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Add prefer-json-parse-buffer rule (#1676)
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‎.github/workflows/main.yml

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@@ -41,7 +41,7 @@ jobs:
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AVA_FORCE_CI: not-ci
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- run: npm run generate-rules-table
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- run: npm run generate-usage-example
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- run: git diff --exit-code --name-only
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- run: git diff --exit-code
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- uses: codecov/codecov-action@v1
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with:
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fail_ci_if_error: true

‎configs/recommended.js

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@@ -70,6 +70,7 @@ module.exports = {
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'unicorn/prefer-dom-node-text-content': 'error',
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'unicorn/prefer-export-from': 'error',
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'unicorn/prefer-includes': 'error',
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'unicorn/prefer-json-parse-buffer': 'error',
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'unicorn/prefer-keyboard-event-key': 'error',
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'unicorn/prefer-math-trunc': 'error',
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'unicorn/prefer-modern-dom-apis': 'error',

‎docs/rules/prefer-json-parse-buffer.md

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# Prefer reading a JSON file as a buffer
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✅ *This rule is part of the [recommended](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config) config.*
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🔧 *This rule is [auto-fixable](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems).*
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When reading and parsing a JSON file, it's unnecessary to read it as a string, because [`JSON.parse()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse) can also parse [`Buffer`](https://nodejs.org/api/buffer.html#buffer).
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## Fail
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```js
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const packageJson = JSON.parse(await fs.readFile('./package.json', 'utf8'));
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```
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```js
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const promise = fs.readFile('./package.json', {encoding: 'utf8'});
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const packageJson = JSON.parse(promise);
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```
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## Pass
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```js
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const packageJson = JSON.parse(await fs.readFile('./package.json'));
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```
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```js
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const promise = fs.readFile('./package.json', {encoding: 'utf8', signal});
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const packageJson = JSON.parse(await promise);
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```
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```js
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const data = JSON.parse(await fs.readFile('./file.json', 'buffer'));
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```
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```js
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const data = JSON.parse(await fs.readFile('./file.json', 'gbk'));
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```

‎readme.md

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@@ -103,6 +103,7 @@ Configure it in `package.json`.
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"unicorn/prefer-dom-node-text-content": "error",
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"unicorn/prefer-export-from": "error",
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"unicorn/prefer-includes": "error",
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"unicorn/prefer-json-parse-buffer": "error",
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"unicorn/prefer-keyboard-event-key": "error",
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"unicorn/prefer-math-trunc": "error",
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"unicorn/prefer-modern-dom-apis": "error",
@@ -219,6 +220,7 @@ Each rule has emojis denoting:
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| [prefer-dom-node-text-content](docs/rules/prefer-dom-node-text-content.md) | Prefer `.textContent` over `.innerText`. | ✅ | | 💡 |
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| [prefer-export-from](docs/rules/prefer-export-from.md) | Prefer `export…from` when re-exporting. | ✅ | 🔧 | 💡 |
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| [prefer-includes](docs/rules/prefer-includes.md) | Prefer `.includes()` over `.indexOf()` and `Array#some()` when checking for existence or non-existence. | ✅ | 🔧 | 💡 |
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| [prefer-json-parse-buffer](docs/rules/prefer-json-parse-buffer.md) | Prefer reading a JSON file as a buffer. | ✅ | 🔧 | |
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| [prefer-keyboard-event-key](docs/rules/prefer-keyboard-event-key.md) | Prefer `KeyboardEvent#key` over `KeyboardEvent#keyCode`. | ✅ | 🔧 | |
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| [prefer-math-trunc](docs/rules/prefer-math-trunc.md) | Enforce the use of `Math.trunc` instead of bitwise operators. | ✅ | 🔧 | 💡 |
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| [prefer-modern-dom-apis](docs/rules/prefer-modern-dom-apis.md) | Prefer `.before()` over `.insertBefore()`, `.replaceWith()` over `.replaceChild()`, prefer one of `.before()`, `.after()`, `.append()` or `.prepend()` over `insertAdjacentText()` and `insertAdjacentElement()`. | ✅ | 🔧 | |

