From c46115268a04d20607e968ed8f93ce57bcd584e5 Mon Sep 17 00:00:00 2001
From: Timofei Iatsenko <timiatsenko@gmail.com>
Date: Sat, 21 Dec 2024 14:53:47 +0100
Subject: [PATCH] feat: add meaningful error when locale is not set

---
 packages/core/src/i18n.test.ts | 13 +++++++++++++
 packages/core/src/i18n.ts      |  8 ++++++++
 2 files changed, 21 insertions(+)

diff --git a/packages/core/src/i18n.test.ts b/packages/core/src/i18n.test.ts
index 4e64511e4..34e132dc3 100644
--- a/packages/core/src/i18n.test.ts
+++ b/packages/core/src/i18n.test.ts
@@ -431,4 +431,17 @@ describe("I18n", () => {
     expect(i18n._("Software development")).toEqual("Software­entwicklung")
     expect(i18n._("Software development")).toEqual("Software­entwicklung")
   })
+
+  it("._ should throw a meaningful error when locale is not set", () => {
+    const i18n = setupI18n({})
+    expect(() =>
+      i18n._(
+        "Text {0, plural, offset:1 =0 {No books} =1 {1 book} other {# books}}"
+      )
+    ).toThrowErrorMatchingInlineSnapshot(`
+      "Lingui: Attempted to call a translation function without setting a locale.
+      Make sure to call \`i18n.activate(locale)\` before using Lingui functions.
+      This issue may also occur due to a race condition in your initialization logic."
+    `)
+  })
 })
diff --git a/packages/core/src/i18n.ts b/packages/core/src/i18n.ts
index afcb7b640..a133b7cf2 100644
--- a/packages/core/src/i18n.ts
+++ b/packages/core/src/i18n.ts
@@ -240,6 +240,14 @@ export class I18n extends EventEmitter<Events> {
     values?: Values,
     options?: MessageOptions
   ): string {
+    if (!this.locale) {
+      throw new Error(
+        "Lingui: Attempted to call a translation function without setting a locale.\n" +
+          "Make sure to call `i18n.activate(locale)` before using Lingui functions.\n" +
+          "This issue may also occur due to a race condition in your initialization logic."
+      )
+    }
+
     let message = options?.message
 
     if (!id) {