Add prettier

[giuseppeg]

Currently we use xo to lint our code.
We should replace it with standard.js

Let's just add Prettier. See https://github.com/zeit/now-cli/blob/master/package.json#L39-L52

[nkzawa]

I wonder if we can just format by https://github.com/jlongster/prettier instead. @rauchg

[giuseppeg]

We can have "prettier" fixtures but we still need a linter for the library code

[giuseppeg]

oh wait I thought prettier was only for JSX, awesome!

[rauchg]

prettier + linting rules for mistakes / warnings

[niksurff]

I started experimenting with this.

My starting point was to lint using eslint-config-standard as base and resetting styling rules with eslint-config-prettier. The idea was then to auto-fix styling on a pre-commit hook and only lint for common mistakes. This way a dev isn't bothered at all with errors like there should be a space at line 22 column 68. Also vanilla eslint makes it easy to use editor plugins for real time feedback.

The problem: I noticed prettier adds semicolons to the output which might not be configurable any time soon (discussion here). There is a workaround for this, like piping prettier's output into standard --fix (There is a package for that). In this case code gets formatted once using prettier's advanced algorithm and then again using standard --fix. Which—due to different styling rules—does more than just removing semicolons. In my opinion this gets more complicated than it needs to be.

This might not be a big problem. But before I continue I wanted to check what the general consent is or rather what the expected developer experience is concerning linting and (auto-fixing) code style.

My suggestion is to use prettier as is or just use standard by itself (which again leaves a dev with styling errors, also fixable by using --fix somewhere in the chain).

📓 You may experiment with the changes here. After cloning (or c/p package.json) run yarn install followed by npm run lint and npm run prettier or npm run prettier-standard. Diff the output.

cc @giuseppeg @rauchg

Update: I just found prettier-eslint and the corresponding cli—both part of the prettier org—which we might just use instead of vanilla prettier and add a no semicolons eslint rule (plus other styling rules we want to keep)!? This seems relatively clean.

[niksurff]

I just realized me rambling along last night and maybe not making any sense. 🙉

Anyways I submitted a PR which I believe is a good starting point for further discussion.

[giuseppeg]

@nikvm cool! Maybe we can just use prettier-eslint + omit semicolons?
Do we need other plugins from standard.js? It'd be nice to keep the setup minimal and unopinionated – the semicolons is the only exception I'd allow.

[niksurff]

@giuseppeg I continued the discussion in the PR thread.