‎rules/prefer-json-parse-buffer.js

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'use strict';
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const {findVariable, getStaticValue} = require('eslint-utils');
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const {methodCallSelector} = require('./selectors/index.js');
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const {removeArgument} = require('./fix/index.js');
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const getKeyName = require('./utils/get-key-name.js');
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const MESSAGE_ID = 'prefer-json-parse-buffer';
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const messages = {
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[MESSAGE_ID]: 'Prefer reading the JSON file as a buffer.',
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};
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const jsonParseArgumentSelector = [
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methodCallSelector({
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object: 'JSON',
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method: 'parse',
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argumentsLength: 1,
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}),
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' > .arguments:first-child',
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].join('');
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const getAwaitExpressionArgument = node => {
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while (node.type === 'AwaitExpression') {
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node = node.argument;
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}
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return node;
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};
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function getIdentifierDeclaration(node, scope) {
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if (!node) {
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return;
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}
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node = getAwaitExpressionArgument(node);
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if (!node || node.type !== 'Identifier') {
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return node;
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}
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const variable = findVariable(scope, node);
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if (!variable) {
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return;
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}
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const {identifiers, references} = variable;
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if (identifiers.length !== 1 || references.length !== 2) {
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return;
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}
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const [identifier] = identifiers;
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if (
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identifier.parent.type !== 'VariableDeclarator'
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|| identifier.parent.id !== identifier
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) {
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return;
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}
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return getIdentifierDeclaration(identifier.parent.init, variable.scope);
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}
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const isUtf8EncodingStringNode = (node, scope) => {
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const staticValue = getStaticValue(node, scope);
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return staticValue && isUtf8EncodingString(staticValue.value);
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};
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const isUtf8EncodingString = value => {
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if (typeof value !== 'string') {
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return false;
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}
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value = value.toLowerCase();
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return value === 'utf8' || value === 'utf-8';
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};
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function isUtf8Encoding(node, scope) {
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if (
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node.type === 'ObjectExpression'
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&& node.properties.length === 1
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&& node.properties[0].type === 'Property'
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&& getKeyName(node.properties[0], scope) === 'encoding'
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&& isUtf8EncodingStringNode(node.properties[0].value, scope)
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) {
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return true;
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}
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if (isUtf8EncodingStringNode(node, scope)) {
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return true;
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}
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const staticValue = getStaticValue(node, scope);
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if (!staticValue) {
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return false;
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}
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const {value} = staticValue;
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if (
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typeof value === 'object'
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&& Object.keys(value).length === 1
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&& isUtf8EncodingString(value.encoding)
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) {
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return true;
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}
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return false;
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}
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/** @param {import('eslint').Rule.RuleContext} context */
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const create = context => ({
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[jsonParseArgumentSelector](node) {
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const scope = context.getScope();
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node = getIdentifierDeclaration(node, scope);
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if (
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!(
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node
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&& node.type === 'CallExpression'
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&& !node.optional
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&& node.arguments.length === 2
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&& !node.arguments.some(node => node.type === 'SpreadElement')
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&& node.callee.type === 'MemberExpression'
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&& !node.callee.optional
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)
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) {
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return;
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}
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const method = getKeyName(node.callee, scope);
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if (method !== 'readFile' && method !== 'readFileSync') {
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return;
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}
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const [, charsetNode] = node.arguments;
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if (!isUtf8Encoding(charsetNode, scope)) {
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return;
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}
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return {
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node: charsetNode,
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messageId: MESSAGE_ID,
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fix: fixer => removeArgument(fixer, charsetNode, context.getSourceCode()),
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};
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},
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});
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/** @type {import('eslint').Rule.RuleModule} */
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module.exports = {
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create,
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meta: {
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type: 'suggestion',
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docs: {
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description: 'Prefer reading a JSON file as a buffer.',
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},
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fixable: 'code',
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messages,
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},
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};

