From 43fa09c721f60cfb85f5a5a3831425cfaa4dc771 Mon Sep 17 00:00:00 2001 From: Scott O'Hara Date: Thu, 9 May 2019 02:41:37 +1000 Subject: [PATCH] feat(eslint-plugin): add no-magic-numbers rule (#373) --- packages/eslint-plugin/README.md | 1 + .../docs/rules/no-magic-numbers.md | 44 +++++ .../src/rules/no-magic-numbers.ts | 152 ++++++++++++++++++ .../tests/rules/no-magic-numbers.test.ts | 134 +++++++++++++++ .../eslint-plugin/typings/eslint-rules.d.ts | 22 +++ 5 files changed, 353 insertions(+) create mode 100644 packages/eslint-plugin/docs/rules/no-magic-numbers.md create mode 100644 packages/eslint-plugin/src/rules/no-magic-numbers.ts create mode 100644 packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts diff --git a/packages/eslint-plugin/README.md b/packages/eslint-plugin/README.md index 044ff064372..b296291f4ae 100644 --- a/packages/eslint-plugin/README.md +++ b/packages/eslint-plugin/README.md @@ -134,6 +134,7 @@ Then you should add `airbnb` (or `airbnb-base`) to your `extends` section of `.e | [`@typescript-eslint/no-extraneous-class`](./docs/rules/no-extraneous-class.md) | Forbids the use of classes as namespaces (`no-unnecessary-class` from TSLint) | | | | | [`@typescript-eslint/no-for-in-array`](./docs/rules/no-for-in-array.md) | Disallow iterating over an array with a for-in loop (`no-for-in-array` from TSLint) | | | :thought_balloon: | | [`@typescript-eslint/no-inferrable-types`](./docs/rules/no-inferrable-types.md) | Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean. (`no-inferrable-types` from TSLint) | :heavy_check_mark: | :wrench: | | +| [`@typescript-eslint/no-magic-numbers`](./docs/rules/no-magic-numbers.md) | Disallows magic numbers. | :heavy_check_mark: | | | [`@typescript-eslint/no-misused-new`](./docs/rules/no-misused-new.md) | Enforce valid definition of `new` and `constructor`. (`no-misused-new` from TSLint) | :heavy_check_mark: | | | | [`@typescript-eslint/no-namespace`](./docs/rules/no-namespace.md) | Disallow the use of custom TypeScript modules and namespaces (`no-namespace` from TSLint) | :heavy_check_mark: | | | | [`@typescript-eslint/no-non-null-assertion`](./docs/rules/no-non-null-assertion.md) | Disallows non-null assertions using the `!` postfix operator (`no-non-null-assertion` from TSLint) | :heavy_check_mark: | | | diff --git a/packages/eslint-plugin/docs/rules/no-magic-numbers.md b/packages/eslint-plugin/docs/rules/no-magic-numbers.md new file mode 100644 index 00000000000..2ff5aab519d --- /dev/null +++ b/packages/eslint-plugin/docs/rules/no-magic-numbers.md @@ -0,0 +1,44 @@ +# Disallow Magic Numbers (@typescript-eslint/no-magic-numbers) + +'Magic numbers' are numbers that occur multiple times in code without an explicit meaning. +They should preferably be replaced by named constants. + +## Rule Details + +The `@typescript-eslint/no-magic-numbers` rule extends the `no-magic-numbers` rule from ESLint core, and adds support for handling Typescript specific code that would otherwise trigger the rule. + +See the [ESLint documentation](https://eslint.org/docs/rules/no-magic-numbers) for more details on the `no-magic-numbers` rule. + +## Rule Changes + +```cjson +{ + // note you must disable the base rule as it can report incorrect errors + "no-magic-numbers": "off", + "@typescript-eslint/no-magic-numbers": ["error", { "ignoreNumericLiteralTypes": true }] +} +``` + +In addition to the options supported by the `no-magic-numbers` rule in ESLint core, the rule adds the following options: + +### ignoreNumericLiteralTypes + +A boolean to specify if numbers used in Typescript numeric literal types are considered okay. `false` by default. + +Examples of **incorrect** code for the `{ "ignoreNumericLiteralTypes": false }` option: + +```ts +/*eslint @typescript-eslint/no-magic-numbers: ["error", { "ignoreNumericLiteralTypes": false }]*/ + +type SmallPrimes = 2 | 3 | 5 | 7 | 11; +``` + +Examples of **correct** code