chore: Enabling more ESLint checks and fixing errors

.eslintrc.js

@@ -28,17 +28,21 @@ module.exports = {
   rules: {
     // Following checks are temporarily disabled. We shall incrementally enable them in the
     // future, fixing any violations as we go.
-    "@typescript-eslint/no-explicit-any": 0,
-    "@typescript-eslint/no-use-before-define": 0,
-    "@typescript-eslint/explicit-function-return-type": 0,
-    "@typescript-eslint/camelcase": 0,
-    "@typescript-eslint/no-non-null-assertion": 0,
-    "@typescript-eslint/no-var-requires": 0,
-    "@typescript-eslint/ban-types": 0,
-    "no-useless-escape": 0,
-    "no-prototype-builtins": 0,
+    '@typescript-eslint/no-non-null-assertion': 0,
+
+    // Disabled checks
+    '@typescript-eslint/no-explicit-any': 0,
+    '@typescript-eslint/no-use-before-define': 0,
 
     // Required checks
-    "indent": ["error", 2]
+    'indent': ['error', 2],
+    '@typescript-eslint/explicit-function-return-type': [
+      'error',
+      {
+        'allowExpressions': true,
+        'allowTypedFunctionExpressions': true,
+        'allowHigherOrderFunctions': true
+      }
+    ],
   }
 };

src/auth/action-code-settings-builder.ts

@@ -169,7 +169,7 @@ export class ActionCodeSettingsBuilder {
     };
     // Remove all null and undefined fields from request.
     for (const key in request) {
-      if (request.hasOwnProperty(key)) {
+      if (Object.prototype.hasOwnProperty.call(request, key)) {
         if (typeof request[key] === 'undefined' || request[key] === null) {
           delete request[key];
         }

src/auth/auth-api-request.ts

@@ -187,7 +187,7 @@ class TenantAwareAuthResourceUrlBuilder extends AuthResourceUrlBuilder {
  *
  * @param {any} request The providerUserInfo request object.
  */
-function validateProviderUserInfo(request: any) {
+function validateProviderUserInfo(request: any): void {
   const validKeys = {
     rawId: true,
     providerId: true,
@@ -247,7 +247,7 @@ function validateProviderUserInfo(request: any) {
  * @param {any} request The create/edit request object.
  * @param {boolean=} uploadAccountRequest Whether to validate as an uploadAccount request.
  */
-function validateCreateEditRequest(request: any, uploadAccountRequest = false) {
+function validateCreateEditRequest(request: any, uploadAccountRequest = false): void {
   // Hash set of whitelisted parameters.
   const validKeys = {
     displayName: true,
@@ -370,7 +370,7 @@ function validateCreateEditRequest(request: any, uploadAccountRequest = false) {
     const invalidClaims: string[] = [];
     // Check for any invalid claims.
     RESERVED_CLAIMS.forEach((blacklistedClaim) => {
-      if (developerClaims.hasOwnProperty(blacklistedClaim)) {
+      if (Object.prototype.hasOwnProperty.call(developerClaims, blacklistedClaim)) {
         invalidClaims.push(blacklistedClaim);
       }
     });

src/auth/auth-config.ts

@@ -179,10 +179,10 @@ export class EmailSignInConfig implements EmailSignInProviderConfig {
   public static buildServerRequest(options: EmailSignInProviderConfig): EmailSignInConfigServerRequest {
     const request: EmailSignInConfigServerRequest = {};
     EmailSignInConfig.validate(options);
-    if (options.hasOwnProperty('enabled')) {
+    if (Object.prototype.hasOwnProperty.call(options, 'enabled')) {
       request.allowPasswordSignup = options.enabled;
     }
-    if (options.hasOwnProperty('passwordRequired')) {
+    if (Object.prototype.hasOwnProperty.call(options, 'passwordRequired')) {
       request.enableEmailLinkSignin = !options.passwordRequired;
     }
     return request;
@@ -193,7 +193,7 @@ export class EmailSignInConfig implements EmailSignInProviderConfig {
    *
    * @param {any} options The options object to validate.
    */
-  private static validate(options: EmailSignInProviderConfig) {
+  private static validate(options: EmailSignInProviderConfig): void {
     // TODO: Validate the request.
     const validKeys = {
       enabled: true,
@@ -349,7 +349,7 @@ export class SAMLConfig implements SAMLAuthProviderConfig {
    * @param {SAMLAuthProviderRequest} options The options object to validate.
    * @param {boolean=} ignoreMissingFields Whether to ignore missing fields.
    */
-  public static validate(options: SAMLAuthProviderRequest, ignoreMissingFields = false) {
+  public static validate(options: SAMLAuthProviderRequest, ignoreMissingFields = false): void {
     const validKeys = {
       enabled: true,
       displayName: true,
@@ -590,7 +590,7 @@ export class OIDCConfig implements OIDCAuthProviderConfig {
    * @param {OIDCAuthProviderRequest} options The options object to validate.
    * @param {boolean=} ignoreMissingFields Whether to ignore missing fields.
    */
-  public static validate(options: OIDCAuthProviderRequest, ignoreMissingFields = false) {
+  public static validate(options: OIDCAuthProviderRequest, ignoreMissingFields = false): void {
     const validKeys = {
       enabled: true,
       displayName: true,