‎test/prefer-json-parse-buffer.mjs

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/* eslint-disable no-template-curly-in-string */
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import outdent from 'outdent';
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import {getTester} from './utils/test.mjs';
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const {test} = getTester(import.meta);
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test.snapshot({
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valid: [
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'JSON.parse(await fs.readFile(file, "buffer"));',
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'JSON.parse(await fs.readFile(file, "gbk"));',
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'JSON.parse(await fs.readFile(file, ));',
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'JSON.parse(await fs.readFile(file, unknown));',
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'JSON.parse(await fs.readFile(...file, "utf8"));',
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'JSON.parse(await fs.readFile(file, ..."utf8"));',
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'JSON.parse(await fs.readFile(file, 0));',
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'JSON.parse(await fs.readFile(file, "utf8", extraArgument));',
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'JSON.parse(await fs.readFile?.(file, "utf8"));',
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'JSON.parse(await fs?.readFile(file, "utf8"));',
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'JSON.parse(await fs.notReadFileMethod(file, "utf8"));',
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'JSON.parse?.(await fs.readFile(file, "utf8"));',
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'JSON?.parse(await fs.readFile(file, "utf8"));',
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'window.JSON.parse(await fs.readFile(file, "utf8"));',
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'JSON.stringify(await fs.readFile(file, "utf8"));',
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'NOT_JSON.parse(await fs.readFile(file, "utf8"));',
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'for (const string of []) JSON.parse(string);',
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'JSON.parse(await fs.readFile(file, "utf8"), extraArgument);',
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'JSON.parse(foo);',
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'JSON.parse();',
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'JSON.parse(await fs.readFile(file, {encoding: "not-utf8"}));',
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'JSON.parse(await fs.readFile(file, {encoding: "utf8", extraProperty: "utf8"}));',
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'JSON.parse(await fs.readFile(file, {...encoding}));',
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'JSON.parse(await fs.readFile(file, {encoding: unknown}));',
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'const encoding = "gbk";JSON.parse(await fs.readFile(file, {encoding: encoding}));',
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'const readingOptions = {encoding: "utf8", extraProperty: undefined};JSON.parse(await fs.readFile(file, readingOptions));',
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outdent`
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const {string} = await fs.readFile(file, "utf8");
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JSON.parse(string);
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`,
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outdent`
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const string = fs.readFile(file, () => {});
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JSON.parse(string);
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`,
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outdent`
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const abortControl = new AbortControl();
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const {signal} = abortControl;
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const promise = readFile(fileName, { encoding: "utf8", signal });
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if (foo) {
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JSON.parse(await promise);
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} else {
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controller.abort();
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}
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`,
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outdent`
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const string= await fs.readFile(file, "utf8");
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console.log(string);
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JSON.parse(string);
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`,
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outdent`
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const string= await fs.readFile(file, "utf8");
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JSON.parse(\`[\${string}]\`);
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`,
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outdent`
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const foo = {};
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foo.bar = await fs.readFile(file, "utf8");
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JSON.parse(foo.bar);
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`,
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outdent`
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const foo = await fs.readFile(file, "utf8");
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const bar = await foo;
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console.log(baz);
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const baz = await bar;
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JSON.parse(baz);
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`,
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outdent`
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const foo = fs.readFile(file, "utf8");
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function fn1() {
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const foo = "{}";
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JSON.parse(foo);
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}
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`,
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],
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invalid: [
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'JSON.parse(await fs.readFile(file, "utf8"));',
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'JSON.parse(await fs.readFile(file, "utf8",));',
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'JSON.parse(await fs.readFile(file, "UTF-8"));',
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'JSON.parse(await fs.readFileSync(file, "utf8"));',
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'JSON.parse(fs.readFileSync(file, "utf8"));',
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'const CHARSET = "UTF8"; JSON.parse(await fs.readFile(file, CHARSET));',
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'const EIGHT = 8; JSON.parse(await fs.readFile(file, `utf${EIGHT}`));',
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'JSON.parse(await fs["readFile"](file, "utf8"));',
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'JSON.parse(await fs.readFile(file, {encoding: "utf8"}));',
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'const EIGHT = 8; JSON.parse(await fs.readFile(file, {encoding: `utf${EIGHT}`}));',
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'JSON.parse(await fs.readFile(file, {...({encoding: "utf8"})}));',
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'const encoding = "utf8";JSON.parse(await fs.readFile(file, {encoding}));',
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'const CHARSET = "utF-8", readingOptions = {encoding: CHARSET}; JSON.parse(await fs.readFile(file, readingOptions));',
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'const EIGHT = 8, ENCODING = "encoding"; JSON.parse(await fs.readFile(file, {[ENCODING]: `utf${EIGHT}`}));',
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outdent`
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const string = await fs.readFile(file, "utf8");
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JSON.parse(string);
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`,
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outdent`
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let string = await fs.readFile(file, "utf8");
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JSON.parse(string);
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`,
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outdent`
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const foo = await await fs.readFile(file, "utf8");
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const bar = await await foo;
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const baz = await bar;
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JSON.parse(baz);
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`,
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outdent`
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var foo = await fs.readFile(file, "utf8");
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let bar = await foo;
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const baz = await bar;
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JSON.parse(baz);
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`,
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outdent`
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const foo = fs.readFile(file, "utf8");
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async function fn1() {
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const bar = await foo;
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function fn2() {
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const baz = bar;
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JSON.parse(baz);
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}
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}
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`,
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outdent`
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const buffer = fs.readFile(file, "utf8"); /* Should report */
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const foo = buffer;
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async function fn1() {
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const buffer = fs.readFile(file, "utf8"); /* Should NOT report */
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JSON.parse(await foo);
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}
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`,
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outdent`
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const buffer = fs.readFile(file, "utf8"); /* Should report */
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const foo = buffer;
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async function fn1() {
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const buffer = fs.readFile(file, "utf8"); /* Should NOT report */
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const baz = foo;
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for (;;) {
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const buffer = fs.readFile(file, "utf8"); /* Should NOT report */
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JSON.parse(await baz);
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}
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}
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`,
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outdent`
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const foo = fs.readFile(file, "utf8");
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function fn1() {
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JSON.parse(foo);
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function fn2() {
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const foo = "{}";
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}
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}
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`,
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// Maybe false positive, we can trace the callee if necessary
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outdent`
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const string = await NOT_A_FS_MODULE.readFile(file, "utf8");
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JSON.parse(string);
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`,
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],
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});

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