no-new-buffer: Use suggestion for unknown arguments

docs/rules/no-new-buffer.md

@@ -2,25 +2,29 @@
 
 Enforces the use of [Buffer.from](https://nodejs.org/api/buffer.html#buffer_class_method_buffer_from_array) and [Buffer.alloc()](https://nodejs.org/api/buffer.html#buffer_class_method_buffer_alloc_size_fill_encoding) instead of [new Buffer()](https://nodejs.org/api/buffer.html#buffer_new_buffer_array), which has been deprecated since Node.js 4.
 
-This rule is fixable.
-
+This rule is partly fixable.
 
 ## Fail
 
 ```js
 const buffer = new Buffer('7468697320697320612074c3a97374', 'hex');
+```
+
+```
 const buffer = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
 ```
 
 ```js
 const buffer = new Buffer(10);
 ```
 
-
 ## Pass
 
 ```js
 const buffer = Buffer.from('7468697320697320612074c3a97374', 'hex');
+```
+
+```js
 const buffer = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72])
 ```
 

readme.md

@@ -137,7 +137,7 @@ Configure it in `package.json`.
 - [no-lonely-if](docs/rules/no-lonely-if.md) - Disallow `if` statements as the only statement in `if` blocks without `else`. *(fixable)*
 - [no-nested-ternary](docs/rules/no-nested-ternary.md) - Disallow nested ternary expressions. *(partly fixable)*
 - [no-new-array](docs/rules/no-new-array.md) - Disallow `new Array()`. *(partly fixable)*
-- [no-new-buffer](docs/rules/no-new-buffer.md) - Enforce the use of `Buffer.from()` and `Buffer.alloc()` instead of the deprecated `new Buffer()`. *(fixable)*
+- [no-new-buffer](docs/rules/no-new-buffer.md) - Enforce the use of `Buffer.from()` and `Buffer.alloc()` instead of the deprecated `new Buffer()`. *(partly fixable)*
 - [no-null](docs/rules/no-null.md) - Disallow the use of the `null` literal.
 - [no-object-as-default-parameter](docs/rules/no-object-as-default-parameter.md) - Disallow the use of objects as default parameters.
 - [no-process-exit](docs/rules/no-process-exit.md) - Disallow `process.exit()`.

rules/no-new-buffer.js

@@ -1,40 +1,91 @@
 'use strict';
+const {getStaticValue} = require('eslint-utils');
 const getDocumentationUrl = require('./utils/get-documentation-url');
+const isNewExpressionWithParentheses = require('./utils/is-new-expression-with-parentheses');
 
-const MESSAGE_ID = 'no-new-buffer';
+const ERROR = 'error';
+const ERROR_UNKNOWN = 'error-unknown';
+const SUGGESTION = 'suggestion';
 const messages = {
-	[MESSAGE_ID]: '`new Buffer()` is deprecated, use `Buffer.{{method}}()` instead.'
+	[ERROR]: '`new Buffer()` is deprecated, use `Buffer.{{method}}()` instead.',
+	[ERROR_UNKNOWN]: '`new Buffer()` is deprecated, use `Buffer.alloc()` or `Buffer.from()` instead.',
+	[SUGGESTION]: 'Switch to `Buffer.{{method}}()`.'
 };
 
-const inferMethod = arguments_ => {
-	if (arguments_.length > 0) {
-		const [firstArgument] = arguments_;
+const inferMethod = (bufferArguments, scope) => {
+	if (bufferArguments.length !== 1) {
+		return 'from';
+	}
+
+	const [firstArgument] = bufferArguments;
+	if (firstArgument.type === 'SpreadElement') {
+		return;
+	}
+
+	if (firstArgument.type === 'ArrayExpression' || firstArgument.type === 'TemplateLiteral') {
+		return 'from';
+	}
+
+	const staticResult = getStaticValue(firstArgument, scope);
+	if (staticResult) {
+		const {value} = staticResult;
+		if (typeof value === 'number') {
+			return 'alloc';
+		}
+
 		if (
-			firstArgument.type === 'Literal' &&
-			typeof firstArgument.value === 'number'
+			typeof value === 'string' ||
+			Array.isArray(value)
 		) {
-			return 'alloc';
+			return 'from';
 		}
 	}
-
-	return 'from';
 };
 
+function fix(node, sourceCode, method) {
+	return function * (fixer) {
+		const [start] = node.range;
+		let end = start + 3; // `3` = length of `new`
+		const textAfter = sourceCode.text.slice(end);
+		const [leadingSpaces] = textAfter.match(/^\s*/);
+		end += leadingSpaces.length;
+		yield fixer.removeRange([start, end]);
+
+		yield fixer.insertTextAfter(node.callee, `.${method}`);
+
+		if (!isNewExpressionWithParentheses(node, sourceCode)) {
+			yield fixer.insertTextAfter(node, '()');
+		}
+	};
+}
+
 const create = context => {
+	const sourceCode = context.getSourceCode();
 	return {
 		'NewExpression[callee.name="Buffer"]': node => {
-			const method = inferMethod(node.arguments);
-			const range = [
-				node.range[0],
-				node.callee.range[1]
-			];
-
-			context.report({
-				node,
-				messageId: MESSAGE_ID,
-				data: {method},
-				fix: fixer => fixer.replaceTextRange(range, `Buffer.${method}`)
-			});
+			const method = inferMethod(node.arguments, context.getScope());
+
+			if (method) {
+				context.report({
+					node,
+					messageId: ERROR,
+					data: {method},
+					fix: fix(node, sourceCode, method)
+				});
+			} else {
+				context.report({
+					node,
+					messageId: ERROR_UNKNOWN,
+					suggest: [
+						'from',
+						'alloc'
+					].map(method => ({
+						messageId: SUGGESTION,
+						data: {method},
+						fix: fix(node, sourceCode, method)
+					}))
+				});
+			}
 		}
 	};
 };

test/no-new-buffer.js

@@ -1,71 +1,67 @@
 import {outdent} from 'outdent';
 import {test} from './utils/test.js';
 
