From 7e89379e568dd12ad336f625d74fd4d9d4dc0a96 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Thu, 5 Oct 2023 23:42:34 +0200
Subject: [PATCH 01/20] infra: enable strictNullChecks in tsconfig

---
 cypress/e2e/api.cy.ts                         |  2 +-
 docs/.vitepress/config.ts                     | 13 +++--
 docs/.vitepress/versions.ts                   |  3 +-
 scripts/apidoc/fakerClass.ts                  |  6 ++-
 scripts/apidoc/signature.ts                   |  2 +-
 src/definitions/definitions.ts                |  2 +-
 src/locales/ar/date/weekday.ts                | 10 +++-
 src/locales/ur/date/month.ts                  | 15 +++++-
 src/locales/ur/date/weekday.ts                |  2 +-
 src/modules/airline/index.ts                  |  2 +-
 src/modules/commerce/index.ts                 |  2 +-
 src/modules/date/index.ts                     | 44 ++++++++++++-----
 src/modules/finance/index.ts                  |  6 +--
 src/modules/helpers/index.ts                  | 22 +++++----
 src/modules/helpers/unique.ts                 |  4 +-
 src/modules/internet/index.ts                 |  2 +
 src/modules/person/index.ts                   | 47 ++++++++++++++-----
 src/modules/random/index.ts                   |  2 +-
 test/faker.spec.ts                            |  4 +-
 test/modules/airline.spec.ts                  |  8 ++--
 test/modules/finance_iban.spec.ts             | 12 ++---
 test/modules/helpers.spec.ts                  |  3 +-
 test/scripts/apidoc/verify-jsdoc-tags.spec.ts |  2 +-
 test/vitest-extensions.ts                     |  1 +
 tsconfig.json                                 |  1 -
 25 files changed, 147 insertions(+), 70 deletions(-)

diff --git a/cypress/e2e/api.cy.ts b/cypress/e2e/api.cy.ts
index be61f5dfc5b..d46434cb46d 100644
--- a/cypress/e2e/api.cy.ts
+++ b/cypress/e2e/api.cy.ts
@@ -34,7 +34,7 @@ describe('API Test', () => {
       cy.get('.api-group li').each(($el) => {
         const anchor = $el.find('a');
         const text = anchor.text();
-        const link = anchor.attr('href').split('#')[0];
+        const link = anchor.attr('href')!.split('#')[0];
         if (checked.has(link)) {
           return;
         }
diff --git a/docs/.vitepress/config.ts b/docs/.vitepress/config.ts
index 12fea107d34..e8484526a74 100644
--- a/docs/.vitepress/config.ts
+++ b/docs/.vitepress/config.ts
@@ -121,11 +121,14 @@ const config = defineConfig({
       { icon: 'github', link: 'https://github.com/faker-js/faker' },
     ],
 
-    algolia: {
-      apiKey: process.env.API_KEY,
-      appId: process.env.APP_ID,
-      indexName: 'fakerjs',
-    },
+    algolia:
+      process.env.API_KEY == null || process.env.APP_ID == null
+        ? undefined
+        : {
+            apiKey: process.env.API_KEY,
+            appId: process.env.APP_ID,
+            indexName: 'fakerjs',
+          },
 
     footer: {
       message: 'Released under the MIT License.',
diff --git a/docs/.vitepress/versions.ts b/docs/.vitepress/versions.ts
index 2964557cee9..c9e34e8c73d 100644
--- a/docs/.vitepress/versions.ts
+++ b/docs/.vitepress/versions.ts
@@ -23,8 +23,9 @@ function readOtherLatestReleaseTagNames(): string[] {
       }
       return acc;
     }, {});
+
   return Object.entries(latestReleaseTagNames)
-    .map(([major, tags]) => semver.maxSatisfying(tags, `^${major}`))
+    .map(([major, tags]) => semver.maxSatisfying(tags, `^${major}`)!)
     .sort(semver.rcompare);
 }
 
diff --git a/scripts/apidoc/fakerClass.ts b/scripts/apidoc/fakerClass.ts
index ea190cc7e7c..9bbd7650f8d 100644
--- a/scripts/apidoc/fakerClass.ts
+++ b/scripts/apidoc/fakerClass.ts
@@ -28,6 +28,10 @@ export async function processFakerRandomizer(
     .getChildrenByKind(ReflectionKind.Interface)
     .find((clazz) => clazz.name === 'Randomizer');
 
+  if (randomizerClass == null) {
+    throw new Error('Randomizer class not found');
+  }
+
   return processClass(randomizerClass);
 }
 
@@ -62,7 +66,7 @@ async function processClass(
 function hasConstructor(clazz: DeclarationReflection): boolean {
   return clazz
     .getChildrenByKind(ReflectionKind.Constructor)
-    .some((constructor) => constructor.signatures.length > 0);
+    .some((constructor) => constructor.signatures!.length > 0);
 }
 
 async function processConstructor(
diff --git a/scripts/apidoc/signature.ts b/scripts/apidoc/signature.ts
index 113df911650..89d8cafde2f 100644
--- a/scripts/apidoc/signature.ts
+++ b/scripts/apidoc/signature.ts
@@ -305,7 +305,7 @@ async function signatureTypeToText(
     await Promise.all(
       signature.parameters?.map(
         async (p) => `${p.name}: ${await typeToText(p.type)}`
-      )
+      ) ?? []
     )
   ).join(', ')}) => ${await typeToText(signature.type)}`;
 }
diff --git a/src/definitions/definitions.ts b/src/definitions/definitions.ts
index ca495e3477a..c2a3b560099 100644
--- a/src/definitions/definitions.ts
+++ b/src/definitions/definitions.ts
@@ -50,4 +50,4 @@ export type LocaleDefinition = {
   system?: SystemDefinition;
   vehicle?: VehicleDefinition;
   word?: WordDefinition;
-} & Record<string, Record<string, unknown> | undefined>;
+} & Record<string, Record<string, unknown>>;
diff --git a/src/locales/ar/date/weekday.ts b/src/locales/ar/date/weekday.ts
index 7034cd26fc6..080b33bd4b0 100644
--- a/src/locales/ar/date/weekday.ts
+++ b/src/locales/ar/date/weekday.ts
@@ -1,5 +1,13 @@
 export default {
-  abbr: null,
+  abbr: [
+    'الأحَد',
+    'الإثنين',
+    'الثلاثاء',
+    'الأربعاء',
+    'الخميس',
+    'الجمعة',
+    'السبت',
+  ],
   wide: [
     'الأحَد',
     'الإثنين',
diff --git a/src/locales/ur/date/month.ts b/src/locales/ur/date/month.ts
index 37fdfa288fd..7a72f10ea5e 100644
--- a/src/locales/ur/date/month.ts
+++ b/src/locales/ur/date/month.ts
@@ -1,5 +1,18 @@
 export default {
-  abbr: null,
+  abbr: [
+    'جنوری',
+    'فروری',
+    'مارچ',
+    'اپریل',
+    'مئ',
+    'جون',
+    'جولائ',
+    'اگست',
+    'ستمبر',
+    'اکتوبر',
+    'نومبر',
+    'دسمبر',
+  ],
   wide: [
     'جنوری',
     'فروری',
diff --git a/src/locales/ur/date/weekday.ts b/src/locales/ur/date/weekday.ts
index 25f239f2c09..013fc789db7 100644
--- a/src/locales/ur/date/weekday.ts
+++ b/src/locales/ur/date/weekday.ts
@@ -1,4 +1,4 @@
 export default {
-  abbr: null,
+  abbr: ['اتور', 'پیر', 'منگل', 'بدھ', 'جمعرات', 'جمعہ', 'ہفتہ'],
   wide: ['اتور', 'پیر', 'منگل', 'بدھ', 'جمعرات', 'جمعہ', 'ہفتہ'],
 };
diff --git a/src/modules/airline/index.ts b/src/modules/airline/index.ts
index f6d2fdc7cea..12416e61e08 100644
--- a/src/modules/airline/index.ts
+++ b/src/modules/airline/index.ts
@@ -160,7 +160,7 @@ export class AirlineModule {
   ): string {
     const { allowNumerics = false, allowVisuallySimilarCharacters = false } =
       options;
-    const excludedChars = [];
+    const excludedChars: string[] = [];
     if (!allowNumerics) {
       excludedChars.push(...numerics);
     }
diff --git a/src/modules/commerce/index.ts b/src/modules/commerce/index.ts
index 2464af03020..843e7b025ad 100644
--- a/src/modules/commerce/index.ts
+++ b/src/modules/commerce/index.ts
@@ -386,7 +386,7 @@ export class CommerceModule {
 
