[#IP-86] tslint to eslint migration

.eslintrc.js

@@ -1,34 +1,22 @@
 module.exports = {
-    "env": {
-        "browser": true,
-        "es6": true,
-        "node": true
-    },
-    "ignorePatterns": [
-        "node_modules",
-        "generated",
-        "**/__tests__/*",
-        "**/__mocks__/*",
-        "Dangerfile.*",
-        "*.d.ts"
-    ],
-    "parser": "@typescript-eslint/parser",
-    "parserOptions": {
-        "project": "tsconfig.json",
-        "sourceType": "module"
-    },
-    "extends": [
-        "@pagopa/eslint-config/strong",
-    ],
-    "rules": {
-        "import/order": "off",
-        "@typescript-eslint/array-type": "off",
-        "@typescript-eslint/explicit-member-accessibility": "off",
-        "functional/prefer-readonly-type": "off",
-        "@typescript-eslint/explicit-function-return-type": "off",
-        "no-invalid-this": "off",
-        "prefer-arrow/prefer-arrow-functions": "off",
-        "@typescript-eslint/prefer-optional-chain": "off",
-        "no-underscore-dangle": "off"
-    }
-}
+  env: {
+    browser: true,
+    es6: true,
+    node: true
+  },
+  ignorePatterns: [
+    "node_modules",
+    "generated",
+    "**/__tests__/*",
+    "**/__mocks__/*",
+    "Dangerfile.*",
+    "*.d.ts"
+  ],
+  parser: "@typescript-eslint/parser",
+  parserOptions: {
+    project: "tsconfig.json",
+    sourceType: "module"
+  },
+  extends: ["@pagopa/eslint-config/strong"],
+  rules: {}
+};

src/ExpressAdapter.ts

@@ -1,5 +1,5 @@
-import { Context } from "@azure/functions";
 import EventEmitter = require("events");
+import { Context } from "@azure/functions";
 import { Application } from "express";
 
 import IncomingMessage from "./IncomingMessage";
@@ -21,7 +21,7 @@ const isValidContext = (context: any): context is Context =>
   context.bindings.req.originalUrl &&
   typeof context.bindings.req.originalUrl === "string";
 
-export type RequestListener = (...args: readonly unknown[]) => void;
+export type RequestListener = (...args: ReadonlyArray<unknown>) => void;
 
 /**
  * Express adapter allowing to handle Azure Function requests by wrapping in request events.
@@ -33,7 +33,7 @@ export default class ExpressAdapter extends EventEmitter {
   /**
    * @param {Object=} application Request listener (typically an express/connect instance)
    */
-  public constructor(application: Application) {
+  constructor(application: Application) {
     super();
 
     if (application !== undefined) {
@@ -53,25 +53,27 @@ export default class ExpressAdapter extends EventEmitter {
   /**
    * Create function ready to be exposed to Azure Function for request handling.
    */
-  public createAzureFunctionHandler = () => (context: Context) => {
-    if (!isValidContext(context)) {
-      return;
-    }
+  public createAzureFunctionHandler() {
+    return (context: Context): void => {
+      if (!isValidContext(context)) {
+        return;
+      }
 
-    const updateResponse = (
-      updater: (
-        prev: NonNullable<Context["res"]>
-      ) => NonNullable<Context["res"]>
-    ) => {
-      // eslint-disable-next-line functional/immutable-data
-      context.res = updater(context.res || {});
-    };
+      const updateResponse = (
+        updater: (
+          prev: NonNullable<Context["res"]>
+        ) => NonNullable<Context["res"]>
+      ): void => {
+        // eslint-disable-next-line functional/immutable-data
+        context.res = updater(context.res || {});
+      };
 
-    // 2. Wrapping
-    const req = new IncomingMessage(context);
-    const res = new OutgoingMessage(updateResponse, context.done);
+      // 2. Wrapping
+      const req = new IncomingMessage(context);
+      const res = new OutgoingMessage(updateResponse, context.done);
 