-const allocError = {
-	messageId: 'no-new-buffer',
-	data: {method: 'alloc'}
-};
-
-const fromError = {
-	messageId: 'no-new-buffer',
-	data: {method: 'from'}
-};
-
-test({
+test.snapshot({
 	valid: [
-		'const buf = Buffer.from(\'buf\')',
-		'const buf = Buffer.from(\'7468697320697320612074c3a97374\', \'hex\')',
-		'const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72])',
-		'const buf = Buffer.alloc(10)'
+		'const buffer = Buffer',
+		'const buffer = new NotBuffer(1)',
+		'const buffer = Buffer.from(\'buf\')',
+		'const buffer = Buffer.from(\'7468697320697320612074c3a97374\', \'hex\')',
+		'const buffer = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72])',
+		'const buffer = Buffer.alloc(10)'
 	],
 	invalid: [
-		{
-			code: 'const buf = new Buffer()',
-			errors: [fromError],
-			output: 'const buf = Buffer.from()'
-		},
-		{
-			code: 'const buf = new Buffer(\'buf\')',
-			errors: [fromError],
-			output: 'const buf = Buffer.from(\'buf\')'
-		},
-		{
-			code: 'const buf = new Buffer(\'7468697320697320612074c3a97374\', \'hex\')',
-			errors: [fromError],
-			output: 'const buf = Buffer.from(\'7468697320697320612074c3a97374\', \'hex\')'
-		},
-		{
-			code: 'const buf = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72])',
-			errors: [fromError],
-			output: 'const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72])'
-		},
-		{
-			code: 'const buf = new Buffer(10)',
-			errors: [allocError],
-			output: 'const buf = Buffer.alloc(10)'
-		},
-		{
-			code: outdent`
-				const ab = new ArrayBuffer(10);
-				const buf = new Buffer(ab, 0, 2);
-			`,
-			errors: [fromError],
-			output: outdent`
-				const ab = new ArrayBuffer(10);
-				const buf = Buffer.from(ab, 0, 2);
-			`
-		},
-		{
-			code: outdent`
-				const buf1 = new Buffer('buf');
-				const buf2 = new Buffer(buf1);
-			`,
-			errors: [fromError, fromError],
-			output: outdent`
-				const buf1 = Buffer.from('buf');
-				const buf2 = Buffer.from(buf1);
-			`
-		}
+		// `new Buffer(array)`
+		// https://nodejs.org/api/buffer.html#buffer_new_buffer_array
+		'const buffer = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72])',
+		'const buffer = new Buffer([0x62, bar])',
+		outdent`
+			const array = [0x62];
+			const buffer = new Buffer(array);
+		`,
+
+		// `new Buffer(arrayBuffer[, byteOffset[, length]])`
+		// https://nodejs.org/api/buffer.html#buffer_new_buffer_arraybuffer_byteoffset_length
+		outdent`
+			const arrayBuffer = new ArrayBuffer(10);
+			const buffer = new Buffer(arrayBuffer);
+		`,
+		outdent`
+			const arrayBuffer = new ArrayBuffer(10);
+			const buffer = new Buffer(arrayBuffer, 0, );
+		`,
+		outdent`
+			const arrayBuffer = new ArrayBuffer(10);
+			const buffer = new Buffer(arrayBuffer, 0, 2);
+		`,
+
+		// `new Buffer(size)`
+		// https://nodejs.org/api/buffer.html#buffer_new_buffer_size
+		'const buffer = new Buffer(10);',
+		outdent`
+			const size = 10;
+			const buffer = new Buffer(size);
+		`,
+
+		// `new Buffer(string[, encoding])`
+		// https://nodejs.org/api/buffer.html#buffer_new_buffer_string_encoding
+		'const buffer = new Buffer("string");',
+		'const buffer = new Buffer("7468697320697320612074c3a97374", "hex")',
+		outdent`
+			const string = "string";
+			const buffer = new Buffer(string);
+		`,
+		// eslint-disable-next-line no-template-curly-in-string
+		'const buffer = new Buffer(`${unknown}`)',
+
+		// Unknown
+		'const buffer = new (Buffer)(unknown)',
+		'const buffer = new Buffer(unknown, 2)',
+		'const buffer = new Buffer(...unknown)',
+
+		// Misc
+		'const buffer = new /* comment */ Buffer()',
+		'const buffer = new /* comment */ Buffer'
 	]
 });
 
@@ -74,13 +70,8 @@ test.typescript({
 	invalid: [
 		{
 			code: 'new Buffer(input, encoding);',
-			errors: [fromError],
-			output: 'Buffer.from(input, encoding);'
+			output: 'Buffer.from(input, encoding);',
+			errors: 1
 		}
 	]
 });
-
-test.snapshot([
-	'const buf = new Buffer()',
-	'const buf = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72])'
-]);