src/auth/auth.ts

@@ -444,7 +444,7 @@ export class BaseAuth<T extends AbstractAuthRequestHandler> {
         providerConfigs,
       };
       // Delete result.pageToken if undefined.
-      if (response.hasOwnProperty('nextPageToken')) {
+      if (Object.prototype.hasOwnProperty.call(response, 'nextPageToken')) {
         result.pageToken = response.nextPageToken;
       }
       return result;

src/auth/credential.ts

@@ -132,6 +132,7 @@ export class ServiceAccountCredential implements Credential {
       ].join(' '),
     };
 
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
     const jwt = require('jsonwebtoken');
     // This method is actually synchronous so we can capture and return the buffer.
     return jwt.sign(claims, this.privateKey, {
@@ -189,6 +190,7 @@ class ServiceAccount {
       throw new FirebaseAppError(AppErrorCodes.INVALID_CREDENTIAL, errorMessage);
     }
 
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
     const forge = require('node-forge');
     try {
       forge.pki.privateKeyFromPem(this.privateKey);
@@ -386,7 +388,7 @@ export function isApplicationDefault(credential?: Credential): boolean {
  * @param key Name of the property to copy.
  * @param alt Alternative name of the property to copy.
  */
-function copyAttr(to: {[key: string]: any}, from: {[key: string]: any}, key: string, alt: string) {
+function copyAttr(to: {[key: string]: any}, from: {[key: string]: any}, key: string, alt: string): void {
   const tmp = from[key] || from[alt];
   if (typeof tmp !== 'undefined') {
     to[key] = tmp;

src/auth/tenant.ts

@@ -95,7 +95,7 @@ export class Tenant {
    * @param {any} request The tenant options object to validate.
    * @param {boolean} createRequest Whether this is a create request.
    */
-  private static validate(request: any, createRequest: boolean) {
+  private static validate(request: any, createRequest: boolean): void {
     const validKeys = {
       displayName: true,
       emailSignInConfig: true,

src/auth/token-generator.ts

@@ -101,7 +101,7 @@ export class ServiceAccountSigner implements CryptoSigner {
    * @inheritDoc
    */
   public sign(buffer: Buffer): Promise<Buffer> {
-    const crypto = require('crypto');
+    const crypto = require('crypto'); // eslint-disable-line @typescript-eslint/no-var-requires
     const sign = crypto.createSign('RSA-SHA256');
     sign.update(buffer);
     return Promise.resolve(sign.sign(this.credential.privateKey));
@@ -285,7 +285,7 @@ export class FirebaseTokenGenerator {
     if (typeof developerClaims !== 'undefined') {
       for (const key in developerClaims) {
         /* istanbul ignore else */
-        if (developerClaims.hasOwnProperty(key)) {
+        if (Object.prototype.hasOwnProperty.call(developerClaims, key)) {
           if (BLACKLISTED_CLAIMS.indexOf(key) !== -1) {
             throw new FirebaseAuthError(
               AuthClientErrorCode.INVALID_ARGUMENT,
@@ -311,6 +311,7 @@ export class FirebaseTokenGenerator {
         uid,
       };
       if (this.tenantId) {
+        // eslint-disable-next-line @typescript-eslint/camelcase
         body.tenant_id = this.tenantId;
       }
       if (Object.keys(claims).length > 0) {
@@ -324,9 +325,9 @@ export class FirebaseTokenGenerator {
     });
   }
 
-  private encodeSegment(segment: object | Buffer) {
+  private encodeSegment(segment: object | Buffer): string {
     const buffer: Buffer = (segment instanceof Buffer) ? segment : Buffer.from(JSON.stringify(segment));
-    return toWebSafeBase64(buffer).replace(/\=+$/, '');
+    return toWebSafeBase64(buffer).replace(/=+$/, '');
   }
 
