Add typescript support

[louisyuenll]

I want to add TypeScript language support in the generator so that developers can enjoy strong-typed programming and use ES6 features in their applications.

Related issue: #125

[dougwilson]

Should the types package version pach the debug package version?

[dougwilson]

Should the types package version pach the express package version?

[louisyuenll]

Agree, better align with express v4.16.1.
Per check, @types/express also support typing on v4.16.

[dougwilson]

Would this cause an issue when generated and used on an older node.js like, say 10.x?

[louisyuenll]

It should be safe on older node environment as the version of the generated codes are controlled via tsconfig.json (line 5, "target": "es5"). Currently it is set compiling codes down to ES5 to support most of the older node.js.

[dougwilson]

Gotcha. I guess i mean typescript-wise. As in I assume that the node 13 types include definitions that do not apply/work on node 10, which then reduces the useful type checking that would prevent that?

[louisyuenll]

Yes, you are correct.

As the typing version of node is not one-to-one, perhaps we can adjust it to match the major version of current node.

However, during testing I found that node typing below v8 causes typing mismatch errors so that I suggest setting the minimum of @types/node to v8.

// When below v8 (tested with v6.17.1):

node_modules/@types/connect/index.d.ts:21:42 - error TS2689: Cannot extend an interface 'http.IncomingMessage'. Did you mean 'implements'?

21     export class IncomingMessage extends http.IncomingMessage {

pkg.devDependencies['@types/node'] = '^' + Math.max(8, parseInt(process.version.replace('v', '')))
// example output => "@types/node": "^12"

[dougwilson]

The www script shouldn't have an extension; it follows the pattern of being an executable (with shebang on the top).

[louisyuenll]

Got it, may be adding a post-build script to create a symbolic link with name www, pointing to www .js?

As some people may want to generate source-maps for the compiled JS files, I afraid directly renaming it may break the file linkage.

For example,

// add postbuild.js

var fs = require('fs')
var path = require('path')

// Create a symlink, linking www to www.js
var wwwScriptPath = path.join(__dirname, 'bin/www.js')
var wwwPath = path.join(__dirname, 'bin/www')
if (fs.existsSync(wwwScriptPath) && !fs.existsSync(wwwPath)) {
  fs.symlinkSync(wwwScriptPath, wwwPath)
}

[dougwilson]

Unfortunately normal users cannot create symbolic links on windows.

[louisyuenll]

How about if coping www .js as www?

var fs = require('fs')
var path = require('path')

// Polyfill copyFileSync for node < 8.5.0
if (!fs.copyFileSync) {
  fs.copyFileSync = function (src, dest, flags) {
    fs.writeFileSync(dest, fs.readFileSync(src), flags)
  }
}

// Copy www.js to www
var wwwScriptPath = path.join(__dirname, 'bin/www.js')
var wwwPath = path.join(__dirname, 'bin/www')
if (fs.existsSync(wwwScriptPath)) {
  fs.copyFileSync(wwwScriptPath, wwwPath)
}

[dougwilson]

It is probably not add this if there are none; npm will end up removing it on the next npm I command a user uses. That's why we sort them in the same way npm does as well, so it doesn't cause churn in the file after the fact.

[louisyuenll]

Got it, will remove it and only add devDependencies on TypeScript templates.

pkg.devDependencies = {}
pkg.devDependencies['typescript'] = '~3.7.5'
// ...rest of codes

[dougwilson]

Awesome, I love this idea! I added a few questions/comments above. Note that I'm not familiar with TypeScript, so take them with a gain of salt :) It would be great if a test could be added as well.

[louisyuenll]

As current settings automatically add the helper codes (e.g. ES6+ polyfills) into every related output files, I added tslib so that code duplication can be avoided.

[samsan1212]

Hi @dougwilson ,
May I know if this feature is released?
I also love Typescript. It would be so nice if express generator supports typescript.
Is there anything I can help?

[validity-check]

When will this be released? I can't stand using plain javascript

[siddharthvp]

Doesn't look like the correct use of debug. See documentation and/or the corresponding js code. I think this should be

import debugLogger from 'debug'; 
const debug = debugLogger('<%- name %>:server');