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] ?? 'MISSING';
         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

@@ -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

scripts/apidoc/faker-class.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) > 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/date.ts

@@ -26,8 +26,9 @@
 
   /**
    * 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.

src/definitions/definitions.ts

@@ -50,4 +50,4 @@
   system?: SystemDefinition;
   vehicle?: VehicleDefinition;
   word?: WordDefinition;
-} & Record<string, Record<string, unknown> | undefined>;
+} & Record<string, Record<string, unknown>>;

src/locale-proxy.ts

@@ -54,6 +54,30 @@ 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) {
+    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 +103,10 @@ 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,

src/modules/airline/index.ts

@@ -155,7 +155,7 @@ export class AirlineModule extends ModuleBase {
   ): string {
     const { allowNumerics = false, allowVisuallySimilarCharacters = false } =
       options;
-    const excludedChars = [];
+    const excludedChars: string[] = [];
     if (!allowNumerics) {
       excludedChars.push(...numerics);
     }

src/modules/commerce/index.ts

@@ -1,3 +1,4 @@
+import { FakerError } from '../../errors/faker-error';
 import { deprecated } from '../../internal/deprecated';
 import { ModuleBase } from '../../internal/module-base';
 
@@ -381,7 +382,14 @@
 
     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);

src/modules/date/index.ts

@@ -3,6 +3,7 @@ import type { DateEntryDefinition } from '../../definitions';
 import { FakerError } from '../../errors/faker-error';
 import { deprecated } from '../../internal/deprecated';
 import { SimpleModuleBase } from '../../internal/module-base';
+import { assertLocaleData } from '../../locale-proxy';
 
 /**
  * Converts date passed as a string, number or Date to a Date object.
@@ -15,6 +16,10 @@ function toDate(
   date: string | Date | number | undefined,
   fallback: () => Date
 ): Date {
+  if (date == null) {
+    return fallback();
+  }
+
   date = new Date(date);
   if (Number.isNaN(date.valueOf())) {
     date = fallback();
@@ -383,14 +388,15 @@ export class SimpleDateModule extends SimpleModuleBase {
         },
     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;
@@ -559,14 +565,15 @@ export class SimpleDateModule extends SimpleModuleBase {
     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;
@@ -864,12 +871,6 @@ export class SimpleDateModule extends SimpleModuleBase {
       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();
@@ -894,6 +895,12 @@ export class SimpleDateModule extends SimpleModuleBase {
       );
     }
 
+    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 }));
   }
 }
@@ -1074,12 +1081,8 @@ export class DateModule extends SimpleDateModule {
       context?: boolean;
     } = {}
   ): string {
-    const {
-      // eslint-disable-next-line deprecation/deprecation
-      abbr,
-      abbreviated = abbr ?? false,
-      context = false,
-    } = options;
+    // eslint-disable-next-line deprecation/deprecation
+    const { abbr, abbreviated = abbr ?? false, context = false } = options;
 
     if (abbr != null) {
       deprecated({
@@ -1100,7 +1103,9 @@ export class DateModule extends SimpleDateModule {
       type = useContext ? 'wide_context' : 'wide';
     }
 
-    return this.faker.helpers.arrayElement(source[type]);
+    const values = source[type];
+    assertLocaleData(values, 'date.month', type);
+    return this.faker.helpers.arrayElement(values);
   }
 
   /**
@@ -1260,12 +1265,8 @@ export class DateModule extends SimpleDateModule {
       context?: boolean;
     } = {}
   ): string {
-    const {
-      // eslint-disable-next-line deprecation/deprecation
-      abbr,
-      abbreviated = abbr ?? false,
-      context = false,
-    } = options;
+    // eslint-disable-next-line deprecation/deprecation
+    const { abbr, abbreviated = abbr ?? false, context = false } = options;
 
     if (abbr != null) {
       deprecated({
@@ -1286,6 +1287,8 @@ export class DateModule extends SimpleDateModule {
       type = useContext ? 'wide_context' : 'wide';
     }
 
-    return this.faker.helpers.arrayElement(source[type]);
+    const values = source[type];
+    assertLocaleData(values, 'date.weekday', type);
+    return this.faker.helpers.arrayElement(values);
   }
 }

src/modules/finance/index.ts

@@ -23,6 +23,22 @@ 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.
  *
@@ -663,9 +679,9 @@ export class FinanceModule extends ModuleBase {
    */
   currencySymbol(): string {
     let symbol: string;
-    while (!symbol) {
+    do {
       symbol = this.currency().symbol;
-    }
+    } while (symbol.length === 0);
 
     return symbol;
   }
@@ -1147,7 +1163,7 @@ export class FinanceModule extends ModuleBase {
 
     const result = `${ibanFormat.country}${checksum}${s}`;
 
-    return formatted ? result.match(/.{1,4}/g).join(' ') : result;
+    return formatted ? prettyPrintIban(result) : result;
   }
 
   /**

src/modules/helpers/index.ts

@@ -1120,7 +1120,7 @@ export class SimpleHelpersModule extends SimpleModuleBase {
     ) => 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

@@ -97,9 +97,9 @@ export function exec<
     maxRetries = 50,
     currentIterations = 0,
     compare = defaultCompare,
-    store,
+    store = {},
   } = options;
-  let { exclude } = options;
+  let { exclude = [] } = options;
   options.currentIterations = currentIterations;
 
   // Support single exclude argument as string