flow-experience.md

Trying Flow on my node.js code…Let’s see how this goes

Finding the getting started guide:

1. google flow
2. click “getflow.com”
3. was something else
4. google flow javascript
5. found flowtype.org
6. Click “get started” and landed here https://flowtype.org/docs/getting-started.html#_

Following the guide:

First thoughts, okay this is for a new project, but I’m not making a new project, so adapting to my life. In this case we’ll try with my node.js project.

2. touch .flowconfig
3. npm install --save-dev flow-bin
4. Add // @flow to my index.js file // seems gross to me, but doing it anyway
5. Typing npm run-script flow thought maybe it would work, but it doesn’t. get “missing script: flow”
6. Typing ./node_modules/.bin/flow instead (not from docs)
7. lots of weird startup stuff…. “flow is still initializing”
8. “Found 43 errors”

node_modules/findup/test/fixture/f/e/d/c/b/a/top.json:1
  1: 
     ^ Unexpected end of input

node_modules/findup/test/fixture/f/e/d/c/config.json:1
  1: 
     ^ Unexpected end of input
.... // goes on an on

Errors some pretty unrelated to anything I'm doing. Giving up.

Will Try Some More Things....

1. google the error messages
2. Found facebook/flow#1420 (comment) trying it
3. "Found 49 errors" > 6 more errors than last time!!?!?
4. Okay there's a not about the main field with that regex, trying another regex .*/node_modules/.*/\(lib\|test\).*\.json$
5. "Found 36 errors" > hey progress
6. Let's look at the last two

node_modules/react/node_modules/fbjs/lib/Deferred.js.flow:60
 60:     Promise.prototype.done.apply(this._promise, arguments);
                           ^^^^ property `done`. Property not found in
497: declare class Promise<+R> {
     ^ Promise. See lib: /private/tmp/flow/flowlib_22c9017e/core.js:497

node_modules/react/node_modules/fbjs/lib/shallowEqual.js.flow:29
 29:     return x !== 0 || 1 / (x: $FlowIssue) === 1 / (y: $FlowIssue);

1. Seems like facebook is breaking flow. Pretty weird.
2. Googling it.
3. Found facebookarchive/draft-js#305
4. @zpao says we need to update fbjs. I don't even use that dep directly, so I don't agree.
5. Getting annoyed again, but running npm ls fbjs

p2pnodeweb@1.29.0 /Users/jamuferguson/dev/paypal/web
├─┬ flux@2.1.1
│ └─┬ fbemitter@2.0.2
│   └── fbjs@0.7.2 
└─┬ react@15.3.1
  └── fbjs@0.8.4 

6. grep 'version":' ./node_modules/fbjs/package.json
7. "0.1.0-alpha.7"
8. Hmm, seems old npm i fbjs
9. grep 'version":' ./node_modules/fbjs/package.json
10. "version": "0.8.4"
11. seems better, let's
12. ./node_modules/.bin/flow
13. "Found 38 Errors" > Okay ,that's 2 more than before" and more JSON errors in there

giving up again, for now

Nothing seems to work.

Here's the results of trying return void next()

118:            return void next()
                ^^^^^^^^^^^^^^^^^^ async return. Missing annotation

Here's the results of putting them on separate lines:

119:            return
                ^^^^^^ async return. Missing annotation

And async function always returns a Promise, so maybe it's getting confused? Or maybe there's just some special way that it needs to be annotated.

Okay got it. While I think it should be built-in, adding this to the end of the functional declaration seems to work

: Promise<void>

So our async middleware looks like this:

async function middleware(req: ExpressReq, res: any, next: function): Promise<void> {

Now running into this issue:

 const [contacts, fancyList: CustomType[] = [], randomThing = ''] = results
                                         ^^^^^^^^^^^^^^^^^^^ assignment of identifier `randomThing`. Could not resolve name

But I think it will be sorted out by:
facebook/flow#2239

Was still getting these errors

node_modules/fbjs/lib/Deferred.js.flow:60
 60:     Promise.prototype.done.apply(this._promise, arguments);
                           ^^^^ property `done`. Property not found in
[libs]
497: declare class Promise<+R> {
     ^ Promise. See lib: /private/tmp/flow/flowlib_25b721b0/core.js:497

node_modules/react/node_modules/fbjs/lib/Deferred.js.flow:60
 60:     Promise.prototype.done.apply(this._promise, arguments);
                           ^^^^ property `done`. Property not found in
497: declare class Promise<+R> {
     ^ Promise. See lib: /private/tmp/flow/flowlib_25b721b0/core.js:497

So I added the following to the [ignore]:

.*/node_modules/.*fbjs/*

Now trying to get babel to work. Seems kind of busted. Lots of these errors.

express-session deprecated undefined saveUninitialized option; provide saveUninitialized option node_modules/kraken-js/node_modules/meddleware/index.js:105:20
express-session deprecated req.secret; provide secret option node_modules/kraken-js/node_modules/meddleware/index.js:105:20
Tue, 30 Aug 2016 04:34:14 GMT unhandledRejection
SyntaxError: /Users/jamuferguson/dev/paypal/code/controllers/app/controller.js: Unexpected token (110:76)
  109 |  */
> 110 | export async function middleware(req: ExpressReq, res: any, next: function): Promise<void> {
      |                                                                             ^
  111 | 
    at Parser.pp.raise (/Users/jamuferguson/dev/paypal/code/node_modules/babylon/lib/parser/location.js:22:13)
    at Parser.pp.unexpected (/Users/jamuferguson/dev/paypal/code/node_modules/babylon/lib/parser/util.js:91:8)
    at Parser.pp.flowParsePrimaryType (/Users/jamuferguson/dev/paypal/code/node_modules/babylon/lib/plugins/flow.js:1101:8)

I guess we need to do this instead?

Replace next: function with next: Function

Weird that flow didn't mind the issue. Not actually seeing how to annotate functions very clearly. Looking here:
https://flowtype.org/docs/functions.html

this is totally fascinating.