-    // 3. Synchronously calls each of the listeners registered for the event
-    this.emit("request", req, res);
-  };
+      // 3. Synchronously calls each of the listeners registered for the event
+      this.emit("request", req, res);
+    };
+  }
 }

src/IncomingMessage.ts

@@ -1,34 +1,32 @@
-import { Context } from "@azure/functions";
 import { Socket } from "net";
 import { Readable } from "stream";
 import { TLSSocket } from "tls";
+import { Context } from "@azure/functions";
 
-const NOOP = () => true;
+const NOOP = (): true => true;
 
-function removePortFromAddress(address: string): string {
-  return address ? address.replace(/:[0-9]*$/, "") : address;
-}
+const removePortFromAddress = (address: string): string =>
+  address ? address.replace(/:[0-9]*$/, "") : address;
 
 /**
  * Create a fake connection object
  *
  * @param {Object} context Raw Azure context object for a single HTTP request
  * @returns {object} Connection object
  */
-function createConnectionObject(
+const createConnectionObject = (
   context: Context
-): Pick<Socket, "remoteAddress"> & Pick<TLSSocket, "encrypted"> {
+): Pick<Socket, "remoteAddress"> & Pick<TLSSocket, "encrypted"> => {
   const { req } = context.bindings;
   const xForwardedFor = req.headers
     ? req.headers["x-forwarded-for"]
     : undefined;
 
   return {
-    encrypted:
-      req.originalUrl && req.originalUrl.toLowerCase().startsWith("https"),
+    encrypted: req.originalUrl?.toLowerCase().startsWith("https"),
     remoteAddress: removePortFromAddress(xForwardedFor)
   };
-}
+};
 
 /**
  * Copy useful context properties from the native context provided by the Azure
@@ -41,15 +39,13 @@ function createConnectionObject(
  * @param {Object} context Raw Azure context object for a single HTTP request
  * @returns {Object} Filtered context
  */
-function sanitizeContext(context: Context): Context {
-  return {
-    ...context,
-    // We don't want the developer to mess up express flow
-    // See https://github.com/yvele/azure-function-express/pull/12#issuecomment-336733540
-    done: NOOP,
-    log: context.log.bind(context)
-  };
-}
+const sanitizeContext = (context: Context): Context => ({
+  ...context,
+  // We don't want the developer to mess up express flow
+  // See https://github.com/yvele/azure-function-express/pull/12#issuecomment-336733540
+  done: NOOP,
+  log: context.log.bind(context)
+});
 
 /**
  * Request object wrapper

src/OutgoingMessage.ts

@@ -1,11 +1,11 @@
 // eslint-disable camelcase
 
-import { Context } from "@azure/functions";
 import {
   OutgoingHttpHeaders,
   OutgoingMessage as NativeOutgoingMessage,
   ServerResponse
 } from "http";
+import { Context } from "@azure/functions";
 
 import { statusCodes } from "./statusCodes";
 
@@ -17,12 +17,13 @@ import { statusCodes } from "./statusCodes";
  * @private
  */
 export default class OutgoingMessage extends NativeOutgoingMessage {
-  public _hasBody = true;
-  public _headerNames = {};
-  public _headers = null;
-  public _removedHeader = {};
+  public readonly _hasBody = true;
+  public readonly _headerNames = {};
+  public readonly _headers = null;
+  public readonly _removedHeader = {};
+  // eslint-disable-next-line functional/prefer-readonly-type
   public statusMessage!: string;
-  public statusCode!: number;
+  public readonly statusCode!: number;
 
   /**
    * Original implementation: https://github.com/nodejs/node/blob/v6.x/lib/_http_outgoing.js#L48
@@ -40,27 +41,29 @@ export default class OutgoingMessage extends NativeOutgoingMessage {
 