     const registrantLength = groupRules.find(
       ([rangeMaximum]) => elementValue <= rangeMaximum
-    )[1];
+    )![1];
 
     const registrant = element.slice(0, registrantLength);
     const publication = element.slice(registrantLength);
diff --git a/src/modules/date/index.ts b/src/modules/date/index.ts
index 8f7efaaeed4..251e11151cd 100644
--- a/src/modules/date/index.ts
+++ b/src/modules/date/index.ts
@@ -15,6 +15,10 @@ function toDate(
   date: string | Date | number | undefined,
   fallback: () => Date
 ): Date {
+  if (date == null) {
+    return fallback();
+  }
+
   date = new Date(date);
   if (isNaN(date.valueOf())) {
     date = fallback();
@@ -387,14 +391,15 @@ export class SimpleDateModule {
         },
     legacyTo?: string | Date | number
   ): Date {
-    if (typeof options !== 'object' || options instanceof Date) {
+    if (options instanceof Date || typeof options !== 'object') {
       deprecated({
         deprecated: 'faker.date.between(from, to)',
         proposed: 'faker.date.between({ from, to })',
         since: '8.0',
         until: '9.0',
       });
-      options = { from: options, to: legacyTo };
+      // We use options as fallback for legacyTo avoid TS errors for unintended usage.
+      options = { from: options, to: legacyTo ?? options };
     }
 
     const { from, to } = options;
@@ -563,14 +568,15 @@ export class SimpleDateModule {
     legacyTo?: string | Date | number,
     legacyCount: number = 3
   ): Date[] {
-    if (typeof options !== 'object' || options instanceof Date) {
+    if (options instanceof Date || typeof options !== 'object') {
       deprecated({
         deprecated: 'faker.date.betweens(from, to, count)',
         proposed: 'faker.date.betweens({ from, to, count })',
         since: '8.0',
         until: '9.0',
       });
-      options = { from: options, to: legacyTo, count: legacyCount };
+      // We use options as fallback for legacyTo avoid TS errors for unintended usage.
+      options = { from: options, to: legacyTo ?? options, count: legacyCount };
     }
 
     const { from, to, count = 3 } = options;
@@ -868,12 +874,6 @@ export class SimpleDateModule {
       refDate?: string | Date | number;
     } = {}
   ): Date {
-    if (options.max < options.min) {
-      throw new FakerError(
-        `Max ${options.max} should be larger than or equal to min ${options.min}.`
-      );
-    }
-
     const mode = options.mode === 'age' ? 'age' : 'year';
     const refDate = toDate(options.refDate, this.faker.defaultRefDate);
     const refYear = refDate.getUTCFullYear();
@@ -898,6 +898,12 @@ export class SimpleDateModule {
       );
     }
 
+    if (max < min) {
+      throw new FakerError(
+        `Max ${options.max} should be larger than or equal to min ${options.min}.`
+      );
+    }
+
     return new Date(this.faker.number.int({ min, max }));
   }
 }
@@ -1108,7 +1114,14 @@ export class DateModule extends SimpleDateModule {
       type = 'wide';
     }
 
-    return this.faker.helpers.arrayElement(source[type]);
+    const values = source[type];
+
+    if (values == null) {
+      // This should never happen due to the checks above, but TS doesn't know that
+      throw new FakerError(`No month values found for type '${type}'.`);
+    }
+
+    return this.faker.helpers.arrayElement(values);
   }
 
   /**
@@ -1298,6 +1311,13 @@ export class DateModule extends SimpleDateModule {
       type = 'wide';
     }
 
-    return this.faker.helpers.arrayElement(source[type]);
+    const values = source[type];
+
+    if (values == null) {
+      // This should never happen due to the checks above, but TS doesn't know that
+      throw new FakerError(`No weekday values found for type '${type}'.`);
+    }
+
+    return this.faker.helpers.arrayElement(values);
   }
 }
diff --git a/src/modules/finance/index.ts b/src/modules/finance/index.ts
index 43cd16a1c5e..2fb27d42bde 100644
--- a/src/modules/finance/index.ts
+++ b/src/modules/finance/index.ts
@@ -679,9 +679,9 @@ export class FinanceModule {
    */
   currencySymbol(): string {
     let symbol: string;
-    while (!symbol) {
+    do {
       symbol = this.currency().symbol;
-    }
+    } while (!symbol);
 
     return symbol;
   }
@@ -1163,7 +1163,7 @@ export class FinanceModule {
 
     const result = `${ibanFormat.country}${checksum}${s}`;
 
-    return formatted ? result.match(/.{1,4}/g).join(' ') : result;
+    return formatted ? result.replace(/(.{4})(?=.)/g, '$1 ') : result;
   }
 
   /**
diff --git a/src/modules/helpers/index.ts b/src/modules/helpers/index.ts
index f5e7e1771a8..65f94c11c04 100644
--- a/src/modules/helpers/index.ts
+++ b/src/modules/helpers/index.ts
@@ -422,6 +422,7 @@ export class SimpleHelpersModule {
       const quantifierMin: string = token[2];
       const quantifierMax: string = token[3];
       const quantifierSymbol: string = token[4];
+      const tokenIndex: number = token.index!;
 
       repetitions = getRepetitionsBasedOnQuantifierParameters(
         this.faker,
@@ -431,9 +432,9 @@ export class SimpleHelpersModule {
       );
 
       pattern =
-        pattern.slice(0, token.index) +
+        pattern.slice(0, tokenIndex) +
         token[1].repeat(repetitions) +
-        pattern.slice(token.index + token[0].length);
+        pattern.slice(tokenIndex + token[0].length);
       token = pattern.match(SINGLE_CHAR_REG);
     }
 
@@ -448,6 +449,7 @@ export class SimpleHelpersModule {
       const quantifierMin: string = token[4];
       const quantifierMax: string = token[5];
       const quantifierSymbol: string = token[6];
+      const tokenIndex: number = token.index!;
 
       const rangeCodes: number[] = [];
 
@@ -542,9 +544,9 @@ export class SimpleHelpersModule {
       ).join('');
 
       pattern =
-        pattern.slice(0, token.index) +
+        pattern.slice(0, tokenIndex) +
         generatedString +
-        pattern.slice(token.index + token[0].length);
+        pattern.slice(tokenIndex + token[0].length);
       token = pattern.match(RANGE_ALPHANUMEMRIC_REG);
     }
 
@@ -554,6 +556,7 @@ export class SimpleHelpersModule {
     while (token != null) {
       min = parseInt(token[2]);
       max = parseInt(token[3]);
+      const tokenIndex = token.index!;
       // throw error if min larger than max
       if (min > max) {
         throw new FakerError('Numbers out of order in {} quantifier.');
@@ -561,9 +564,9 @@ export class SimpleHelpersModule {
 
       repetitions = this.faker.number.int({ min, max });
       pattern =
-        pattern.slice(0, token.index) +
+        pattern.slice(0, tokenIndex) +
         token[1].repeat(repetitions) +
-        pattern.slice(token.index + token[0].length);
+        pattern.slice(tokenIndex + token[0].length);
       token = pattern.match(RANGE_REP_REG);
     }
 
@@ -572,10 +575,11 @@ export class SimpleHelpersModule {
     token = pattern.match(REP_REG);
     while (token != null) {
       repetitions = parseInt(token[2]);
+      const tokenIndex = token.index!;
       pattern =
-        pattern.slice(0, token.index) +
+        pattern.slice(0, tokenIndex) +
         token[1].repeat(repetitions) +
-        pattern.slice(token.index + token[0].length);
+        pattern.slice(tokenIndex + token[0].length);
       token = pattern.match(REP_REG);
     }
 
