Add ESLint rule to enforce Lingui msg usage (#9789)

* Add ESLint rule to enforce Lingui msg usage

Adds a custom ESLint rule 'lingui-msg-rule' that ensures the Lingui _()
function is called with msg`` template literals or plural/select macros,
preventing accidental misuse like _('string') which bypasses i18n.

https://claude.ai/code/session_01JMXXPUgAHiSBGmfGwUojKy

* Support msg({...}) descriptor form and add auto-fix

- Allow msg() function call form: _(msg({message: 'Hello'}))
- Add auto-fix for string literals: _('Bad') -> _(msg`Bad`)
- Add auto-fix for untagged templates: _(`Bad`) -> _(msg`Bad`)
- No auto-fix for variables/function calls (not safely fixable)

https://claude.ai/code/session_01JMXXPUgAHiSBGmfGwUojKy

* fix complex cases

* run autofix HELL YEAH

---------

Co-authored-by: Claude <noreply@anthropic.com>

eslint.config.mjs

@@ -121,6 +121,7 @@ export default defineConfig(
       ],
       'bsky-internal/use-exact-imports': 'error',
       'bsky-internal/use-prefixed-imports': 'error',
+      'bsky-internal/lingui-msg-rule': 'error',
 
       /**
        * React & React Native

eslint/__tests__/lingui-msg-rule.test.js

@@ -0,0 +1,188 @@
+const {RuleTester} = require('eslint')
+const tseslint = require('typescript-eslint')
+const linguiMsgRule = require('../lingui-msg-rule')
+
+const ruleTester = new RuleTester({
+  languageOptions: {
+    parser: tseslint.parser,
+    parserOptions: {
+      ecmaFeatures: {
+        jsx: true,
+      },
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+    },
+  },
+})
+
+describe('lingui-msg-rule', () => {
+  const tests = {
+    valid: [
+      // msg template literal
+      {
+        code: `
+const {_} = useLingui()
+const x = _(msg\`Hello\`)
+        `,
+      },
+      // msg template literal with interpolation
+      {
+        code: `
+const {_} = useLingui()
+const name = 'World'
+const x = _(msg\`Hello \${name}\`)
+        `,
+      },
+      // plural macro
+      {
+        code: `
+const {_} = useLingui()
+const count = 5
+const x = _(plural(count, {one: '# item', other: '# items'}))
+        `,
+      },
+      // select macro
+      {
+        code: `
+const {_} = useLingui()
+const gender = 'female'
+const x = _(select(gender, {male: 'He', female: 'She', other: 'They'}))
+        `,
+      },
+      // selectOrdinal macro
+      {
+        code: `
+const {_} = useLingui()
+const position = 1
+const x = _(selectOrdinal(position, {one: '#st', two: '#nd', few: '#rd', other: '#th'}))
+        `,
+      },
+      // msg function call with object (descriptor form)
+      {
+        code: `
+const {_} = useLingui()
+const x = _(msg({message: 'Hello'}))
+        `,
+      },
+      // msg function call with object and context
+      {
+        code: `
+const {_} = useLingui()
+const x = _(msg({message: 'Hello', context: 'greeting'}))
+        `,
+      },
+    ],
+    invalid: [
+      // Plain string literal (single quotes) - with auto-fix
+      {
+        code: `
+const {_} = useLingui()
+const x = _('Bad')
+        `,
+        output: `
+const {_} = useLingui()
+const x = _(msg\`Bad\`)
+        `,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Plain string literal (double quotes) - with auto-fix
+      {
+        code: `
+const {_} = useLingui()
+const x = _("Bad")
+        `,
+        output: `
+const {_} = useLingui()
+const x = _(msg\`Bad\`)
+        `,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Template literal without msg tag - with auto-fix
+      {
+        code: `
+const {_} = useLingui()
+const x = _(\`Bad\`)
+        `,
+        output: `
+const {_} = useLingui()
+const x = _(msg\`Bad\`)
+        `,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Template literal with interpolation - with auto-fix
+      {
+        code: `
+const {_} = useLingui()
+const name = 'World'
+const x = _(\`Hello \${name}\`)
+        `,
+        output: `
+const {_} = useLingui()
+const name = 'World'
+const x = _(msg\`Hello \${name}\`)
+        `,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // String with backticks that need escaping
+      {
+        code: `
+const {_} = useLingui()
+const x = _('Use \\\`code\\\` here')
+        `,
+        output: `
+const {_} = useLingui()
+const x = _(msg\`Use \\\`code\\\` here\`)
+        `,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Variable/identifier - no auto-fix possible
+      {
+        code: `
+const {_} = useLingui()
+const message = 'Hello'
+const x = _(message)
+        `,
+        output: null,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Arbitrary function call - no auto-fix possible
+      {
+        code: `
+const {_} = useLingui()
+const x = _(getMessage())
+        `,
+        output: null,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Empty call - no auto-fix possible
+      {
+        code: `
+const {_} = useLingui()
+const x = _()
+        `,
+        output: null,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Tagged template with wrong tag - no auto-fix (would need to replace tag)
+      {
+        code: `
+const {_} = useLingui()
+const x = _(html\`Hello\`)
+        `,
+        output: null,
+        errors: [{messageId: 'missingMsg'}],
+      },
+      // Number literal - no auto-fix possible
+      {
+        code: `
+const {_} = useLingui()
+const x = _(123)
+        `,
+        output: null,
+        errors: [{messageId: 'missingMsg'}],
+      },
+    ],
+  }
+
+  ruleTester.run('lingui-msg-rule', linguiMsgRule, tests)
+})