   // Those methods cannot be prototyped because express explicitelly overrides __proto__
   // See https://github.com/expressjs/express/blob/master/lib/middleware/init.js#L29
-  public end: NativeOutgoingMessage["end"] = (
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    chunkOrCb?: any
+  public readonly end: NativeOutgoingMessage["end"] = (
+    chunkOrCb: Parameters<NativeOutgoingMessage["end"]>[0]
   ) => {
     // 1. Write head
+    // eslint-disable-next-line no-invalid-this
     this.writeHead(this.statusCode); // Make jshttp/on-headers able to trigger
 
     // 2. Return raw body to Azure Function runtime
+    // eslint-disable-next-line no-invalid-this
     this.updateResponse(res => ({
       ...res,
       body: chunkOrCb,
       isRaw: true
     }));
+    // eslint-disable-next-line no-invalid-this
     this.done();
   };
 
   /**
    * https://nodejs.org/api/http.html#http_response_writehead_statuscode_statusmessage_headers
    * Original implementation: https://github.com/nodejs/node/blob/v6.x/lib/_http_server.js#L160
    */
-  public writeHead: ServerResponse["writeHead"] = (
+  public readonly writeHead: ServerResponse["writeHead"] = (
     statusCode: number,
     reasonOrHeaders?: string | OutgoingHttpHeaders,
     headersOrUndefined?: OutgoingHttpHeaders
@@ -72,7 +75,7 @@ export default class OutgoingMessage extends NativeOutgoingMessage {
     }
 
     // 2. Status message
-    // eslint-disable-next-line functional/immutable-data
+    // eslint-disable-next-line functional/immutable-data, no-invalid-this
     this.statusMessage =
       typeof reasonOrHeaders === "string"
         ? reasonOrHeaders
@@ -85,24 +88,28 @@ export default class OutgoingMessage extends NativeOutgoingMessage {
         ? reasonOrHeaders
         : headersOrUndefined;
 
+    // eslint-disable-next-line no-underscore-dangle, no-invalid-this
     if (this._headers && headers !== undefined) {
       // Slow-case: when progressive API and header fields are passed.
       Object.keys(headers).forEach(k => {
         const v = headers[k];
         if (v) {
+          // eslint-disable-next-line no-invalid-this
           this.setHeader(k, v);
         }
       });
     }
 
     // 4. Sets everything
+    // eslint-disable-next-line no-invalid-this
     this.updateResponse(res => ({
       ...res,
       // In order to uniformize node 6 behaviour with node 8 and 10,
       // we want to never have undefined headers, but instead empty object
       headers:
+        // eslint-disable-next-line no-underscore-dangle, no-invalid-this
         this._headers && headers === undefined
-          ? // eslint-disable-next-line @typescript-eslint/no-explicit-any
+          ? // eslint-disable-next-line no-underscore-dangle, @typescript-eslint/no-explicit-any, no-invalid-this
             (this as any)._renderHeaders()
           : headers !== undefined
           ? headers

src/createAzureFunctionsHandler.ts

@@ -9,9 +9,11 @@ import ExpressAdapter from "./ExpressAdapter";
  * @param {Object} requestListener Request listener (typically an express/connect instance)
  * @returns {function(context: Object)} Azure Function handle
  */
-export default function createAzureFunctionHandler(
+const createAzureFunctionHandler = (
   application: Application
-): (context: Context) => void {
+): ((context: Context) => void) => {
   const adapter = new ExpressAdapter(application);
   return adapter.createAzureFunctionHandler();
-}
+};
+
+export default createAzureFunctionHandler;

src/statusCodes.ts

@@ -1,4 +1,4 @@
-export const statusCodes: { [key: number]: string | undefined } = {
+export const statusCodes: { readonly [key: number]: string | undefined } = {
   100: "Continue",
   101: "Switching Protocols",
   102: "Processing", // RFC 2518, obsoleted by RFC 4918