@@ -1117,7 +1121,7 @@ export class SimpleHelpersModule {
     ) => RecordKey,
   >(
     method: TMethod,
-    args: Parameters<TMethod> = [] as Parameters<TMethod>,
+    args: Parameters<TMethod> = [] as unknown as Parameters<TMethod>,
     options: {
       /**
        * This parameter does nothing.
diff --git a/src/modules/helpers/unique.ts b/src/modules/helpers/unique.ts
index c096854a6eb..efb4956088d 100644
--- a/src/modules/helpers/unique.ts
+++ b/src/modules/helpers/unique.ts
@@ -96,9 +96,9 @@ export function exec<
     maxTime = 50,
     maxRetries = 50,
     compare = defaultCompare,
-    store,
+    store = {},
   } = options;
-  let { exclude } = options;
+  let { exclude = [] } = options;
   options.currentIterations = options.currentIterations ?? 0;
 
   // Support single exclude argument as string
diff --git a/src/modules/internet/index.ts b/src/modules/internet/index.ts
index 842ab1538af..e8fa358e2cf 100644
--- a/src/modules/internet/index.ts
+++ b/src/modules/internet/index.ts
@@ -625,6 +625,7 @@ export class InternetModule {
           firstName + this.faker.helpers.arrayElement(['.', '_']) + lastName;
         break;
       case 2:
+      default:
         result = `${firstName}${this.faker.helpers.arrayElement([
           '.',
           '_',
@@ -810,6 +811,7 @@ export class InternetModule {
           firstName + this.faker.helpers.arrayElement(['.', '_']) + lastName;
         break;
       case 2:
+      default:
         result = `${firstName}${this.faker.helpers.arrayElement([
           '.',
           '_',
diff --git a/src/modules/person/index.ts b/src/modules/person/index.ts
index f07727a2c96..8b0688f508f 100644
--- a/src/modules/person/index.ts
+++ b/src/modules/person/index.ts
@@ -1,4 +1,5 @@
 import type { Faker } from '../..';
+import { FakerError } from '../../errors/faker-error';
 import { bindThisToMemberFunctions } from '../../internal/bind-this-to-member-functions';
 
 export enum Sex {
@@ -26,9 +27,13 @@ function selectDefinition<T>(
   elementSelectorFn: (values: T[]) => string,
   sex: SexType | undefined,
   // TODO @Shinigami92 2022-03-21: Remove fallback empty object when `strict: true`
-  { generic, female, male }: { generic?: T[]; female?: T[]; male?: T[] } = {}
+  {
+    generic,
+    female,
+    male,
+  }: { generic?: T[] | null; female?: T[] | null; male?: T[] | null } = {}
 ): string {
-  let values: T[] | undefined;
+  let values: T[] | undefined | null;
 
   switch (sex) {
     case Sex.Female:
@@ -50,6 +55,12 @@ function selectDefinition<T>(
     } else {
       values = generic;
     }
+
+    if (values == null) {
+      throw new FakerError(
+        'Neither female, male or generic definitions are available.'
+      );
+    }
   }
 
   return elementSelectorFn(values);
@@ -97,7 +108,7 @@ export class PersonModule {
       this.faker.rawDefinitions.person ?? {};
 
     return selectDefinition(this.faker, this.faker.helpers.arrayElement, sex, {
-      generic: first_name,
+      generic: first_name ?? undefined,
       female: female_first_name,
       male: male_first_name,
     });
@@ -352,9 +363,13 @@ export class PersonModule {
    * @since 8.0.0
    */
   jobDescriptor(): string {
-    return this.faker.helpers.arrayElement(
-      this.faker.definitions.person.title.descriptor
-    );
+    const values = this.faker.definitions.person.title.descriptor;
+
+    if (values == null) {
+      throw new FakerError('No person.title.descriptor definitions available.');
+    }
+
+    return this.faker.helpers.arrayElement(values);
   }
 
   /**
@@ -366,9 +381,13 @@ export class PersonModule {
    * @since 8.0.0
    */
   jobArea(): string {
-    return this.faker.helpers.arrayElement(
-      this.faker.definitions.person.title.level
-    );
+    const values = this.faker.definitions.person.title.level;
+
+    if (values == null) {
+      throw new FakerError('No person.title.area definitions available.');
+    }
+
+    return this.faker.helpers.arrayElement(values);
   }
 
   /**
@@ -380,9 +399,13 @@ export class PersonModule {
    * @since 8.0.0
    */
   jobType(): string {
-    return this.faker.helpers.arrayElement(
-      this.faker.definitions.person.title.job
-    );
+    const values = this.faker.definitions.person.title.job;
+
+    if (values == null) {
+      throw new FakerError('No person.title.job definitions available.');
+    }
+
+    return this.faker.helpers.arrayElement(values);
   }
 
   /**
diff --git a/src/modules/random/index.ts b/src/modules/random/index.ts
index 7fa16f40bfe..4644864cc24 100644
--- a/src/modules/random/index.ts
+++ b/src/modules/random/index.ts
@@ -128,7 +128,7 @@ export class RandomModule {
       '_',
       '-',
     ];
-    let result: string;
+    let result = '';
 
     let iteration = 0;
 
diff --git a/test/faker.spec.ts b/test/faker.spec.ts
index 2ff5aab9468..116505a9fd8 100644
--- a/test/faker.spec.ts
+++ b/test/faker.spec.ts
@@ -41,7 +41,7 @@ describe('faker', () => {
   describe('rawDefinitions', () => {
     it('locale rawDefinition accessibility', () => {
       // Metadata
-      expect(faker.rawDefinitions.metadata.title).toBeDefined();
+      expect(faker.rawDefinitions.metadata!.title).toBeDefined();
       // Standard modules
       expect(faker.rawDefinitions.location?.city_name).toBeDefined();
       // Non-existing module
@@ -62,7 +62,7 @@ describe('faker', () => {
       // Non-existing module
       expect(faker.definitions.missing).toBeDefined();
       // Non-existing definition in a non-existing module
-      expect(() => faker.definitions.missing.missing).toThrow();
+      expect(() => faker.definitions.missing?.missing).toThrow();
       // Non-existing definition in an existing module
       expect(() => faker.definitions.location.missing).toThrow();
     });
diff --git a/test/modules/airline.spec.ts b/test/modules/airline.spec.ts
index 2cbb47c3a14..d43cad19f16 100644
--- a/test/modules/airline.spec.ts
+++ b/test/modules/airline.spec.ts
@@ -95,7 +95,7 @@ describe('airline', () => {
         const seatRegex = /^(\d{1,2})([A-K])$/;
         it('should return a random narrowbody seat when not passing an argument', () => {
           const seat = faker.airline.seat();
-          const matchResult = seat.match(seatRegex);
+          const matchResult = seat.match(seatRegex)!;
           expect(matchResult).not.toBeNull();
           const row = matchResult[1];
           const seatLetter = matchResult[2];
@@ -106,7 +106,7 @@ describe('airline', () => {
           const seat = faker.airline.seat({
             aircraftType: Aircraft.Narrowbody,
           });
-          const matchResult = seat.match(seatRegex);
+          const matchResult = seat.match(seatRegex)!;
           expect(matchResult).not.toBeNull();
           const row = matchResult[1];
           const seatLetter = matchResult[2];
@@ -115,7 +115,7 @@ describe('airline', () => {
         });
         it('should return a random regional seat', () => {
           const seat = faker.airline.seat({ aircraftType: Aircraft.Regional });
-          const matchResult = seat.match(seatRegex);
+          const matchResult = seat.match(seatRegex)!;
           expect(matchResult).not.toBeNull();
           const row = matchResult[1];
           const seatLetter = matchResult[2];
@@ -124,7 +124,7 @@ describe('airline', () => {
         });
         it('should return a random widebody seat', () => {
           const seat = faker.airline.seat({ aircraftType: Aircraft.Widebody });
-          const matchResult = seat.match(seatRegex);
+          const matchResult = seat.match(seatRegex)!;
           expect(matchResult).not.toBeNull();
           const row = matchResult[1];
           const seatLetter = matchResult[2];
diff --git a/test/modules/finance_iban.spec.ts b/test/modules/finance_iban.spec.ts
index 5c32fed384c..f43d0954399 100644
--- a/test/modules/finance_iban.spec.ts
+++ b/test/modules/finance_iban.spec.ts
@@ -36,7 +36,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormatted = iban.match(/.{1,4}/g).join(' ');
+          const ibanFormatted = iban.match(/.{1,4}/g)!.join(' ');
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -96,7 +96,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g).join(' ');
+          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -162,7 +162,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g).join(' ');
+          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -232,7 +232,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g).join(' ');
+          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -291,7 +291,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g).join(' ');
+          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -336,7 +336,7 @@ describe('finance_iban', () => {
           // Bank account number    16 digit
 
