presence-queries](docs/rules/prefer-presence-queries.md)                 | Ensure appropriate `get*`/`query*` queries are used with their respective matchers           | ![badge-angular][] ![badge-dom][] ![badge-marko][] ![badge-react][] ![badge-vue][] |                                                                     |     |
 | [prefer-query-by-disappearance](docs/rules/prefer-query-by-disappearance.md)     | Suggest using `queryBy*` queries when waiting for disappearance                              | ![badge-angular][] ![badge-dom][] ![badge-marko][] ![badge-react][] ![badge-vue][] |                                                                     |     |
 | [prefer-query-matchers](docs/rules/prefer-query-matchers.md)                     | Ensure the configured `get*`/`query*` query is used with the corresponding matchers          |                                                                                    |                                                                     |     |

diff --git a/docs/rules/prefer-explicit-assert.md b/docs/rules/prefer-explicit-assert.md
@@ -72,7 +72,10 @@ This is how you can use these options in eslint configuration:
 
 ## When Not To Use It
 
-If you prefer to use `getBy*` queries implicitly as an assert-like method itself, then this rule is not recommended.
+If you prefer to use `getBy*` queries implicitly as an assert-like method itself, then this rule is not recommended. Instead check out this rule [prefer-implicit-assert](https://github.com/testing-library/eslint-plugin-testing-library/blob/main/docs/rules/prefer-implicit-assert.md)
+
+- Never use both `prefer-explicit-assert` & `prefer-implicit-assert` choose one.
+- This library recommends `prefer-explicit-assert` to make it more clear to readers that it is not just a query without an assertion, but that it is checking for existence of an element
 
