New rule: no-relative-packages

Use this rule to prevent importing packages through relative paths.

It's useful in Yarn/Lerna workspaces, were it's possible to import a sibling
package using `../package` relative path, while direct `package` is the correct one.

docs/rules/no-relative-packages.md

@@ -0,0 +1,66 @@
+# no-relative-packages
+
+Use this rule to prevent importing packages through relative paths.
+
+It's useful in Yarn/Lerna workspaces, were it's possible to import a sibling
+package using `../package` relative path, while direct `package` is the correct one.
+
+
+### Examples
+
+Given the following folder structure:
+
+```
+my-project
+├── packages
+│   ├── foo
+│   │   ├── index.js
+│   │   └── package.json
+│   └── bar
+│       ├── index.js
+│       └── package.json
+└── entry.js
+```
+
+And the .eslintrc file:
+```
+{
+  ...
+  "rules": {
+    "import/no-relative-packages": "error"
+  }
+}
+```
+
+The following patterns are considered problems:
+
+```js
+/**
+ *  in my-project/packages/foo.js
+ */
+
+import bar from '../bar'; // Import sibling package using relative path
+import entry from '../../entry.js'; // Import from parent package using relative path
+
+/**
+ *  in my-project/entry.js
+ */
+
+import bar from './packages/bar'; // Import child package using relative path
+```
+
+The following patterns are NOT considered problems:
+
+```js
+/**
+ *  in my-project/packages/foo.js
+ */
+
+import bar from 'bar'; // Import sibling package using package name
+
+/**
+ *  in my-project/entry.js
+ */
+
+import bar from 'bar'; // Import sibling package using package name
+```

src/index.js

@@ -9,6 +9,7 @@ export const rules = {
   'extensions': require('./rules/extensions'),
   'no-restricted-paths': require('./rules/no-restricted-paths'),
   'no-internal-modules': require('./rules/no-internal-modules'),
+  'no-relative-packages': require('./rules/no-relative-packages'),
 
   'no-named-default': require('./rules/no-named-default'),
   'no-named-as-default': require('./rules/no-named-as-default'),

src/rules/no-relative-packages.js

@@ -0,0 +1,69 @@
+import path from 'path'
+import readPkgUp from 'read-pkg-up'
+
+import resolve from 'eslint-module-utils/resolve'
+import importType from '../core/importType'
+import isStaticRequire from '../core/staticRequire'
+
+module.exports = {
+  meta: {
+    docs: {},
+  },
+
+  create: function noRelativePackages(context) {
+
+    function findNamedPackage(filePath) {
+      const found = readPkgUp.sync({cwd: filePath, normalize: false})
+      // console.log(found)
+      if (found.pkg && !found.pkg.name) {
+        return findNamedPackage(path.join(found.path, '../..'))
+      }
+      return found
+    }
+
+    function checkImportForRelativePackage(importPath, node) {
+      const potentialViolationTypes = ['parent', 'index', 'sibling']
+      if (potentialViolationTypes.indexOf(importType(importPath, context)) === -1) {
+        return
+      }
+
+      const resolvedImport = resolve(importPath, context)
+      const resolvedContext = context.getFilename()
+
+      if (!resolvedImport || !resolvedContext) {
+        return
+      }
+
+      const importPkg = findNamedPackage(resolvedImport)
+      const contextPkg = findNamedPackage(resolvedContext)
+
+      if (importPkg.pkg && contextPkg.pkg && importPkg.pkg.name !== contextPkg.pkg.name) {
+        const importBaseName = path.basename(importPath)
+        const importRoot = path.dirname(importPkg.path)
+        const properPath = path.relative(importRoot, resolvedImport)
+        const properImport = path.join(
+          importPkg.pkg.name, 
+          path.dirname(properPath),
+          importBaseName === path.basename(importRoot) ? '' : importBaseName
+        )
+        context.report({
+          node,
+          message: 'Relative import from another package is not allowed. ' + 
+            `Use "${properImport}" instead of "${importPath}"`,
+        })
+      }
+    }
+
+    return {
+      ImportDeclaration(node) {
+        checkImportForRelativePackage(node.source.value, node.source)
+      },
+      CallExpression(node) {
+        if (isStaticRequire(node)) {
+          const [ firstArgument ] = node.arguments
+          checkImportForRelativePackage(firstArgument.value, firstArgument)
+        }
+      },
+    }
+  },
+}

tests/files/package-named/index.js

@@ -0,0 +1 @@
+export default function () {}

tests/files/package-named/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "package-named",
+  "description": "Standard, named package",
+  "main": "index.js"  
+}

tests/files/package/index.js

@@ -0,0 +1 @@
+export default function () {}

tests/files/package/package.json

@@ -0,0 +1,4 @@
+{
+  "description": "Unnamed package for reaching through main field - rxjs style",
+  "main": "index.js"
+}

tests/src/rules/no-relative-packages.js

@@ -0,0 +1,66 @@
+import { RuleTester } from 'eslint'
+import rule from 'rules/no-relative-packages'
+
+import { test, testFilePath } from '../utils'
+
+const ruleTester = new RuleTester()
+
+ruleTester.run('no-relative-packages', rule, {
+  valid: [
+    test({
+      code: 'import foo from "./index.js"',
+      filename: testFilePath('./package/index.js'),
+    }),
+    test({
+      code: 'import bar from "../bar"',
+      filename: testFilePath('./package/index.js'),
+    }),
+    test({
+      code: 'import {foo} from "a"',
+      filename: testFilePath('./package-named/index.js'),
+    }),
+    test({
+      code: 'const bar = require("../bar.js")',
+      filename: testFilePath('./package/index.js'),
+    }),
+  ],
+
+  invalid: [
+    test({
+      code: 'import foo from "./package-named"',
+      filename: testFilePath('./bar.js'),
+      errors: [ {
+        message: 'Relative import from another package is not allowed. Use "package-named" instead of "./package-named"',
+        line: 1,
+        column: 17,
+      } ],
+    }),
+    test({
+      code: 'import foo from "../package-named"',
+      filename: testFilePath('./package/index.js'),
+      errors: [ {
+        message: 'Relative import from another package is not allowed. Use "package-named" instead of "../package-named"',
+        line: 1,
+        column: 17,
+      } ],
+    }),
+    test({
+      code: 'import foo from "../package-scoped"',
+      filename: testFilePath('./package/index.js'),
+      errors: [ {
+        message: 'Relative import from another package is not allowed. Use "@scope/package-named" instead of "../package-scoped"',
+        line: 1,
+        column: 17,
+      } ],
+    }),
+    test({
+      code: 'import bar from "../bar"',
+      filename: testFilePath('./package-named/index.js'),
+      errors: [ {
+        message: 'Relative import from another package is not allowed. Use "eslint-plugin-import/tests/files/bar" instead of "../bar"',
+        line: 1,
+        column: 17,
+      } ],
+    }),
+  ],
+})