           const iban = faker.finance.iban(false, 'AL');
-          const ibanFormated = iban.match(/.{1,4}/g).join(' ');
+          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
 
           expect(iban).toSatisfy(validator.isIBAN);
 
diff --git a/test/modules/helpers.spec.ts b/test/modules/helpers.spec.ts
index 7b709373f24..9c167498aa9 100644
--- a/test/modules/helpers.spec.ts
+++ b/test/modules/helpers.spec.ts
@@ -222,7 +222,6 @@ describe('helpers', () => {
         });
 
         it('should throw on an empty array', () => {
-          // eslint-disable-next-line @typescript-eslint/no-unsafe-return
           expect(() => faker.helpers.arrayElement([])).toThrow(
             new FakerError('Cannot get value from empty dataset.')
           );
@@ -1062,7 +1061,7 @@ describe('helpers', () => {
         });
 
         it('should be able to return locale definition strings', () => {
-          expect(faker.definitions.cell_phone.formats).toContain(
+          expect(faker.definitions.cell_phone?.formats).toContain(
             faker.helpers.fake('{{cell_phone.formats}}')
           );
         });
diff --git a/test/scripts/apidoc/verify-jsdoc-tags.spec.ts b/test/scripts/apidoc/verify-jsdoc-tags.spec.ts
index 586605a6610..19ffb4d0e88 100644
--- a/test/scripts/apidoc/verify-jsdoc-tags.spec.ts
+++ b/test/scripts/apidoc/verify-jsdoc-tags.spec.ts
@@ -110,7 +110,7 @@ describe('verify JSDoc tags', () => {
             // Write temp files to disk
 
             // Extract examples and make them runnable
-            const examples = extractJoinedRawExamples(signature);
+            const examples = extractJoinedRawExamples(signature) ?? '';
 
             // Save examples to a file to run them later in the specific tests
             const dir = resolveDirToModule(moduleName);
diff --git a/test/vitest-extensions.ts b/test/vitest-extensions.ts
index c241fcf99ea..e5f2a57dca8 100644
--- a/test/vitest-extensions.ts
+++ b/test/vitest-extensions.ts
@@ -11,6 +11,7 @@ expect.extend({
     return {
       pass: uniqueDuplication.length !== 0,
       message: () =>
+        // @ts-expect-error: `isNot` is incorrectly inferred as `function`.
         isNot
           ? `Duplicated values are [${uniqueDuplication.join(', ')}]`
           : `No duplicate values in [${received.join(', ')}]`,
diff --git a/tsconfig.json b/tsconfig.json
index cda27929e8f..da5cd4e6926 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -9,7 +9,6 @@
     "stripInternal": true,
 
     // We need to disable these for now, and need to tackle them in another PR
-    "strictNullChecks": false,
     "noImplicitAny": false,
 
     // These are configs specifically for !build and have to be reverted in the tsconfig.build.json

From 8d3497bafed95a898a6a12063e721f895037634a Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 00:05:07 +0200
Subject: [PATCH 02/20] Apply suggestions from code review

---
 src/modules/person/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/modules/person/index.ts b/src/modules/person/index.ts
index 8b0688f508f..693ca2d88be 100644
--- a/src/modules/person/index.ts
+++ b/src/modules/person/index.ts
@@ -108,7 +108,7 @@ export class PersonModule {
       this.faker.rawDefinitions.person ?? {};
 
     return selectDefinition(this.faker, this.faker.helpers.arrayElement, sex, {
-      generic: first_name ?? undefined,
+      generic: first_name,
       female: female_first_name,
       male: male_first_name,
     });

From 3ba4b4e978e2a71175a615b5e84826f7f5df1d30 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 00:06:39 +0200
Subject: [PATCH 03/20] Apply suggestions from code review

---
 docs/.vitepress/versions.ts | 1 -
 1 file changed, 1 deletion(-)

diff --git a/docs/.vitepress/versions.ts b/docs/.vitepress/versions.ts
index c9e34e8c73d..4ac78f8c095 100644
--- a/docs/.vitepress/versions.ts
+++ b/docs/.vitepress/versions.ts
@@ -23,7 +23,6 @@ function readOtherLatestReleaseTagNames(): string[] {
       }
       return acc;
     }, {});
-
   return Object.entries(latestReleaseTagNames)
     .map(([major, tags]) => semver.maxSatisfying(tags, `^${major}`)!)
     .sort(semver.rcompare);

From c555cb8d1ee97b25761533d76c872a1671ef02b1 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 00:21:12 +0200
Subject: [PATCH 04/20] build it


From 2c3c7c6796d8f3fc93a799f67cdddec8c369e1d8 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 01:38:56 +0200
Subject: [PATCH 05/20] Update src/modules/finance/index.ts

Co-authored-by: DivisionByZero <leyla.jaehnig@gmx.de>
---
 src/modules/finance/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/modules/finance/index.ts b/src/modules/finance/index.ts
index 2fb27d42bde..d00652e1d6f 100644
--- a/src/modules/finance/index.ts
+++ b/src/modules/finance/index.ts
@@ -681,7 +681,7 @@ export class FinanceModule {
     let symbol: string;
     do {
       symbol = this.currency().symbol;
-    } while (!symbol);
+    } while (symbol.length === 0);
 
     return symbol;
   }

From 3caf9d51a510ead83a3da48988925aec3c24b443 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 01:43:00 +0200
Subject: [PATCH 06/20] Apply suggestions from code review

---
 cypress/e2e/api.cy.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cypress/e2e/api.cy.ts b/cypress/e2e/api.cy.ts
index d46434cb46d..e87ea856f50 100644
--- a/cypress/e2e/api.cy.ts
+++ b/cypress/e2e/api.cy.ts
@@ -34,7 +34,7 @@ describe('API Test', () => {
       cy.get('.api-group li').each(($el) => {
         const anchor = $el.find('a');
         const text = anchor.text();
-        const link = anchor.attr('href')!.split('#')[0];
+        const link = anchor.attr('href')?.split('#')[0] ?? 'MISSING';
         if (checked.has(link)) {
           return;
         }

From 28188477d489148c3d992e82262a99979af4ec14 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 21:08:35 +0200
Subject: [PATCH 07/20] Update test/faker.spec.ts

Co-authored-by: DivisionByZero <leyla.jaehnig@gmx.de>
---
 test/faker.spec.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/faker.spec.ts b/test/faker.spec.ts
index 116505a9fd8..bd42246a5a5 100644
--- a/test/faker.spec.ts
+++ b/test/faker.spec.ts
@@ -41,7 +41,7 @@ describe('faker', () => {
   describe('rawDefinitions', () => {
     it('locale rawDefinition accessibility', () => {
       // Metadata
-      expect(faker.rawDefinitions.metadata!.title).toBeDefined();
+      expect(faker.rawDefinitions.metadata?.title).toBeDefined();
       // Standard modules
       expect(faker.rawDefinitions.location?.city_name).toBeDefined();
       // Non-existing module

From 50531c84decfb07a706835c52bf08ae44ba4b5b2 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 21:10:55 +0200
Subject: [PATCH 08/20] Update scripts/apidoc/fakerClass.ts

Co-authored-by: DivisionByZero <leyla.jaehnig@gmx.de>
---
 scripts/apidoc/fakerClass.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/apidoc/fakerClass.ts b/scripts/apidoc/fakerClass.ts
index 9bbd7650f8d..3bd6e551f8f 100644
--- a/scripts/apidoc/fakerClass.ts
+++ b/scripts/apidoc/fakerClass.ts
@@ -66,7 +66,7 @@ async function processClass(
 function hasConstructor(clazz: DeclarationReflection): boolean {
   return clazz
     .getChildrenByKind(ReflectionKind.Constructor)
-    .some((constructor) => constructor.signatures!.length > 0);
+    .some((constructor) => (constructor.signatures?.length ?? 0) > 0);
 }
 
 async function processConstructor(

From ebc6ac5d61ffbb1c1ee79750fd2f6d0796ed9b08 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 21:15:03 +0200
Subject: [PATCH 09/20] chore: work around ts error in vitest extension

