fix(no-unlocalized-strings): ignore React directives

Ignore React directives "use client" and "use server" which were
incorrectly flagged as unlocalized strings. Supports both file-level
directives and "use server" inside async function bodies.

Author: swernerx

src/rules/no-unlocalized-strings.test.ts

@@ -393,12 +393,14 @@ ruleTester.run("no-unlocalized-strings", noUnlocalizedStrings, {
     { code: 'import name from "hello"', filename: "test.tsx" },
     { code: 'export * from "hello_export_all"', filename: "test.tsx" },
 
-    // JavaScript/React directive prologues
-    { code: '"use strict"', filename: "test.tsx" },
+    // React directives
     { code: '"use client"', filename: "test.tsx" },
     { code: '"use server"', filename: "test.tsx" },
     { code: '"use client"\nimport React from "react"', filename: "test.tsx" },
     { code: '"use server"\nexport async function action() {}', filename: "test.tsx" },
+    // "use server" inside function body (server actions)
+    { code: 'async function myAction() { "use server"; return null }', filename: "test.tsx" },
+    { code: 'const action = async () => { "use server"; return null }', filename: "test.tsx" },
 
     // =========================================================================
     // Branded types with __linguiIgnore

src/rules/no-unlocalized-strings.ts

@@ -853,35 +853,49 @@ function isInsideStylingConstant(node: TSESTree.Node): boolean {
 // Syntax Context Checks (non-user-facing locations)
 // ============================================================================
 
-/** Known JavaScript/React directive prologues */
-const DIRECTIVE_PROLOGUES = new Set(["use strict", "use client", "use server"])
+/** React directive strings */
+const REACT_DIRECTIVES = new Set(["use client", "use server"])
 
 /**
- * Checks if a string literal is a JavaScript directive prologue.
+ * Checks if a string literal is a React directive.
  *
- * Directive prologues are special string literals at the start of a script/module:
- * - "use strict" - JavaScript strict mode
- * - "use client" - React Server Components client boundary
- * - "use server" - React Server Components server actions
+ * React directives are special string literals:
+ * - "use client" - marks a client component boundary (file level)
+ * - "use server" - marks server actions (file level or inside async functions)
  */
-function isDirectivePrologue(node: TSESTree.Node): boolean {
+function isReactDirective(node: TSESTree.Node): boolean {
   if (node.type !== AST_NODE_TYPES.Literal || typeof node.value !== "string") {
     return false
   }
 
-  // Check if this is a known directive
-  if (!DIRECTIVE_PROLOGUES.has(node.value)) {
+  if (!REACT_DIRECTIVES.has(node.value)) {
     return false
   }
 
-  // Directive prologues must be expression statements at the program level
+  // Must be wrapped in an expression statement
   const parent = node.parent
   if (parent.type !== AST_NODE_TYPES.ExpressionStatement) {
     return false
   }
 
   const grandparent = parent.parent
-  return grandparent.type === AST_NODE_TYPES.Program
+
+  // File-level directive
+  if (grandparent.type === AST_NODE_TYPES.Program) {
+    return true
+  }
+
+  // Function-level directive (e.g., "use server" inside async function)
+  if (grandparent.type === AST_NODE_TYPES.BlockStatement) {
+    const functionParent = grandparent.parent
+    return (
+      functionParent.type === AST_NODE_TYPES.FunctionDeclaration ||
+      functionParent.type === AST_NODE_TYPES.FunctionExpression ||
+      functionParent.type === AST_NODE_TYPES.ArrowFunctionExpression
+    )
+  }
+
+  return false
 }
 
 /**
@@ -1387,8 +1401,8 @@ export const noUnlocalizedStrings = createRule<[Options], MessageId>({
         return
       }
 
-      // JavaScript/React directive prologues: "use strict", "use client", "use server"
-      if (isDirectivePrologue(node)) {
+      // React directives: "use client", "use server"
+      if (isReactDirective(node)) {
         return
       }