docs: improve missing data error (#3406)

Author: ST-DDT

docs/guide/localization.md

@@ -181,11 +181,11 @@ As a workaround, you can provide additional fallbacks to your `Faker` instance:
 
 ```ts
 import { Faker, el } from '@faker-js/faker'; // [!code --]
-import { Faker, el, en } from '@faker-js/faker'; // [!code ++]
+import { Faker, base, el, en } from '@faker-js/faker'; // [!code ++]
 
 const faker = new Faker({
   locale: [el], // [!code --]
-  locale: [el, en], // [!code ++]
+  locale: [el, en, base], // [!code ++]
 });
 console.log(faker.location.country()); // 'Belgium'
 ```

src/faker.ts

@@ -120,7 +120,9 @@ export class Faker extends SimpleFaker {
    * For more information see our [Localization Guide](https://fakerjs.dev/guide/localization.html).
    *
    * @param options The options to use.
-   * @param options.locale The locale data to use.
+   * @param options.locale The locale data to use for this instance.
+   * If an array is provided, the first locale that has a definition for a given property will be used.
+   * Please make sure that all required locales and their parent locales are present, e.g. `[de_AT, de, en, base]`.
    * @param options.randomizer The Randomizer to use.
    * Specify this only if you want to use it to achieve a specific goal,
    * such as sharing the same random generator with other instances/tools.
@@ -148,6 +150,7 @@ export class Faker extends SimpleFaker {
     /**
      * The locale data to use for this instance.
      * If an array is provided, the first locale that has a definition for a given property will be used.
+     * Please make sure that all required locales and their parent locales are present, e.g. `[de_AT, de, en, base]`.
      *
      * @see mergeLocales(): For more information about how the locales are merged.
      */

src/internal/locale-proxy.ts

@@ -72,6 +72,7 @@ export function assertLocaleData<T>(
   } else if (value === undefined) {
     throw new FakerError(
       `The locale data for '${path.join('.')}' are missing in this locale.
+  If this is a custom Faker instance, please make sure all required locales are used e.g. '[de_AT, de, en, base]'.
   Please contribute the missing data to the project or use a locale/Faker instance that has these data.
   For more information see https://fakerjs.dev/guide/localization.html`
     );

test/internal/locale-proxy.spec.ts

@@ -97,6 +97,7 @@ describe('LocaleProxy', () => {
       expect(() => locale.category.missing).toThrow(
         new FakerError(
           `The locale data for 'category.missing' are missing in this locale.
+  If this is a custom Faker instance, please make sure all required locales are used e.g. '[de_AT, de, en, base]'.
   Please contribute the missing data to the project or use a locale/Faker instance that has these data.
   For more information see https://fakerjs.dev/guide/localization.html`
         )
@@ -107,6 +108,7 @@ describe('LocaleProxy', () => {
       expect(() => locale.airline.missing).toThrow(
         new FakerError(
           `The locale data for 'airline.missing' are missing in this locale.
+  If this is a custom Faker instance, please make sure all required locales are used e.g. '[de_AT, de, en, base]'.
   Please contribute the missing data to the project or use a locale/Faker instance that has these data.
   For more information see https://fakerjs.dev/guide/localization.html`
         )

test/modules/location.spec.ts

@@ -220,6 +220,7 @@ describe('location', () => {
           expect(() => faker.location.zipCode({ state: 'XX' })).toThrow(
             new FakerError(
               `The locale data for 'location.postcode_by_state' are missing in this locale.
+  If this is a custom Faker instance, please make sure all required locales are used e.g. '[de_AT, de, en, base]'.
   Please contribute the missing data to the project or use a locale/Faker instance that has these data.
   For more information see https://fakerjs.dev/guide/localization.html`
             )