---
 test/vitest-extensions.ts | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/test/vitest-extensions.ts b/test/vitest-extensions.ts
index e5f2a57dca8..b704e901744 100644
--- a/test/vitest-extensions.ts
+++ b/test/vitest-extensions.ts
@@ -2,7 +2,7 @@ import { expect } from 'vitest';
 
 expect.extend({
   toContainDuplicates<T>(received: T[]) {
-    const { isNot } = this;
+    const { isNot = false } = this;
 
     const uniques = new Set(received);
     const duplications = received.filter((entry) => !uniques.delete(entry));
@@ -11,7 +11,6 @@ expect.extend({
     return {
       pass: uniqueDuplication.length !== 0,
       message: () =>
-        // @ts-expect-error: `isNot` is incorrectly inferred as `function`.
         isNot
           ? `Duplicated values are [${uniqueDuplication.join(', ')}]`
           : `No duplicate values in [${received.join(', ')}]`,

From 00f0fcf6e08b2dd23d4bdef61ac9092d0aa6bea0 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 21:39:42 +0200
Subject: [PATCH 10/20] chore: simplify version grouping

---
 docs/.vitepress/versions.ts | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/docs/.vitepress/versions.ts b/docs/.vitepress/versions.ts
index 4ac78f8c095..90b0fc8dd25 100644
--- a/docs/.vitepress/versions.ts
+++ b/docs/.vitepress/versions.ts
@@ -14,18 +14,23 @@ function readOtherLatestReleaseTagNames(): string[] {
     .toString('utf8')
     .split('\n')
     .filter((tag) => semver.valid(tag))
-    .reduce<Record<number, string[]>>((acc, tag) => {
-      const majorVersion = semver.major(tag);
+    .filter((tag) => {
       // Only consider tags for our deployed website versions,
       // excluding the current major version.
-      if (majorVersion >= 6 && majorVersion !== currentMajorVersion) {
-        (acc[majorVersion] = acc[majorVersion] ?? []).push(tag);
+      const majorVersion = semver.major(tag);
+      return majorVersion >= 6 && majorVersion !== currentMajorVersion;
+    })
+    .reduce<Record<number, string>>((latestTagByMajor, tag) => {
+      const majorVersion = semver.major(tag);
+
+      const latestTag = latestTagByMajor[majorVersion];
+      if (latestTag == null || semver.lt(latestTag, tag)) {
+        latestTagByMajor[majorVersion] = tag;
       }
-      return acc;
+
+      return latestTagByMajor;
     }, {});
-  return Object.entries(latestReleaseTagNames)
-    .map(([major, tags]) => semver.maxSatisfying(tags, `^${major}`)!)
-    .sort(semver.rcompare);
+  return Object.values(latestReleaseTagNames).sort(semver.rcompare);
 }
 
 // Set by netlify

From 0042bdfeb71289aced69b7547c536264019c6c34 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 6 Oct 2023 23:55:50 +0200
Subject: [PATCH 11/20] chore: prettyPrintIban helper function

---
 src/modules/finance/index.ts      | 18 +++++++++++++++++-
 test/modules/finance_iban.spec.ts | 13 +++++++------
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/src/modules/finance/index.ts b/src/modules/finance/index.ts
index d00652e1d6f..5a60eb4d10e 100644
--- a/src/modules/finance/index.ts
+++ b/src/modules/finance/index.ts
@@ -24,6 +24,22 @@ export interface Currency {
   symbol: string;
 }
 
+/**
+ * Puts a space after every 4 characters.
+ *
+ * @internal
+ *
+ * @param iban The iban to pretty print.
+ */
+export function prettyPrintIban(iban: string): string {
+  let pretty = '';
+  for (let i = 0; i < iban.length; i += 4) {
+    pretty += `${iban.substring(i, i + 4)} `;
+  }
+
+  return pretty.trimEnd();
+}
+
 /**
  * Module to generate finance and money related entries.
  *
@@ -1163,7 +1179,7 @@ export class FinanceModule {
 
     const result = `${ibanFormat.country}${checksum}${s}`;
 
-    return formatted ? result.replace(/(.{4})(?=.)/g, '$1 ') : result;
+    return formatted ? prettyPrintIban(result) : result;
   }
 
   /**
diff --git a/test/modules/finance_iban.spec.ts b/test/modules/finance_iban.spec.ts
index f43d0954399..695dfb84b20 100644
--- a/test/modules/finance_iban.spec.ts
+++ b/test/modules/finance_iban.spec.ts
@@ -1,6 +1,7 @@
 import validator from 'validator';
 import { describe, expect, it } from 'vitest';
 import { faker } from '../../src';
+import { prettyPrintIban } from '../../src/modules/finance';
 import ibanLib from '../../src/modules/finance/iban';
 import { times } from './../support/times';
 
@@ -36,7 +37,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormatted = iban.match(/.{1,4}/g)!.join(' ');
+          const ibanFormatted = prettyPrintIban(iban);
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -96,7 +97,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
+          const ibanFormated = prettyPrintIban(iban);
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -162,7 +163,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
+          const ibanFormated = prettyPrintIban(iban);
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -232,7 +233,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
+          const ibanFormated = prettyPrintIban(iban);
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -291,7 +292,7 @@ describe('finance_iban', () => {
 
           expect(iban).toSatisfy(validator.isIBAN);
 
-          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
+          const ibanFormated = prettyPrintIban(iban);
           const bban = iban.substring(4) + iban.substring(0, 4);
 
           expect(
@@ -336,7 +337,7 @@ describe('finance_iban', () => {
           // Bank account number    16 digit
 
           const iban = faker.finance.iban(false, 'AL');
-          const ibanFormated = iban.match(/.{1,4}/g)!.join(' ');
+          const ibanFormated = prettyPrintIban(iban);
 
           expect(iban).toSatisfy(validator.isIBAN);
 

From 45f6b0636f7b801e576921ce7c726672303292e2 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Sat, 7 Oct 2023 00:55:02 +0200
Subject: [PATCH 12/20] chore: add assertLocaleData

---
 src/definitions/date.ts        |  3 +-
 src/locale-proxy.ts            | 44 +++++++++++++------
 src/locales/ar/date/weekday.ts | 10 +----
 src/locales/ur/date/month.ts   | 15 +------
 src/locales/ur/date/weekday.ts |  2 +-
 src/modules/date/index.ts      | 15 ++-----
 src/modules/person/index.ts    | 79 ++++++++++++++++++++++------------
 7 files changed, 90 insertions(+), 78 deletions(-)

diff --git a/src/definitions/date.ts b/src/definitions/date.ts
index 16cfb28aa26..2265a0256cf 100644
--- a/src/definitions/date.ts
+++ b/src/definitions/date.ts
@@ -26,8 +26,9 @@ export interface DateEntryDefinition {
 
   /**
    * The short name/abbreviation of the entry.
+   * If null, the locale does not support a short name/abbreviation for the entry.
    */
-  abbr: string[];
+  abbr: string[] | null;
 
   /**
    * The wide name of the entry when used in context. If absent wide will be used instead.
diff --git a/src/locale-proxy.ts b/src/locale-proxy.ts
index 67b29d473cc..6c59ec291f3 100644
--- a/src/locale-proxy.ts
+++ b/src/locale-proxy.ts
@@ -54,6 +54,34 @@ export function createLocaleProxy(locale: LocaleDefinition): LocaleProxy {
   }) as LocaleProxy;
 }
 