   /**

src/auth/token-verifier.ts

@@ -214,7 +214,7 @@ export class FirebaseTokenVerifier {
     }
 
     return this.fetchPublicKeys().then((publicKeys) => {
-      if (!publicKeys.hasOwnProperty(header.kid)) {
+      if (!Object.prototype.hasOwnProperty.call(publicKeys, header.kid)) {
         return Promise.reject(
           new FirebaseAuthError(
             AuthClientErrorCode.INVALID_ARGUMENT,
@@ -299,7 +299,7 @@ export class FirebaseTokenVerifier {
         // error responses.
         throw new HttpError(resp);
       }
-      if (resp.headers.hasOwnProperty('cache-control')) {
+      if (Object.prototype.hasOwnProperty.call(resp.headers, 'cache-control')) {
         const cacheControlHeader: string = resp.headers['cache-control'];
         const parts = cacheControlHeader.split(',');
         parts.forEach((part) => {

src/database/database.ts

@@ -77,8 +77,8 @@ export class DatabaseService implements FirebaseServiceInterface {
 
     let db: Database = this.INTERNAL.databases[dbUrl];
     if (typeof db === 'undefined') {
-      const rtdb = require('@firebase/database');
-      const { version } = require('../../package.json');
+      const rtdb = require('@firebase/database'); // eslint-disable-line @typescript-eslint/no-var-requires
+      const { version } = require('../../package.json'); // eslint-disable-line @typescript-eslint/no-var-requires
       db = rtdb.initStandalone(this.appInternal, dbUrl, version).instance;
 
       const rulesClient = new DatabaseRulesClient(this.app, dbUrl);

src/firebase-app.ts

@@ -189,7 +189,7 @@ export class FirebaseAppInternals {
    *
    * @param {function(string)} listener The listener that will be called with each new token.
    */
-  public addAuthTokenListener(listener: (token: string) => void) {
+  public addAuthTokenListener(listener: (token: string) => void): void {
     this.tokenListeners_.push(listener);
     if (this.cachedToken_) {
       listener(this.cachedToken_.accessToken);
@@ -201,7 +201,7 @@ export class FirebaseAppInternals {
    *
    * @param {function(string)} listener The listener to remove.
    */
-  public removeAuthTokenListener(listener: (token: string) => void) {
+  public removeAuthTokenListener(listener: (token: string) => void): void {
     this.tokenListeners_ = this.tokenListeners_.filter((other) => other !== listener);
   }
 

src/firebase-namespace.ts

@@ -237,7 +237,7 @@ export class FirebaseNamespaceInternals {
    * @param {FirebaseApp} app The FirebaseApp instance whose app hooks to call.
    * @param {string} eventName The event name representing which app hooks to call.
    */
-  private callAppHooks_(app: FirebaseApp, eventName: string) {
+  private callAppHooks_(app: FirebaseApp, eventName: string): void {
     Object.keys(this.serviceFactories).forEach((serviceName) => {
       if (this.appHooks_[serviceName]) {
         this.appHooks_[serviceName](eventName, app);
@@ -340,6 +340,8 @@ export class FirebaseNamespace {
     const fn: FirebaseServiceNamespace<Database> = (app?: FirebaseApp) => {
       return this.ensureApp(app).database();
     };
+
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
     return Object.assign(fn, require('@firebase/database'));
   }
 
@@ -375,6 +377,8 @@ export class FirebaseNamespace {
     let fn: FirebaseServiceNamespace<Firestore> = (app?: FirebaseApp) => {
       return this.ensureApp(app).firestore();
     };
+
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
     const firestore = require('@google-cloud/firestore');
 
     fn = Object.assign(fn, firestore.Firestore);

src/firestore/firestore.ts

@@ -73,12 +73,13 @@ export function getFirestoreOptions(app: FirebaseApp): Settings {
 
   const projectId: string | null = utils.getExplicitProjectId(app);
   const credential = app.options.credential;
+  // eslint-disable-next-line @typescript-eslint/no-var-requires
   const { version: firebaseVersion } = require('../../package.json');
   if (credential instanceof ServiceAccountCredential) {
     return {
       credentials: {
-        private_key: credential.privateKey,
-        client_email: credential.clientEmail,
+        private_key: credential.privateKey, // eslint-disable-line @typescript-eslint/camelcase
+        client_email: credential.clientEmail, // eslint-disable-line @typescript-eslint/camelcase
       },
       // When the SDK is initialized with ServiceAccountCredentials an explicit projectId is
       // guaranteed to be available.

src/index.d.ts

@@ -18,6 +18,8 @@ import { Bucket } from '@google-cloud/storage';
 import * as _firestore from '@google-cloud/firestore';
 import { Agent } from 'http';
 
+/* eslint-disable @typescript-eslint/ban-types */
+
 /**
  * `admin` is a global namespace from which all Firebase Admin
  * services are accessed.