 ## Further Reading
 

diff --git a/docs/rules/prefer-implicit-assert.md b/docs/rules/prefer-implicit-assert.md
@@ -0,0 +1,57 @@
+# Suggest using implicit assertions for getBy* & findBy* queries (`testing-library/prefer-implicit-assert`)
+
+<!-- end auto-generated rule header -->
+
+Testing Library `getBy*` & `findBy*` queries throw an error if the element is not
+found. Therefore it is not necessary to also assert existance with things like `expect(getBy*.toBeInTheDocument()` or `expect(awaint findBy*).not.toBeNull()`
+
+## Rule Details
+
+This rule aims to reuduce uncecessary assertion's for presense of an element,
+when using queries that implicitly fail when said element is not found.
+
+Examples of **incorrect** code for this rule with the default configuration:
+
+```js
+// wrapping the getBy or findBy queries within a `expect` and using existence matchers for
+// making the assertion is not necessary
+expect(getByText('foo')).toBeInTheDocument();
+expect(await findByText('foo')).toBeInTheDocument();
+
+expect(getByText('foo')).toBeDefined();
+expect(await findByText('foo')).toBeDefined();
+
+const utils = render(<Component />);
+expect(utils.getByText('foo')).toBeInTheDocument();
+expect(await utils.findByText('foo')).toBeInTheDocument();
+
+expect(await findByText('foo')).not.toBeNull();
+expect(await findByText('foo')).not.toBeUndified();
+```
+
+Examples of **correct** code for this rule with the default configuration:
+
+```js
+getByText('foo');
+await findByText('foo');
+
+const utils = render(<Component />);
+utils.getByText('foo');
+await utils.findByText('foo');
+
+// When using queryBy* queries thees do not implicitly fial therefore you should explicitly check if your elements eixst or not
+expect(queryByText('foo')).toBeInTheDocument();
+expect(queryByText('foo')).not.toBeInTheDocument();
+```
+
+## When Not To Use It
+
+If you prefer to use `getBy*` & `findBy*` queries with explicitly asserting existence of elements, then this rule is not recommended. Instead check out this rule [prefer-explicit-assert](https://github.com/testing-library/eslint-plugin-testing-library/blob/main/docs/rules/prefer-explicit-assert.md)
+
+- Never use both `prefer-implicit-assert` & `prefer-explicit-assert` choose one.
+- This library recommends `prefer-explicit-assert` to make it more clear to readers that it is not just a query without an assertion, but that it is checking for existence of an element
+
+## Further Reading
+
+- [getBy query](https://testing-library.com/docs/dom-testing-library/api-queries#getby)
+- [findBy query](https://testing-library.com/docs/dom-testing-library/api-queries#findBy)
diff --git a/lib/rules/prefer-implicit-assert.ts b/lib/rules/prefer-implicit-assert.ts
@@ -0,0 +1,136 @@
+import {
+	TSESTree,
+	ASTUtils,
+	AST_NODE_TYPES,
+	TSESLint,
+} from '@typescript-eslint/utils';
+
+import { createTestingLibraryRule } from '../create-testing-library-rule';
+import { TestingLibrarySettings } from '../create-testing-library-rule/detect-testing-library-utils';
+import { isCallExpression, isMemberExpression } from '../node-utils';
+
+export const RULE_NAME = 'prefer-implicit-assert';
+export type MessageIds = 'preferImplicitAssert';
+type Options = [];
+
+const isCalledUsingSomeObject = (node: TSESTree.Identifier) =>
+	isMemberExpression(node.parent) &&
+	node.parent.object.type === AST_NODE_TYPES.Identifier;
+
+const isCalledInExpect = (
+	node: TSESTree.Identifier | TSESTree.Node,
+	isAsyncQuery: boolean
+) => {
+	if (isAsyncQuery) {
+		return (
+			isCallExpression(node.parent) &&
+			ASTUtils.isAwaitExpression(node.parent.parent) &&
+			isCallExpression(node.parent.parent.parent) &&
+			ASTUtils.isIdentifier(node.parent.parent.parent.callee) &&
+			node.parent.parent.parent.callee.name === 'expect'
+		);
+	}
+	return (
+		isCallExpression(node.parent) &&
+		isCallExpression(node.parent.parent) &&
+		ASTUtils.isIdentifier(node.parent.parent.callee) &&
+		node.parent.parent.callee.name === 'expect'
+	);
+};
+
+const reportError = (
+	context: Readonly<
+		TSESLint.RuleContext<'preferImplicitAssert', []> & {
+			settings: TestingLibrarySettings;
+		}
+	>,
+	node: TSESTree.Identifier | TSESTree.Node | undefined,
+	queryType: string
+) => {
+	if (node) {
+		return context.report({
+			node,
+			messageId: 'preferImplicitAssert',
+			data: {
+				queryType,
+			},
+		});
+	}
+};
+
+export default createTestingLibraryRule<Options, MessageIds>({
+	name: RULE_NAME,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			description:
+				'Suggest using implicit assertions for getBy* & findBy* queries',
+			recommendedConfig: {
+				dom: false,
+				angular: false,
+				react: false,
+				vue: false,
+				marko: false,
+			},
+		},
+		messages: {
+			preferImplicitAssert:
+				"Don't wrap `{{queryType}}` query with `expect` & presence matchers like `toBeInTheDocument` or `not.toBeNull` as `{{queryType}}` queries fail implicitly when element is not found",
+		},
+		schema: [],
+	},
+	defaultOptions: [],
+	create(context, _, helpers) {
+		const findQueryCalls: TSESTree.Identifier[] = [];
+		const getQueryCalls: TSESTree.Identifier[] = [];
+
+		return {
+			'CallExpression Identifier'(node: TSESTree.Identifier) {
+				if (helpers.isFindQueryVariant(node)) {
+					findQueryCalls.push(node);
+				}
+				if (helpers.isGetQueryVariant(node)) {
+					getQueryCalls.push(node);
+				}
+			},
+			'Program:exit'() {
+				findQueryCalls.forEach((queryCall) => {
+					const isAsyncQuery = true;
+					const node: TSESTree.Identifier | TSESTree.Node | undefined =
+						isCalledUsingSomeObject(queryCall) ? queryCall.parent : queryCall;
+
+					if (node) {
+						if (isCalledInExpect(node, isAsyncQuery)) {
+							if (
+								isMemberExpression(node.parent?.parent?.parent?.parent) &&
+								node.parent?.parent?.parent?.parent.property.type ===
+									AST_NODE_TYPES.Identifier &&
+								helpers.isPresenceAssert(node.parent.parent.parent.parent)
+							) {
+								return reportError(context, node, 'findBy*');
+							}
+						}
+					}
+				});
+
+				getQueryCalls.forEach((queryCall) => {
+					const isAsyncQuery = false;
+					const node: TSESTree.Identifier | TSESTree.Node | undefined =
+						isCalledUsingSomeObject(queryCall) ? queryCall.parent : queryCall;
+					if (node) {
+						if (isCalledInExpect(node, isAsyncQuery)) {
+							if (
+								isMemberExpression(node.parent?.parent?.parent) &&
+								node.parent?.parent?.parent.property.type ===
+									AST_NODE_TYPES.Identifier &&
+								helpers.isPresenceAssert(node.parent.parent.parent)
+							) {
+								return reportError(context, node, 'getBy*');
+							}
+						}
+					}
+				});
+			},
+		};
+	},
+});
diff --git a/tests/index.test.ts b/tests/index.test.ts
@@ -3,7 +3,7 @@ import { resolve } from 'path';
 
 import plugin from '../lib';
 
-const numberOfRules = 26;
+const numberOfRules = 27;
 const ruleNames = Object.keys(plugin.rules);
 
 // eslint-disable-next-line jest/expect-expect