+/**
+ * Checks that the value is not null or undefined and throws an error if it is.
+ *
+ * @param value The value to check.
+ * @param path The path to the locale data.
+ */
+export function assertLocaleData<T>(
+  value: T,
+  ...path: string[]
+): asserts value is NonNullable<T> {
+  if (value == null) {
+    if (value === null) {
+      throw new FakerError(
+        `The locale data for '${path.join(
+          '.'
+        )}' aren't applicable to this locale.
+  If you think this is a bug, please report it at: https://github.com/faker-js/faker`
+      );
+    } else if (value === undefined) {
+      throw new FakerError(
+        `The locale data for '${path.join('.')}' are missing in this locale.
+  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`
+      );
+    }
+  }
+}
+
 /**
  * Creates a proxy for a category that throws an error when accessing an undefined property.
  *
@@ -79,20 +107,10 @@ function createCategoryProxy<
       const value = target[entryName];
       if (typeof entryName === 'symbol' || entryName === 'nodeType') {
         return value;
-      } else if (value === null) {
-        throw new FakerError(
-          `The locale data for '${categoryName}.${entryName.toString()}' aren't applicable to this locale.
-  If you think this is a bug, please report it at: https://github.com/faker-js/faker`
-        );
-      } else if (value === undefined) {
-        throw new FakerError(
-          `The locale data for '${categoryName}.${entryName.toString()}' are missing in this locale.
-  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`
-        );
-      } else {
-        return value;
       }
+
+      assertLocaleData(value, categoryName, entryName.toString());
+      return value;
     },
 
     set: throwReadOnlyError,
diff --git a/src/locales/ar/date/weekday.ts b/src/locales/ar/date/weekday.ts
index 080b33bd4b0..7034cd26fc6 100644
--- a/src/locales/ar/date/weekday.ts
+++ b/src/locales/ar/date/weekday.ts
@@ -1,13 +1,5 @@
 export default {
-  abbr: [
-    'الأحَد',
-    'الإثنين',
-    'الثلاثاء',
-    'الأربعاء',
-    'الخميس',
-    'الجمعة',
-    'السبت',
-  ],
+  abbr: null,
   wide: [
     'الأحَد',
     'الإثنين',
diff --git a/src/locales/ur/date/month.ts b/src/locales/ur/date/month.ts
index 7a72f10ea5e..37fdfa288fd 100644
--- a/src/locales/ur/date/month.ts
+++ b/src/locales/ur/date/month.ts
@@ -1,18 +1,5 @@
 export default {
-  abbr: [
-    'جنوری',
-    'فروری',
-    'مارچ',
-    'اپریل',
-    'مئ',
-    'جون',
-    'جولائ',
-    'اگست',
-    'ستمبر',
-    'اکتوبر',
-    'نومبر',
-    'دسمبر',
-  ],
+  abbr: null,
   wide: [
     'جنوری',
     'فروری',
diff --git a/src/locales/ur/date/weekday.ts b/src/locales/ur/date/weekday.ts
index 013fc789db7..25f239f2c09 100644
--- a/src/locales/ur/date/weekday.ts
+++ b/src/locales/ur/date/weekday.ts
@@ -1,4 +1,4 @@
 export default {
-  abbr: ['اتور', 'پیر', 'منگل', 'بدھ', 'جمعرات', 'جمعہ', 'ہفتہ'],
+  abbr: null,
   wide: ['اتور', 'پیر', 'منگل', 'بدھ', 'جمعرات', 'جمعہ', 'ہفتہ'],
 };
diff --git a/src/modules/date/index.ts b/src/modules/date/index.ts
index 251e11151cd..423a2017afc 100644
--- a/src/modules/date/index.ts
+++ b/src/modules/date/index.ts
@@ -3,6 +3,7 @@ import type { DateEntryDefinition } from '../../definitions';
 import { FakerError } from '../../errors/faker-error';
 import { bindThisToMemberFunctions } from '../../internal/bind-this-to-member-functions';
 import { deprecated } from '../../internal/deprecated';
+import { assertLocaleData } from '../../locale-proxy';
 
 /**
  * Converts date passed as a string, number or Date to a Date object.
@@ -1115,12 +1116,7 @@ export class DateModule extends SimpleDateModule {
     }
 
     const values = source[type];
-
-    if (values == null) {
-      // This should never happen due to the checks above, but TS doesn't know that
-      throw new FakerError(`No month values found for type '${type}'.`);
-    }
-
+    assertLocaleData(values, 'date.month', type);
     return this.faker.helpers.arrayElement(values);
   }
 
@@ -1312,12 +1308,7 @@ export class DateModule extends SimpleDateModule {
     }
 
     const values = source[type];
-
-    if (values == null) {
-      // This should never happen due to the checks above, but TS doesn't know that
-      throw new FakerError(`No weekday values found for type '${type}'.`);
-    }
-
+    assertLocaleData(values, 'date.weekday', type);
     return this.faker.helpers.arrayElement(values);
   }
 }
diff --git a/src/modules/person/index.ts b/src/modules/person/index.ts
index 693ca2d88be..711669d3fbb 100644
--- a/src/modules/person/index.ts
+++ b/src/modules/person/index.ts
@@ -1,6 +1,7 @@
 import type { Faker } from '../..';
 import { FakerError } from '../../errors/faker-error';
 import { bindThisToMemberFunctions } from '../../internal/bind-this-to-member-functions';
+import { assertLocaleData } from '../../locale-proxy';
 
 export enum Sex {
   Female = 'female',
@@ -19,6 +20,7 @@ export type SexType = `${Sex}`;
  * @param param2.generic Non-sex definitions.
  * @param param2.female Female definitions.
  * @param param2.male Male definitions.
+ * @param type Type of the definition.
  *
  * @returns Definition based on given sex.
  */
@@ -26,12 +28,12 @@ function selectDefinition<T>(
   faker: Faker,
   elementSelectorFn: (values: T[]) => string,
   sex: SexType | undefined,
-  // TODO @Shinigami92 2022-03-21: Remove fallback empty object when `strict: true`
   {
     generic,
     female,
     male,
-  }: { generic?: T[] | null; female?: T[] | null; male?: T[] | null } = {}
+  }: { generic?: T[] | null; female?: T[] | null; male?: T[] | null },
+  type: string
 ): string {
   let values: T[] | undefined | null;
 
@@ -56,11 +58,7 @@ function selectDefinition<T>(
       values = generic;
     }
 
-    if (values == null) {
-      throw new FakerError(
-        'Neither female, male or generic definitions are available.'
-      );
-    }
+    assertLocaleData(values, `person.{${type}, female_${type}, male_${type}}`);
   }
 
   return elementSelectorFn(values);
@@ -107,11 +105,17 @@ export class PersonModule {
     const { first_name, female_first_name, male_first_name } =
       this.faker.rawDefinitions.person ?? {};
 
-    return selectDefinition(this.faker, this.faker.helpers.arrayElement, sex, {
-      generic: first_name,
-      female: female_first_name,
-      male: male_first_name,
-    });
+    return selectDefinition(
+      this.faker,
+      this.faker.helpers.arrayElement,
+      sex,
+      {
+        generic: first_name,
+        female: female_first_name,
+        male: male_first_name,
+      },
+      'first_name'
+    );
   }
 
   /**
@@ -150,16 +154,23 @@ export class PersonModule {
           generic: last_name_pattern,
           female: female_last_name_pattern,
           male: male_last_name_pattern,
-        }
+        },
+        'last_name_pattern'
       );
       return this.faker.helpers.fake(pattern);
     }
 
-    return selectDefinition(this.faker, this.faker.helpers.arrayElement, sex, {
-      generic: last_name,
-      female: female_last_name,
-      male: male_last_name,
-    });
+    return selectDefinition(
+      this.faker,
+      this.faker.helpers.arrayElement,
+      sex,
+      {
+        generic: last_name,
+        female: female_last_name,
+        male: male_last_name,
+      },
+      'last_name'
+    );
   }
 
   /**
@@ -179,11 +190,17 @@ export class PersonModule {
     const { middle_name, female_middle_name, male_middle_name } =
       this.faker.rawDefinitions.person ?? {};
 
-    return selectDefinition(this.faker, this.faker.helpers.arrayElement, sex, {
-      generic: middle_name,
-      female: female_middle_name,
-      male: male_middle_name,
-    });
+    return selectDefinition(
+      this.faker,
+      this.faker.helpers.arrayElement,
+      sex,
+      {
+        generic: middle_name,
+        female: female_middle_name,
+        male: male_middle_name,
+      },
+      'middle_name'
+    );
   }
 
   /**
@@ -320,11 +337,17 @@ export class PersonModule {
     const { prefix, female_prefix, male_prefix } =
       this.faker.rawDefinitions.person ?? {};
 