eslint/index.js

@@ -9,6 +9,7 @@ const plugin = {
     'avoid-unwrapped-text': require('./avoid-unwrapped-text'),
     'use-exact-imports': require('./use-exact-imports'),
     'use-prefixed-imports': require('./use-prefixed-imports'),
+    'lingui-msg-rule': require('./lingui-msg-rule'),
   },
 }
 

eslint/lingui-msg-rule.js

@@ -0,0 +1,110 @@
+'use strict'
+
+/**
+ * @type {import('eslint').Rule.RuleModule}
+ */
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description:
+        'Enforce that Lingui _() function is called with msg`` template literal or plural/select macros',
+      recommended: true,
+    },
+    fixable: 'code',
+    messages: {
+      missingMsg:
+        'Lingui _() must be called with msg`...` or msg({...}) or plural/select/selectOrdinal. Example: _(msg`Hello`)',
+    },
+    schema: [],
+  },
+
+  create(context) {
+    // Valid Lingui macro functions that can be passed to _()
+    const VALID_MACRO_FUNCTIONS = new Set([
+      'msg',
+      'plural',
+      'select',
+      'selectOrdinal',
+    ])
+
+    /**
+     * Escape backticks and backslashes for template literal
+     */
+    function escapeForTemplateLiteral(str) {
+      return str.replace(/\\`/g, '`').replace(/`/g, '\\`')
+    }
+
+    /**
+     * Try to get a fixer for the given argument
+     * Returns null if we can't safely fix it
+     */
+    function getFixer(firstArg) {
+      const sourceCode = context.sourceCode ?? context.getSourceCode()
+
+      // Fix string literals: _('foo') -> _(msg`foo`)
+      if (firstArg.type === 'Literal' && typeof firstArg.value === 'string') {
+        const escaped = escapeForTemplateLiteral(firstArg.value)
+        return function (fixer) {
+          return fixer.replaceText(firstArg, 'msg`' + escaped + '`')
+        }
+      }
+
+      // Fix untagged template literals: _(`foo`) -> _(msg`foo`)
+      if (firstArg.type === 'TemplateLiteral') {
+        const text = sourceCode.getText(firstArg)
+        return function (fixer) {
+          return fixer.replaceText(firstArg, 'msg' + text)
+        }
+      }
+
+      return null
+    }
+
+    return {
+      CallExpression(node) {
+        // Check if this is a call to _()
+        if (node.callee.type !== 'Identifier' || node.callee.name !== '_') {
+          return
+        }
+
+        // Must have at least one argument
+        if (node.arguments.length === 0) {
+          context.report({
+            node,
+            messageId: 'missingMsg',
+          })
+          return
+        }
+
+        const firstArg = node.arguments[0]
+
+        // Valid: _(msg`...`)
+        if (
+          firstArg.type === 'TaggedTemplateExpression' &&
+          firstArg.tag.type === 'Identifier' &&
+          firstArg.tag.name === 'msg'
+        ) {
+          return
+        }
+
+        // Valid: _(msg(...)), _(plural(...)), _(select(...)), _(selectOrdinal(...))
+        if (
+          firstArg.type === 'CallExpression' &&
+          firstArg.callee.type === 'Identifier' &&
+          VALID_MACRO_FUNCTIONS.has(firstArg.callee.name)
+        ) {
+          return
+        }
+
+        // Everything else is invalid
+        const fix = getFixer(firstArg)
+        context.report({
+          node,
+          messageId: 'missingMsg',
+          fix,
+        })
+      },
+    }
+  },
+}

src/components/Post/Embed/VideoEmbed/VideoEmbedInner/web-controls/VideoControls.tsx

