[New] extensions: accept both a string, and an object to override it.

Fixes #390.

Author: ljharb

docs/rules/extensions.md

@@ -6,10 +6,12 @@ In order to provide a consistent use of file extensions across your code base, t
 
 ## Rule Details
 
-This rule has one option which could be either a string or an object. If it is `"never"` (the default value) the rule forbids the use for any extension. If `"always"` then the rule enforces the use of extensions for all import statements.
+This rule either takes one string option, one object option, or a string and an object option. If it is the string `"never"` (the default value) the rule forbids the use for any extension. If the string `"always"` then the rule enforces the use of extensions for all import statements.
 
 By providing an object you can configure each extension separately, so for example `{ "js": "always", "json": "never" }` would always enforce the use of the `.js` extension but never allow the use of the `.json` extension.
 
+By providing both a string and an object, the string will set the default setting for all extensions, and the object can be used to set granular overrides for specific extensions. For example, `[<enabled>, "never", { "svg": "always" }]` would require that all extensions are omitted, except for "svg".
+
 ### Exception
 
 When disallowing the use of certain extensions this rule makes an exception and allows the use of extension when the file would not be resolvable without extension.

src/rules/extensions.js

@@ -6,13 +6,15 @@ import { isBuiltIn } from '../core/importType'
 
 module.exports = function (context) {
   const configuration = context.options[0] || 'never'
+  const defaultConfig = typeof configuration === 'string' ? configuration : null
+  const modifiers = typeof configuration === 'object' ? configuration : context.options[1] || {}
 
-  function isUseOfExtensionEnforced(extension) {
-    if (typeof configuration === 'object') {
-      return configuration[extension] === 'always'
-    }
+  function isUseOfExtensionRequired(extension) {
+    return (modifiers[extension] || defaultConfig) === 'always'
+  }
 
-    return configuration === 'always'
+  function isUseOfExtensionForbidden(extension) {
+    return (modifiers[extension] || defaultConfig) === 'never'
   }
 
   function isResolvableWithoutExtension(file) {
@@ -37,15 +39,15 @@ module.exports = function (context) {
     const extension = path.extname(resolvedPath || importPath).substring(1)
 
     if (!extension || !endsWith(importPath, extension)) {
-      if (isUseOfExtensionEnforced(extension)) {
+      if (isUseOfExtensionRequired(extension) && !isUseOfExtensionForbidden(extension)) {
         context.report({
           node: source,
           message:
             `Missing file extension ${extension ? `"${extension}" ` : ''}for "${importPath}"`,
         })
       }
     } else if (extension) {
-      if (!isUseOfExtensionEnforced(extension) && isResolvableWithoutExtension(importPath)) {
+      if (isUseOfExtensionForbidden(extension) && isResolvableWithoutExtension(importPath)) {
         context.report({
           node: source,
           message: `Unexpected use of file extension "${extension}" for "${importPath}"`,
@@ -59,18 +61,31 @@ module.exports = function (context) {
   }
 }
 
-module.exports.schema = [
-  {
-    oneOf: [
-      {
-        enum: [ 'always', 'never' ],
-      },
-      {
-        type: 'object',
-        patternProperties: {
-          '.*': { enum: [ 'always', 'never' ] },
-        },
-      },
-    ],
-  },
-]
+const enumValues = { enum: [ 'always', 'never' ] }
+const patternProperties = {
+  type: 'object',
+  patternProperties: { '.*': enumValues },
+}
+
+module.exports.schema = {
+  anyOf: [
+    {
+      type: 'array',
+      items: [enumValues],
+      additionalItems: false,
+    },
+    {
+      type: 'array',
+      items: [patternProperties],
+      additionalItems: false,
+    },
+    {
+      type: 'array',
+      items: [
+        enumValues,
+        patternProperties,
+      ],
+      additionalItems: false,
+    },
+  ],
+}

tests/src/rules/extensions.js

@@ -33,6 +33,25 @@ ruleTester.run('extensions', rule, {
       settings: { 'import/resolve': { 'extensions': [ '.js', '.jsx', '.json' ] } },
     }),
 
+    test({
+      code: [
+        'import lib from "./bar"',
+        'import lib from "./bar.json"',
+        'import lib from "./bar.hbs"',
+      ].join('\n'),
+      options: [ 'always', { js: 'never', jsx: 'never' } ],
+      settings: { 'import/resolve': { 'extensions': [ '.js', '.jsx', '.json', '.hbs' ] } },
+    }),
+
+    test({
+      code: [
+        'import lib from "./bar.js"',
+        'import lib from "./package"',
+      ].join('\n'),
+      options: [ 'never', { js: 'always', json: 'never' } ],
+      settings: { 'import/resolve': { 'extensions': [ '.js', '.json' ] } },
+    }),
+
     // unresolved (#271/#295)
     test({ code: 'import path from "path"' }),
     test({ code: 'import path from "path"', options: [ 'never' ] }),
@@ -124,6 +143,40 @@ ruleTester.run('extensions', rule, {
       ],
     }),
 
+    test({
+      code: [
+        'import lib from "./bar.js"',
+        'import lib from "./bar.json"',
+        'import lib from "./bar"',
+      ].join('\n'),
+      options: [ 'always', { json: 'always', js: 'never', jsx: 'never' } ],
+      settings: { 'import/resolve': { 'extensions': [ '.js', '.jsx', '.json' ] } },
+      errors: [
+        {
+            message: 'Unexpected use of file extension "js" for "./bar.js"',
+            line: 1,
+            column: 17,
+        },
+      ],
+    }),
+
+    test({
+      code: [
+        'import lib from "./bar.js"',
+        'import lib from "./bar.json"',
+        'import lib from "./bar"',
+      ].join('\n'),
+      options: [ 'never', { json: 'always', js: 'never', jsx: 'never' } ],
+      settings: { 'import/resolve': { 'extensions': [ '.js', '.jsx', '.json' ] } },
+      errors: [
+        {
+            message: 'Unexpected use of file extension "js" for "./bar.js"',
+            line: 1,
+            column: 17,
+        },
+      ],
+    }),
+
     // unresolved (#271/#295)
     test({
       code: 'import thing from "./fake-file.js"',