-    return selectDefinition(this.faker, this.faker.helpers.arrayElement, sex, {
-      generic: prefix,
-      female: female_prefix,
-      male: male_prefix,
-    });
+    return selectDefinition(
+      this.faker,
+      this.faker.helpers.arrayElement,
+      sex,
+      {
+        generic: prefix,
+        female: female_prefix,
+        male: male_prefix,
+      },
+      'prefix'
+    );
   }
 
   /**

From a2a303dd2fe5d68ed101ce072f005c860805ae2a Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Sat, 7 Oct 2023 13:27:53 +0200
Subject: [PATCH 13/20] chore: apply suggestions

---
 src/locale-proxy.ts | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/src/locale-proxy.ts b/src/locale-proxy.ts
index 6c59ec291f3..e99ba655156 100644
--- a/src/locale-proxy.ts
+++ b/src/locale-proxy.ts
@@ -64,21 +64,17 @@ export function assertLocaleData<T>(
   value: T,
   ...path: string[]
 ): asserts value is NonNullable<T> {
-  if (value == null) {
-    if (value === null) {
-      throw new FakerError(
-        `The locale data for '${path.join(
-          '.'
-        )}' aren't applicable to this locale.
+  if (value === null) {
+    throw new FakerError(
+      `The locale data for '${path.join('.')}' aren't applicable to this locale.
   If you think this is a bug, please report it at: https://github.com/faker-js/faker`
-      );
-    } else if (value === undefined) {
-      throw new FakerError(
-        `The locale data for '${path.join('.')}' are missing in this locale.
+    );
+  } else if (value === undefined) {
+    throw new FakerError(
+      `The locale data for '${path.join('.')}' are missing in this locale.
   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`
-      );
-    }
+    );
   }
 }
 

From 6fe42533ea99891060c8f16cf8b5a00d480df0b0 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 20 Oct 2023 10:46:23 +0200
Subject: [PATCH 14/20] revert: helpers changes

---
 src/modules/helpers/index.ts | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/src/modules/helpers/index.ts b/src/modules/helpers/index.ts
index 6c3f6ba04ee..dd4fdb3d284 100644
--- a/src/modules/helpers/index.ts
+++ b/src/modules/helpers/index.ts
@@ -422,7 +422,6 @@ export class SimpleHelpersModule {
       const quantifierMin: string = token[2];
       const quantifierMax: string = token[3];
       const quantifierSymbol: string = token[4];
-      const tokenIndex: number = token.index;
 
       repetitions = getRepetitionsBasedOnQuantifierParameters(
         this.faker,
@@ -432,11 +431,9 @@ export class SimpleHelpersModule {
       );
 
       pattern =
-        pattern.slice(0, tokenIndex) +
+        pattern.slice(0, token.index) +
         token[1].repeat(repetitions) +
-        pattern.slice(tokenIndex + token[0].length);
-
-      pattern.slice(token.index + token[0].length);
+        pattern.slice(token.index + token[0].length);
       token = SINGLE_CHAR_REG.exec(pattern);
     }
 
@@ -451,7 +448,6 @@ export class SimpleHelpersModule {
       const quantifierMin: string = token[4];
       const quantifierMax: string = token[5];
       const quantifierSymbol: string = token[6];
-      const tokenIndex: number = token.index;
 
       const rangeCodes: number[] = [];
 
@@ -550,9 +546,9 @@ export class SimpleHelpersModule {
       ).join('');
 
       pattern =
-        pattern.slice(0, tokenIndex) +
+        pattern.slice(0, token.index) +
         generatedString +
-        pattern.slice(tokenIndex + token[0].length);
+        pattern.slice(token.index + token[0].length);
       token = RANGE_ALPHANUMEMRIC_REG.exec(pattern);
     }
 
@@ -562,7 +558,6 @@ export class SimpleHelpersModule {
     while (token != null) {
       min = parseInt(token[2]);
       max = parseInt(token[3]);
-      const tokenIndex = token.index;
       // throw error if min larger than max
       if (min > max) {
         throw new FakerError('Numbers out of order in {} quantifier.');
@@ -570,9 +565,9 @@ export class SimpleHelpersModule {
 
       repetitions = this.faker.number.int({ min, max });
       pattern =
-        pattern.slice(0, tokenIndex) +
+        pattern.slice(0, token.index) +
         token[1].repeat(repetitions) +
-        pattern.slice(tokenIndex + token[0].length);
+        pattern.slice(token.index + token[0].length);
       token = RANGE_REP_REG.exec(pattern);
     }
 
@@ -581,11 +576,10 @@ export class SimpleHelpersModule {
     token = REP_REG.exec(pattern);
     while (token != null) {
       repetitions = parseInt(token[2]);
-      const tokenIndex = token.index;
       pattern =
-        pattern.slice(0, tokenIndex) +
+        pattern.slice(0, token.index) +
         token[1].repeat(repetitions) +
-        pattern.slice(tokenIndex + token[0].length);
+        pattern.slice(token.index + token[0].length);
       token = REP_REG.exec(pattern);
     }
 

From bf88c588d50118f857eec1409679f775846eb410 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Mon, 6 Nov 2023 10:06:18 +0100
Subject: [PATCH 15/20] chore: fix lint issues

---
 src/modules/commerce/index.ts | 10 +++++++++-
 test/modules/airline.spec.ts  | 20 ++++++++++++--------
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/src/modules/commerce/index.ts b/src/modules/commerce/index.ts
index 1e37af3231e..2f22239c6e4 100644
--- a/src/modules/commerce/index.ts
+++ b/src/modules/commerce/index.ts
@@ -1,3 +1,4 @@
+import { FakerError } from '../../errors/faker-error';
 import type { Faker } from '../../faker';
 import { bindThisToMemberFunctions } from '../../internal/bind-this-to-member-functions';
 import { deprecated } from '../../internal/deprecated';
@@ -386,7 +387,14 @@ export class CommerceModule {
 
     const registrantLength = groupRules.find(
       ([rangeMaximum]) => elementValue <= rangeMaximum
-    )![1];
+    )?.[1];
+
+    if (!registrantLength) {
+      // This can only happen if the ISBN_LENGTH_RULES are corrupted
+      throw new FakerError(
+        `Unable to find a registrant length for the group ${group}`
+      );
+    }
 
     const registrant = element.slice(0, registrantLength);
     const publication = element.slice(registrantLength);
diff --git a/test/modules/airline.spec.ts b/test/modules/airline.spec.ts
index df5f2fd7d42..bf674570c76 100644
--- a/test/modules/airline.spec.ts
+++ b/test/modules/airline.spec.ts
@@ -95,8 +95,8 @@ describe('airline', () => {
         const seatRegex = /^(\d{1,2})([A-K])$/;
         it('should return a random narrowbody seat when not passing an argument', () => {
           const seat = faker.airline.seat();
-          const matchResult = seatRegex.exec(seat)!;
-          expect(matchResult).not.toBeNull();
+          const matchResult = seatRegex.exec(seat);
+          expectNotNull(matchResult);
           const row = matchResult[1];
           const seatLetter = matchResult[2];
           expect(row).toSatisfy((row: number) => row >= 1 && row <= 35);
@@ -106,8 +106,8 @@ describe('airline', () => {
           const seat = faker.airline.seat({
             aircraftType: Aircraft.Narrowbody,
           });
-          const matchResult = seatRegex.exec(seat)!;
-          expect(matchResult).not.toBeNull();
+          const matchResult = seatRegex.exec(seat);
+          expectNotNull(matchResult);
           const row = matchResult[1];
           const seatLetter = matchResult[2];
           expect(row).toSatisfy((row: number) => row >= 1 && row <= 35);
@@ -115,8 +115,8 @@ describe('airline', () => {
         });
         it('should return a random regional seat', () => {
           const seat = faker.airline.seat({ aircraftType: Aircraft.Regional });
-          const matchResult = seatRegex.exec(seat)!;
-          expect(matchResult).not.toBeNull();
+          const matchResult = seatRegex.exec(seat);
+          expectNotNull(matchResult);
           const row = matchResult[1];
           const seatLetter = matchResult[2];
           expect(row).toSatisfy((row: number) => row >= 1 && row <= 20);
@@ -124,8 +124,8 @@ describe('airline', () => {
         });
         it('should return a random widebody seat', () => {
           const seat = faker.airline.seat({ aircraftType: Aircraft.Widebody });
-          const matchResult = seatRegex.exec(seat)!;
-          expect(matchResult).not.toBeNull();
+          const matchResult = seatRegex.exec(seat);
+          expectNotNull(matchResult);
           const row = matchResult[1];
           const seatLetter = matchResult[2];
           expect(row).toSatisfy((row: number) => row >= 1 && row <= 60);
@@ -179,3 +179,7 @@ describe('airline', () => {
     }
   );
 });
+
+function expectNotNull<T>(value: T): asserts value is NonNullable<T> {
+  expect(value).not.toBeNull();
+}

