feat: adds no jest import rule

docs/rules/no-jest-import.md

@@ -0,0 +1,20 @@
+# Disallow importing Jest(no-jest-import)
+
+The jest object is automatically in scope within every test file. The methods in
+the jest object help create mocks and let you control Jest's overall behavior.
+It is therefore completely unnecessary to import in Jest, as Jest doesn't export
+anything in the first place.
+
+### Rule details
+
+This rule reports on any importing of Jest.
+
+To name a few: *var jest = require('jest'); *const jest = require('jest');
+*import jest from 'jest'; *import {jest as test} from 'jest';
+
+There is no correct usage of this code, other than to not import Jest it in the
+first place.
+
+## Further Reading
+
+\*[The Jest Object](https://facebook.github.io/jest/docs/en/jest-object.html)

index.js

@@ -6,6 +6,7 @@ const noDisabledTests = require('./rules/no-disabled-tests');
 const noFocusedTests = require('./rules/no-focused-tests');
 const noHooks = require('./rules/no-hooks');
 const noIdenticalTitle = require('./rules/no-identical-title');
+const noJestImport = require('./rules/no-jest-import');
 const noLargeSnapshots = require('./rules/no-large-snapshots');
 const noTestPrefixes = require('./rules/no-test-prefixes');
 const preferToBeNull = require('./rules/prefer-to-be-null');
@@ -29,6 +30,7 @@ module.exports = {
  'jest/no-disabled-tests': 'warn',
  'jest/no-focused-tests': 'error',
  'jest/no-identical-title': 'error',
+ 'jest/no-jest-import': 'error',
  'jest/prefer-to-have-length': 'warn',
  'jest/valid-expect': 'error',
  },
@@ -67,6 +69,7 @@ module.exports = {
  'no-focused-tests': noFocusedTests,
  'no-hooks': noHooks,
  'no-identical-title': noIdenticalTitle,
+ 'no-jest-import': noJestImport,
  'no-large-snapshots': noLargeSnapshots,
  'no-test-prefixes': noTestPrefixes,
  'prefer-to-be-null': preferToBeNull,

rules/__tests__/no-jest-import.test.js

@@ -0,0 +1,71 @@
+'use strict';
+
+const rule = require('../no-jest-import.js');
+const RuleTester = require('eslint').RuleTester;
+const ruleTester = new RuleTester();
+
+ruleTester.run('no-jest-import', rule, {
+ valid: [
+ {
+ code: 'import something from "something"',
+ parserOptions: { sourceType: 'module' },
+ },
+ 'require("somethingElse")',
+ 'entirelyDifferent(fn)',
+ ],
+ invalid: [
+ {
+ code: 'require("jest")',
+ errors: [
+ {
+ endColumn: 15,
+ column: 9,
+ message: `Jest is automatically in scope. Do not import Jest, as it doesn't export anything.`,
+ },
+ ],
+ },
+ {
+ code: 'import jest from "jest"',
+ parserOptions: { sourceType: 'module' },
+ errors: [
+ {
+ endColumn: 24,
+ column: 1,
+ message: `Jest is automatically in scope. Do not import Jest, as it doesn't export anything.`,
+ },
+ ],
+ },
+ {
+ code: 'var jest = require("jest")',
+ errors: [
+ {
+ endColumn: 26,
+ column: 20,
+ message: `Jest is automatically in scope. Do not import Jest, as it doesn't export anything.`,
+ },
+ ],
+ },
+ {
+ code: 'import {jest as test} from "jest"',
+ parserOptions: { sourceType: 'module' },
+ errors: [
+ {
+ endColumn: 34,
+ column: 1,
+ message: `Jest is automatically in scope. Do not import Jest, as it doesn't export anything.`,
+ },
+ ],
+ },
+ {
+ code: 'const jest = require("jest")',
+ parserOptions: { sourceType: 'module' },
+ errors: [
+ {
+ endColumn: 28,
+ column: 22,
+ message: `Jest is automatically in scope. Do not import Jest, as it doesn't export anything.`,
+ },
+ ],
+ },
+ ],
+});

rules/no-jest-import.js

@@ -0,0 +1,39 @@
+'use strict';
+
+const getDocsUrl = require('./util').getDocsUrl;
+const getNodeName = require('./util').getNodeName;
+
+module.exports = {
+ meta: {
+ docs: {
+ url: getDocsUrl(__filename),
+ },
+ },
+ create(context) {
+ return {
+ ImportDeclaration(node) {
+ if (node.source.value === 'jest') {
+ context.report({
+ node,
+ message: `Jest is automatically in scope. Do not import Jest, as it doesn't export anything.`,
+ });
+ }
+ },
+ CallExpression(node) {
+ const calleeName = getNodeName(node.callee);
+ if (calleeName === 'require' && node.arguments[0].value === 'jest') {
+ context.report({
+ loc: {
+ end: {
+ column: node.arguments[0].loc.end.column,
+ line: node.arguments[0].loc.end.line,
+ },
+ start: node.arguments[0].loc.start,
+ },
+ message: `Jest is automatically in scope. Do not import Jest, as it doesn't export anything.`,
+ });
+ }
+ },
+ };
+ },
+};