for the `{ "ignoreNumericLiteralTypes": true }` option: + +```ts +/*eslint @typescript-eslint/no-magic-numbers: ["error", { "ignoreNumericLiteralTypes": true }]*/ + +type SmallPrimes = 2 | 3 | 5 | 7 | 11; +``` + +Taken with ❤️ [from ESLint core](https://github.com/eslint/eslint/blob/master/docs/rules/no-magic-numbers.md) diff --git a/packages/eslint-plugin/src/rules/no-magic-numbers.ts b/packages/eslint-plugin/src/rules/no-magic-numbers.ts new file mode 100644 index 00000000000..049aa2b35b8 --- /dev/null +++ b/packages/eslint-plugin/src/rules/no-magic-numbers.ts @@ -0,0 +1,152 @@ +/** + * @fileoverview Rule to flag statements that use magic numbers (adapted from https://github.com/danielstjules/buddy.js) + * @author Scott O'Hara + */ + +import { TSESTree, AST_NODE_TYPES } from '@typescript-eslint/typescript-estree'; +import baseRule from 'eslint/lib/rules/no-magic-numbers'; +import * as util from '../util'; +import { JSONSchema4 } from 'json-schema'; + +type Options = util.InferOptionsTypeFromRule; +type MessageIds = util.InferMessageIdsTypeFromRule; + +const baseRuleSchema = (baseRule.meta.schema as JSONSchema4[])[0]; + +export default util.createRule({ + name: 'no-magic-numbers', + meta: { + type: 'suggestion', + docs: { + description: 'Disallow magic numbers', + category: 'Best Practices', + recommended: false, + }, + // Extend base schema with additional property to ignore TS numeric literal types + schema: [ + { + ...baseRuleSchema, + properties: { + ...baseRuleSchema.properties, + ignoreNumericLiteralTypes: { + type: 'boolean', + }, + }, + }, + ], + messages: baseRule.meta.messages, + }, + defaultOptions: [ + { + ignore: [], + ignoreArrayIndexes: false, + enforceConst: false, + detectObjects: false, + ignoreNumericLiteralTypes: false, + }, + ], + create(context, [options]) { + const rules = baseRule.create(context); + + /** + * Returns whether the node is number literal + * @param node the node literal being evaluated + * @returns true if the node is a number literal + */ + function isNumber(node: TSESTree.Literal): boolean { + return typeof node.value === 'number'; + } + + /** + * Checks if the node grandparent is a Typescript type alias declaration + * @param node the node to be validated. + * @returns true if the node grandparent is a Typescript type alias declaration + * @private + */ + function isGrandparentTSTypeAliasDeclaration(node: TSESTree.Node): boolean { + return node.parent && node.parent.parent + ? node.parent.parent.type === AST_NODE_TYPES.TSTypeAliasDeclaration + : false; + } + + /** + * Checks if the node grandparent is a Typescript union type and its parent is a type alias declaration + * @param node the node to be validated. + * @returns true if the node grandparent is a Typescript untion type and its parent is a type alias declaration + * @private + */ + function isGrandparentTSUnionType(node: TSESTree.Node): boolean { + if ( + node.parent && + node.parent.parent && + node.parent.parent.type === AST_NODE_TYPES.TSUnionType + ) { + return isGrandparentTSTypeAliasDeclaration(node.parent); + } + + return false; + } + + /** + * Checks if the node parent is a Typescript literal type + * @param node the node to be validated. + * @returns true if the node parent is a Typescript literal type + * @private + */ + function isParentTSLiteralType(node: TSESTree.Node): boolean { + return node.parent + ? node.parent.type === AST_NODE_TYPES.TSLiteralType + : false; + } + + /** + * Checks if the node is a valid TypeScript numeric literal type. + * @param node the node to be validated. + * @returns true if the node is a TypeScript numeric literal type. + * @private + */ + function isTSNumericLiteralType(node: TSESTree.Node): boolean { + // For negative numbers, update the parent node + if ( + node.parent && + node.parent.type === AST_NODE_TYPES.UnaryExpression && + node.parent.operator === '-' + ) { + node = node.parent; + } + + // If