infra: enable strictNullChecks in tsconfig

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;
         }

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.',

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);
 }
 

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(

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)}`;
 }

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>>;

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',

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',

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'],
 };

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);
     }

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);

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);
   }
 }

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;
   }
 
   /**

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);
     }
 
@@ -554,16 +556,17 @@ 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.');
       }
 
       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.

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

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([
           '.',
           '_',