Feature/max dependencies

CHANGELOG.md

@@ -17,6 +17,10 @@ This change log adheres to standards from [Keep a CHANGELOG](http://keepachangel
 ### Fixed
 - [`namespace`] exception for get property from `namespace` import, which are re-export from commonjs module ([#499] fixes [#416], thanks [@wKich])
 
+## [1.14.0] - 2016-08-21
+### Added
+- [`max-dependencies`] for specifying the maximum number of dependencies (both `import` and `require`) a module can have. (see [#489], thanks [@tizmagik])
+
 ## [1.13.0] - 2016-08-11
 ### Added
 - `allowComputed` option for [`namespace`] rule. If set to `true`, won't report
@@ -293,11 +297,13 @@ for info on changes for earlier releases.
 [`no-mutable-exports`]: ./docs/rules/no-mutable-exports.md
 [`prefer-default-export`]: ./docs/rules/prefer-default-export.md
 [`no-restricted-paths`]: ./docs/rules/no-restricted-paths.md
+[`max-dependencies`]: ./docs/rules/max-dependencies.md
 
 [#509]: https://github.com/benmosher/eslint-plugin-import/pull/509
 [#508]: https://github.com/benmosher/eslint-plugin-import/pull/508
 [#503]: https://github.com/benmosher/eslint-plugin-import/pull/503
 [#499]: https://github.com/benmosher/eslint-plugin-import/pull/499
+[#489]: https://github.com/benmosher/eslint-plugin-import/pull/489
 [#461]: https://github.com/benmosher/eslint-plugin-import/pull/461
 [#444]: https://github.com/benmosher/eslint-plugin-import/pull/444
 [#428]: https://github.com/benmosher/eslint-plugin-import/pull/428
@@ -430,3 +436,4 @@ for info on changes for earlier releases.
 [@zloirock]: https://github.com/zloirock
 [@rhys-vdw]: https://github.com/rhys-vdw
 [@wKich]: https://github.com/wKich
+[@tizmagik]: https://github.com/tizmagik

README.md

@@ -52,6 +52,7 @@ This plugin intends to support linting of ES2015+ (ES6+) import/export syntax, a
 [`no-amd`]: ./docs/rules/no-amd.md
 [`no-nodejs-modules`]: ./docs/rules/no-nodejs-modules.md
 
+
 **Style guide:**
 
 * Ensure all imports appear before other statements ([`imports-first`])
@@ -61,6 +62,7 @@ This plugin intends to support linting of ES2015+ (ES6+) import/export syntax, a
 * Enforce a convention in module import order ([`order`])
 * Enforce a newline after import statements ([`newline-after-import`])
 * Prefer a default export if module exports a single name ([`prefer-default-export`])
+* Limit the maximum number of dependencies a module can have. ([`max-dependencies`])
 
 [`imports-first`]: ./docs/rules/imports-first.md
 [`no-duplicates`]: ./docs/rules/no-duplicates.md
@@ -69,7 +71,7 @@ This plugin intends to support linting of ES2015+ (ES6+) import/export syntax, a
 [`order`]: ./docs/rules/order.md
 [`newline-after-import`]: ./docs/rules/newline-after-import.md
 [`prefer-default-export`]: ./docs/rules/prefer-default-export.md
-
+[`max-dependencies`]: ./docs/rules/max-dependencies.md
 
 ## Installation
 

docs/rules/max-dependencies.md

@@ -0,0 +1,44 @@
+# max-dependencies
+
+Forbid modules to have too many dependencies (`import` or `require` statements).
+
+This is a useful rule because a module with too many dependencies is a code smell, and usually indicates the module is doing too much and/or should be broken up into smaller modules.
+
+Importing multiple named exports from a single module will only count once (e.g. `import {x, y, z} from './foo'` will only count as a single dependency).
+
+### Options
+
+This rule takes the following option:
+
+`max`: The maximum number of dependencies allowed. Anything over will trigger the rule. **Default is 10** if the rule is enabled and no `max` is specified.
+
+You can set the option like this:
+
+```js
+"import/max-dependencies": ["error", {"max": 10}]
+```
+
+
+## Example
+
+Given a max value of `{"max": 2}`:
+
+### Fail
+
+```js
+import a from './a'; // 1
+const b = require('./b'); // 2
+import c from './c'; // 3 - exceeds max!
+```
+
+### Pass
+
+```js
+import a from './a'; // 1
+const anotherA = require('./a'); // still 1
+import {x, y, z} from './foo'; // 2
+```
+
+## When Not To Use It
+
+If you don't care how many dependencies a module has.