From 234c12fdf08fd31edc793c7ed25d101c823e5eb5 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Mon, 6 Nov 2023 10:16:51 +0100
Subject: [PATCH 16/20] chore: fix another lint warning

---
 src/modules/date/index.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/modules/date/index.ts b/src/modules/date/index.ts
index 9cb76015b21..d5f36ddf112 100644
--- a/src/modules/date/index.ts
+++ b/src/modules/date/index.ts
@@ -1081,6 +1081,7 @@ export class DateModule extends SimpleDateModule {
       context?: boolean;
     } = {}
   ): string {
+    // eslint-disable-next-line deprecation/deprecation
     const { abbr, abbreviated = abbr ?? false, context = false } = options;
 
     if (abbr != null) {
@@ -1264,6 +1265,7 @@ export class DateModule extends SimpleDateModule {
       context?: boolean;
     } = {}
   ): string {
+    // eslint-disable-next-line deprecation/deprecation
     const { abbr, abbreviated = abbr ?? false, context = false } = options;
 
     if (abbr != null) {

From 85e9096d782b8d6f7c071bb7d4880af2ff32a7d1 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Mon, 6 Nov 2023 10:32:37 +0100
Subject: [PATCH 17/20] chore: fix import issue

---
 src/modules/date/index.ts   | 24 ++++++++++++++++++++++++
 src/modules/person/index.ts |  2 +-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/modules/date/index.ts b/src/modules/date/index.ts
index d5f36ddf112..eca0097cb2a 100644
--- a/src/modules/date/index.ts
+++ b/src/modules/date/index.ts
@@ -1292,3 +1292,27 @@ export class DateModule extends SimpleDateModule {
     return this.faker.helpers.arrayElement(values);
   }
 }
+
+/**
+ *
+ * @param options asd
+ * @param options.deprecated as
+ * @param options.replacement asd
+ */
+export function demo(
+  options: {
+    /**
+     * @deprecated
+     */
+    deprecated?: boolean;
+    replacement?: boolean;
+  } = {}
+): boolean {
+  const {
+    // eslint-disable-next-line deprecation/deprecation
+    deprecated = false,
+    // eslint-disable-next-line deprecation/deprecation
+    replacement = deprecated,
+  } = options;
+  return replacement;
+}
diff --git a/src/modules/person/index.ts b/src/modules/person/index.ts
index af580b81d99..f5a2811cb13 100644
--- a/src/modules/person/index.ts
+++ b/src/modules/person/index.ts
@@ -1,5 +1,5 @@
 import type { Faker } from '../..';
-import { FakerError } from '../..';
+import { FakerError } from '../../errors/faker-error';
 import { ModuleBase } from '../../internal/module-base';
 import { assertLocaleData } from '../../locale-proxy';
 

From 109738fd71f97a132455c4beb509f9f60033bb3c Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Mon, 6 Nov 2023 21:56:41 +0100
Subject: [PATCH 18/20] Update src/modules/date/index.ts

---
 src/modules/date/index.ts | 24 ------------------------
 1 file changed, 24 deletions(-)

diff --git a/src/modules/date/index.ts b/src/modules/date/index.ts
index eca0097cb2a..d5f36ddf112 100644
--- a/src/modules/date/index.ts
+++ b/src/modules/date/index.ts
@@ -1292,27 +1292,3 @@ export class DateModule extends SimpleDateModule {
     return this.faker.helpers.arrayElement(values);
   }
 }
-
-/**
- *
- * @param options asd
- * @param options.deprecated as
- * @param options.replacement asd
- */
-export function demo(
-  options: {
-    /**
-     * @deprecated
-     */
-    deprecated?: boolean;
-    replacement?: boolean;
-  } = {}
-): boolean {
-  const {
-    // eslint-disable-next-line deprecation/deprecation
-    deprecated = false,
-    // eslint-disable-next-line deprecation/deprecation
-    replacement = deprecated,
-  } = options;
-  return replacement;
-}

From cb4383a91e731ce5223705c45e45d3813070ed46 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 10 Nov 2023 17:50:52 +0100
Subject: [PATCH 19/20] chore: fix lint warning

---
 src/modules/color/index.ts | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/modules/color/index.ts b/src/modules/color/index.ts
index 5962ef71b67..792b0c0b673 100644
--- a/src/modules/color/index.ts
+++ b/src/modules/color/index.ts
@@ -52,12 +52,14 @@ export type Casing = 'lower' | 'upper' | 'mixed';
  */
 function formatHexColor(
   hexColor: string,
-  options?: {
+  options: {
     prefix?: string;
     casing?: Casing;
-  }
+  } = {}
 ): string {
-  switch (options?.casing) {
+  const { prefix = '0x', casing = 'mixed' } = options;
+
+  switch (casing) {
     case 'upper':
       hexColor = hexColor.toUpperCase();
       break;
@@ -68,7 +70,7 @@ function formatHexColor(
     // Do nothing
   }
 
-  if (options?.prefix) {
+  if (prefix) {
     hexColor = options.prefix + hexColor;
   }
 

From 6efe430bbafcd94dc42d205671ea2e97e257ba62 Mon Sep 17 00:00:00 2001
From: ST-DDT <ST-DDT@gmx.de>
Date: Fri, 10 Nov 2023 18:13:35 +0100
Subject: [PATCH 20/20] chore: remove wrong defaults and make the properties
 required

---
 src/modules/color/index.ts | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/src/modules/color/index.ts b/src/modules/color/index.ts
index 792b0c0b673..57b906a376d 100644
--- a/src/modules/color/index.ts
+++ b/src/modules/color/index.ts
@@ -47,17 +47,17 @@ export type Casing = 'lower' | 'upper' | 'mixed';
  *
  * @param hexColor Hex color string to be formatted.
  * @param options Options object.
- * @param options.prefix Prefix of the generated hex color. Defaults to `'0x'`.
- * @param options.casing Letter type case of the generated hex color. Defaults to `'mixed'`.
+ * @param options.prefix Prefix of the generated hex color.
+ * @param options.casing Letter type case of the generated hex color.
  */
 function formatHexColor(
   hexColor: string,
   options: {
-    prefix?: string;
-    casing?: Casing;
-  } = {}
+    prefix: string;
+    casing: Casing;
+  }
 ): string {
-  const { prefix = '0x', casing = 'mixed' } = options;
+  const { prefix, casing } = options;
 
   switch (casing) {
     case 'upper':
@@ -71,7 +71,7 @@ function formatHexColor(
   }
 
   if (prefix) {
-    hexColor = options.prefix + hexColor;
+    hexColor = prefix + hexColor;
   }
 
   return hexColor;
@@ -362,19 +362,20 @@ export class ColorModule extends ModuleBase {
      */
     includeAlpha?: boolean;
   }): string | number[];
-  rgb(options?: {
-    prefix?: string;
-    casing?: Casing;
-    format?: 'hex' | ColorFormat;
-    includeAlpha?: boolean;
-  }): string | number[] {
+  rgb(
+    options: {
+      prefix?: string;
+      casing?: Casing;
+      format?: 'hex' | ColorFormat;
+      includeAlpha?: boolean;
+    } = {}
+  ): string | number[] {
     const {
       format = 'hex',
       includeAlpha = false,
       prefix = '#',
       casing = 'lower',
-    } = options || {};
-    options = { format, includeAlpha, prefix, casing };
+    } = options;
     let color: string | number[];
     let cssFunction: CssFunctionType = 'rgb';
     if (format === 'hex') {
@@ -382,7 +383,7 @@ export class ColorModule extends ModuleBase {
         length: includeAlpha ? 8 : 6,
         prefix: '',
       });
-      color = formatHexColor(color, options);
+      color = formatHexColor(color, { prefix, casing });
       return color;
     }