the parent node is not a TSLiteralType, early return + if (!isParentTSLiteralType(node)) { + return false; + } + + // If the grandparent is a TSTypeAliasDeclaration, ignore + if (isGrandparentTSTypeAliasDeclaration(node)) { + return true; + } + + // If the grandparent is a TSUnionType and it's parent is a TSTypeAliasDeclaration, ignore + if (isGrandparentTSUnionType(node)) { + return true; + } + + return false; + } + + return { + Literal(node) { + // Check TypeScript specific nodes + if ( + options.ignoreNumericLiteralTypes && + isNumber(node) && + isTSNumericLiteralType(node) + ) { + return; + } + + // Let the base rule deal with the rest + rules.Literal(node); + }, + }; + }, +}); diff --git a/packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts b/packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts new file mode 100644 index 00000000000..2b184ad76b2 --- /dev/null +++ b/packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts @@ -0,0 +1,134 @@ +import rule from '../../src/rules/no-magic-numbers'; +import { RuleTester } from '../RuleTester'; + +const ruleTester = new RuleTester({ + parser: '@typescript-eslint/parser', +}); + +ruleTester.run('no-magic-numbers', rule, { + valid: [ + { + code: 'const FOO = 10;', + options: [{ ignoreNumericLiteralTypes: true }], + }, + { + code: 'type Foo = "bar";', + }, + { + code: 'type Foo = true;', + }, + { + code: 'type Foo = 1;', + options: [{ ignoreNumericLiteralTypes: true }], + }, + { + code: 'type Foo = -1;', + options: [{ ignoreNumericLiteralTypes: true }], + }, + { + code: 'type Foo = 1 | 2 | 3;', + options: [{ ignoreNumericLiteralTypes: true }], + }, + { + code: 'type Foo = 1 | -1;', + options: [{ ignoreNumericLiteralTypes: true }], + }, + ], + + invalid: [ + { + code: 'type Foo = 1;', + options: [{ ignoreNumericLiteralTypes: false }], + errors: [ + { + messageId: 'noMagic', + data: { + raw: '1', + }, + line: 1, + column: 12, + }, + ], + }, + { + code: 'type Foo = -1;', + options: [{ ignoreNumericLiteralTypes: false }], + errors: [ + { + messageId: 'noMagic', + data: { + raw: '-1', + }, + line: 1, + column: 12, + }, + ], + }, + { + code: 'type Foo = 1 | 2 | 3;', + options: [{ ignoreNumericLiteralTypes: false }], + errors: [ + { + messageId: 'noMagic', + data: { + raw: '1', + }, + line: 1, + column: 12, + }, + { + messageId: 'noMagic', + data: { + raw: '2', + }, + line: 1, + column: 16, + }, + { + messageId: 'noMagic', + data: { + raw: '3', + }, + line: 1, + column: 20, + }, + ], + }, + { + code: 'type Foo = 1 | -1;', + options: [{ ignoreNumericLiteralTypes: false }], + errors: [ + { + messageId: 'noMagic', + data: { + raw: '1', + }, + line: 1, + column: 12, + }, + { + messageId: 'noMagic', + data: { + raw: '-1', + }, + line: 1, + column: 16, + }, + ], + }, + { + code: 'interface Foo { bar: 1; }', + options: [{ ignoreNumericLiteralTypes: true }], + errors: [ + { + messageId: 'noMagic', + data: { + raw: '1', + }, + line: 1, + column: 22, + }, + ], + }, + ], +}); diff --git a/packages/eslint-plugin/typings/eslint-rules.d.ts b/packages/eslint-plugin/typings/eslint-rules.d.ts index aac61ca5848..28d05114e26 100644 --- a/packages/eslint-plugin/typings/eslint-rules.d.ts +++ b/packages/eslint-plugin/typings/eslint-rules.d.ts @@ -174,6 +174,28 @@ declare module 'eslint/lib/rules/no-implicit-globals' { export = rule; } +declare module 'eslint/lib/rules/no-magic-numbers' { + import { TSESTree } from '@typescript-eslint/typescript-estree'; + import RuleModule from 'ts-eslint'; + + const rule: RuleModule< + 'noMagic', + [ + { + ignore?: string[]; + ignoreArrayIndexes?: boolean; + enforceConst?: boolean; + detectObjects?: boolean; + ignoreNumericLiteralTypes?: boolean; + } + ], + { + Literal(node: TSESTree.Literal): void; + } + >; + export = rule; +} + declare module 'eslint/lib/rules/no-redeclare' { import { TSESTree } from '@typescript-eslint/typescript-estree'; import RuleModule from 'ts-eslint';