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bradzacherbradzacher
authoredJan 18, 2020
feat(eslint-plugin): add no-non-null-asserted-optional-chain (#1469)
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v8.31.1v2.17.0
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‎packages/eslint-plugin/README.md

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‎packages/eslint-plugin/docs/rules/no-non-null-asserted-optional-chain.md

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# Disallows using a non-null assertion after an optional chain expression (`no-non-null-asserted-optional-chain`)
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## Rule Details
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Optional chain expressions are designed to return `undefined` if the optional property is nullish.
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Using non-null assertions after an optional chain expression is wrong, and introduces a serious type safety hole into your code.
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Examples of **incorrect** code for this rule:
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```ts
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/* eslint @typescript-eslint/no-non-null-asserted-optional-chain: "error" */
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foo?.bar!;
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foo?.bar!.baz;
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foo?.bar()!;
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foo?.bar!();
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foo?.bar!().baz;
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```
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Examples of **correct** code for this rule:
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```ts
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/* eslint @typescript-eslint/no-non-null-asserted-optional-chain: "error" */
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foo?.bar;
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(foo?.bar).baz;
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foo?.bar();
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foo?.bar();
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foo?.bar().baz;
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```
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## When Not To Use It
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If you are not using TypeScript 3.7 (or greater), then you will not need to use this rule, as the operator is not supported.
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## Further Reading
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- [TypeScript 3.7 Release Notes](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html)
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- [Optional Chaining Proposal](https://github.com/tc39/proposal-optional-chaining/)

‎packages/eslint-plugin/src/configs/all.json

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"@typescript-eslint/no-misused-new": "error",
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"@typescript-eslint/no-misused-promises": "error",
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"@typescript-eslint/no-namespace": "error",
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"@typescript-eslint/no-non-null-asserted-optional-chain": "error",
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"@typescript-eslint/no-non-null-assertion": "error",
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"@typescript-eslint/no-parameter-properties": "error",
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"@typescript-eslint/no-require-imports": "error",

‎packages/eslint-plugin/src/rules/index.ts

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@@ -38,6 +38,7 @@ import noMisusedNew from './no-misused-new';
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import noMisusedPromises from './no-misused-promises';
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import noNamespace from './no-namespace';
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import noNonNullAssertion from './no-non-null-assertion';
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import noNonNullAssertedOptionalChain from './no-non-null-asserted-optional-chain';
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import noParameterProperties from './no-parameter-properties';
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import noRequireImports from './no-require-imports';
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import noThisAlias from './no-this-alias';
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'no-misused-promises': noMisusedPromises,
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'no-namespace': noNamespace,
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'no-non-null-assertion': noNonNullAssertion,
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'no-non-null-asserted-optional-chain': noNonNullAssertedOptionalChain,
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'no-parameter-properties': noParameterProperties,
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'no-require-imports': noRequireImports,
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'no-this-alias': noThisAlias,

‎packages/eslint-plugin/src/rules/no-non-null-asserted-optional-chain.ts

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import { TSESTree, TSESLint } from '@typescript-eslint/experimental-utils';
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import * as util from '../util';
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type MessageIds = 'noNonNullOptionalChain' | 'suggestRemovingNonNull';
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export default util.createRule<[], MessageIds>({
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name: 'no-non-null-asserted-optional-chain',
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meta: {
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type: 'problem',
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docs: {
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description:
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'Disallows using a non-null assertion after an optional chain expression',
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category: 'Possible Errors',
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recommended: false,
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},
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messages: {
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noNonNullOptionalChain:
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'Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong.',
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suggestRemovingNonNull: 'You should remove the non-null assertion.',
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},
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schema: [],
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},
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defaultOptions: [],
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create(context) {
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return {
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'TSNonNullExpression > :matches(OptionalMemberExpression, OptionalCallExpression)'(
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node:
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| TSESTree.OptionalCallExpression
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| TSESTree.OptionalMemberExpression,
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): void {
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// selector guarantees this assertion
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const parent = node.parent as TSESTree.TSNonNullExpression;
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context.report({
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node,
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messageId: 'noNonNullOptionalChain',
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// use a suggestion instead of a fixer, because this can obviously break type checks
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suggest: [
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{
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messageId: 'suggestRemovingNonNull',
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fix(fixer): TSESLint.RuleFix {
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return fixer.removeRange([
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parent.range[1] - 1,
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parent.range[1],
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]);
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},
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},
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],
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});
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},
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};
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},
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});

‎packages/eslint-plugin/tests/rules/no-non-null-asserted-optional-chain.test.ts

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import rule from '../../src/rules/no-non-null-asserted-optional-chain';
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import { RuleTester } from '../RuleTester';
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const ruleTester = new RuleTester({
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parser: '@typescript-eslint/parser',
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});
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ruleTester.run('no-non-null-asserted-optional-chain', rule, {
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valid: [
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'foo.bar!',
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'foo.bar()!',
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'foo?.bar',
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'foo?.bar()',
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'(foo?.bar).baz!',
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'(foo?.bar()).baz!',
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],
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invalid: [
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{
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code: 'foo?.bar!',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: 'foo?.bar',
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},
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],
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},
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],
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},
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{
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code: 'foo?.["bar"]!',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: 'foo?.["bar"]',
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},
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],
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},
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],
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},
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{
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code: 'foo?.bar()!',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: 'foo?.bar()',
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},
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],
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},
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],
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},
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{
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code: 'foo.bar?.()!',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: 'foo.bar?.()',
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},
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],
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},
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],
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},
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{
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code: 'foo?.bar!()',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: 'foo?.bar()',
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},
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],
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},
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],
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},
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{
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code: '(foo?.bar)!.baz',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: '(foo?.bar).baz',
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},
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],
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},
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],
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},
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{
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code: 'foo?.["bar"]!.baz',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: 'foo?.["bar"].baz',
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},
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],
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},
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],
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},
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{
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code: '(foo?.bar)!().baz',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: '(foo?.bar)().baz',
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},
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],
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},
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],
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},
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{
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code: '(foo?.bar)!',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: '(foo?.bar)',
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},
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],
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},
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],
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},
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{
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code: '(foo?.bar)!()',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: '(foo?.bar)()',
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},
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],
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},
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],
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},
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{
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code: '(foo?.bar!)',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: '(foo?.bar)',
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},
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],
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},
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],
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},
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{
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code: '(foo?.bar!)()',
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errors: [
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{
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messageId: 'noNonNullOptionalChain',
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suggestions: [
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{
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messageId: 'suggestRemovingNonNull',
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output: '(foo?.bar)()',
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},
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],
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},
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],
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},
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],
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});

‎packages/eslint-plugin/tools/generate-configs.ts

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}
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const RULE_NAME_PREFIX = '@typescript-eslint/';
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const MAX_RULE_NAME_LENGTH = 32;
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const MAX_RULE_NAME_LENGTH = Object.keys(rules).reduce(
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(acc, name) => Math.max(acc, name.length),
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0,
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);
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const DEFAULT_RULE_SETTING = 'warn';
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const BASE_RULES_TO_BE_OVERRIDDEN = new Map(
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Object.entries(rules)

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