src/index.js

@@ -16,6 +16,7 @@ export const rules = {
   'no-amd': require('./rules/no-amd'),
   'no-duplicates': require('./rules/no-duplicates'),
   'imports-first': require('./rules/imports-first'),
+  'max-dependencies': require('./rules/max-dependencies'),
   'no-extraneous-dependencies': require('./rules/no-extraneous-dependencies'),
   'no-nodejs-modules': require('./rules/no-nodejs-modules'),
   'order': require('./rules/order'),

src/rules/max-dependencies.js

@@ -0,0 +1,49 @@
+import Set from 'es6-set'
+import isStaticRequire from '../core/staticRequire'
+
+const DEFAULT_MAX = 10
+
+const countDependencies = (dependencies, lastNode, context) => {
+  const {max} = context.options[0] || { max: DEFAULT_MAX }
+
+  if (dependencies.size > max) {
+    context.report(
+      lastNode,
+      `Maximum number of dependencies (${max}) exceeded.`
+    )
+  }
+}
+
+module.exports = context => {
+  const dependencies = new Set() // keep track of dependencies
+  let lastNode // keep track of the last node to report on
+
+  return {
+    ImportDeclaration(node) {
+      dependencies.add(node.source.value)
+      lastNode = node.source
+    },
+
+    CallExpression(node) {
+      if (isStaticRequire(node)) {
+        const [ requirePath ] = node.arguments
+        dependencies.add(requirePath.value)
+        lastNode = node
+      }
+    },
+
+    'Program:exit': function () {
+      countDependencies(dependencies, lastNode, context)
+    },
+  }
+}
+
+module.exports.schema = [
+  {
+    'type': 'object',
+    'properties': {
+      'max': { 'type': 'number' },
+    },
+    'additionalProperties': false,
+  },
+]

tests/src/rules/max-dependencies.js

@@ -0,0 +1,78 @@
+import { test } from '../utils'
+
+import { RuleTester } from 'eslint'
+
+const ruleTester = new RuleTester()
+    , rule = require('rules/max-dependencies')
+
+ruleTester.run('max-dependencies', rule, {
+  valid: [
+    test({ code: 'import "./foo.js"' }),
+
+    test({ code: 'import "./foo.js"; import "./bar.js";',
+      options: [{
+        max: 2,
+      }],
+    }),
+
+    test({ code: 'import "./foo.js"; import "./bar.js"; const a = require("./foo.js"); const b = require("./bar.js");',
+      options: [{
+        max: 2,
+      }],
+    }),
+
+    test({ code: 'import {x, y, z} from "./foo"'}),
+  ],
+  invalid: [
+    test({
+      code: 'import { x } from \'./foo\'; import { y } from \'./foo\'; import {z} from \'./bar\';',
+      options: [{
+        max: 1,
+      }],
+      errors: [
+        'Maximum number of dependencies (1) exceeded.',
+      ],
+    }),
+
+    test({
+      code: 'import { x } from \'./foo\'; import { y } from \'./bar\'; import { z } from \'./baz\';',
+      options: [{
+        max: 2,
+      }],
+      errors: [
+        'Maximum number of dependencies (2) exceeded.',
+      ],
+    }),
+
+    test({
+      code: 'import { x } from \'./foo\'; require("./bar"); import { z } from \'./baz\';',
+      options: [{
+        max: 2,
+      }],
+      errors: [
+        'Maximum number of dependencies (2) exceeded.',
+      ],
+    }),
+
+    test({
+      code: 'import { x } from \'./foo\'; import { z } from \'./foo\'; require("./bar"); const path = require("path");',
+      options: [{
+        max: 2,
+      }],
+      errors: [
+        'Maximum number of dependencies (2) exceeded.',
+      ],
+    }),
+
+    test({
+      code: 'import type { x } from \'./foo\'; import type { y } from \'./bar\'',
+      parser: 'babel-eslint',
+      options: [{
+        max: 1,
+      }],
+      errors: [
+        'Maximum number of dependencies (1) exceeded.',
+      ],
+    }),
+  ],
+})