@@ -312,13 +312,13 @@ export function Controls({
         onPointerEnter={onPointerMoveEmptySpace}
         onPointerMove={onPointerMoveEmptySpace}
         onPointerLeave={onPointerLeaveEmptySpace}
-        accessibilityLabel={_(
+        accessibilityLabel={
           !focused
-            ? msg`Unmute video`
+            ? _(msg`Unmute video`)
             : playing
-              ? msg`Pause video`
-              : msg`Play video`,
-        )}
+              ? _(msg`Pause video`)
+              : _(msg`Play video`)
+        }
         accessibilityHint=""
         style={[
           a.flex_1,

src/components/StarterPack/ProfileStarterPacks.tsx

@@ -101,7 +101,7 @@ export function ProfileStarterPacks({
             message={
               emptyStateMessage ??
               _(
-                'Starter packs let you share your favorite feeds and people with your friends.',
+                msg`Starter packs let you share your favorite feeds and people with your friends.`,
               )
             }
             button={emptyStateButton}

src/components/dms/LeaveConvoPrompt.tsx

@@ -40,11 +40,13 @@ export function LeaveConvoPrompt({
     <Prompt.Basic
       control={control}
       title={_(msg`Leave conversation`)}
-      description={_(
+      description={
         hasMessages
-          ? msg`Are you sure you want to leave this conversation? Your messages will be deleted for you, but not for the other participant.`
-          : msg`Are you sure you want to leave this conversation?`,
-      )}
+          ? _(
+              msg`Are you sure you want to leave this conversation? Your messages will be deleted for you, but not for the other participant.`,
+            )
+          : _(msg`Are you sure you want to leave this conversation?`)
+      }
       confirmButtonCta={_(msg`Leave`)}
       confirmButtonColor="negative"
       onConfirm={() => leaveConvo()}

src/screens/VideoFeed/index.tsx

@@ -1109,7 +1109,7 @@ function PlayPauseTapArea({
         isPlaying ? _(msg`Video is playing`) : _(msg`Video is paused`)
       }
       label={_(
-        `Video from ${sanitizeHandle(
+        msg`Video from ${sanitizeHandle(
           post.author.handle,
           '@',
         )}. Tap to play or pause the video`,

src/view/com/feeds/FeedSourceCard.tsx

@@ -182,11 +182,15 @@ export function FeedSourceCardLoaded({
     return (
       <Link
         testID={`feed-${feed.displayName}`}
-        label={_(
+        label={
           feed.type === 'feed'
-            ? msg`${feed.displayName}, a feed by ${sanitizeHandle(feed.creatorHandle, '@')}, liked by ${feed.likeCount || 0}`
-            : msg`${feed.displayName}, a list by ${sanitizeHandle(feed.creatorHandle, '@')}`,
-        )}
+            ? _(
+                msg`${feed.displayName}, a feed by ${sanitizeHandle(feed.creatorHandle, '@')}, liked by ${feed.likeCount || 0}`,
+              )
+            : _(
+                msg`${feed.displayName}, a list by ${sanitizeHandle(feed.creatorHandle, '@')}`,
+              )
+        }
         to={{
           screen: feed.type === 'feed' ? 'ProfileFeed' : 'ProfileList',
           params: {name: feed.creatorDid, rkey: new AtUri(feed.uri).rkey},

src/view/shell/Drawer.tsx

@@ -39,8 +39,10 @@ import {
   HomeOpen_Filled_Corner0_Rounded as HomeFilled,
   HomeOpen_Stoke2_Corner0_Rounded as Home,
 } from '#/components/icons/HomeOpen'
-import {MagnifyingGlass_Filled_Stroke2_Corner0_Rounded as MagnifyingGlassFilled} from '#/components/icons/MagnifyingGlass'
-import {MagnifyingGlass_Stroke2_Corner0_Rounded as MagnifyingGlass} from '#/components/icons/MagnifyingGlass'
+import {
+  MagnifyingGlass_Filled_Stroke2_Corner0_Rounded as MagnifyingGlassFilled,
+  MagnifyingGlass_Stroke2_Corner0_Rounded as MagnifyingGlass,
+} from '#/components/icons/MagnifyingGlass'
 import {
   Message_Stroke2_Corner0_Rounded as Message,
   Message_Stroke2_Corner0_Rounded_Filled as MessageFilled,
@@ -495,10 +497,10 @@ let NotificationsMenuItem = ({
         numUnreadNotifications === ''
           ? ''
           : _(
-              msg`${plural(numUnreadNotifications ?? 0, {
+              plural(numUnreadNotifications ?? 0, {
                 one: '# unread item',
                 other: '# unread items',
-              })}` || '',
+              }),
             )
       }
       count={numUnreadNotifications}

src/view/shell/bottom-bar/BottomBar.tsx

@@ -219,10 +219,10 @@ export function BottomBar({navigation}: BottomTabBarProps) {
               accessibilityHint={
                 numUnreadMessages.count > 0
                   ? _(
-                      msg`${plural(numUnreadMessages.numUnread ?? 0, {
+                      plural(numUnreadMessages.numUnread ?? 0, {
                         one: '# unread item',
                         other: '# unread items',
-                      })}` || '',
+                      }),
                     )
                   : ''
               }
@@ -251,10 +251,10 @@ export function BottomBar({navigation}: BottomTabBarProps) {
                 numUnreadNotifications === ''
                   ? ''
                   : _(
-                      msg`${plural(numUnreadNotifications ?? 0, {
+                      plural(numUnreadNotifications ?? 0, {
                         one: '# unread item',
                         other: '# unread items',
-                      })}` || '',
+                      }),
                     )
               }
             />