Improve monorepo support for no-extraneous-dependencies rule

docs/rules/no-extraneous-dependencies.md

@@ -35,6 +35,11 @@ Also there is one more option called `packageDir`, this option is to specify the
 "import/no-extraneous-dependencies": ["error", {"packageDir": './some-dir/'}]
 ```
 
+Or, as an array - for when you need this rule to lookup multiple package.json files (for ex, if you are using a monnorepo).
+```js
+"import/no-extraneous-dependencies": ["error", {"packageDir": ['./some-dir/', './some/other/dir/']}]
+```
+
 ## Rule Details
 
 Given the following `package.json`:

src/rules/no-extraneous-dependencies.js

@@ -7,22 +7,61 @@ import importType from '../core/importType'
 import isStaticRequire from '../core/staticRequire'
 import docsUrl from '../docsUrl'
 
+function hasKeys(obj) {
+  return Object.keys(obj).length > 0
+}
+
+function extractDependencies(manifest = {}) {
+  const {
+    dependencies = {},
+    devDependencies = {},
+    optionalDependencies = {},
+    peerDependencies = {},
+  } = manifest
+
+  return {
+    dependencies,
+    devDependencies,
+    optionalDependencies,
+    peerDependencies,
+  }
+}
+
 function getDependencies(context, packageDir) {
+  const packageDirs = Array.isArray(packageDir)
+      ? packageDir
+      : (packageDir ? [packageDir] : [])
+  const packageContent = {
+    dependencies: {},
+    devDependencies: {},
+    optionalDependencies: {},
+    peerDependencies: {},
+  }
+
   try {
-    const packageContent = packageDir
-      ? JSON.parse(fs.readFileSync(path.join(packageDir, 'package.json'), 'utf8'))
-      : readPkgUp.sync({cwd: context.getFilename(), normalize: false}).pkg
+    if (!packageDirs.length) {
+      Object.assign(
+        packageContent,
+        extractDependencies(
+          readPkgUp.sync({cwd: context.getFilename(), normalize: false}).pkg
+        )
+      )
+    } else {
+      for (const dir of packageDirs) {
+        const manifest = extractDependencies(
+          JSON.parse(fs.readFileSync(path.join(dir, 'package.json'), 'utf8'))
+        )
+        Object.keys(manifest).forEach(depType => {
+          Object.assign(packageContent[depType], manifest[depType])
+        })
+      }
+    }
 
-    if (!packageContent) {
+    if (!Object.keys(packageContent).some(depType => hasKeys(packageContent[depType]))) {
       return null
     }
 
-    return {
-      dependencies: packageContent.dependencies || {},
-      devDependencies: packageContent.devDependencies || {},
-      optionalDependencies: packageContent.optionalDependencies || {},
-      peerDependencies: packageContent.peerDependencies || {},
-    }
+    return packageContent
   } catch (e) {
     if (packageDir && e.code === 'ENOENT') {
       context.report({
@@ -36,9 +75,9 @@ function getDependencies(context, packageDir) {
         loc: { line: 0, column: 0 },
       })
     }
-
-    return null
   }
+
+  return null
 }
 
 function missingErrorMessage(packageName) {
@@ -124,7 +163,7 @@ module.exports = {
           'devDependencies': { 'type': ['boolean', 'array'] },
           'optionalDependencies': { 'type': ['boolean', 'array'] },
           'peerDependencies': { 'type': ['boolean', 'array'] },
-          'packageDir': { 'type': 'string' },
+          'packageDir': { 'type': ['string', 'array'] },
         },
         'additionalProperties': false,
       },

tests/src/rules/no-extraneous-dependencies.js

@@ -70,6 +70,10 @@ ruleTester.run('no-extraneous-dependencies', rule, {
       code: 'import "doctrine"',
       options: [{packageDir: path.join(__dirname, '../../../')}],
     }),
+    test({
+      code: 'import "chai"',
+      options: [{packageDir: [path.join(__dirname, '../../../')]}],
+    }),
     test({
       code: 'import type MyType from "myflowtyped";',
       options: [{packageDir: packageDirWithFlowTyped}],